Taking four wheat varieties developed by Northwest Institute of Plateau Biology, Chinese Academy of Sciences, as test materials, with the measurement of content of photosynthetic pig- ments, leaf area, fresh and dry mass of flag leaf, the PS II photochemistry efficiency of abaxial and adaxial surface of flag leaf and its adaptation to strong solar radiation during the period of heading stage in Xiangride region were investigated with the pulse-modulated in-vivo chlorophyll fluorescence technique. The results indicated that flag leaf angle mainly grew in horizontal state in Gaoyuan 314, Gaoyuan 363 and Gaoyuan 584, and mainly in vertical state in Gaoyuan 913 because of its smaller leaf area and larger width. Photosynthetic pigments were different among the 4 varieties, and positively correlated with intrinsic PS II photochemistry efficiencies (Fv/Fm). In clear days, especially at noon, the photosynthetic photoinhibition was more serious in abaxial surface of flag leaf due to directly facing the solar radiation, but it could recover after reduction of sunlight intensity in the afternoon, which meant that no inactive damage happened in PS II reaction centers. There were significant differences of PS II actual and maximum photochemical efficiencies at the actinic light intensity (ΦPS II and Fv'/Fm') between abaxial and adaxial surface, and their relative variation trends were on the contrary. The photochemical and non-photochemical quenching coefficients (qP and NPQ) had a similar tendency in both abaxial and adaxial surfaces. Although ΦPS II and qP were lower in adaxial surface of flag leaf, the Fv'/Fm' was significantly higher, which indicated that the potential PS II capture efficiency of excited energy was higher. The results demonstrated that process of photochemical and non-photochemical quenching could effectively dissipate excited energy caused by strong solar radiation, and there were higher adaptation capacities in wheat varieties natively cultivated in Qinghai-Tibetan Plateau area.
Emerging wildlife diseases pose a significant threat to natural and human systems. Because of real or perceived risks of delayed actions, disease management strategies such as culling are often implemented before thorough scientific knowledge of disease dynamics is available. Adaptive management is a valuable approach in addressing the uncertainty and complexity associated with wildlife disease problems and can be facilitated by using a formal model.
We developed a multi-state computer simulation model using age, sex, infection-stage, and seasonality as a tool for scientific learning and managing chronic wasting disease (CWD) in white-tailed deer Odocoileus virginianus. Our matrix model used disease transmission parameters based on data collected through disease management activities. We used this model to evaluate management issues on density- (DD) and frequency-dependent (FD) transmission, time since disease introduction, and deer culling on the demographics, epizootiology, and management of CWD.
Both DD and FD models fit the Wisconsin data for a harvested white-tailed deer population, but FD was slightly better. Time since disease introduction was estimated as 36 (95% CI, 24–50) and 188 (41–>200) years for DD and FD transmission, respectively. Deer harvest using intermediate to high non-selective rates can be used to reduce uncertainty between DD and FD transmission and improve our prediction of long-term epidemic patterns and host population impacts. A higher harvest rate allows earlier detection of these differences, but substantially reduces deer abundance.
Results showed that CWD has spread slowly within Wisconsin deer populations, and therefore, epidemics and disease management are expected to last for decades. Non-hunted deer populations can develop and sustain a high level of infection, generating a substantial risk of disease spread. In contrast, CWD prevalence remains lower in hunted deer populations, but at a higher prevalence the disease competes with recreational hunting to reduce deer abundance.
Synthesis and applications. Uncertainty about density- or frequency-dependent transmission hinders predictions about the long-term impacts of chronic wasting disease on cervid populations and the development of appropriate management strategies. An adaptive management strategy using computer modelling coupled with experimental management and monitoring can be used to test model predictions, identify the likely mode of disease transmission, and evaluate the risks of alternative management responses.
