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The Influence of Scale and Geography on Relationships between Stream Community Composition and Landscape Variables: Description and Prediction
Abstract
SUMMARY 1. We analysed an existing database of macroinvertebrates and fish in the context of a newly established geographical information system (GIS) of physical features to determine the relationships between stream community composition and physical factors measured at three landscape scales – catchment, reach and bedform. Both an exploratory (concordance analysis) and a predictive (ausrivas) approach were used.
2. The environmental variables that most successfully accounted for variation in macroinvertebrate assemblages were mainly ‘natural’ and at the catchment-scale (relief ratio, basin diameter, etc.) but the human-induced physical setting of percentage of pasture in the riparian zone was also influential. For fish, ‘natural’ variables were also dominant, but these were mostly at the bedform or reach scales and land use featured strongly.
3. Geographic location accounted for some of the variation in invertebrate assemblages, partly because geography and influential conditions/resources are correlated but also because different species may have evolved in different places and have not colonised every ‘ecologically appropriate’ location. Geographic location was not influential in accounting for variation in assemblages of strongly flying invertebrates, supporting the hypothesis that organisms having high dispersal potential can be expected to break down geographic barriers more readily than those with poor dispersal powers. In accord with what is known about the local evolution and restricted distributions of native and exotic species, history (reflected in geography) appeared to account for some variation in fish assemblages.
4. Given their different mathematical bases, the fact that exploratory and predictive analyses yielded similar results provides added confidence to our conclusions.
... In ecosystems, biodiversity patterns are structured by factors operating at multiple, nested spatial scales (Townsend et al. 2003). At the global scale, climate is usually considered the predominant factor shaping biodiversity patterns, whilst at more local scales, factors including topography, land-use intensity and natural resource availability become increasingly important . ...
... Therefore, our study highlights a need to further understand temporal trajectories in both taxonomic and functional components of species communities, which could enable a clearer picture of how biodiversity and ecosystems will respond to future global changes. In ecosystems, biodiversity patterns are structured by factors operating at multiple, nested spatial scales (Townsend et al., 2003). ...
The speed and intensity of global changes have pushed scientists to monitor and analyse changes that operate in nature and specifically on biodiversity. To truly understand the impact of human activities on the Earth’s species, it is necessary to conduct empirical studies of biodiversity time-series. Despite more than 20 years of research in global change ecology and an increasing global public awareness,
the decline of biodiversity is persisting and intensifying. Our knowledge in ecology is also incomplete, though of increasing interest to science. This PhD thesis uses a time-series database (1991-2016) of river macroinvertebrates located in 64 New Zealand River sites to analyse the effects of global changes on patterns of biodiversity. This database provides a unique picture of South-western pacific and endemic river benthic macroinvertebrates. In the first chapter, we show that macroinvertebrate biodiversity homogenises spatially with time from a taxonomic standpoint but differentiates through time from a functional standpoint. In the second chapter, we show that the observed temporal reorganisation of communities through time, involves greater gain than loss of species and latitudinal range shifts of species of 50 kilometres South on average per decade. In the third chapter, we show that the species richness/latitude relationship has reversed with time and that increases in species richness and trait redundancy come with the cost of reduced trait richness. To conclude, this PhD thesis demonstrates the multiple facets by which global change alters biodiversity and shows the need to analyse biodiversity changes considering all its complexity.
... River flow is one such geologic factor which forms the landscape and its components (Benda et al. 2011), thus possessing the relationship from very beginning. In the late 1990s and early 2000s rivers were researched both from the point of view of landscape (Wiens 1989;Ward 1998;Robinson et al. 2002) and as an ecosystem under the influence of their surroundings (Schlosser 1991;Allan et al. 1997;Fausch et al. 2002;Townsend et al. 2003) (Figure 11.1). It has been ascertained long back by the riverine ecologists that rivers are affected by the landscapes through which they flow (Hynes 1975;Vannote et al. 1980). ...
... It has been ascertained long back by the riverine ecologists that rivers are affected by the landscapes through which they flow (Hynes 1975;Vannote et al. 1980). It has been identified by scientists that anthropogenic activities are the principal threat to the ecology and biology of the riverine system, thus having impact on organisms and water quality via complex pathways (Allan et al. 1997;Strayer et al. 2003;Townsend et al. 2003). Land use affects the riverine system both directly and indirectly (Meyer et al. 1999;Nilsson and Berggren 2000;Scott and Helfman 2001) (Figure 11.1). ...
The present deteriorating condition of the river Ganga needs to channelize a research with pursuit of understanding the relation between parcels of land along which the river flows. Considering riverine landscape as important determinant of the river health, the paper explores the connectivity associated between land use features, river water quality, phytoplankton diversity and mankind associated with this landscape. The study was conducted in the catchment of river Ganga extending between 25°12′56.61″N, 83°00′37.98″E (upstream) to 25°20′15.67″N, 83°04′41.32″E (downstream) in the Varanasi district (the cultural capital of India). The riparian belt of river Ganga catchment in Varanasi is characterised by two major riverine landscape viz. agricultural and urban with natural riparian vegetation accounting for only 1.76% as revealed by land use land cover analysis. The river water adjoining the agricultural landscape have more of the organic matter content and dominance of the Chlorophycean algae as depicted by the physio‐chemical and biological analysis. On the other hand, water of the river surrounded by the urban landscape shows the presence of high content of metals and dominance of pollution tolerant Bacillariophycean and Cyanophycean algae, pointing towards high level of pollution in this landscape. The urban landscape of river Ganga in Varanasi act as a fulcrum between the society (locals and tourists) and the river, which subsequently prompts towards aggravation of pollution problems in the river. The pollution perception analysis reveals that society too condemns the rising urbanisation flanking the riverfront but still respondents such as livelihood earners on the bank deeply revere the river and consider it to be pure instead of polluted. The society especially Indians are unable to differentiate between purity and pollution. The study provides a preliminary insight into relooking the problems of river Ganga as complete socio‐ecological systems, because in India rivers are the part of civilization.
... Another approach is to investigate the scale at which a single factor has the strongest effect on local diversity. For instance, the stream slope can be quantified at multiple scales, such as the stream site, segment, or catchment (Frissell et al. 1986;Townsend et al. 2003;Gido et al. 2006;Camana et al. 2016). This is important because we still lack empirical tests on how natural riverscape features influence local diversity patterns of stream fish, mainly if we consider the highly diverse Neotropical region (Castro and Polaz 2004). ...
... In this case, the topological and geomorphological features of the stream channel seem to be of great importance. We also found that other spatial scales, e.g., the distance between stream confluences, seem to have a smaller yet important influence on biological responses, suggesting that the slope can operate on multiple spatial scales (Gering and Crist 2002;Townsend et al. 2003;Johnson et al. 2004;Higgins 2010). These multiple effects are relevant since the different scales measured presented a low correlation (r \ 0.6), except for CHANNEL and UPSTREAM ( Fig. S2; Camana et al. 2016). ...
The stream slope influences the diversity of stream fish, as it is an important riverscape characteristic related to flow energy, substrate size, and channel morphology. These conditions limit the movement and local persistence of species across the network, affecting local and regional species composition. Therefore, we can predict that streams with steep channels and harsh flow conditions would select a restricted set of species and ecomorphological traits, whereas those with gentle slopes would allow more species to coexist. This would cause a nested pattern in which the species and trait composition of streams with steep slopes (e.g., high swimming capacity) are a subset of those with gentle slopes (e.g., varied swimming capacities). We evaluated the influence of stream slope on a fish metacommunity, investigating the response of trait-based diversity to the stream slope for 21 fish assemblages sampled in two subtropical watersheds of Brazil. We found that trait-based alpha diversity was negatively related to slope. Moreover, stream sites with steep channels showed a subset of species and traits present in streams with gentle slopes. Finally, the spatial scale at which slope was measured had different effects on fish diversity, and the strongest effect was observed when the slope was estimated using the entire channel. Thus, we suggest caution in choosing the spatial scale, as the local slope may not be a good representation of the riverscape characteristics that drive the taxonomic and trait diversity of local fish. The stream slope is an important driver of fish diversity in streams by filtering species traits and determining species occurrence, while nestedness is a relevant pattern emerging from differences in stream gradient among sites.
... Riverine networks are hierarchically structured systems and, hence, lotic biodiversity patterns are generally structured by multi-scale spatial (i.e., local environmental conditions, catchment features and climatic condition) and temporal features (Poff et al., 2010;Townsend et al., 2003). Many previous studies have shown that (1) at local scale, water chemistry (e.g., nutrient concentrations) and physical (e.g., current velocity, substrate) conditions were important in structuring stream biodiversity patterns (Beisel et al., 2000;Jiang et al., 2010); (2) at catchment scale, land cover and land use characteristics, have been demonstrated to be correlated with lotic communities (Allan, 2004;Townsend et al., 2003); (3) at regional scale, climatic factors (e.g., temperature and rainfall) also have a significant influence on lotic biodiversity (Lawrence et al., 2010;Miserendino et al., 2018). ...
... Riverine networks are hierarchically structured systems and, hence, lotic biodiversity patterns are generally structured by multi-scale spatial (i.e., local environmental conditions, catchment features and climatic condition) and temporal features (Poff et al., 2010;Townsend et al., 2003). Many previous studies have shown that (1) at local scale, water chemistry (e.g., nutrient concentrations) and physical (e.g., current velocity, substrate) conditions were important in structuring stream biodiversity patterns (Beisel et al., 2000;Jiang et al., 2010); (2) at catchment scale, land cover and land use characteristics, have been demonstrated to be correlated with lotic communities (Allan, 2004;Townsend et al., 2003); (3) at regional scale, climatic factors (e.g., temperature and rainfall) also have a significant influence on lotic biodiversity (Lawrence et al., 2010;Miserendino et al., 2018). In addition, according to the metacommunity concept (Leibold et al., 2004), spatial processes and environmental conditions jointly affect community composition , as environmental filters can only act once individuals have been able to disperse to a new location (Kärnä et al., 2015). ...
There is a growing recognition that examining patterns of ecological communities and their underlying determinants is not only feasible based on taxonomic data, but also functional and phylogenetic approaches. This is because these additional facets can enhance the understanding of the relative contribution of multiple processes in shaping biodiversity. However, few studies have focused on multifaceted beta diversities in lotic macroinvertebrates, especially when considering driving factors operating at multiple spatial scales. Here, we examined the spatial patterns of multi-faceted (i.e., taxonomic, functional and phylogenetic) beta diversity and their components (i.e., turnover and nestedness) of macroinvertebrates in 50 sites in 10 streams situated in the north and south slope of the Qinling Mountains, the geographical dividing line of Northern and Southern China. We found that the streams draining the north slope showed significantly lower values of beta diversity based on all three facets than the streams draining the south slope. Such north-to-south increases of beta diversity were caused by the distinct climatic and local environmental conditions between the sides of the mountain range. Moreover, spatial variables generally played the most important role in structuring all facets and components of beta diversity, followed by local environmental and climatic variables, whereas catchment variables were less important. Despite the similar results of relative contribution of explanatory variables on each beta diversity facet, the details of community-environment relationships (e.g., important explanatory variables and explanatory power) were distinct among different diversity facets and their components. In conclusion, measuring functional and phylogenetic beta diversity provides complementary information to traditional taxonomic approach. Therefore, an integrative approach embracing multiple facets of diversity can better reveal the mechanisms shaping biodiversity, which is essential in assessing and valuing aquatic ecosystems for biodiversity management and conservation.
... Patterns in biodiversity (i.e. taxonomic composition and functional attributes) are determined by a combination of large-scale landscape attributes and habitat properties (Townsend et al. 2003), among which climate plays a central role. Northern ecosystems are experiencing rapid and large-scale changes driven by accelerated warming (AMAP 2011), and climate change is already responsible for ecological shifts observed on freshwater biodiversity (Heino et al. 2009;Lento et al. 2019;Lau et al. 2020). ...
... The observed strong effects of elevation in structuring trait composition of chironomid communities demonstrate that both temperature and large-scale landscape attributes (e.g. land use and vegetation composition/cover) strongly influence the functional diversity of northern aquatic invertebrate assemblages, confirming similar findings for temperate lakes (Poff 1997;Richards et al. 1997;Statzner et al. 2004;Townsend et al. 2003;Motta and Massaferro 2019). However, our results also show a strong influence on trait composition of habitat characteristics, such as water depth, suggesting that some functional features of chironomid communities also showed strong relationships with ecosystem types and local environmental conditions (c.f. ...
Northern ecosystems are experiencing rapid and large-scale changes driven by accelerated warming, which have profound effects on the terrestrial and freshwater biodiversity. A comprehensive understanding of the distribution of aquatic biodiversity of subarctic ecosystems is therefore needed to better predict future trajectories of their unique biodiversity. In this study, we examined the functional diversity of chironomid communities in subarctic lakes across a 1000 m-elevation gradient, reflecting gradual changes in temperature and landscape characteristics. Using fuzzy correspondence analyses, we investigated spatial variability in trait composition of chironomid communities from 100 lakes in northern Sweden, and tested the hypotheses that (1) climate directly and indirectly shapes chironomid trait composition across the studied gradient, and (2) that generalist taxa with smaller body size and broader food preferences are more able to persist in cold environments. Our results showed that complex interplays between direct (e.g. temperature) and indirect climate processes (e.g. elevation-driven changes in vegetation/habitats) affect the functional diversity of chironomid communities. Specifically, traits such as larval size, food preference and feeding habits were well separated along the gradient, and this pattern revealed that low elevation lakes with forested catchments tended to have more sediment-feeding taxa and larger larvae than those above the tree line. As expected, food resource availability in lakes is strongly linked to vegetation composition/cover, and traits related to resource exploitation in chironomid communities are therefore well constrained by landscape characteristics. Furthermore, our findings suggested that short life cycles could facilitate the development of viable population in northern and high-elevation lakes where the short ice-free period is a limiting factor, thus contradicting patterns showing smaller organisms in warmer environments reported for other invertebrates. As a consequence of climate warming, the highest elevation lakes in subarctic landscapes will likely lose their typical cold-adapted chironomid taxa along with their functional attributes leading to potential impacts on the food web structure and the overall functioning of northern lake ecosystems.
... Hynes (1975) argued with a lasting impact that 'In every respect, the valley rules the stream.' Streams are progressively investigated from a landscape perspective, both as landscapes in their own right and as ecosystems that are being strongly influenced by their catchment characteristics at multiple scales (Allan et al. 1997;Townsend et al. 2003). Effect of land use on a stream ecosystem can vary depending on many factors, including riparian forest buffer quality, watershed size, reach location within its watershed, the presence of other pressures, and the scale on which land use is measured (Roy et al. 2003). ...
... Land-use patterns in a watershed influence the delivery of nutrients, sediments and contaminants into receiving waters through surface flow, groundwater flow, organic inputs and atmospheric deposition (Jordan et al. 1997;Arango and Tank 2008;Huang et al. 2014). Streams are progressively investigated from a landscape perspective, both as landscapes in their own right and as ecosystems that are being strongly influenced by their catchment characteristics at multiple scales (Allan et al. 1997;Fausch et al. 2002;Townsend et al. 2003). Percentage of agricultural land use/land cover at catchment scale is a prime predictor for nitrogen and phosphorus (Hill 1981;Liu et al 2004;Johnson et al. 1997;Smart et al. 1998;Ferrier et al. 2001;Ahearn et al. 2005). ...
It is important to have reliable information on various natural and anthropogenic factors responsible for influencing and shaping stream water quality parameters as long as water resource conservation and management planning are concerned from the local to global scale. Daunting environmental pressures at multiple scales makes this necessity more pronounced owing to the special role of stream ecosystems in providing regional services. Understanding how coupled effect of natural and anthropogenic factors controls stream water quality parameters and how the relationships change over space and time will help policy makers and resource managers to target appropriate scales at watershed level for the quality management of stream waters. This paper sums up the information on various natural and anthropocentric factors as major determinants responsible for conditioning and shaping stream water quality parameters and their simultaneous influence on biota and its use.