Three light intensities (100% , 56.2%, and 12.5%) were installed to simulate the light regimes of opening field (cutting blank), forest gap, and understory, respectively, aimed to understand the effects of different light regimes on the seedling growth, photosynthetic characteristics, and biomass accumulation and allocation of alien species Alnus formosana and native species A. cremastogyne. Low light regime limited the seedling growth of the two alder species, while the light regime of forest gap was more favorable for the growth, in comparison with that of the opening field. Regardless of the light regimes, A. formosana seedlings had higher specific leaf area (SLA), relative growth rate (RGR) , leaf area, leaf length, leaf width, plant height, and basal diameter, but smaller leaf number, leaf area ratio (LAR), and petiole length. Under low light regime, A. formosana seedlings had higher maximum net photosynthetic rate (Pn max), light saturation point (LSP), and apparent quantum yield (AQY), but smaller light compensation point (LCP) and dark respiration rate (Rday). With the decrease of light intensity, A. formosana seedlings had much higher root mass ratio (RMR) and much lower leaf mass ratio (LMR), implying that more carbon was allocated and stored to the roots rather than new leaves, whereas the A. cremastogyne seedlings were in adverse, i.e. , more carbon was allocated to the above-ground parts, which might increase the risk of animal feeding and mechanical damage.
Anthrax is endemic throughout Africa, causing considerable livestock and wildlife losses and severe, sometimes fatal, infection in humans. Predicting the risk of infection is therefore important for public health, wildlife conservation and livestock economies. However, because of the intermittent and variable nature of anthrax outbreaks, associated environmental and climatic conditions, and diversity of species affected, the ecology of this multihost pathogen is poorly understood.We explored records of anthrax from the Serengeti ecosystem in north-west Tanzania where the disease has been documented in humans, domestic animals and a range of wildlife. Using spatial and temporal case-detection and seroprevalence data from wild and domestic animals, we investigated spatial, environmental, climatic and species-specific associations in exposure and disease.Anthrax was detected annually in numerous species, but large outbreaks were spatially localized, mostly affecting a few focal herbivores.Soil alkalinity and cumulative weather extremes were identified as useful spatial and temporal predictors of exposure and infection risk, and for triggering the onset of large outbreaks.Interacting ecological and behavioural factors, specifically functional groups and spatiotemporal overlap, helped to explain the variable patterns of infection and exposure among species.Synthesis and applications. Our results shed light on ecological drivers of anthrax infection and suggest that soil alkalinity and prolonged droughts or rains are useful predictors of disease occurrence that could guide risk-based surveillance. These insights should inform strategies for managing anthrax including prophylactic livestock vaccination, timing of public health warnings and antibiotic provision in high-risk areas. However, this research highlights the need for greater surveillance (environmental, serological and case-detection-orientated) to determine the mechanisms underlying anthrax dynamics.
Environmental risk assessment of contaminants is conventionally based on toxic effects assessed in organism-level test systems. We suggest that, for the prediction of toxicant effects, population- and community-level effects should be considered. The aim of this study was to investigate how predation could alter a prey population's response to a toxicant to reveal effects at population and community levels.Populations of the brine shrimp Artemia sp. were maintained in the laboratory with and without simulated predation. Individuals were exposed for 1 h to the pyrethroid insecticide esfenvalerate (0, 0.01, 0.04 and 0.08 microg L(-1)) and subsequently observed for 6 weeks.Unpredated exposed populations showed a reduced population density compared with the control. However, even at the highest concentration of insecticide, populations were sustained until the end of the experiment. The lower density in the exposed populations led to reduced competition and subsequently to enhanced development of surviving individuals and an increased proportion of young individuals. In contrast, the combination of predation and short-term toxicant exposure at concentrations of 0.04 and 0.08 microg L(-1) produced extinction of the populations after 39 and 32 days of exposure, respectively.Synthesis and applications. The response of populations of brine shrimp to toxicants at the community level may be stronger when predation is present than the response of populations without predation pressure, as the regulation capacity of the population (measured as an increased production of offspring at reduced population densities) is exhausted when predation is present. Future ecotoxicological risk assessment schemes should consider relevant community characteristics such as predation as part of an environmental risk assessment.
Carabids and other epigeal arthropods make important contributions to biodiversity, food webs and biocontrol of invertebrate pests and weeds. Pitfall trapping is widely used for sampling carabid populations, but this technique yields biased estimates of abundance (‘activity-density’) because individual activity – which is affected by climatic factors – affects the rate of catch. To date, the impact of temperature on pitfall catches, while suspected to be large, has not been quantified, and no method is available to account for it. This lack of knowledge and the unavailability of a method for bias correction affect the confidence that can be placed on results of ecological field studies based on pitfall data.