... Freshwater ecosystems, especially streams, are among the natural ecosystems most affected by land use changes (Reid et al. 2019;Dudgeon 2019). The effects of land use changes on stream ecosystems are scale-dependent and may vary across space (Townsend et al. 2003;Allan 2004;Petsch et al. 2021). Deforestation of native vegetation within a sub-basin to agricultural practice is associated with the input of sediment and nutrients into the streams (Roth et al. 1996;Burdon et al. 2013), leading to the loss of local microhabitats (Teresa and Casatti 2012). ...
Environmental characteristics, spatial structures, and landscape features are ecological factors that drive beta diversity in stream communities, but the effects of these factors, considering multiple spatial scales on beta diversity in aquatic communities, still remain a goal of community ecology. Using the distance-based redundancy analysis (db-RDA) and variance partitioning, we evaluated the contribution of the local environment, regional, and spatial variables to total beta diversity and its components (i.e., species replacement and richness difference) for fish communities in 59 streams from the Brazilian Cerrado. The influence of local environmental, regional, and spatial variables on beta diversity was distinct along different spatial scales. Specifically, local environmental variables were the main drivers of dissimilarity between streams. We suggest that the environmental filter is the primary structuring mechanism of local communities in stream fishes in the Cerrado, regardless of the spatial scale. Together, spatial and regional variables may be considered complementary mechanisms to explain the variation in the beta diversity pattern. Thus, based on high beta diversity values and the number of unique species, our findings suggest that the preservation of stream structural features is necessary to maintain regional diversity.
... CONTAG [80] is used to describe the connectivity between patches in the study area. ...
Protected areas (PAs) play a crucial role in safeguarding biological resources and preserving ecosystems. However, the lack of standardized and highly operational criteria for evaluating their conservation effectiveness, particularly across different ecological types, remains a significant gap in the literature. This study aims to address this gap by constructing a conservation effectiveness evaluation model for two distinct types of PAs in Heilongjiang Province, China: the Zhalong National Nature Reserve (ZlNNR), a wetland ecological reserve; and the Mudanfeng National Nature Reserve (MdfNNR), a forest ecological reserve. We employed various methods, including land use dynamic index, visual analysis of landscape patterns, remote sensing inversion, and a multi-factor comprehensive assessment model, to assess changes in conservation effectiveness from 2000 to 2020. Our findings reveal a contrast between the two PAs. In the ZlNNR, croplands and water bodies increased significantly by 4069.4 ha (K = 1.5820%) and 2541.58 ha (K = 3.2692%). In the MdfNNR, impervious lands increased greatly by 65.35 ha (K = 7.4021%), whereas forest lands decreased by 125 ha (K = −0.067%). The core area of the two PAs displayed increased landscape regularity, whereas the experimental area showed heightened landscape diversity. In ZlNNR, the MPSL value increased by 134.91%, whereas the PDL value decreased by 57.43%, indicating a more regular landscape pattern. In MdfNNR, the SHDIL value decreased by 110.7%, whereas the PDL value increased by 52.55%, indicating a more fragmented landscape pattern. The area with improved vegetation trends in ZlNNR was 8.59% larger than in MdfNNR, whereas the area with degraded vegetation trends was 4.86% smaller than in MdfNNR. In all years, the high effectiveness area was larger in ZlNNR than in MdfNNR, whereas the medium and low effectiveness areas were smaller in ZlNNR compared to MdfNNR. This study provides a scientifically rigorous assessment method for evaluating the conservation effectiveness of different types of PAs, laying a solid theoretical foundation and practical guidance for future conservation strategies.
... The river landscape should be understood as an ecosystem, which is strongly influenced by its surroundings at different spatial levels [14,15]. The river system is a carrier of water resources, a component of the ecological environment, and the basis of economic and social development [16]. ...
This article investigates public spaces near urban rivers that contribute to the interaction between natural and urbanized areas and between people from different socio-economic backgrounds. The main goal of this study was to evaluate the environment of the largest urbanized areas of the Czech Republic, through which a large watercourse flows and creates a direct interaction with the city center. To evaluate the state of connectivity and comfort of urban rivers in the Czech Republic, a set of tools was applied to three cities: Prague, České Budějovice, and Hradec Králové. The methodology was created to correspond to the territory of Central Europe and was used for the specific assessment of rivers in four dimensions: (a) the spatial and visual accessibility, (b) the condition of the green corridor, (c) the condition of public space, and (d) the condition of the first built line. The dimensions are expressed using thirteen quantitative indicators of the environmental condition. The methodology uses the Urban River Sustainability Index (URSI), which was necessary to adjust the calculations of the indicators and resources for the Central European area. The best results were found in the central part of Prague and the worst in the peripheral part of Hradec Králové. The results call for the use of connectivity and comfort assessments of urban rivers for comparison, motivation, and future improvement in practice.
... In this respect, the 'filter' conceptual framework posits that landscape-scale habitat features constitute selective filters that constrain the presence or abundance of species according to adaptive traits (Poff, 1997). At a regional scale, largescale variables such as geology play an important role (de Moor, 1992;Townsend et al., 2003;Bonada et al., 2005). At a more local scale and for unimpaired streams and rivers, the most influential environmental factors appear to be associated with stream morphology (stream order, altitude, bed width, etc.) and hydrology (e.g. ...
1. Community patterns are generated by multiple processes and constraints generated at different spatial and temporal scales. 2. A large-scale study was carried out on the Trichoptera of four Algerian regions with contrasting climates, vegetation cover, and human pressures. 3. Overall, 22 identified taxa were recorded, including nine families and 14 genera. The genus Hydropsyche was represented by eight species, with Hydropsyche maroccana and Hydropsyche lobata being the most abundant species. 4. With one exception, localities in the subhumid Collo and the high-altitude Batna were the most species rich, whereas localities in the semi-arid Oum el Bouaghi were the most species poor. 5. Nonmetric multidimensional scaling (NMDS) separated the caddisflies recorded into four assemblages organized by a set of constraining environmental factors (land use, altitude, water depth, helophyte cover, and flow velocity gradients) acting at different scales. 6. As inadequate knowledge of insect biodiversity is a major limitation to their conservation, this article discusses how these results might help predict caddisfly communities in adjacent regions and enhance conservation efforts.
K E Y W O R D S caddisflies, community ecology, conservation, freshwater biodiversity, Maghreb, Mediterranean basin, multivariate analysis, taxonomy
... Por otro lado, aunque son no-diádromos, los insectos acuáticos, que contribuyen en un alto porcentaje a la diversidad y dinámica trófica de los ecosistemas lóticos, también se desplazan sobre largas distancias y en algunos casos realizan migraciones propiamente dichas (Dingle 1996). Taxones con estadios aéreos y amplios rangos de distribución pueden explorar diversos hábitats, los cuales están ubicados en diferentes escalas del paisaje, por lo que factores como los vientos y los niveles de precipitación, operando a escalas gruesas (región y cuenca) influyen en su movilidad y por tanto en su capacidad para colonizar nuevos hábitats (Townsend et al. 2003). ...
Los ecosistemas fluviales presentes en las islas son importantes ya que albergan especies con historias de vida particulares. Algunas de ellas son organismos diádromos como peces, camarones, cangrejos y caracoles que constantemente migran entre las cabeceras de los ríos y los estuarios o el océano para completar sus ciclos de vida. Otros, como los insectos, constituyen la fauna no-diádroma, la cual debido a su limitada capacidad de dispersión, a las altas tasas de especiación y al aislamiento propio de cada isla, podría encontrarse restringida a una región insular. Esta clara diferencia en las estrategias de vida, hace necesario el relevamiento de información acerca de los patrones de abundancia y distribución y de los procesos responsables en todos los niveles de la jerarquía espacial (regiones, microcuencas, segmentos, tramos, hábitats y microhábitats), con el fin de establecer medidas que garanticen un manejo adecuado tendiente a la conservación de estos ecosistemas. Por ello, este trabajo presenta una revisión sobre los principales factores que determinan la estructura de los ensambles diádromos y no-diádromos, y que operan en cada nivel jerárquico de las quebradas insulares.
... substrate, aquatic vegetation) than coarser ones (e.g. land-use in the upstream drainage area, position of the stream in the hydrographic network) whereas Townsend et al. [74] found the opposite. Overall, it seems that the organization of aquatic communities is ruled by the interplay of different spatial scales, with broad-scale processes influencing those occurring at finer scales [17,58,73,75,76]. ...
In large-scale aquatic ecological studies, direct habitat descriptors (e.g. water temperature, hydraulics in river reaches) are often approximated by coarse-grain surrogates (e.g. air temperature, discharge respectively) since they are easier to measure or model. However, as biological variability can be very strong at the habitat scale, surrogate variables may have a limited ability to capture all of this variability, which may lead to a lesser understanding of the ecological processes or patterns of interest. In this study, we aimed to compare the capacity of direct habitat descriptors vs. surrogate environmental variables to explain the organization of fish and macroinvertebrate communities across the Loire catchment in France (10 ⁵ km ² ). For this purpose, we relied on high-resolution environmental data, extensive biological monitoring data (>1000 sampling stations) and multivariate analyses. Fish and macroinvertebrate abundance datasets were considered both separately and combined to assess the value of a cross-taxa approach. We found that fish and macroinvertebrate communities exhibited weak concordance in their organization and responded differently to the main ecological gradients. Such variations are probably due to fundamental differences in their life-history traits and mobility. Regardless of the biological group considered, direct habitat descriptors (water temperature and local hydraulic variables) consistently explained the organization of fish and macroinvertebrate communities better than surrogate descriptors (air temperature and river discharge). Furthermore, the organization of fish and macroinvertebrate communities was slightly better explained by the combination of direct or surrogate environmental variables when the two biological groups were considered together than when considered separately. Tied together, these results emphasize the importance of using a cross-taxa approach in association with high-resolution direct habitat variables to more accurately explain the organization of aquatic communities.
... Rivers are easily affected by the ow process of water bodies and the surrounding environment (Vrebos et al., 2018). This results in changes of morphology and different river hierarchical system (Townsend et al., 2010). From watershed scale to riparian zone and river scale, different topographic characteristics, ecological environment and human activities factors affect river water quality (Baker 2006). ...
To explore the relationship between land use and basin water quality can effectively contribute to the protection of the latter at the landscape level. This research concentrates on the Weihe River Basin (WRB), a multi spatial scale correlation model was established in the WRB for both dry and wet seasons based on multiple linear regression analysis (MLR). A quantitative analysis of relationship between land use structure and basin water quality at the sub-basin, riparian zone, and river scales. The slopes were selected as the topographic characteristics to further, to explore the complex relationship between land use structure and topographic characteristics. By analyzing samples collected at 40 sites, it was shown that the correlation between water quality variables and different land use patterns was higher in the dry season than in the wet season, and that the land use at the riparian zone scale explained the overall water quality variations better than that at the sub-basin and river scales. Compared with other land uses, agricultural and urban lands had a better relationship with water quality, which was most affected by land use area and morphological indicators. In addition, the greater the area and aggregation of forest land and grassland, the better the water quality; while urban land presented larger areas with poorer water quality. The influence of steeper slopes on water quality was more remarkable than that of plains at the sub-basin scale, while the impact of flatter areas was greater at the riparian zone scale. The present study makes a number of recommendations related to the adoption of water quality protection and construction planning in the WRB.
... Studies on the relationship between surface water quality and landscape patterns began in the late 1960s (Kuehne 1962). At first, the studies usually focused on the composition of landscape patterns to explain the changes in water quality indicators (Townsend et al. 2003). Landscape types related to human development activities usually have a negative impact on water quality, while undeveloped land (such as forest land and grassland) is usually related to good water quality (Ouyang et al. 2010;Tu 2011). ...
Landscape patterns affect river water quality by influencing hydrological processes. However, with changes in spatial scale and season, landscape factors may have different effects on water pollution. Therefore, quantitative analysis of the scale effect of each landscape index was carried out to determine the mutation point of river water quality and its index relationship, which is of great significance to landscape planning and water quality protection. Based on the water quality monitoring data of 19 sampling points in the Tumen River Basin, we used redundant methods to quantify the spatial scale effects and seasonal dependencies of various landscape indicators on river water quality, then determined the mutation point of the water quality along the landscape-scale gradient. The results showed that different types of landscape indicators have different effects on river water quality, and the spatial-scale effect of landscape composition affects a river’s water quality, while landscape configuration indicators had the highest sensitivity. The landscape characteristics of river straps better explained the overall water quality, a phenomenon that is more obvious in the wet season than the dry season. We identified a key landscape indicator of urban area proportion (Urban%) and a contagion index (CONTAG) as the river strap scale. An Urban% < 30% and a CONTAG > 70% suggest effective landscape planning parameters that effectively protect water quality. The results indicated that, to protect water quality, landscape regulation should follow scale-adaptability measures and consider landscape thresholds, which cause abrupt changes in water quality.
... From the perspective of analysis methods, statistical analysis method, GIS correlation analysis, factor analysis coupled with grey correlation method (Schilling et al. 2010;Wang et al. 2020), regression analysis method (Royer et al. 2006), and system dynamics method (Dietzel et al. 2013) are among the most widely applied. From the perspective of driving factors, researchers studied the effects of population growth (Townsend et al. 2003), public health (Brennan 1999), urbanization (Azizullah et al. 2011), economic development (Schoonover and Lockaby 2006), industrial structure change (Qian 2016), environmental protection investment (Machiwa 2003), and land use pattern on water quality (Skoulikidis et al. 2006;James et al. 2011). In addition, some researchers also analyzed the driving effect of various factors on water quality change from the perspectives of time scale and spatial scale (Buck et al. 2004;Mou et al. 2004). ...
Surface water quality deterioration is commonly associated with environmental changes and human activities. Although some research has been carried out to evaluate the relationship between various influencing factors and water quality, there is still very little scientific understanding on how to accurately define the key factors of water quality deterioration. This study aims to quantify the impact of environmental factors and land use land cover (LULC) changes on water quality in the Ebinur Lake Watershed, Xinjiang, China. A total of 20 water parameters were used to calculate the Environment Water Quality Index (CWQI). Meanwhile, the partial least squares-structural equation model (PLS-SEM) was used to quantify the impact of eleven factors influencing water quality in the watershed. About 33.3% of the monitoring points that located mostly in the downstream region with dominant anthropogenic activities were detected as poor quality. There were no obvious temporal changes in water quality from 2016 to 2019. The PLS-SEM simulation shows that the latent variable “land use/cover types” (path coefficient = − 0.600) and “Environmental factor” (path coefficient = − 0.313) are two major factors affected water quality in the Ebinur Lake Watershed, with a strong explanatory power to water quality change (R² = 0.727). In the latent variable “Environmental factors”, the “NDVI” and “night light brightness value” have a great influence on water quality, with the weights of 0.451 and 0.427, respectively. Correspondingly, the “farmland” and “forest land” within the latent variable of “Land use/cover type” have a considerable impact water quality, with the weights of 0.361 and − 0.340, respectively. In conclusion, the influence of anthropogenic activities on surface water quality of the Ebinur Lake Watershed is greater than that of environmental factors. Compared with the traditional multivariate statistical method, PLS-SEM provides a new insight for quantifying the complex relationship between different influencing factors and water quality.
... Example from the evergreen temperate forest and coast range (b) reflect typical U-shaped glacial valleys, with stream generation in the alpine or deciduous subalpine forest and transitioning to evergreen forest. Topographic constraints may limit land use impacts to the lower valleys structure correspond with Townsend et al. (2003), who showed a major role of catchment scale variables, together with geographic location along the river system accounting for invertebrate assemblages. Heino et al. (2007) also found some support for this: spatial variables were more important for taxonomic than for functional structure, and local environmental factors were more important for functional than taxonomic structure. ...
• We investigated how interacting multi-scale environmental variables affect taxonomic composition and functional feeding groups of macroinvertebrates in headwater streams of western Patagonia in southern Chile (45–47°S), a region characterised by extreme climatic gradients, intact forested catchments, and recent intense land use change. The opportunity of establishing biological/functional diversity patterns for near-reference conditions of headwaters streams is paramount.
• We used multi-dimensional scaling ordination and boosted regression tree analysis to evaluate the link between reach, catchment, spatial, and regional climatic variables and macroinvertebrate community structure.
• The high diversity of predators in low productivity streams, together with genera previously unreported for this latitudinal range underscore the unique characteristics and very limited understanding of Patagonian freshwater stream communities.