Here, we develop a simple model for the effect of temperature, assuming a constant proportional change in the rate of catch per °C change in temperature, r, consistent with an exponential Q10 response to temperature. We fit this model to 38 time series of pitfall catches and accompanying temperature records from the literature, using first differences and other detrending methods to account for seasonality. We use meta-analysis to assess consistency of the estimated parameter r among studies.
The mean rate of increase in total catch across data sets was 0·0863 ± 0·0058 per °C of maximum temperature and 0·0497 ± 0·0107 per °C of minimum temperature. Multiple regression analyses of 19 data sets showed that temperature is the key climatic variable affecting total catch. Relationships between temperature and catch were also identified at species level. Correction for temperature bias had substantial effects on seasonal trends of carabid catches.
Synthesis and Applications. The effect of temperature on pitfall catches is shown here to be substantial and worthy of consideration when interpreting results of pitfall trapping. The exponential model can be used both for effect estimation and for bias correction of observed data. Correcting for temperature-related trapping bias is straightforward and enables population estimates to be more comparable. It may thus improve data interpretation in ecological, conservation and monitoring studies, and assist in better management and conservation of habitats and ecosystem services. Nevertheless, field ecologists should remain vigilant for other sources of bias.
Vegetation coverage is an important parameter in terrestrial ecological process, meteorological, and climatic models. By eliminating the errors from the precision of image classification and the noises of remote sensing images, and by using the actual data from fieldwork, this paper determined the maximum and minimum values of normalized difference vegetation index (NDVI), improved the sub-pixel model, and verified this model by calculating the vegetation coverage of Beijing. The results showed that the estimation value of the improved model was very close to the measurements, especially for the herbaceous plants whose vegetation types were the same but the densities were different. However, the estimation error of arborous vegetation coverage was relatively large, probably due to the effects of remote sensing image resolution, vegetation fragmentation, and mixed pixel model.
Parents determine habitat selection for precocial young by leading their young to foraging areas until the chicks attain full independence. There are potential benefits and costs to reproductive success associated with changing habitats while caring for young. This study investigated the relationship between different types of habitats and their quality on chick survival and brood movements of a declining upland shorebird, the mountain plover Charadrius montanus.
From 2004 to 2006, a total of 153 mountain plover broods were monitored on the primary breeding habitats in eastern Colorado, USA; two shortgrass prairie habitats that were either occupied or unoccupied by black-tailed prairie dogs Cynomys ludovicianus and agricultural lands. Habitat quality hypotheses were tested using newly developed statistical applications to estimate survival of chicks and brood movement patterns.
Chick survival and brood movements were influenced by habitat. Chick survival over the 30-day brood-rearing period was substantially higher on nesting habitat of shortgrass occupied by prairie dogs compared with agricultural land and shortgrass unoccupied by prairie dogs. The rate of brood movement away from shortgrass with prairie dogs was lower than shortgrass without prairie dogs, but higher than agricultural lands for each year of the study.
This study suggests that complex processes influence how different habitats affect brood-rearing activity of mountain plovers. Even though broods moved off nesting habitat of shortgrass occupied by prairie dogs, this habitat had the highest survival rate and is highly important to mountain plover reproductive success.
Synthesis and applications. In order to develop effective conservation strategies, the provision of adequate breeding habitat should include information on patterns of habitat selection for all stages of the breeding cycle, including the nesting and dependent young periods. From a conservation perspective, understanding the habitat use of young birds is critical when population dynamics show great sensitivity to survival of young. Previous studies on mountain plovers have suggested that nest success is similar among shortgrass prairie habitats and agricultural lands. Thus, conservation measures that increase nest success may be ineffective for mountain plovers unless they are accompanied by measures promoting chick survival.