• Two main groups of environmental variables were linked to both taxonomic and functional feeding group diversity. The strongly associated variables were related to forest cover (and inversely alpine zone) at the catchment scale, together with stream velocity at the local scale. The second group reflected local indicators of productivity and weathering inputs, associated with the regional east–west precipitation gradient.
• We present a conceptual model for the catchment scale effects on invertebrate functional groups in forested headwater streams. While the results highlight potentially singular characteristics of the study region, they also suggest a macro-ecological generalisation of how global change variables, operating on mountain catchments, may differentially affect stream ecosystems as a consequence of the variations in the forest/alpine gradient, across both deciduous and evergreen temperate biomes.
... The effects on stream ecosystems due to land use practices such as forestry and agriculture have intensified in many areas, the impact of long-range transport of air pollutants is felt over very large regions, and climate change is a truly global issue. All of these perturbations affect surface water ecosystems over a range of spatial and temporal scales (Oliveira et al., 2012), and are mediated by interactions with the terrestrial landscape (Strayer et al., 2003;Townsend et al., 2003). ...
We used the distribution of stream-dwelling brown trout (Salmo trutta) in a 67 km2 boreal catchment to explore the importance of environmental organizing factors at a range of spatial scales, including whole-catchment characteristics derived from map data, and stream reach chemical and physical characteristics. Brown trout were not observed at any sites characterized by pH < 5.0 during the spring snowmelt episode, matching published toxicity thresholds. Brown trout distributions were patchy even in less acidic regions of the stream network, positively associated with glaciofluvial substrate and negatively associated with fine sand/silty sediments. A multivariate model including only whole-catchment characteristics explained 43% of the variation in brown trout densities, while models with local site physical habitat characteristics or local stream chemistry explained 33 and 25%, respectively. At the stream reach scale, physical habitat apparently played a primary role in organizing brown trout distributions in this stream network, with acidity placing an additional restriction by excluding brown trout from acidic headwater streams. Much of the strength of the catchment characteristics-fish association could be explained by the correlation of catchment-scale landscape characteristics with local stream chemistry and site physical characteristics. These results, consistent with the concept of multiple hierarchical environmental filters regulating the distribution of this fish species, underline the importance of considering a range of spatial scales and both physical and chemical environments when attempting to manage or restore streams for brown trout.
... Streams and rivers represent the most threatened freshwater systems due to the combined effects of climate change, frequency of droughts, and floods (Milly et al., 2005;Xenopoulos et al., 2005), habitat fragmentation, and multiple anthropic stressors (Ormerod et al., 2010;Vörösmarty et al., 2010;Woodward et al., 2010). Some studies, such as those by Sponseller et al. (2001), Townsend et al. (2003) and Allan (2004) recognize that the increment of human actions at the landscape scale is one of the main threats to the ecological integrity of a basin. In consequence, understanding the relationships of species with the environment has been essential for the development of monitoring systems, and each water quality assessment will be more precise if the indicator species and habitat preferences are known (McGeoch and Chown, 1998;Tickner et al., 2000). ...
The increase of urbanized areas produces disturbances in rivers and streams, and its widespread effects reduce water quality and threaten aquatic biota. The aim of this study was to analyze changes in the invertebrate communities of the Luján River basin (Buenos Aires Province, Argentina) in an urbanization gradient and to determine the specific indicator taxa of urbanized habitats. Nine sampling sites were selected in the Luján River basin, distributed along a land use gradient. At each sampling site physicochemical variables of water were recorded, and invertebrate samples were collected during four seasons. A Principal Component Analysis separated three groups of sites with different urbanization conditions: low (<15%), moderate (between 15% and 60%) and high urbanization (>60%). These groups showed differences in the concentration of dissolved oxygen, suspended particulate organic matter, and nitrates. The communities changed with urbanization conditions, with a simplification of the community composition and a decrease in richness towards the lower basin (moderate and high urbanization). The IndVal method found three indicator taxa for the low urbanization sites ( Heleobia sp. (Cochliopidae), Uncancylus sp. (Ancylidae) and Callibaetis sp. (Baetidae)) and three for the moderate urbanization habitats (Nematoda, Hyalella curvispina (Hyalellidae) and Chironominae). These taxa were useful to identify different disturbance conditions due to urbanization, which makes them potential bioindicators in the diagnosis and monitoring of water quality in the Luján River basin.
... Nas últimas décadas, os sistemas de riacho têm sido intensamente estudados através da perspectiva de paisagem, com grande avanço no Brasil. As principais abordagens incluem a avaliação dos efeitos das mudanças do uso do solo sobre os peixes de riacho (Wiens 1989, Ward 1998, Teresa & Casatti 2012 em múltiplas escalas espaciais (Schlosser 1991, Fausch et al. 2002, Townsend et al. 2003b, Gerhard et al. 2004, Gerhard & Verdade 2016, Leal et al. 2016, Roa-Fuentes & Casatti 2017Leitão et al. 2018). E, mais recentemente, alguns estudos brasileiros começaram a incluir a escala temporal (Zeni et al. 2017, Brejão et al. 2018, Camana et al. 2020) para compreender melhor como o legado histórico das mudanças da paisagem direciona a diversidade de peixes de riacho observada no presente. ...
Landscape ecology emphasizes the interaction between spatial patterns and ecological processes, i.e., the consequences of spatial heterogeneity across various scales. It is an interdisciplinary science that seeks to understand the relationships between ecological patterns and processes considering different spatial and temporal scales. This understanding has been supported by the rapid development of a methodological framework, largely based on Geographic Information Systems (GIS). Thus, it has allowed understanding how ecological processes are affected by anthropogenic activities that trigger profound changes in ecosystems, such as habitat loss and fragmentation. Although commonly applied to studies in terrestrial ecosystems, there is a time lag in both theoretical development and methodological adaptation of landscape ecology applied to studies in streams, especially in Brazil. Methodological adaptations are necessary considering the particularities of aquatic environments in relation to terrestrial ones. For example, streams have a hierarchical spatial organization that results in local conditions dependent on the regional context. In fact, streams are connected to the landscape in which they are inserted through multiple spatial and temporal scales. This hydrologic connectivity, and the low ratio/proportion of aquatic/terrestrial areas, in turn results in anthropogenic impacts accumulating along the hydrographic networks. Considering the above, the objectives of this chapter are: (1) Introduce the general concepts of landscape ecology; (2) Present the main methods of spatial data acquisition and management relevant to stream approaches; (3) Describe the spatial and temporal scales relevant to stream ecology and (4) Discuss the potential of landscape ecology to assess human impacts on streams. Landscape ecology has much to offer to the study of stream fish in Brazil and has shown to be a promising approach for advancing this frontier of knowledge.
... For example, spatial non-stationarity, auto-correlation, and multi-collinearity are qualities of spatial data which may obscure meaningful results of statistical analysis such as regressions, one of the most commonly used types of analysis of stream habitat data [21] [22]. In addition to the pitfalls caused by spatial auto-correlation and multi-collinearity, there are issues caused by moving between scale though cross scale analysis is important for ecological analysis [4] [23] [24] [25]. ...
... If our activities in the stream disrupt the system, we may then draw inaccurate conclusions about the status or function of the system. Assessments of stream fish are increasing, including measurements of biomass or abundance at lower trophic levels, such as macroinvertebrates and benthic biofilms, to account for bottom-up drivers of fish production (Townsend et al. 2003;Segura et al. 2011;Kiffney et al. 2014). While researchers have considered the effects of electrofishing on fish and aquatic invertebrates (Elliot and Bagenal 1972;Fowles 1975;Bisson 1976;McMichael et al. 1998;Hastie and Boon 2001;Snyder 2003;Kruzic et al. 2005;Myrvold and Kennedy 2017), no studies to date have considered how the activity of conducting multiple passes through a stream may affect the benthic biofilms that constitute a key resource at the base of stream food webs. ...
Humans impact ecosystems in many ways and scientific field studies are no exception. If data collection disrupts environments or biota too much, it can lead to inaccurate conclusions in the study of interest or in subsequent studies. We evaluated whether stream electrofishing surveys could measurably impact benthic biofilms in two forested headwaters in western Oregon, USA. While impacts of electrofishing on macroinvertebrates and fish have been assessed, to date, no studies have quantified effects of electrofishing on benthic biofilms. We observed declines in standing stocks of accrued benthic chlorophyll‐a directly after electrofishing in both streams. After electrofishing, standing stocks declined by an average of ~15% in Oak Creek, a small third‐order stream in the Oregon Coast Range Mountains, and by an average of ~34 % in a third‐order section of Lookout Creek in the western Cascade Mountains of Oregon, USA. In returning to Oak Creek two weeks after electrofishing, standing stocks had fully recovered to pre‐fishing levels. While benthic biofilm standing stocks did decline in association with electrofishing, the effects were small when compared to common flow event disturbances and when scaling to the whole stream system. In Oak Creek, the proportional standing stock decline from electrofishing was about three times less than from a moderate flow event (40% of bankfull), and it was nearly six times less than declines in standing stocks associated with a complete bankfull discharge event (140% of bankfull).
... In ecosystems, biodiversity patterns are structured by factors operating at multiple, nested spatial scales (Townsend et al., 2003). ...
Global change is increasing biotic homogenization globally, which modifies the functioning of ecosystems. While tendencies towards taxonomic homogenization in biological communities have been extensively studied, functional homogenization remains an understudied facet of biodiversity. Here, we tested four hypotheses related to long-term changes (1991–2016) in the taxonomic and functional arrangement of freshwater macroinvertebrate assemblages across space and possible drivers of these changes. Using data collected annually at 64 river sites in mainland New Zealand, we related temporal changes in taxonomic and functional spatial β-diversity, and the contribution of individual sites to β-diversity, to a set of global, regional, catchment and reach-scale environmental descriptors. We observed long-term, mostly climate-induced, temporal trends towards taxonomic homogenization but functional differentiation among macroinvertebrate assemblages. These changes were mainly driven by replacements of species and functional traits among assemblages, rather than nested species loss. In addition, there was no difference between the mean rate of change in the taxonomic and functional facets of β-diversity. Climatic processes governed overall population and community changes in these freshwater ecosystems, but were amplified by multiple anthropogenic, topographic and biotic drivers of environmental change, acting widely across the landscape. The functional diversification of communities could potentially provide communities with greater stability, resistance and resilience capacity to environmental change, despite ongoing taxonomic homogenization. Therefore, our study highlights a need to further understand temporal trajectories in both taxonomic and functional components of species communities, which could enable a clearer picture of how biodiversity and ecosystems will respond to future global changes.
... This finding stands in line with previous studies focusing on communities of high-mountain stream systems with large elevational gradients (Shah et al., 2015;Tonkin et al., 2016). A large elevational gradient is often coupled with changes in local environmental variables, like DO, water temperature, conductivity, riparian vegetation, wind exposure, solar radiation, and precipitation (Townsend et al., 2003;Körner, 2007;Jacobsen, 2008;Sundqvist et al., 2013;Willig and Presley, 2015;Kim and Lee, 2017). Local environmental conditions play a critical role in determining which organisms can be found at a given site through species sorting or environmental filtering. ...
The metacommunity concept has received increasing interest in the past two decades. However, there has been limited research examining metacommunity structure of communities in high mountain streams. These ecosystems are often physically constrained and can display large environmental gradients within a relatively small spatial extent. Here, we examined metacommunity structures of stream organisms in a high mountain region, which is part of the Hengduan Mountains region in Southwest China. Macroinvertebrates and diatoms were collected from six streams in two opposite aspects of the same mountain with different connectivity between streams. On the west aspect, streams are tributaries of a river (i.e., river-connected) while streams flow into a lake (i.e., lake-connected) on the east aspect. We used Elements of Metacommunity Structure analysis to explore the metacommunity structuring of these two biological models. We also compared the contribution of dispersal and environmental filtering in structuring metacommunities by looking at Euclidean, network, topographic, and environmental distances. Communities of diatoms and macroinvertebrates were structured with clear turnover on both aspects. Further, diatom communities exhibited Clementsian structure on both aspects. Macroinvertebrates exhibited different metacommunity structures on the river-connected aspect (Quasi-Clementsian) and lake-connected aspect (Clementsian). Our results indicated that on the lake-connected aspect, environmental filtering had a stronger association with community dissimilarity than on the river-connected aspect for both macroinvertebrate and diatom communities. Diatom communities were more influenced by environmental filtering on the east aspect with weakened network connectivity compared with those on the west aspect. Our results also emphasized the potential effects of biotic interactions between macroinvertebrates and diatoms on shaping community structures of one other. Our study provides substantial elements to further understand metacommunity structure and highlights the necessity of future research to reveal the underlying mechanisms of community structuring in these remote ecosystems.
... In fact, the in-stream and riparian habitat conditions in most sites had a wide and wooded riparian zone and were in rather good condition of ecosystem integrity. In future studies, in order to explore ecological quality in a holistic sense, we highly recommend the use of riparian and landscape scale assessment applications (Wiens, 2002;Fausch et al., 2002;Townsend et al., 2003) and propose that supplementary methods to assess pressures at the riparian and landscape scale should be incorporated in the analyses, to complement on-site field-based assessments (e.g. Chatzinikolaou et al., 2011;Dimitriou et al., 2012;Vlami et al., 2019). ...
Fish assemblages and their distributions in the western Balkan rivers have rarely been investigated. This study provides initial insights into the spatial patterns of fish distributions in the main-stem of the White Drin in Kosovo. Sampling primarily utilized back-pack electrofishing at 11 sites along the river's entire main stem, recording 21 species. Identification of most fish species was confirmed through DNA barcode analyses; two yet unnamed species are present and some taxonomic problems were discovered. The abundance of non-native species was low (5.9% of the catch) but seven of the eight non-natives have established populations. A longitudinal fish zonation pattern was described for the first time in this river; fish assemblages in an upstream-to-downstream gradient were characterized by a decrease of cold-water species (salmonids, minnows) and an increase of large-river cyprinids and non-native species. Multivariate ordination and network analyses demarcate preliminary fish assemblage types and specific environmental and anthropogenic pressure attributes are shown to influence assemblage structure. Natural assemblage patterns may be locally disrupted by anthropogenic pressures such as pollution and hydromorphological disturbances, however most sites show semi-natural features and conditions. Recommendations for conservation and further research are provided.
... Here, we simply illustrate how this comparison approach could assist those involved in stream research in formulating hypotheses about responses to types and spatial scales of stressors among different biological groups. While some studies have found fish and macroinvertebrate community composition to be more responsive to a specific stressor at a particular scale (e.g., Townsend et al., 2003;Walsh et al., 2005), these studies did not account for watershed-scale influences on biological communities, as we have done here. Thus, the plot comparisons using different types of biological indicators could provide a more precise assessment of the scale(s) that most influences biotic conditions and the spatial extent at which management is applied. ...
Incorporating information on landscape condition (or integrity) across multiple spatial scales and over large spatial extents in biological assessments may allow for a more integrated measure of stream biological condition and better management of streams. However, these systems are often assessed and managed at an individual scale (e.g., a single watershed) without a larger regional multiscale context. In this paper, our goals were: (1) To develop a conceptual framework that could combine stream biological condition to abiotic landscape integrity (or, conversely, stressor) data at three spatial scales: watershed, catchment and stream-reach scale, to enable more targeted management actions. Measures of landscape integrity and stressors are negatively related, i.e., integrity on a 0–1 scale is equal or equivalent to stressors on a 1–0 scale. (2) To develop the framework in such a way that allows operational flexibility, whereby different indicators can be used to represent biological condition, and landscape integrity (or stressors) at various scales. (3) To provide different examples of the framework's use to demonstrate the flexibility of its application and relevance to management. Examples include stream biological assessments from different regions and states across the U.S. for fish, macroinvertebrates and diatoms using a variety of assessment tools (e.g., the Biological Condition Gradient (BCG), and an Index of Biotic Integrity (IBI)). Landscape integrity indicators comprise U.S. EPA's nationally available Index of Watershed Integrity (IWI) and Index of Catchment Integrity (ICI), and state and regional derived watershed and stream-reach scale integrity indicators. Scatterplots and a landscape integrity map were used to relate samples of stream condition classes (e.g., good, fair, poor) to watershed, catchment and stream-reach scale integrity. This framework and approach could provide a powerful tool for prioritizing, targeting, and communicating management actions to protect and restore stream habitats, and for informing the spatial extent at which management is applied.