1. Flying foxes Pteropus spp. play a key role in forest regeneration as seed dispersers and are also the reservoir of many viruses, including Nipah virus in Bangladesh. Little is known about their habitat requirements, particularly in South Asia. Identifying Pteropus habitat preferences could assist in understanding the risk of zoonotic disease transmission broadly, and in Bangladesh, could help explain the spatial distribution of human Nipah virus cases. 2. We analysed characteristics of Pteropus giganteus roosts and constructed an ecological niche model to identify suitable habitat in Bangladesh. We also assessed the distribution of suitable habitat in relation to the location of human Nipah virus cases. 3. Compared to non-roost trees, P. giganteus roost trees are taller with larger diameters, and are more frequently canopy trees. Colony size was larger in densely forested regions and smaller in flood-affected areas. Roosts were located in areas with lower annual precipitation and higher human population density than non-roost sites. 4. We predicted that 2-17% of Bangladesh's land area is suitable roosting habitat. Nipah virus outbreak villages were 2.6 times more likely to be located in areas predicted as highly suitable habitat for P. giganteus compared to non-outbreak villages. 5. Synthesis and applications. Habitat suitability modelling may help identify previously undocumented Nipah outbreak locations and improve our understanding of Nipah virus ecology by highlighting regions where there is suitable bat habitat but no reported human Nipah virus. Conservation and public health education is a key component of P. giganteus management in Bangladesh due to the general misunderstanding and fear of bats that are a reservoir of Nipah virus. Affiliation between Old World fruit bats (Pteropodidae) and people is common throughout their range, and in order to conserve these keystone bat species and prevent emergence of zoonotic viruses, it is imperative that we continue to improve our understanding of Pteropus resource requirements and routes of virus transmission from bats to people. Results presented here can be utilized to develop land management strategies and conservation policies that simultaneously protect fruit bats and public health.
1. Environmental variables are often used as indirect surrogates for mapping biodiversity because species survey data are scant at regional scales, especially in the marine realm. However, environmental variables are measured on arbitrary scales unlikely to have simple, direct relationships with biological patterns. Instead, biodiversity may respond nonlinearly and to interactions between environmental variables.
2. To investigate the role of the environment in driving patterns of biodiversity composition in large marine regions, we collated multiple biological survey and environmental data sets from tropical NE Australia, the deep Gulf of Mexico and the temperate Gulf of Maine. We then quantified the shape and magnitude of multispecies responses along >30 environmental gradients and the extent to which these variables predicted regional distributions. To do this, we applied a new statistical approach, Gradient Forest, an extension of Random Forest, capable of modelling nonlinear and threshold responses.
3. The regional-scale environmental variables predicted an average of 13–35% (up to 50–85% for individual species) of the variation in species abundance distributions. Important predictors differed among regions and biota and included depth, salinity, temperature, sediment composition and current stress. The shapes of responses along gradients also differed and were nonlinear, often with thresholds indicative of step changes in composition. These differing regional responses were partly due to differing environmental indicators of bioregional boundaries and, given the results to date, may indicate limited scope for extrapolating bio-physical relationships beyond the region of source data sets.
Synthesis and applications. Gradient Forest offers a new capability for exploring relationships between biodiversity and environmental gradients, generating new information on multispecies responses at a detail not available previously. Importantly, given the scarcity of data, Gradient Forest enables the combined use of information from disparate data sets. The gradient response curves provide biologically informed transformations of environmental layers to predict and map expected patterns of biodiversity composition that represent sampled composition better than uninformed variables. The approach can be applied to support marine spatial planning and management and has similar applicability in terrestrial realms.
Gradient Forest offers a new capability for exploring relationships between biodiversity and environmental gradients, generating new information on multispecies responses at a detail not available previously. Importantly, given the scarcity of data, Gradient Forest enables the combined use of information from disparate data sets. The gradient response curves provide biologically informed transformations of environmental layers to predict and map expected patterns of biodiversity composition that represent sampled composition better than uninformed variables. The approach can be applied to support marine spatial planning and management and has similar applicability in terrestrial realms.
1. One approach to biodiversity conservation is to set aside small woodland key habitats (WKHs) in intensively managed landscapes. The aim is to support species, such as epiphytes, which often depend on old trees and are negatively affected by intensive forestry. However, it is not known whether the number of host trees within these areas can sustain species in the long term.
2. We studied metapopulation dynamics and assessed the future persistence of epiphytes assuming host tree numbers similar to those observed in large north European WKHs. The study species were seven cyanolichens confined to Populus tremula in the boreal study area. Colonizations and extinctions were recorded in 2008 on trees that had been surveyed 13 years earlier. We applied generalized (non)linear models to test the importance of environmental conditions, facilitation and spatial connectivity on the metapopulation dynamics. We also simulated the effects of tree numbers and tree fall rates on future species persistence.