... Distance (geographical location) has opposite effects on the total variation of beta diversity, depending on whether the species have low or high dispersal capacity (Thompson & Townsend, 2006). In the case of invertebrates with strongly flying adults, distance does not influence the community composition (Townsend et al., 2003). In this study, some of the Heteroptera families collected presented strongly flying adults, which can fly for an average distance of 151.3 km over a 48-h period (Lu et al., 2007). ...
In the present study, we assessed the assemblages of terrestrial Heteroptera along a 500-km latitudinal and 500-km longitudinal gradient in the north of Argentine Patagonia and investigated the potential effects of the environment, vegetation factors and spatial structure on the community composition of terrestrial Heteroptera at regional scale. To identify the terrestrial Heteroptera assemblages and evaluate their association with different factors, we used multivariate analyses. A total of 840 samplings were carried out in 21 sites of three phytogeographic provinces (Patagonian steppe, Subantarctic province and Monte) along two sampling years. We captured a total of 2007 specimens, 1890 of which were identified to species and morphospecies level, and 57 of which were immature-stage specimens that could not be identified due to their unknown morphology and biology. We identified two distinct terrestrial Heteroptera assemblages: a) one from sites belonging to the Patagonian steppe and Subantarctic province and b) the other from sites belonging to the Patagonian steppe and Monte. The variation in the terrestrial Heteroptera assemblages explained mainly by Isothermality was significant and greater than that explained by the vegetation and the spatial structure. The results showed that, in northern Argentine Patagonia, the different Heteroptera assemblages are more associated with geographic areas with different environmental conditions than with areas with different vegetation types. The results also suggest that the variation in Heteroptera species composition at regional scale is driven by environmental variables related to thermal amplitude and precipitation.
... urban development, introduction of invasive species) that can significantly impact the physical habitat and ecological functioning of these systems (Giller 2005). It has been increasingly recognized that anthropogenic influence at the landscape scale is a substantial threat to freshwater ecosystems and can impact habitat, water quality, and native biota, while ultimately altering ecological states (Allan et al. 1997;Søndergaard and Jeppesen 2007;Strayer et al. 2003;Townsend et al. 2003). Notably, habitat diversity of streams is strongly influenced by land use within the surrounding areas at multiple scales (Allan 2004). ...
Agricultural land use is widely accepted to elicit changes on surrounding environment and neighboring ecosystems. Meanwhile, the impact of different types of agricultural land use likely cause a variety of impacts on nearby ecosystems and the organisms that inhabit them. Freshwater systems support a wide range of organisms—from infaunal or epifaunal invertebrates to mobile pelagic and littoral fish species. The focus of this study was to determine how agricultural activity in the upstream catchment influences sediment properties and the resulting ability of three distinct invertebrate species to survive and reproduce in these different sediments. This will be the first study that evaluates the utility of the sediment quality triad when assessing the impact of agricultural activity on invertebrate growth, reproduction, and survival. In analyzing sediment and water chemistry, as well as metal and pesticide levels, none of the predictor variables were able to adequately explain the variation seen in any of the biological endpoints (reproduction, mortality, growth, or biomass). Although none of the factors measured in this experiment could explain the variation seen in biological endpoints, the experimental approach was informative in delineating biological trends between sediments subject to varying levels of agricultural activity. Although an experiment of this nature was not able to identify a causal mechanism to explain the variation in invertebrate biological endpoint, it is still extremely useful as an exploratory approach to assess relative sediment toxicity.
... Morley and Karr (2002) and Tudesque et al. (2014) concluded that land use at both local and watershed scale were equally important in structuring stream biota in the Puget Sound Basin, USA and the Adour-Garonne basin, South-Western France respectively. Inconsistency in these results is likely attributed to variations in study design and differences in geographic location (Allan and Johnson, 1997;Townsend et al., 2003;Potter et al., 2004;Schiff and Benoit, 2007). Schiff and Benoit (2007) urged that more work is needed to create a larger set of consistent results to achieve the goal of establishing land-use management strategies to protect water quality, physical habitat, and stream biotic integrity. ...
Understanding the influence of land-use activities on river quality has been a key focus of river monitoring programs worldwide. However, defining which land-use spatial scale is relevant remains elusive. In this study, therefore, we contrasted the influence of land use on river quality using three types of land-use estimators, namely circular buffers around a monitoring site, circular buffers upstream of the monitoring site and the entire watershed area upstream of the monitoring site. The land-use percentage compositions within the Usa-Kikuletwa River catchment in northeastern Tanzania were quantified using Landsat-8 satellite images with a maximum mapping resolution of 30 m. Redundancy analysis models and generalized linear models were used to evaluate the influence of land use on macroinvertebrate assemblages and physico-chemical water quality at different spatial scales in the dry and wet seasons. Overall, a substantial fraction of variation in physico-chemical water quality, macroinvertebrate taxon richness, Chao-1 and TARISS (Tanzania River Scoring System) score could be explained by land use of the entire watershed area upstream of the monitoring site in the dry and wet seasons. However, macroinvertebrate abundances showed strong links with more local land-use patterns within 100 m and 2 km radii. Circular buffers upstream of monitoring sites were more informative for macroinvertebrate assemblages than circular buffers around the monitoring sites. However, the latter did correlate well with physico-chemical water quality variables. Land-use variables correlated across spatial scales (i.e., 100 m up to 2 km radii), but not with the land use in the entire watershed area above the monitoring site. Our results indicate that physico-chemical water quality variables and macroinvertebrates may respond differently to land-uses at different scales. More importantly, our results illustrate that the choice regarding spatial land-use metrics can bias conclusions of environmental impact studies in river systems.
... Beispiele bei Oppel et al. 2004;Rolstad et al. 2000). Um einen Filter zu passieren, muss die Art funktionale Eigenschaften (traits) aufweisen, die der selektiven Charakteristik des Filters entsprechen (Poff 1997;Townsend et al. 2003;Weiher & Keddy 1999). In der von Schröder (2001) definierten Filterkaskade (Abb. ...
... Following an early work by Kuehne, dated from the 1960s [16], numerous studies investigated the impacts of landscape composition and patterns on stream and lake water quality [17], even reporting that landscape characteristics are critical to water quality [18,19]. The reports evolved from cases where the relationship between the composition of landscape and the variation in water quality indicators was explored [20], to cases where the focus was moved to the spatial arrangement of the landscape (patterns) [21,22]. In the earlier studies, good water quality was generally associated with undeveloped watersheds dominated by forest land use, while poor water quality was linked to human development activities, such as agriculture [23]. ...
Riparian vegetation represents a protective barrier between human activities installed in catchments and capable of generating and exporting large amounts of contaminants, and stream water that is expected to keep quality overtime. This study explored the combined effect of landscape composition and buffer strip width (L) on stream water quality. The landscape composition was assessed by the forest (F) to agriculture (A) ratio (F/A), and the water quality by an index (IWQ) expressed as a function of physico-chemical parameters. The combined effect (F/A × L) was quantified by a multiple regression model with an interaction term. The study was carried out in eight catchments of Uberaba River Basin Environmental Protection Area, located in the state of Minas Gerais, Brazil, and characterized by very different F/A and L values. The results related to improved water quality (larger IWQ values) with increasing values of F/A and L, which were not surprising given the abundant similar reports widespread in the scientific literature. But the effect of F/A × L on IWQ was enlightening. The interaction between F/A and L reduced the range of L values required to sustain IWQ at a fair level by some 40%, which is remarkable. The interaction was related to the spatial distribution of infiltration capacity within the studied catchments. The high F/A catchments should comprise a larger number of infiltration patches, allowing a dominance of subsurface flow widespread within the soil layer, a condition that improves the probability of soil water to cross and interact with a buffer strip before reaching the stream. Conversely, the low F/A catchments are prone to the generation of an overland flow network, because the absence of permanent vegetation substantially reduces the number of infiltration patches. The overland flow network channelizes runoff and conveys the surface water into specific confluence points within the stream, reducing or even hampering an interaction with a buffer strip. Notwithstanding the interaction, the calculated L ranges (45–175 m) are much larger than the maximum width imposed by the Brazilian Forest Code (30 m), a result that deserves reflection.
... Researchers have claimed that the climate, geology, and topography at large scales can influence geomorphic processes and control the nutrient input, riparian habitat, and water quality at smaller scales, especially the reach and site scales, and the aquatic fauna via various and complicated pathways [15][16][17][18]. Land use, from undisturbed to human-dominated landscapes, represents anthropogenic disturbance at the catchment scale, and it has been used for decades to illustrate the direct and indirect anthropogenic effects on freshwater ecosystems [19][20][21][22][23][24]. ...
Identifying the key drivers of aquatic fauna structuring at multiple spatial scales is critical in reducing biodiversity loss. Macroinvertebrates are the most sensitive indicators of disturbance and they are used as a cost-effective tool for bioassessment at catchment and site scales. The focus of our study was to identify the key drivers from three classes of environmental variables (geophysical landscape, land use, and site habitat) that influence macroinvertebrate richness in different aquatic ecological function regions (AEFRs) of the Liaohe River Basin. We sampled macroinvertebrate assemblages, extracted geophysical and climate variables from geospatial data, and quantified physical and chemical habitats from 407 randomly distributed sites that belong to the three level-I AEFRs. We analyzed our data through multiple linear regression models by using the three classes of predicted variables alone and in combination. The models that were constructed in the first level-I AEFR explained similar amounts of macroinvertebrate richness and had the maximum ability to explain how macroinvertebrate richness distributed (denoted “explaining ability”; geophysical landscape: RGL2 ≈ 60%, land use and site habitat: RLU2 and RSH2 ≈ 50%, and combined: RCB2 ≈ 75%). The explaining abilities for the third level-I AEFR were as follows: RGL2 ≈ 11%, RLU2 ≈ 14%, RSH2 ≈ 25%, and RCB2 ≈ 38%. The explaining abilities for the 4th level-I AEFR were as follows: RGL2 ≈ 30%, RLU2 ≈ 7%, RSH2 ≈ 40%, and RCB2 ≈ 55%. We conclude that: (1) all of the combined models explained more interaction as compared with the single models; (2) the environmental variables differed among different level-I AEFRs; and, (3) variables in the site habitat scale were the most robust explainers when analyzing the relationship between environmental variables and macroinvertebrate richness and they can be recommended as the optimal candidate explainer. These results may provide cost-effective tools for distinguishing and identifying the drivers of sensitive aquatic organisms at regional scales.
We investigated the relationship between benthic macroinvertebrate community attributes (richness, abundance, biodiversity, and climate-specific and resistance forms) and the physical characteristics of distinct mesohabitats (hydromorphological unit types) discretized into fast (e.g., riffles or rapids) and slow (e.g., pools or glides) flow types in four Mediterranean rivers of Spain. Key attributes of hydromorphological units, including length, width, depth, shade, substrate composition, embeddedness, abundance of aquatic vegetation, and density of woody debris, were considered. Through a comprehensive suite of multivariate analyses, we unraveled taxonomic and habitat distinctions among rivers and hydromorphological unit types, with a notable influence of spatial proximity
(greater similarity within the same river basin). In slow hydromorphological units, aquatic vegetation, depth, and abundance of coarse substrate emerged as pivotal factors shaping macroinvertebrate assemblages, whereas in fast-flowing units, vegetation, substrate embeddedness, and density of woody debris were the most important. Contrary to the remaining community attributes, the studied resistance
forms (absent, eggs, cocoons, and cells against desiccation and diapause) exhibited uniformity across rivers despite observed variations in macroinvertebrate communities, underscoring regional functional analogies in biological and ecological mechanisms within the investigated Mediterranean river basins. This study contributes valuable insights for anticipating the repercussions of ongoing climate change, particularly in regions where fast-flowing hydromorphological units are more susceptible to depletion during drought periods.
Introducción:
Las comunidades de macroinvertebrados son afectadas simultáneamente por la calidad del agua y las características físicas del hábitat acuático, complicando su uso en la bioindicación.
Objetivo:
Determinar cuáles variables del hábitat condicionan la comunidad de macroinvertebrados acuáticos en algunas corrientes (quebradas) de montaña del Oriente antioqueño (Colombia).
Métodos:
El muestreo se realizó en febrero 2021 (periodo de transición seco-lluvia), para evaluar variables físicas y químicas en tres tipos de mesohábitats: rápidos, rizos y pozas en corrientes con coberturas vegetales contrastantes. Los macroinvertebrados fueron recolectados en diez sitios de muestreo con red tipo net, pantalla y manual, y preservados en etanol al 70 %.
Resultados:
Se recolectaron 4 484 macroinvertebrados (16 órdenes, 46 familias y 75 géneros). El mesohábitat rizo presentó mayores valores de diversidad y abundancia, mientras las pozas presentaron los menores. Hubo diferencias en la concentración de oxígeno, profundidad, velocidad y abundancia de macroinvertebrados entre mesohábitats. Las pozas defirieron de los otros mesohábitats en profundidad, velocidad, así como en la composición, abundancia y riqueza de macroinvertebrados, y fue el hábitat de menor preferencia.
Conclusión:
La velocidad, profundidad y concentración de oxígeno disuelto, desempeñan un papel muy importante en el establecimiento de las comunidades de macroinvertebrados en los diferentes mesohábitats. En el mismo tipo de mesohábitat, la calidad de la cobertura vegetal determinó la diversidad y abundancia de esta comunidad.
In the sub-Antarctic region, climate change is particularly rapid, while their freshwater ecosystems, such as ponds, host plant species with limited spatial distributions. These particular systems and their plant communities remain however poorly known and the context of their changing habitat calls for deeper insights into these systems. We performed an extensive survey of 45 ponds over three locations of the Iles Kerguelen during the winter and summer seasons of two years, which included the measurement of 12 abiotic parameters and the assessment of the plant community composition. Overall, our results showed that Iles Kerguelen ponds are shallow freshwater ecosystems harbouring species-poor plant communities with high evenness, of which structure did not vary among the sampled locations. Three different habitats were identified among ponds in relation with nutrient supply by marine animals, which ultimately influenced plant community structure and cover. We highlight that these habitats are mostly determined by water depth, nutrients, and temperature (mean and variance). Present plant community composition was more strongly correlated with plant community composition in the previous year than with abiotic conditions. Overall, this study provides new knowledge on the aquatic plant communities and the functioning of Iles Kerguelen freshwater ecosystems, which can serve as a basis for future studies dealing with the impact of climate change in the sub-Antarctic region.
Abstract
The Legedadie-Dire catchments in central Ethiopia have experienced soil erosion owing to inappropriate land use practices, population pressure, topography, and intense rainfall. The impacts of Ecosystem-Based Water Supply Management (EBWSM) interventions with five scenarios were assessed using the Soil and Water Assessment Tool (SWAT), which includes grassed filter strips, hillside terraces, reforestation, vegetated buffers, and their combination on runoff and sediment yield. The EBWSM was assigned to selected subbasins and hydrological response units (HRUs) based on land use land cover situations, proximity to water bodies, altitude, and suitability issues. The model was calibrated and validated for inflow discharge using transformed flow data obtained from the Sibilu River Gauging Station and calculated data based on the reservoir volume difference approach. Similarly, sediment yield was calibrated and validated using the data from bathymetric inspection and in situ sediment pit survey results. The SWAT model performed well during the calibration and validation periods. The combined implementation of the two scenarios at a time significantly reduced sediment yield. Hillside terraces in combination with reforestation on bare land, reduced sediment yield by 94% and 90% in Legedadie and Dire catchments, respectively. Similarly, filter strips with 10:45 riparian vegetative buffers cut sediment yield by 91% and 82% in Legedadie and Dire catchments, respectively. Surface runoff decreased between 0.35% and 5.76% for all EBWSM scenarios except for the riparian vegetative buffer, wherein it slightly increased between 1.3% and 2.5%. Overall, the results revealed that the implementation of the EBWSM can reduce surface runoff and sediment yield.
Background
The spatial and temporal changes of assemblages of aquatic insect can be used to detect the anthropic impacts that influence the biological communities.
Goals
We compared the assemblages of aquatic insect in 1997 and 2014 in two subtropical river drainages, the association with water characteristics, and we discuss their implications for ecosystems conservation.
Methods
True diversity of the aquatic insect fauna at family level and their community structure for 27 study sites in 1997 and 2014 were assessed. Multivariate analyzes were used to compare aquatic insect assemblages and the abundance of functional feeding groups.
Results
There were significant differences in the dissolved oxygen (DO) of the water between 1997 and 2014, decreasing its values. Other variables correlated to DO were also modified, with a decrease in pH and an increase in temperature. We found a correlation between reduction of DO and water pH with a decline in the overall abundance of aquatic insects; also, with shifts in the community structure, from the decrease of groups such as some Ephemeroptera and scrapers, to the increase in opportunistic families such as Chironomidae, Culicidae, and other predator families such as Coenagrionidae, Corixidae and Veliidae, and more abundance of collectors. Families such as Heptageniidae and Caenidae decreased in abundance, as well as other benthic groups.
Conclusions
The assemblages of aquatic insect are useful to indicate a generalized degradation of environmental conditions across localities and time in two subtropical river drainages, related to water quality degradation symptoms such as reduction of pH levels and dissolved oxygen, usually associated with anthropogenic stressors.
Natural and anthropogenic factors form stream macroinvertebrate communities depending on their combination, intensity, and spatial pattern. The study aimed to identify macroinvertebrate indicators that respond to land cover, hydromorphology, and wastewater releases individually and to their multiple-pressure pattern.
Environmental and macroinvertebrate data from 36 sites were used in the study. Pressure parameters representing hierarchy of their complexity and spatial scale were included in analyses. Correlation analyses were used for evaluation of relationships among pressure characteristics and also pressure–macroinvertebrate relationships. The pressure-based and biological classification of sites was compared and indicator taxa were identified.
The arable land in the sub-corridor extending 2–10 km upstream of an investigated site was the main pressure factor influencing the structure of macroinvertebrate communities in the studied streams. The biological effects of small-scale land cover were followed by catchment-scale land cover and hydromorphology. Almost no association of macroinvertebrates with the risk of point source pollution were detected. Classifications based on pressures and community composition corresponded only by the separation of most degraded sites from others. Among the macroinvertebrate indicators characterizing the severe impairment threshold, chironomids and oligochaetes dominated. Different responses of macroinvertebrates to hydromorphological degradation were observed under conditions of high small- and large-scale agricultural pressures (decrease in macroinvertebrate evenness and increase in oligochaete taxa richness, respectively). Linking biological indicators to pressure components and their combinations improves the efficiency of conservation and restoration strategies applied in fluvial ecosystems.
The importance of Riparian Buffer Zones (RBZs) on riverine landscapes has recently received growing attention, which has led to studying, mapping, and monitoring RBZs areas. Additionally, several studies have examined their influence on water quality, vegetation cover, wild life, sediment, and pollution sources. The Riparian Buffer Zones, which are terrestrial areas located between fluvial water bodies and land, provide several ecosystem services and have a rich biodiversity. The present study aimed to identify and monitor the Riparian Buffer Zones in the Gorganroud basin which is located in the north of Iran and south eastern side of the Caspian Sea. This region is one of the largest basins and one of the most precious regions in Iran due to its humid climate and famous forests. RBZs were monitored in four corners of the basin within three selected sub-basins. Land-use map of the Riparian Buffer Zones was extracted in each part within dense vegetation, low-density vegetation, and water, and the area and percentage of each Buffer class were derived for each sub-basin. Two indexes of NDVI and NDWI were calculated and applied for identifying water and green cover pixels of the region and their dispersion. These two indicators helped extract an accurate map of the buffer zones. The results showed that the water buffer area in the north part was significant in comparison with the southern and eastern parts, which could be due to due to more rice fields. Furthermore, low-density vegetation was higher in the south since it is a mountainous area. Further, dense vegetation was high in the center of the watershed due to forests, which was confirmed by the NDVI index.
The analytical spatial scale and selection of biogeochemical indicators affect interpretations of land-use impacts on coastal marine environments. In this study, nine biogeochemical indicators were sampled from 36 locations of coral reefs fringing a subtropical island, and their relationships with watershed land use were assessed by spatial autoregressive models with spatial weight matrixes based on distance thresholds of a few to 30 km. POM-relevant indicators were associated with agricultural and urban lands of watersheds within relatively small ranges (6–14 km), while the concentrations of inorganic nutrients were associated with watersheds within 20 km or more. The macroalgal δ¹⁵N showed a strong relationship with agricultural lands of watersheds within 7 km and urban/forest lands of watersheds within 24 km. These results demonstrate significant effects of land use on the coral reef ecosystems of the island, and the importance of appropriate combinations of analytical scales and biogeochemical indicators.
The impact of the land use landscape pattern on river hydrochemistry has significant scale effects. It is the premise and foundation of landscape optimization and the conservation of water resources to accurately identify the core scale of the landscape pattern impacting on river hydrochemistry. Taking Binggou River Basin in the source region of Shiyang River Basin as the study area, this paper selected the three spatial scales of catchment area, buffer zone, and riparian zone, and the relationships between land use types and landscape indices and river hydrochemical characteristics were analyzed at different spatio-temporal scales using redundancy analysis. The results showed that the hydrochemistry characteristics of Binggou River Basin had strong temporal variability, and the rainy season was the key period when the land use landscape pattern affected the river hydrochemistry. The sub-watershed and riparian scales were the core scales of influence of the landscape pattern on river hydrochemistry in Binggou River Basin. In particular, the landscape pattern index contributed the most to the river hydrochemistry at the sub-watershed scale on the whole, which was the core scale affecting river hydrochemistry. The “source” or “sink” functions of the same land use type also changed as the scale changed. Forest land showed weak “source” effect at the sub-watered scale, but a strong interception effect on the soil erosion process at the riparian scale, which is a typical “sink” landscape.
Riverine ecosystems form a dendritic network in which landscape and catchment-scale properties influence freshwater community structure. Placed in a restoration framework, this suggests that regional drivers can overrule the benefit of measures aiming at improving local habitat quality. Disentangling the relative influence of local and regional drivers on freshwater communities is thus crucial for ecosystem management and restoration. Along riverbanks, soil bioengineering is often used to both control erosion and improve ecological conditions. Soil bioengineering techniques aim at copying naturally functioning riverbank models and can thus be viewed as riparian ecosystem restoration. Nevertheless, these techniques are mostly designed at the local scale and are implemented in a broad range of rivers. This implies large variations in regional drivers, which may greatly influence the response of freshwater communities to restoration efforts. We studied 37 riverbanks, from civil engineering to soil bioengineering, plus natural willow stands, in the foothills of the Alps and Jura Mountains, and assessed the relative influence of local (terrestrial and aquatic habitat conditions) and regional (water quality, hydrological context and land cover composition) drivers on benthic macroinvertebrate assemblages. Using multivariate GLM and structural equation modelling, we investigated variations in the taxonomic and functional composition and in the diversity of native, exotic, shredder and scraper taxa to both set of drivers. Our results showed that soil bioengineering improved local habitat conditions, with an increase in the vegetation density and in the aquatic habitat quality. These changes directly influenced functional composition but indirectly diversity patterns. Instead, we found that native and shredder species richness increased between civil engineered and soil bioengineered structures, suggesting a positive effect of vegetated riverbanks on other local abiotic factors (i.e. shade, water temperature, organic matter supply). Our results also showed that macroinvertebrates were more influenced by regional than by local drivers. Thus, the hydrological context best explained the composition of taxa feeding habits and variation in taxa diversity, with larger abundance and richness of scrapers and shredders in small headwater streams. Land cover ranked second in explaining variation in functional composition. Also, the diversity of natives, scrapers and shredders increased as the proportion of predominantly urban landscapes decreased. Finally, the abundance of scraper and native species increased with water quality, while the richness of exotic species decreased. Overall, these results highlight the hierarchical structure of local and regional drivers on freshwater communities. Along river networks, catchment-scale properties and landscape attributes are major drivers of macroinvertebrate assemblages. Soil bioengineering improves habitat quality and as such appears to be a good compromise solution to control erosion and support freshwater communities, even though this nature-based solution cannot solve anthropogenic pressures at larger scales. To improve the efficiency of restoration efforts, integrated approaches accounting for both local and regional drivers remains a priority.
Large river management is in increasing demand to establish the ecological quality set by sustainability-oriented legislation. However, there is still a lack of research regarding most relevant scales at which pressures should be addressed. In this study, we compared the relative effects of riparian land-cover at 16 different buffer sizes and hydromorphology at four different river lengths on benthic invertebrate (BI) and fish assemblages in large rivers. Environmental data were obtained digitally (applying GIS) on a broad range of abiotic conditions and were related to biological data using direct gradient analyses. Compared to land-cover, hydromorphology showed greater effect on BI and fish, with in-channel habitat quality characteristics explaining most biotic variability. Both assemblages were best explained by hydromorphology inventoried at the largest 5,000 m scale. We found, however, consideration of longer river segments to be more important for explaining fish variability. Riparian land-cover explained similar percentages of biotic variability across most analysed riparian buffers. Nevertheless, a significant effect of riparian length rather than width was identified. Our findings indicate that, in large rivers, hydromorphological and riparian land-cover conditions affect BI and especially fish at generally longer river segments, implying potential ecological benefits of management measures implemented at larger spatial scales.
Downstream of hydroelectric plants, hydropeaking can cause frequent flow variations, resulting in habitat modifications (e.g. hydraulics, reach morphology, temperature, water quality), which can impact organisms (stranding, dewatering, forced drift, growth disturbances) and ultimately may have negative and lasting impacts on biological communities, reducing resilience. Nevertheless, the severity of habitat disturbances vary depending on other existing pressures and local site conditions, which need to be taken into account to achieve effective hydropeaking mitigation. Preserving hydropower flexibility is also a priority to ensure the stability of electric systems without recourse to more polluting alternatives. Given these apparently opposing objectives, we propose a consensual technico-economic framework to guarantee the feasibility and effectiveness of site-specific hydropeaking mitigation, based on our experience as a hydropower operator and a literature review. While existing tools (such as habitat models) can be used to predict expected local effects of proposed mitigation and compare scenarios, predicting biological community responses is not currently possible (lack of in-situ evaluations of mitigation efficacy). These uncertainties and complex socio-ecosystems necessitate a forward-looking global approach that accounts for climate change, multi-purpose water use and electric system requirements, combined with site-specific analyses of the relative importance of hydropeaking impacts with respect to other pressures.
Příbřežní zóna vodních toků představuje území, které může v optimálních podmínkách plnit řadu významných funkcí, avšak zároveň jde o prostor výrazně degradovaný antropogenní činností. Degradace příbřežních zón toků je nejvýraznější v zemědělské a urbanizované krajině a souvisí obvykle se snahou majitelů přiléhajících pozemků o intenzivní využívání tohoto území. Z těchto důvodů je příbřežní zóna dnes obvykle tvořena velmi úzkým pásem vegetace v nevyhovujícím ekologickém stavu, který neumožňuje plnění ekosystémových funkcí a služeb v plném rozsahu a kvalitě. Cílem článku je představit čtenářům nově vyvinutou metodiku pro hodnocení aktuálního stavu příbřežních biotopů, která vznikla jako reakce na absenci informací, týkajících se stavu využití příbřežních zón a jejich kvalitativních parametrů. Metodika byla experimentálně aplikována v zájmovém území - povodí drobného vodního toku, protékajícího leso-zemědělskou krajinou s různou mírou antropogenního tlaku na krajinu v rámci povodí. Výstupy metodiky lze v praxi využít například při plánování revitalizačních akcí v nivách vodních toků, při plánování rutinní údržby břehových porostů ze strany správců vodních toků, pro potřeby identifikace kriticky de-gradovaných úseků nebo v obecné rovině při analýze proměnných, ovlivňujících klíčové funkce říčních ekosystémů.
The first biogeographical division of the Carpathians, the second largest mountain range in Europe, was based on qualitative observational floristic data > 100 years ago and has also been applied for the regional zoogeography. In this study, the recent availability of detailed quantitative data allowed us to perform a more powerful evaluation of the classical biogeographical regions of the area. Thus, we analysed updated distribution patterns of 137 Orthoptera species native to the Carpathian Mountains and, by using published species range maps, we compiled data on species presence or absence within 2576 cells of a 10 km × 10 km universal transverse mercator grid in the area. Pattern analysis of the data was based on non-metric multidimensional scaling and clustering using six different algorithms applied to a β sim dissimilarity matrix. The unweighted pair-group method using arithmetic averages, which gave the best performance in the analysis of species turnover, delineated four regions. Environmental variables and species richness were used in logistic regression as predictors of delineated clusters, and indicator species were identified for each of the inferred regions. The pattern can be explained, in part, by environmental variables and species richness (34.2%) and was also influenced by connections with the orthopterofauna from adjacent areas. The observed discrepancy between regionalization based on expert knowledge and the pattern revealed using quantitative data provides a warning that the biogeography of the Carpathians might also have been revised in other taxa, where only classical qualitative regionalization exists.
The drivers of dissimilarity in biological communities among habitats and the mechanisms that modulate the distribution of functional diversity in streams are still important gaps in ecological knowledge. This study was designed to assess how the taxonomic and functional composition of Cerrado stream insect assemblages are distributed among multiple spatial scales (i.e., habitat, stream sites and hydrological units). To do so we used a hierarchical series of four diversity components: stream transect (α), among transects (β1), among stream sites (β2), and among hydrological units (β3). Our aim was to identify the spatial scales at which variation in aquatic insect assemblage structure was greatest and whether turnover or nestedness mainly explain the patterns of β-diversity. We found that β-diversity among streams (β2) is highest and contributes most to total richness (γ-diversity) of aquatic insects in Cerrado streams as opposed to dissimilarities among habitats or among hydrological units. Moreover, β-diversity among transects had the lowest contribution to total insect richness (γ-diversity). The turnover component of taxonomic β-diversity was high for all spatial scales, but highest at stream scale. Conversely, for functional β-diversity, nestedness was the main component at stream scale. Understanding how biodiversity changes from local to regional scales is a first step towards understanding the variation in species and trait composition across space. Our results emphasize the importance of conserving Cerrado headwater streams because each stream harbors different taxa and human disturbance of any stream will result in loss of diversity and ecosystem functions.
Разнообразие природных условий ландшафтных комплексов, различия в геологическом строении и рельефе водосборных площадей бассейна р. Вычегда лежат в основе формирования основных гидробиологических характеристик ее притоков. Для дифференциации малых и средних притоков р. Вычегды предложено использовать районирование, основанное на различиях в строении геологического фундамента, геоморфологии, современном рельефе, почвообразующих породах и растительном покрове. Для анализа особенностей распределения доминирующих наземных экосистем в пределах бассейна использованы результаты сегментации мозаик изображений Landsat. Приведены результаты гидробиологических и гидрохимических наблюдений на 59 малых и средних реках в пределах выделенных ландшафтных комплексов Лузско-Вычегодской и Вычегодско-Мезенской равнин и Тиманской гряды. Дан обзор многолетних исследований планктонных и донных сообществ водотоков Вычегодского бассейна. Установлено, что ландшафтная приуроченность малых и средних притоков реки Вычегда определяет особенности водных сообществ: ординация результатов измерений численности и массы бентоса методом многомерного неметрического шкалирования (NMDS) показала наличие и формирование полярных по локализации ядер по показателям общей численности и биомассы для Вычегодско-Мезенского и Тиманского ландшафтных районов. Промежуточное положение занимает группа Лузско-Вычегодской равнины. Многообразие экологических условий малых и средних водотоков обусловили взаимные «проникновения» и размытый характер выделенных групп. Не выявлено выраженной дифференциации для характеристик зоопланктона. (The diversity of natural conditions of landscape complexes, differences in the geological structure and relief of the catchment areas of the Vychegda river basin are the basis for the formation of the main hydrobiological characteristics of its tributaries. To differentiate small and medium-sized tributaries of the Vychegda River, it was proposed to use zoning based on differences in the structure of the geological foundation, geomorphology, modern relief, soil-forming rocks and vegetation cover. The results of segmentation of Landsat image mosaic were used to analyze the distribution features of dominant terrestrial ecosystems within the basin. The results of hydrobiological and hydrochemical observations on 59 small and medium-sized rivers within the selected landscape complexes of the Luzhsko- Vychegodsky and Vychegodsko-Mezensky plains and the Timansky ridge were presented. A review of the results of long-term hydrobiological observations on watercourses of the Vychegda River basin with hydrochemical and biological characteristics of plankton and bottom communities was given. It was stated that the landscape confinement of small and medium-sized tributaries of the Vychegda River determined the characteristics of water communities. Ordination of the results of measurements of the number and mass of benthos by the method of multidimensional non-metric scaling (NMDS) showed the presence and formation of polar cores in terms of total population and biomass for the Vychegodsko-Mezensky and Timansky landscape areas. An intermediate position is occupied by the group of the Luzsko-Vychegodsky plain. The variety of environmental conditions of small and medium-sized watercourses caused mutual «penetrations» and the blurred nature of the selected groups. There was no pronounced differentiation found for the zooplankton characteristics.)