3. Metapopulation dynamics were explained by tree quality, size or tree fall. In one species, colonizations increased with increasing connectivity, and in a second species it increased if other lichens sharing the photobiont with the focal species were present, suggesting facilitation. Both stochastic extinctions from standing trees and deterministic extinctions caused by tree fall should be accounted for in projecting epiphyte metapopulation dynamics.
4. One to three infrequent, sexually dispersed study species face a significant extinction risk within 50 years, especially in areas with low tree numbers.
5. Synthesis and applications. During the coming decades, infrequent, sexually dispersed, epiphytic lichens are likely to be lost from small woodland habitat set asides in intensively managed landscapes. Local extinction will be a consequence of low colonization rates and tree fall. Low colonization rates can be prevented by retaining large trees on which lichen species colonization rates are the highest and by assuring a high density of occupied trees. The negative effect of tree fall should be compensated for by assuring continuous availability of old trees. This can be achieved by decreasing the populations of large browsers, or by retaining trees with high conservation value during management operations.
1. Forest reserves are established to preserve biodiversity, and to maintain natural functions and processes. Today there is heightened focus on old-growth stages, with less attention given to early successional stages. The biodiversity potential of younger forests has been overlooked, and the cost-effectiveness of incorporating different age classes in reserve networks has not yet been studied.
2. We performed a reserve selection analysis in boreal Sweden using the Swedish National Forest Inventory plots. Seventeen structural variables were used as biodiversity indicators, and the cost of protecting each plot as a reserve was assessed using the Heureka system. A goal programming approach was applied, which allowed inclusion of several objectives and avoided a situation in which common indicators affected the result more than rare ones. The model was limited either by budget or area.
3. All biodiversity indicators were found in all age classes, with more than half having the highest values in ages ≥ 100 years. Several large-tree indicators and all deadwood indicators had higher values in forests 0–14 years than in forests 15–69 years.
4. It was most cost-effective to protect a large proportion of young forests since they generally have a lower net present value compared to older forests, but still contain structures of importance for biodiversity. However, it was more area-effective to protect a large proportion of old forests since they have a higher biodiversity potential per area.
5. The geographical distribution of reserves selected with the budget-constrained model was strongly biassed towards the north-western section of boreal Sweden, with a large proportion of young forest, whereas the area-constrained model focussed on the south-eastern section, with dominance by the oldest age class.
Synthesis and applications. We show that young forests with large amounts of structures important to biodiversity such as dead wood and remnant trees are cheap and cost-efficient to protect. This suggests that reserve networks should incorporate sites with high habitat quality of different forest ages. Since young forests are generally neglected in conservation, our approach is of interest also to other forest biomes where biodiversity is adapted to disturbance regimes resulting in open, early successional stages.
Compared to bioclimatic variables, remote sensing predictors are rarely used for predictive species modelling. When used, the predictors represent typically habitat classifications or filters rather than gradual spectral, surface or biophysical properties. Consequently, the full potential of remotely sensed predictors for modelling the spatial distribution of species remains unexplored. Here we analysed the partial contributions of remotely sensed and climatic predictor sets to explain and predict the distribution of 19 tree species in Utah. We also tested how these partial contributions were related to characteristics such as successional types or species traits.
We developed two spatial predictor sets of remotely sensed and topo-climatic variables to explain the distribution of tree species. We used variation partitioning techniques applied to generalized linear models to explore the combined and partial predictive powers of the two predictor sets. Non-parametric tests were used to explore the relationships between the partial model contributions of both predictor sets and species characteristics.
More than 60% of the variation explained by the models represented contributions by one of the two partial predictor sets alone, with topo-climatic variables outperforming the remotely sensed predictors. However, the partial models derived from only remotely sensed predictors still provided high model accuracies, indicating a significant correlation between climate and remote sensing variables. The overall accuracy of the models was high, but small sample sizes had a strong effect on cross-validated accuracies for rare species.