The diversity of natural conditions of landscape complexes, differences in the geological structure and relief of the catchment areas of the Vychegda river basin are the basis for the formation of the main hydrobiological characteristics of its tributaries. To differentiate small and medium-sized tributaries of the Vychegda River, it was proposed to use zoning based on differences in the structure of the geological foundation, geomorphology, modern relief, soil-forming rocks and vegetation cover. The results of segmentation of Landsat image mosaic were used to analyze the distribution features of dominant terrestrial ecosystems within the basin. The results of hydrobiological and hydrochemical observations on 59 small and medium-sized rivers within the selected landscape complexes of the Luzhsko-Vychegodsky and Vychegodsko-Mezensky plains and the Timansky ridge were presented. A review of the results of long-term hydrobiological observations on watercourses of the Vychegda River basin with hydrochemical and biological characteristics of plankton and bottom communities was given. It was stated that the landscape confinement of small and medium-sized tributaries of the Vychegda River determined the characteristics of water communities. Ordination of the results of measurements of the number and mass of benthos by the method of multidimensional non-metric scaling (NMDS) showed the presence and formation of polar cores in terms of total population and biomass for the Vychegodsko-Mezensky and Timansky landscape areas. An intermediate position is occupied by the group of the Luzsko-Vychegodsky plain. The variety of environmental conditions of small and medium-sized watercourses caused mutual "penetrations" and the blurred nature of the selected groups. There was no pronounced differentiation found for the zooplankton characteristics.
In stream ecosystems, waterfalls intercept the fluvial continuum and limit the dispersion of aquatic organisms. However, the barrier effect may be minimized or absent for insects whose life cycle is not restricted to the aquatic environment (i.e., winged adults), such as the orders Ephemeroptera, Plecoptera and Trichoptera (EPT). In this study, we investigated EPT diversity (abundance, richness, and composition) in savanna headwater streams (Cerrado Domain, Brazil) to investigate the hypothesis that large waterfalls have little effect on instream assemblage structure. During 2017 and 2018, we sampled EPTs and measured environmental conditions at reaches adjacent (downstream and upstream) to waterfalls (5 to 70 m high). We collected 2532 immature specimens of 33 genera, including the first record of 14 genera of Ephemeroptera, 11 Trichoptera, and three Plecoptera for the Tocantins State. Hydro-geomorphic and streambed conditions varied among sites, but they were not related to the presence of waterfalls. Assemblage structure was similar between downstream and upstream reaches, with no significant difference in taxa richness, abundance, and composition. This pattern was consistently observed considering all data combined, and each order separately. These results support the hypothesis that physical barriers have weak effects on EPT assemblages at small spatial scales, where strong dispersal and habitat similarity probably homogenizes the structure of local assemblages in stream corridors adjacent to large waterfalls. The study provides important information about factors driving the distribution of biodiversity in savanna streams, which are relevant to support conservation and management plans in the Brazilian Cerrado.
The robustness of quantitative measures of compositional dissimilarity between sites was evaluated using extensive computer simulations of species’ abundance patterns over one and two dimensional configurations of sample sites in ecological space. Robustness was equated with the strength, over a range of models, of the linear and monotonic (rank-order) relationship between the compositional dissimilarities and the corresponding Euclidean distances between sites measured in the ecological space. The range of models reflected different assumptions about species’ response curve shape, sampling pattern of sites, noise level of the data, species’ interactions, trends in total site abundance, and beta diversity of gradients.
The Kulczynski, Bray-Curtis and Relativized Manhattan measures were found to have not only a robust monotonic relationship with ecological distance, but also a robust linear (proportional) relationship until ecological distances became large. Less robust measures included Chord distance, Kendall’s coefficient, Chisquared distance, Manhattan distance, and Euclidean distance.
A new ordination method, hybrid multidimensional scaling (HMDS), is introduced that combines metric and nonmetric criteria, and so takes advantage of the particular properties of robust dissimilarity measures such as the Kulczynski measure.
This paper examines the patterns of sediment transport in rivers in terms of the sources of sediment and its transport and deposition through the river network. The analysis is in the context of dramatic human influences on river sediment transport and how they might influence freshwater ecosystems. The review of Australian work shows that erosion of hillslopes and stream banks has greatly increased in historical times, supplying vast quantities of sediment to rivers, much of which is still stored within the river system. The stored sediment will continue to effect in-stream and estuarine ecosystems for many decades. In most Australian catchments the dominant source of sediment is streambank erosion. An analysis of historical channel widening suggests that a conceptual framework of relative stream power can explain the diversity of behaviour observed in the numerous case studies. Sediment delivery through catchments is considered first in a generic whole network sense, which emphasizes the crucial role played by riverine deposition in determining catchment sediment budgets. A method is then presented for analysing the diverse spatial patterns of sediment storage in any river network. Finally, the paper considers the temporal changes to channel morphology in response to a human-induced pulse of sediment.
The intermediate disturbance hypothesis has been influential in the development of ecological theory and has important practical implications for the maintenance of biodiversity but has received few rigorous tests. We tested the hypothesis that maximum taxon richness of macroinvertebrates will occur in communities subject to intermediate levels of disturbance at 54 stream sites that differed in the frequency and intensity of flood‐related episodes of bed movement. Our results support the intermediate disturbance hypothesis, with both highly mobile and relatively sedentary taxa conforming to the predicted bell‐shaped curve. Taxon richness was not related to habitat area (stream width), distance from the headwater, or the diversity of microhabitats (particle size categories) but was significantly and negatively related to the proportion of the substratum made up of small particles. Of all the factors measured, however, bed disturbance was by far the best at accounting for variation in taxonomic richness. We also quantified several kinds of potential refugia for invertebrates and found a positive relationship between richness and a refugia axis that combines amount of dead space with proportion of large substratum particles.
The modelling of water management scenarios and their impacts on the
environment has to date been undertaken using separate models and often
by different organizations. The building and operation of a dam induces
a chain of interlinked responses in the environment and to capture this
in an impact assessment a more integrated approach to modelling is
needed. The mixed spatial and temporal characteristics of the different
variables mean that using a single model development environment is
difficult. This paper shows how an integrated, hierarchically structured
set of model components may be developed using an object-oriented
modelling language linked with a geographical information system (GIS).
This supports the representation of the process dynamics and the spatial
complexity of the riverine environment. The method was applied to the
Roadford Dam project on the River Wolf in south-west England. Water
resource and water quality model components were developed in the
object-oriented language and simulations were run for release regimes
during the filling and operation of the dam for the years 1976, 1978,
1986 and 1989, which represent respectively drought, normal, wet and dry
conditions. The results, when compared with base-case conditions, showed
the changes to the discharge, temperature, and chloride and nitrate-N
ion values. The resulting flow values were an input to the third model
component, that of the biotic system. These data were combined in a GIS
with information on channel form and substrate, and known spawning and
breeding sites of the Atlantic salmon (Salmo salar). Overlay analysis
was used to determine the suitability of the new conditions for the
species.
We present ADE-4, a multivariate analysis and graphical display software. Multivariate analysis methods available in ADE-4 include usual one-table methods like principal component analysis and correspondence analysis, spatial data analysis methods (using a total variance decomposition into local and global components, analogous to Moran and Geary indices), discriminant analysis and within/between groups analyses, many linear regression methods including lowess and polynomial regression, multiple and PLS (partial least squares) regression and orthogonal regression (principal component regression), projection methods like principal component analysis on instrumental variables, canonical correspondence analysis and many other variants, coinertia analysis and the RLQ method, and several three-way table (k-table) analysis methods. Graphical display techniques include an automatic collection of elementary graphics corresponding to groups of rows or to columns in the data table, thus providing a very efficient way for automatic k-table graphics and geographical mapping options. A dynamic graphic module allows interactive operations like searching, zooming, selection of points, and display of data values on factor maps. The user interface is simple and homogeneous among all the programs; this contributes to making the use of ADE-4 very easy for nonspecialists in statistics, data analysis or computer science.
We assessed environmental gradients and the extent to which they induced concordant patterns of taxonomic composition among benthic macroinvertebrate, riparian bird, sedimentary diatom, fish, and pelagic zooplankton assemblages in 186 northeastern U.S.A. lakes. Human population density showed a close correspondence to this region's dominant environmental gradient. This reflected the constraints imposed by climate and geomorphology on land use and, in turn, the effects of land use on the environment (e.g., increasing lake productivity). For the region as a whole, concordance was highest among assemblages whose taxa were relatively similar in body size. The larger-bodied assemblages (benthos, birds, fish) were correlated most strongly with factors of broader scale (climate, forest composition) than the diatoms and zooplankton (pH, lake depth). Assemblage concordance showed little or no relationship to body size when upland and lowland subregions were examined separately. This was presumably because differences in the scales at which each assemblage integrated the environment were obscured more locally. The larger- bodied assemblages showed stronger associations with land use than the diatoms and zooplankton. This occurred, in part, because they responded more strongly to broad-scale, nonanthropogenic factors that also affected land use. We argue, however, that the larger-bodied assemblages have also been more severely affected by human activities.
The earth's major mountain ranges provide opportunities to assess the effects of altitude and land use on stream fauna, but many basic patterns are still undescribed. Macroinvertebrates were therefore sampled from rifle and marginal habitats of 45 streams in three regions of the Ecuadorian Andes. Assemblage structure and richness were assessed in relation to habitat character, water chemistry and catchment land use. Land use varied from humid montane forest in the Western and Eastern Cordillera to transition forest and Paramo in the Central Valley. However, c. 30% of sites in each region were located in managed catchments of cleared forest, pasture or crop plantations. Water chemistry and stream habitat varied significantly between regions, altitudes and land use. Invertebrate assemblages were dominated by Baetidae, Leptophlebiidae, Tricorythidae, Elmidae, and Chironomidae, but ordination revealed major variations in assemblage structure with altitude. Hydropsychidae, Philopotamidae, Ptilodactyidae and Gomphidae were restricted to lower altitude whereas Scritidae and Gammaridae characterised higher altitude sites. Secondary variations in assemblage structure were correlated with habitat structure and metal concentrations (Al, Fe and Mn), and in turn were reflected in taxon richness. Classification revealed generally similar patterns, but showed also potential effects on assemblage structure in the Western Cordillera where humid montane forest had been cleared for agriculture. We conclude that, as in other mountain regions, major downslope patterns are clear among aquatic invertebrates in the Ecuadorian Andes. However, from these data altitude affects assemblage composition more than richness. Downslope patterns might have been modified by human activity at the catchment scale, and also by local site attributes such as habitat structure and stream chemistry. We erect three hypotheses about the effects of land use on Andean rivers that will be testable through further work.
Artificial neural networks (ANN) are models inspired by the structure and processes of biological cognition and learning. To illustrate the ecological applications of ANN, we present analyses of two complementary examples. ANN is first used to predict the diversity of macroinvertebrates, at the macrohabitat scale, in tributaries of a large river in New Zealand and, second, to predict the distribution and abundance of several fish species at the microhabitat scale in a French lake. The predictive abilities of the models were high, with correlation coefficients between observed and estimated values from 0.61 and 0.92. Moreover, the environmental variables found to be associated with invertebrate diversity and fish abundance were in accord with results of previous studies. The combination of ANN with a multivariate analysis offish community composition provided both for accurate prediction of fish assemblages and effective visualisation of their relationships with environmental variables. On the basis of these studies in different locations (New Zealand streams, French lake), involving various population and community attributes, we conclude that ANN is an appropriate tool for both prediction and explanation of ecological relationships at various spatial scales (microhabitat and macrohabitat), and for a range of aquatic ecosystems (lakes and rivers), organisms (invertebrates and fish), and ecological descriptors (abundance, Shannon diversity index, and community composition).
Riparian vegetation has a fundamental influence on the biological, chemical and physical nature of rivers. The quantification of riparian landcover is now recognised as being essential to the holistic study of the ecosystem characteristics of rivers. Medium resolution satellite imagery is now commonly used as an efficient and cost effective method for mapping vegetation cover; however such data often lack the resolution to provide accurate information about vegetation cover within riparian corridors. To assess this, we measure the accuracy of SPOT multispectral satellite imagery for classification of riparian vegetation along the Taieri River in New Zealand. In this paper, we discuss different sampling strategies for the classification of riparian zones. We conclude that SPOT multispectral imagery requires considerable interpretative analysis before being adequate to produce sufficiently detailed maps of riparian vegetation required for use in stream ecological research.
1. The habitat templet approach depends on defining templet axes appropriate to the organism(s) of interest, predicting the traits of species associated with different parts of the templet, and testing these predictions in a range of habitats whose positions in the templet have been determined.
2. In this study of thirty-five benthic insect taxa at fifty-four tributary sites of the Taieri River on the South Island of New Zealand, we chose as the temporal axis the intensity/frequency of disturbance, defined in terms of bed movement during high discharge events. As the spatial axis, we postulated that three features would provide refugia and therefore ameliorate disturbance—percentage of the bed with low shear stress, percentage of the bed made up of large substratum particles and availability of interstitial space in the bed—from which we derived a combined multivariate refugium axis.
3. More disturbed communities contained a significantly higher percentage of individuals possessing the following traits: small size, high adult mobility, habitat generalist (each predicted to confer resilience in response to disturbance), clinger, streamlined/flattened and with two or more life stages outside the stream (each predicted to confer resistance in the face of disturbance). When analyses were performed on the percentage of taxa having particular traits, the predicted positive relationships with average bed movement were found for high adult mobility and habitat generalist traits.
4. The percentage of variance in trait scores explained by intensity of disturbance was generally higher in sites with less refugia available and lower in sites further from the headwaters. The percentage of variance explained was higher in sites recently subject to a major high discharge disturbance, suggesting that disturbances tend to strengthen the pattern of preponderance of resilience/resistance traits.
5. We mapped insect taxa onto the two-dimensional templet, following Grime et al.’s triangular terrestrial plant classification. The full variety of resistance and resilience traits were represented in insect species throughout the templet, but taxa associated with more disturbed conditions generally displayed a larger number of resilience and resistance traits, combined, than taxa associated with more stable stream beds.
1. Piecemeal changes in land use might have cumulative effects on regional biodiversity. However, this hypothesis is difficult to test experimentally at the scales involved, so alternative approaches are required. Here, we illustrate some of the strengths and weaknesses of surveys for evaluating the effects of land use on rivers and river birds over a large area of the Himalayan mountains.
2. We surveyed 180 streams and their catchments in north-west India and Nepal in 1994–96. We then used analysis of covariance (ancova), multiple linear regression and multiple logistic regression to assess how stream habitat structure, stream chemistry, aquatic invertebrate abundance and the occurrence of river birds were affected by land use after accounting for altitudinal pattern.
3. Streams draining terraced catchments differed significantly in habitat structure from other streams. They had more physical modifications, wider channels, fewer cascades, finer substrata and simpler riparian vegetation with fewer trees. We detected no clear effects of land use on stream chemistry, but terracing was accompanied by significantly increased abundances of benthic dipterans, ephemeropterans and total aquatic invertebrates.
4. River bird occurrence was best explained by altitude, and secondarily by habitat structure. Some of the habitat features influenced by terracing significantly affected birds both positively (grey wagtail Motacilla cinerea) and negatively (little forktail Enicurus scouleri, river chat Chaimarrornis leucocephalus, brown dipper Cinclus pallasii, plumbeous redstart Rhyacornis fuliginosus). However, only in the grey wagtail did the presence of terracing per se affect occurrence unequivocally; effects on other species were either small or confounded by altitude.
5. We cannot refute the hypothesis that catchment land use affects Himalayan river ecology, but our data on the regional consequences for river birds were equivocal. We suggest that large-scale surveys, although providing one of the few pragmatic methods of assessing large anthropogenic effects on ecosystems, will need careful design to factor out potential confounds if they are to be used to test hypotheses robustly. They should also be supported where possible with process studies, intervention studies and model applications to independent data.
SUMMARY 1. The prediction of species distributions is of primary importance in ecology and conservation biology. Statistical models play an important role in this regard; however, researchers have little guidance when choosing between competing methodologies because few comparative studies have been conducted.
2. We provide a comprehensive comparison of traditional and alternative techniques for predicting species distributions using logistic regression analysis, linear discriminant analysis, classification trees and artificial neural networks to model: (1) the presence/absence of 27 fish species as a function of habitat conditions in 286 temperate lakes located in south-central Ontario, Canada and (2) simulated data sets exhibiting deterministic, linear and non-linear species response curves.
3. Detailed evaluation of model predictive power showed that approaches produced species models that differed in overall correct classification, specificity (i.e. ability to correctly predict species absence) and sensitivity (i.e. ability to correctly predict speciespresence) and in terms of which of the study lakes they correctly classified. Onaverage, neural networks outperformed the other modelling approaches, although all approaches predicted species presence/absence with moderate to excellent success.
4. Based on simulated non-linear data, classification trees and neural networks greatly outperformed traditional approaches, whereas all approaches exhibited similar correct classification rates when modelling simulated linear data.
5. Detailed evaluation of model explanatory insight showed that the relative importance of the habitat variables in the species models varied among the approaches, where habitat variable importance was similar among approaches for some species and very different for others.
6. In general, differences in predictive power (both correct classification rate and identity of the lakes correctly classified) among the approaches corresponded with differences in habitat variable importance, suggesting that non-linear modelling approaches (i.e. classification trees and neural networks) are better able to capture and model complex, non-linear patterns found in ecological data. The results from the comparisons using simulated data further support this notion.
7. By employing parallel modelling approaches with the same set of data and focusing on comparing multiple metrics of predictive performance, researchers can begin to choose predictive models that not only provide the greatest predictive power, but also best fit the proposed application.
The robustness of quantitative measures of compositional dissimilarity between sites was evaluated using extensive computer simulations of species' abundance patterns over one and two dimensional configurations of sample sites in ecological space. Robustness was equated with the strength over a range of models, of the linear and monotonic (rank-order) relationship between the compositional dissimilarities and the corresponding Euclidean distances between sites measured in the ecological space. The range of models reflected different assumptions about species' response curve shape, sampling pattern of sites, noise level of the data, species' interactions, trends in total site abundance, and beta diversity of gradients.The Kulczynski, Bray-Curtis and Relativized Manhattan measures were found to have not only a robust monotonic relationship with ecological distance, but also a robust linear (proportional) relationship until ecological distances became large. Less robust measures included Chord distance, Kendall's coefficient, Chisquared distance, Manhattan distance, and Euclidean distance.A new ordination method, hybrid multidimensional scaling (HMDS), is introduced that combines metric and nonmetric criteria, and so takes advantage of the particular properties of robust dissimilarity measures such as the Kulczynski measure.
Ecologists and conservation biologists frequently use multipleregression (MR) to try to identify factors influencing response variables suchas species richness or occurrence. Many frequently used regression methods maygenerate spurious results due to multicollinearity. argued that there are actually two kinds of MR modelling: (1)seeking the best predictive model; and (2) isolating amounts of varianceattributable to each predictor variable. The former has attracted most attentionwith a plethora of criteria (measures of model fit penalized for modelcomplexity – number of parameters) and Bayes-factor-based methods havingbeen proposed, while the latter has been little considered, althoughhierarchical methods seem promising (e.g. hierarchical partitioning). If the twoapproaches agree on which predictor variables to retain, then it is more likelythat meaningful predictor variables (of those considered) have been found. Therehas been a problem in that, while hierarchical partitioning allowed the rankingof predictor variables by amounts of independent explanatory power, there was no(statistical) way to decide which variables to retain. A solution usingrandomization of the data matrix coupled with hierarchical partitioning ispresented, as is an ecological example.
1. The relationship between land use and stream conditions was investigated, including physicochemistry, the availability of primary food resources and species richness, species composition and trophic structure of stream macroinvertebrate communities. The survey involved eight subcatchments of the Taieri River (New Zealand) encompassing reasonably homogeneous examples of four major land uses: native forest, native tussock grassland, plantations of introduced pine and agricultural pasture. 2. Each land use was represented by two subcatchments, each subcatchment by two to four tributaries, and each tributary by two to three sampling sites. These three sampling scales each represent typical designs for stream community studies. By recording responses at all scales, it can be determined explicitly whether the scale of sampling influences interpretation of community structure. 3. Elevation, riffle length, proportion of large substrata in the bed, total phosphorus and alkalinity were significantly related to land use, as were canopy cover and the relative abundance of leaves and wood in the streams. Principal components analysis of invertebrate density data identified nine orthogonal community types, the distributions of two of which were significantly related to land use. The role played by browsers and shredders in the stream community depended on land use. 4. Primary analysis was at the level of the tributary. When it focused on sites within tributaries, more variables were related to land use and at a higher level of significance. This was largely a result of enhanced statistical power due to increased replication. When whole subcatchments were the focus of attention, statistical power was so low, even with six to eleven subsamples to generate overall means, that few significant patterns could be identified. However, the community patterns that were revealed were similar whatever the scale of sampling.
Lotic models of disturbance generated by floods and spates suffer from 2 main short-comings: a lack of knowledge regarding the appropriate spatial scale at which to apply models and a poor understanding of the relationship between discharge sizes and actual disturbance frequencies and intensities. Here, we examine the spatial variability in the forces needed to shift rocks and the utility of hydraulic equations that predict critical shear stresses (τ <sub>c</sub>), which are sometimes used to infer disturbance frequencies in streams. We used spring balances to measure directly the forces needed (F<sub>c</sub>) to move rocks up and out of the stream bed in 4 upland streams (Acheron River, Taggerty/Steavenson rivers, Connelly Creek, and Little River) in southeastern Australia. We measured 25 rocks at each of 32 sites overall, with sites distributed in a nested design: sites were paired in 2nd, 3rd, upper 4th, and lower 4th orders on each river. For each rock, we determined whether it was wedged into place by surrounding rocks, estimated percentage burial in fine sediments, and measured rock size and ambient water velocity and depth. Nested analyses of variance indicated that F<sub>c</sub> and its correlates varied most between rivers and greatly between rocks within individual sites; the spatial scales of stream order and site contributed little explanatory power. Hierarchical, log-linear modelling showed that both rock size and bed packing varied systematically between rivers, with the Little and Taggerty/Steavenson rivers having relatively large rocks that were often packed into the bed, whereas Connelly Creek and the Acheron River had many relatively-small rocks lying loosely on top of the bed. A river-by-river analysis showed that values of F<sub>c</sub> were related highly to rock sizes but that the nature of the relationships differed greatly between packed-in rocks and those lying on top of the bed and also varied between rivers. The Little and Taggerty/Steavenson rivers were similar to each other but both differed from the Acheron River and Connelly Creek, which differed from each other. Our estimates of F<sub>c</sub> suggest that an oft used approximation, which equates τ <sub>c</sub> directly with rock sizes in mm, and the commonly-used equations from which the approximation is derived, are likely to produce poor estimates of τ <sub>c</sub>; these poor estimates would cause equally poor estimates of likely disturbance frequencies. The application by ecologists of reach-level hydraulic equations to estimate shear stresses and the sizes and numbers of rocks moved by floods and spates could be flawed by a focus on inappropriate spatial scales. Our data suggest that variation in likely disturbance frequencies between rocks within individual sites might be of a similar magnitude to variability between different rivers. We argue that spatial variation in stream systems need not be organized in the top-to-bottom hierarchical models that have been recently promoted for rivers.
The relative importance of surrounding riparian vegetation and substrate composition on invertebrate community structure was investigated in six streams in Oregon, USA. We found that canopy type was more important than substrate character in influencing total abundance and guild structure. Streams without shading had higher abundances of invertebrates than did shaded steams. Most guilds were influenced by qualitative differences in food availability rather than quantity of food or substrate composition. Open streams had higher abundances in the collector-gatherer, filter feeder, herbivore shredder and piercer, and predator guilds. Contrary to expectations, shredders were no more abundant in shaded streams than in streams lacking a riparian canopy. Scraper density was inversely related to standing crop of aufwuchs, but biomass was positively correlated with quantity of aufwuchs. Examination of dominance-diversity curves showed that both canopy and substrate influenced ranked abundances of taxa, but neither canopy nor substrate strongly influenced number of taxa. Differences in community structure were not always revealed by analysis of community-level properties, although differences in both the absolute and relative abundances of individual taxa were observed.
The study was designed to determine if spatial distributional patterns of lotic macroinvertebrates differed more strongly between eastern deciduous forest (EDF) and grassland (GRASS) biomes than among sites along rivers within a biome. Macroinvertebrates were collected in spring at five sites along each of three rivers within the EDF of southwestern Ontario and three rivers within the grasslands of south-central Alberta. Differences in total density, taxonomic composition, and functional feeding groups of macroinvertebrates were not consistent among sites and between biomes, as shown by the significance of the interaction term (biomes × sites). Variation in total density among rivers within biomes was attributable to differences in land use practices. Only three taxa (Leptophlebiidae, EDF; Ephemerellidae, GRASS; Pulmonata, GRASS) showed significant (negative curvilinear) relationships between density and distance from a river's source. Densities of shredders (EDF), collector-gatherers (GRASS), and predators (GRASS) also decreased in a curvilinear fashion with increasing river distance from source. The longitudinal river profiles of both taxonomic composition and functional feeding groups were weak. Despite differences in land use types within biomes, an overriding influence of biomes on the macroinvertebrate community was evident.
We conducted a survey of 198 sites in eight catchments in the Taieri River drainage of the South Island, New Zealand, and found a strong negative association between the distributions of introduced brown trout and native Galaxias vulgaris. Although habitat degradation due to agricultural and forestry practices was associated with lower densities of fish, these reductions were found in all fish species and did not help to explain the trout/galaxiid pattern. Statistical analyses incorporating a variety of physical, chemical and biological variables showed that presence and abundance of G. vulgaris were best predicted by the absence of trout. In most cases, G. vulgaris were only found above waterfalls that were large enough to inhibit trout migration. We suggest that predation is the most likely mechanism for the observed disjunct distributions between the native fish and trout. Moreover, the strong predation effect is probably a result of New Zealand's comparative paucity of native piscivorous fishes, resulting in a native fish fauna having no evolved defenses.
Although it is well known that metabolism, feeding, and behaviour of lotic organisms is influenced by various flow characteristics, hydraulic variables usually are not accurately measured in lotic ecology studies. Using an approach we call "hydraulic stream ecology", we link organismic responses to a more comprehensive treatment of the physical environment. Since a unified analytical solution for all important hydraulic variables in running waters does not exist at the moment, we advocate a simpler view of the physical system. We demonstrate methods for estimating complex hydraulic key characteristics, like turbulence in the free flow, turbulence close to the stream bottom, and the force of flow prevailing at the bottom. Calculations of these complex key characteristics require measurement of simple hydraulic characteristics like mean velocity, water surface slope, depth, bottom roughness, kinematic viscosity, and density of the water. The hydraulic environment shows characteristic patterns within whole catchments or within reaches of different types of running waters (e.g., high gradient mountain stream, lowland stream, mid-order river). Examples from lotic macroinvertebrates, in particular original data on the water bug Aphelocheirus aestivalis (Fabr.), demonstrate how organismic responses are linked to the hydraulic environment. The body shapes of many lotic zoobenthos are not well adapted to minimize forces of flow, as has been generally believed. Indeed, flow forces are rather stressful for these animals. Critical resources in swift flowing microzones can often be exploited by zoobenthos for only restricted periods, a view that is consistent with the temporal, vertical migration patterns observed for most stream invertebrates. The stress of flow and temporal exposure to it may be correlated with the distribution of lotic zoobenthos. Substratum characteristics, usually perceived as a major factor explaining the distribution of lotic macroinvertebrates, is less important than mean velocity and the complex hydraulic key characteristics. Complex hydraulic characteristics are most useful in modeling specific relationships between the distribution of zoobenthos within a stream reach and the physical habitat, which differ depending on developmental stage of the organism, season, and site. On the catchment scale, the distribution of zoobenthos, and, consequently, longitudinal zonation are also largely dependent on hydraulics. Other groups of organisms found in running waters (e.g., microorganisms and fish) show responses to hydraulics that are comparable to those of lotic macroinvertebrates. There is evidence that some species can alter the hydraulic environment for other individuals (or species). Hydraulic stream ecology provides methods to scale flow in lotic research, which will lead to an increase in replicability and predictability in studies of running water ecosystems. We suggest that researchers who have measured relevant simple hydraulic characteristics in many past studies reevaluate their data considering the role of complex hydraulic key characteristics for the distribution of organisms.
The use of principal components in regression has received a lot of attention in the literature in the past few years, and the topic is now beginning to appear in textbooks. Along with the use of principal component regression there appears to have been a growth in the misconception that the principal components with small eigenvalues will very rarely be of any use in regression. The purpose of this note is to demonstrate that these components can be as important as those with large variance. This is illustrated with four examples, three of which have already appeared in the literature.
The physical features of 20 streams inhabited by four recently discovered species of allopatric, non-migratory galaxiid fishes in the Taieri River, South Island, New Zealand were examined. Significant differences in particle size frequencies, combined waterfall frequency, channel depth variation and stream width: flood channel width ratios, indicated that Galaxias anomalus lived in low gradient shallow streams whereas G. depressiceps and G. eldoni occupied low to high gradient streams with more variability in depth. Climbing ability differed significantly among the species. Their allopatric patterns of distribution were, in part, the probable consequence of the abilities of G. depressiceps and G. eldoni to colonize areas that G. anomalus could not penetrate. Historical factors and reproductive biology of the four species are hypothesized also to be causal determinants of their current distributions.
The relative influence of geologic versus anthropogenic attributes of catchments on stream ecosystems was examined in 45 catchments of a river basin in central Michigan. Each catchment was characterized by land use, surficial geology, elevation, and hydrography, and summaries of these data were related to physical habitat characteristics that had the greatest influence on macroinvertebrate assemblages. Partial redundancy analysis revealed that geologic and land-use variables had similar magnitudes of influence on stream habitats. Of the geologic variables, catchment area, proportion of lacustrine clays, and glacial outwash materials had the strongest influence on physical habitat, particularly on channel dimensions. Row-crop agriculture and the presence of wetlands were the most important land-use variables, particularly influencing amounts of woody debris. Stream buffers (100 m) were more important than whole catchment data for predicting sediment-related habitat variables; however, channel morphology was more strongly related to whole catchments. Results suggest that catchment-wide geology and land-use characteristics may be more important than stream buffers for maintaining or restoring stream ecosystems. These techniques can be used to develop biologic signatures of catchment condition that discriminate causal factors influencing the biodiversity and health of stream ecosystems.
1. In the mid‐1970s, Hynes (1975) wrote eloquently about the complex interactions between aquatic and terrestrial systems. Central theories in stream ecology developed thereafter have dealt with the longitudinal flow of energy, materials and organisms in streams, and, with the exception of the flood pulse concept (Junk, Bayley & Sparks, 1989), have largely ignored areas outside the riparian zone. The structure of the upland and activities occurring there play a more important part than previously recognized in regulating community structure and ecosystem processes in streams.
2. These new perspectives are made possible by developments in hierarchy theory, patch dynamics, and the refinement of tools used to quantify spatial and temporal heterogeneity.