Models of early successional and broadleaf species benefited significantly more from adding remotely sensed predictors than did late seral and needleleaf species. The core-satellite species types differed significantly with respect to overall model accuracies. Models of satellite and urban species, both with low prevalence, benefited more from use of remotely sensed predictors than did the more frequent core species.
Synthesis and applications. If carefully prepared, remotely sensed variables are useful additional predictors for the spatial distribution of trees. Major improvements resulted for deciduous, early successional, satellite and rare species. The ability to improve model accuracy for species having markedly different life history strategies is a crucial step for assessing effects of global change.
1. In farmland biodiversity, a potential risk to the larvae of non-target Lepidoptera from genetically modified (GM) Bt-maize expressing insecticidal Cry1 proteins is the ingestion of harmful amounts of pollen deposited on their host plants. A previous mathematical model of exposure quantified this risk for Cry1Ab protein. We extend this model to quantify the risk for sensitive species exposed to pollen containing Cry1F protein from maize event 1507 and to provide recommendations for management to mitigate this risk.
1. Businesses have an unrivalled ability to mobilize human, physical and financial capital, often manage large land holdings, and draw on resources and supply products that impact a wide array of ecosystems. Businesses therefore have the potential to make a substantial contribution to arresting declines in biodiversity and ecosystem services. To realize this potential, businesses require support from researchers in applied ecology to inform how they measure and manage their impacts on, and opportunities presented to them by, biodiversity and ecosystem services.
Managing wildlife populations for conservation, control or harvesting involves uncertainty. Nevertheless, decisions need to be made based on the available evidence. The two main sources of uncertainty in population modelling are parameter estimates and structural uncertainty. Structural uncertainty in models is not included as often as parameter uncertainty.
We present an approach where parameter and structural uncertainty (strength of density dependence) is included within a model, using the over-wintering English population of cormorants Phalacrocorax carbo L. Because of the damage caused to inland fishery interests by cormorants, there was a change in UK government policy in autumn 2004, increasing the numbers of birds that can be shot under licence.
A stochastic Monte Carlo annual population model was produced to examine the effect of changes to the numbers of birds shot each year. Indices of annual population size were converted to population estimates and used to determine annual growth rates and strength of density dependence.
There is strong evidence for density dependence in the data, which suggests the population is currently slightly above carrying capacity, with a mean growth rate of 4–6% per annum. The 1300 birds shot under licence in 2004/05 represent about 4·5% of the English population, and if this level of culling continues, the population would be expected to decline by 9% by 2007, compared to the long-term average. The a priori preferred model, which included all uncertainty, gave predictions for 2004/05 and 2005/06 in close agreement with field data.
The model was used to produce short-term population projections, with the understanding that Adaptive Resource Management (ARM) will be adopted to iteratively update the parameters and model each year, feeding back into the numbers of available licences.
Synthesis and applications. We recommend the approach used in this study of including parameter and structural uncertainty within a single model, where possible, with the proportion of iterations that utilize a particular structure dependent on the weight of evidence for that structure. This will produce results with wider confidence intervals, but ensures that the evidence for any particular model is not over-interpreted.
1. Wildlife managers often rely on resource users, such as recreational or commercial hunters, to achieve management goals. The use of hunters to control wildlife populations is especially common for predators and ungulates, but managers cannot assume that hunters will always fill annual quotas set by the authorities. It has been advocated that resource management models should account for uncertainty in how harvest rules are realized, requiring that this implementation uncertainty be estimated.
1. Prevention of Chagas disease is mainly dependent on control of the insect vectors that transmit infection. Unfortunately, this control is not wholly successful and the vectors have been resurgent in some areas. Where re-infestation has occurred, it is important to understand the dynamics of the process. We investigated how a metapopulation framework can elucidate key aspects of re-infestation and thereby contribute to more efficient disease control.2.Triatoma infestans, the main vector of Chagas disease, re-infested sites in three villages in north-west Argentina after community-wide insecticide spraying in October 1992. Ten surveys were carried out at 6-monthly intervals from November 1994 to May 1999.3. Comparisons were made of different methods of estimating the sources of dispersal and the number of sites in which bug infestations became established.4. The results indicated that (i) the number of dispersing Triatoma infestans from a given site was proportional to the number of bugs found at the site; (ii) there was a 6-month time lag between detection of a new infestation and dispersal events; (iii) the relationship between infestations and new establishments varied by season.5. Three of 156 sites at which bugs were found were estimated to be the source of more than 50% of establishment events. These three sites were the only ones with large, persistent bug populations.6.Synthesis and applications. To reduce the risk of human Chagas disease, identifying those few sites infested with large, persistent bug populations and targeting control measures at those sites should greatly improve the efficiency of vector control. The appropriate seasonal timing of vector control could also greatly increase its efficiency. Specific recommendations for the timing of insecticide spraying require further research to establish how the observed temporal pattern of bug establishment is associated with the seasonality of bug dispersal.