3. Geographical information systems (GIS), image processing technology and spatial statistical techniques allow quantitative assessment of lateral, longitudinal and vertical components of the landscape that interact at several spatial and temporal scales to influence streams. When GIS is used in concert with geostatistics, multivariate statistics, or landscape models, complex relationships can be elucidated and predicted.
4. To a certain extent, the tools discussed above have only automated functions that were previously performed manually. This suite of tools has improved the ability of aquatic ecologists to examine relationships and test theories over larger, more heterogeneous regions than were previously possible.
5. At the local, state and federal level, management and regulatory frameworks are currently being re‐evaluated to incorporate this new perspective in resource management and policy decision making.
6. We will discuss current and future trends in technologies and tools used for aquatic ecosystem research, and the use of techniques as they are applied in these regional assessments are also discussed.
Patches of large and small pebbles were created in three riffles (fast current velocities) and three pools (slow velocities). It was expected that patches with different sizes of pebbles in the two velocity regimes would vary in the entrapment of fine sediments and organic matter, which in turn would result in differences in benthic community structure. This was not the case, for although deposition of fine material was greater in pools, there were appreciable location-specific differences in the fauna unrelated to the variables monitored in the experiment. Functional feeding groups did not respond predictably to the distribution of detritus. Generally, the community was least influenced by substratum size, with any differences being inconsistent across locations. Most other substratum effects were attributable to the presence of epilithon on undisturbed control patches. Velocity was the most influential factor, with riffles having higher total abundances and higher species richness. Some taxa showed strong location- specific differences. At the level of a small patch of pebbles, the colonization dynamics of the fauna are probably a mixture of species- and location-specific dispersal and selection mechanisms. At larger spatial scales, however, community structure is more predictable, with pools differing substantially from riffles.
Consider two data matrices on the same sample of n individuals, X(p × n), Y(q × n). From these matrices, geometrical representations of the sample are obtained as two configurations of n points, in Rp and Rq. It is shown that the RV-coefficient (Escoufier, 1970, 1973) can be used as a measure of similarity of the two configurations, taking into account the possibly distinct metrics to be used on them to measure the distances between points. The purpose of this paper is to show that most classical methods of linear multivariate statistical analysis can be interpreted as the search for optimal linear transformations or, equivalently, the search for optimal metrics to apply on two data matrices on the same sample; the optimality is defined in terms of the similarity of the corresponing configurations of points. which, in turn, calls for the maximization of the associated RV-coefficient. The methods studied are principal components, principal components of instrumental variables, multivariate regression, canonical variables, discriminant analysis; they are differentiated by the possible relationships existing between the two data matrices involved and by additional constraints under which the maximum of RV is to be obtained. It is also shown that the RV-coefficient can be used as a measure of goodness of a solution to the problem of discarding variables.
1. In the mid-1970s, Hynes (1975) wrote eloquently about the complex interactions between aquatic and terrestrial systems. Central theories in stream ecology developed thereafter have dealt with the longitudinal flow of energy, materials and organisms in streams, and, with the exception of the flood pulse concept (Junk, Bayley & Sparks, 1989), have largely ignored areas outside the riparian zone. The structure of the upland and activities occurring there play a more important part than previously recognized in regulating community structure and ecosystem processes in streams. 2. These new perspectives are made possible by developments in hierarchy theory, patch dynamics, and the refinement of tools used to quantify spatial and temporal heterogeneity. 3. Geographical information systems (GIS), image processing technology and spatial statistical techniques allow quantitative assessment of lateral, longitudinal and vertical components of the landscape that interact at several spatial and temporal scales t
The physical features of 20 streams inhabited by four recently discovered species of allopatric, non-migratory galaxiid fishes in the Taieri River, South Island, New Zealand were examined. Significant differences in particle size frequencies, combined waterfall frequency, channel depth variation and stream width : flood channel width ratios, indicated that Galaxins anomalus lived in low gradient shallow streams whereas G. depressiceps and G. eldoni occupied low to high gradient streams with more variability in depth. Climbing ability differed significantly among the species. Their allopatric patterns of distribution were, in part, the probable consequence of the abilities of G. depressiceps and G. eldoni to colonize areas that G. anomalus could not penetrate. Historical factors and reproductive biology of the four species are hypothesized also to be causal determinants of their current distributions. (C) 1997 The Fisheries Society of the British Isles.
1. We intensively sampled 16 western Oregon streams to characterize: (1) the variability in macroinvertebrate assemblages at seven spatial scales; and (2) the change in taxon richness with increasing sampling effort. An analysis of variance (ANOVA) model calculated spatial variance components for taxon richness, total density, percent individuals of Ephemeroptera, Plecoptera and Trichoptera (EPT), percent dominance and Shannon diversity.
2. At the landscape level, ecoregion and among‐streams components dominated variance for most metrics, accounting for 43–72% of total variance. However, ecoregion accounted for very little variance in total density and 36% of the variance was attributable to differences between streams. For other metrics, variance components were more evenly divided between stream and ecoregion effects.
3. Within streams, approximately 70% of variance was associated with unstructured local spatial variation and not associated with habitat type or transect position. The remaining variance was typically split about evenly between habitat and transect. Sample position within a transect (left, centre or right) accounted for virtually none of the variance for any metric.
4. New taxa per stream increased rapidly with sampling effort with the first four to eight Surber samples (500–1000 individuals counted), then increased more gradually. After counting more than 50 samples, new taxa continued to be added in stream reaches that were 80 times as long as their mean wetted width. Thus taxon richness was highly dependent on sampling effort, and comparisons between sites or streams must be normalized for sampling effort.
5. Characterization of spatial variance structure is fundamental to designing sampling programmes where spatial comparisons range from local to regional scales. Differences in metric responses across spatial scales demonstrate the importance of designing sampling strategies and analyses capable of discerning differences at the scale of interest.
The ratio of the number of observed taxa to that expected to occur in the absence of human-caused stress (O/E) is an intuitive and ecologically meaningful measure of biological integrity. We examined how O/E ratios derived from stream invertebrate data varied among 234 unimpaired reference sites and 254 test sites potentially impaired by past logging. Data were collected from streams in three montane ecoregions in California. Two sets of River Invertebrate Prediction and Classification System (RIVPACS) predictive models were built: one set of models was based on near-species taxonomic resolution; the other was based on family identifications. Two models were built for each level of taxonomic resolution: one calculated O and E based on all taxa with probabilities of capture (Pc) > 0; the other calculated O and E based on only those taxa with Pc ≥ 0.5. Evaluations of the performance of each model were based on three criteria: (1) how well models predicted the taxa found at unimpaired sites, (2) the degree to which O/E values differed among unimpaired reference sites and potentially impaired test sites, and (3) the degree to which test site O/E values were correlated with independent measures of watershed alteration. Predictions of species models were more accurate than those of family models, and predictions of the Pc ≥ 0.5 species model were more robust than predictions of the Pc ≥ 0 model. O/E values derived from both species models were related to land use variables, but only assessments based on the Pc ≥ 0.5 model were insensitive to naturally occurring differences among streams, ecoregions, and years.
1. The relationship between land use and stream conditions was investigated, including physicochemistry, the availability of primary food resources and species richness, species composition and trophic structure of stream macroinvertebrate communities. The survey involved eight subcatchments of the Taieri River (New Zealand) encompassing reasonably homogeneous examples of four major land uses: native forest, native tussock grassland, plantations of introduced pine and agricultural pasture.
2. Each land use was represented by two subcatchments, each subcatchment by two to four tributaries, and each tributary by two to three sampling sites. These three sampling scales each represent typical designs for stream community studies. By recording responses at all scales, it can be determined explicitly whether the scale of sampling influences interpretation of community structure.
3. Elevation, riffle length, proportion of large substrata in the bed, total phosphorus and alkalinity were significantly related to land use, as were canopy cover and the relative abundance of leaves and wood in the streams. Principal components analysis of invertebrate density data identified nine orthogonal community types, the distributions of two of which were significantly related to land use. The role played by browsers and shredders in the stream community depended on land use.
4. Primary analysis was at the level of the tributary. When it focused on sites within tributaries, more variables were related to land use and at a higher level of significance. This was largely a result of enhanced statistical power due to increased replication. When whole subcatchments were the focus of attention, statistical power was so low, even with six to eleven subsamples to generate overall means, that few significant patterns could be identified. However, the community patterns that were revealed were similar whatever the scale of sampling.
1. Biogeographical and on-site. hydrological variables were evaluated to determine spatial distribution of benthic invertebrate assemblages at 100 river sites in northwestern North America.
2. Results of cluster analysis suggested that the river sites comprised sixgroups (A-F), each supporting a characteristic invertebrate assemblage.Distinct groups were best represented by abundant Tricorythidae (C), Amphipoda (F), Rhyacophilidae and Systellognatha (E), and Elmidae and Hydroptilidae (A). Brachycentridae (B) and Oligochaeta (D) were widespread throughout the study area.
2. Both biogeographical and hydrological features contributed to the correct classification of site groupings characterized by distinctive fauna. However, biogeographical features were more useful than variables measured at the river site in discriminating among the site groupings.Groups C and F were most prevalent within the Hudson Bay drainage.Groups A, C and F were typically located within plains; group E sites were in mountainous regions.
4. The hydrological variables most useful in delineating site groupings were mean current velocity and mean depth. Slow, deep waters characterized amphipod sites; shallow, fast flowing waters occurred at Rhyacophilidae Sysellognatha sites.
5. Results substantiate previous views of a strong association between benthic invertebrates in small rivers and the terrestrial biome through which the river flows.
1. The relationships between three habitat scales and lotic invertebrate species composition were investigated for the 15 540 km2 Yakima River basin in south-central Washington, U.S.A.
2. The three spatial scales were sample (the sampled riffle), reach (a length of ten–twenty stream widths) and segment (a length of stream of nearly uniform slope and valley form having no change in stream order).
3. Physical variables were highly correlated between scales and expressed a relationship between altitude, basin form and small-scale physical structure.
4. Multiple discriminant function analyses indicated that segment- and reach-scale variables discriminated among species-defined groups better than sample-scale variables.
5. Species composition varied along a complex altitudinal gradient of changing basin form and resultant land use.
6. There was no clear relationship between species richness and altitude on a site basis. However, when viewed at the basin scale, maximum richness was observed at the transition between montane and valley sites.
This study was designed to test the biome dependency hypothesis, which predicts that similar assemblages of macroinvertebrates occur along rivers both within and among drainage basins if the basins occupy the same biome. Benthic macroinvertebrates were collected from three drainage basins within each of three biomes in Canada, the eastern deciduous forests (EDF) of southwestern Ontario, the grasslands of south-central Alberta, and the montane coniferous forests (MCF) of southeastern British Columbia. A total of 225 benthic samples (3 biomes 3 rivers/biome 5 sites/river 5 samples/site) was collected in spring using a cylinder sampler.The significant interaction effect between biome and a site''s location along a river indicated that spatial patterns of variation in total density and taxonomic composition were not spatially consistent among sites along rivers or among biomes. Total macroinvertebrate densities were equivalent between the EDF and grassland sites. However, total density was substantially lower at the MCF sites than at sites in the other two biomes. The greatest differences in taxonomic composition occurred among biomes, although significant differences also occurred for all other sources of variation examined. Macroinvertebrate composition was more strongly associated with local, site-specific factors (riparian vegetation and land use) than with longitudinal gradients. Distinct site-specific taxonomic assemblages were evident in EDF, but not in the other two biomes where land use was more homogeneous.
The biological integrity of stream ecosystems depends critically on human activities that affect land use/cover along stream
margins and possibly throughout the catchment. We evaluated stream condition using an Index of Biotic Integrity (IBI) and
a habitat index (HI), and compared these measures to landscape and riparian conditions assessed at different spatial scales
in a largely agricultural Midwestern watershed. Our goal was to determine whether land use/cover was an effective predictor
of stream integrity, and if so, at what spatial scale. Twenty-three sites in first-through third-order headwater streams were
surveyed by electrofishing and site IBIs were calculated based on ten metrics of the fish collection. Habitat features were
characterized through field observation, and site HIs calculated from nine instream and bank metrics. Field surveys, aerial
photograph interpretation, and geographic information system (GIS) analyses provided assessments of forested land and other
vegetation covers at the local, reach, and regional (catchment) scales.
The range of conditions among the 23 sites varied from poor to very good based on IBI and HI scores, and habitat and fish
assemblage measures were highly correlated. Stream biotic integrity and habitat quality were negatively correlated with the
extent of agriculture and positively correlated with extent of wetlands and forest. Correlations were strongest at the catchment
scale (IBI with % area as agriculture, r2=0.50, HI with agriculture, r2=0.76), and tended to become weak and non-significant at local scales. Local riparian vegetation was a weak secondary predictor
of stream integrity. In this watershed, regional land use is the primary determinant of stream conditions, able to overwhelm
the ability of local site vegetation to support high-quality habitat and biotic communities.
Basin characteristics such as land use/land cover, slope, and soil attributes affect water quality by regulating sediment and chemical concentration. Among these characteristics, land use/land cover can be manipulated to gain improvements in water quality. These land use/land cover types can serve as nutrient detention media or as nutrient transformers as dissolved or suspended nutrients move towards the stream. This study examines a methodology to determine nitrate pollution ‘contributing zones’ within a given basin based on basin characteristics. In this process, land use/land cover types were classified and basins and ‘contributing zones’ were delineated using geographic information system (GIS) and remote sensing (RS) analysis tools. A ‘land use/land cover-nutrient-linkage-model’ was developed which suggests that forests act as a sink, and as the proportion of forest inside a contributing zone increases (or agricultural land decreases), nitrate levels downstream will decrease. In the model, the residential/urban/built-up areas have been identified as strong contributors of nitrate. Other contributors were orchards; and row crops and other agricultural activities.
. We compare three common types of clustering algorithms for use with community data. TWINSPAN is divisive hierarchical, flexible-UPGMA is agglomerative and hierarchical, and ALOC is non-hierarchical. A balanced design six-factor model was used to generate 480 data sets of known characteristics. Recovery of the embedded clusters suggests that both flexible UPGMA and ALOC are significantly better than TWINSPAN. No significant difference existed between flexible UPGMA and ALOC.
Describes how organisms behave and live in relation to their environment and evolutionary history, bearing in mind the different resources that are required, and the nature of the interactions between these resources. The balance between birth rates and death rates, which indicates abundance, is shown to have profound effects on the behaviour of populations. Dispersal of organisms is linked with escape from unfavourable environments and the colonisation and exploitation of new environments. In looking at interactions between organisms, the nature and consequences of intra- and interspecific competition are explored. The nature of predation and grazing, behaviour of consumers and consumed, and implications of predation/grazing for population dynamics are also discussed. Decomposition and detritivore trophic linkages are reviewed, as are parasitism and disease. The evolution of mutualistic relationships is noted. Surveys of the range of life history strategies exhibited by living organisms, and of the range of patterns of abundance, are used to provide overviews of the organismic and the population levels in the ecological hierarchy. The final section considers interactions at the community level, looking at how community patterns change through space and time, examining the flux of energy and matter through communities, and indicating the influence of competition, predation and disturbance on community structure. Aspects of island biogeography theory are also discussed. The final chapters examine community stability and structure, and patterns of species diversity. -P.J.Jarvis
New Zealand Freshwater Fishes: a Natural History and Guide. Heinemann Reed Aquatic insect-substratum relation-ships. In: The Ecology of Aquatic Insects
- R M Mcdowall
McDowall R.M. (1989) New Zealand Freshwater Fishes: a Natural History and Guide. Heinemann Reed, Auckland. Minshall G.W. (1984) Aquatic insect-substratum relation-ships. In: The Ecology of Aquatic Insects (Eds V.H. Resh & D.M. Rosenberg), pp. 358–400.
Aquatic insect-substratum relationships
- G W Minshall
Minshall G.W. (1984) Aquatic insect-substratum relationships. In: The Ecology of Aquatic Insects (Eds V.H. Resh &
D.M. Rosenberg), pp. 358-400. Praeger, New York.
SAS ⁄ STAT Guide for Personal Computers, Version 6.11. SAS Institute
- Sas Institute
SAS Institute (1995) SAS ⁄ STAT Guide for Personal
Computers, Version 6.11. SAS Institute, Carey, North
Carolina, USA.