1. Vegetated biogeomorphic systems (e.g. mangroves, salt marshes, dunes, riparian vegetation) have been intensively studied for the impact of the biota on sediment transport processes and the resulting self-organization of such landscapes. However, there is a lack of understanding of physical disturbance mechanisms that limit primary colonization in active sedimentary environments.2. This study elucidates the effect of sediment disturbance during the seedling stage of pioneer vegetation, using mangroves as a model system. We performed mesocosm experiments that mimicked sediment disturbance as (i) accretion/burial of plants and (ii) erosion/excavation of plants of different magnitudes and temporal distribution in combination with water movement and inundation stress.3. Cumulative sediment disturbance reduced seedling survival, with the faster-growing Avicennia alba showing less mortality than the slower-growing Sonneratia alba. The presence of the additional stressors (inundation and water movement) predominantly reduced the survival of S. alba.4. Non-lethal accretion treatments increased shoot biomass of the seedlings, whereas non-lethal erosion treatments increased root biomass allocation. This morphological plasticity in combination with the abiotic disturbance history determined how much maximum erosion the seedlings were able to withstand.5.
Synthesis and applications. Seedling survival in dynamic sedimentary environments is determined by the frequency and magnitude of sediment accretion or erosion events, with non-lethal events causing feedbacks to seedling stability. Managers attempting restoration of mangroves, salt marshes, dunes and riparian vegetation should recognize sediment dynamics as a main bottleneck to primary colonization. The temporal distribution of erosion and accretion events has to be evaluated against the ability of the seedlings to outgrow or adjust to disturbances. Our results suggest that selecting fast-growing pioneer species and measures to enhance seedling growth or temporary reduction in sediment dynamics at the restoration site can aid restoration success for vegetated biogeomorphic ecosystems.
1. Much concern has been expressed about the ecological consequences of night-time light pollution. This concern is most often focused on the encroachment of artificial light into previously unlit areas of the night-time environment, but changes in the spectral composition, duration and spatial pattern of light are also recognized as having ecological effects.
2. Here, we examine the potential consequences for organisms of five management options to reduce night-time light pollution. These are to (i) prevent areas from being artificially lit; (ii) limit the duration of lighting; (iii) reduce the ‘trespass’ of lighting into areas that are not intended to be lit (including the night sky); (iv) change the intensity of lighting; and (v) change the spectral composition of lighting.
3. Maintaining and increasing natural unlit areas is likely to be the most effective option for reducing the ecological effects of lighting. However, this will often conflict with other social and economic objectives. Decreasing the duration of lighting will reduce energy costs and carbon emissions, but is unlikely to alleviate many impacts on nocturnal and crepuscular animals, as peak times of demand for lighting frequently coincide with those in the activities of these species. Reducing the trespass of lighting will maintain heterogeneity even in otherwise well-lit areas, providing dark refuges that mobile animals can exploit. Decreasing the intensity of lighting will reduce energy consumption and limit both skyglow and the area impacted by high-intensity direct light. Shifts towards ‘whiter’ light are likely to increase the potential range of environmental impacts as light is emitted across a broader range of wavelengths.
Synthesis and applications. The artificial lightscape will change considerably over coming decades with the drive for more cost-effective low-carbon street lighting solutions and growth in the artificially lit area. Developing lighting strategies that minimize adverse ecological impacts while balancing the often conflicting requirements of light for human utility, comfort and safety, aesthetic concerns, energy consumption and carbon emission reduction constitute significant future challenges. However, as both lighting technology and understanding of its ecological effects develop, there is potential to identify adaptive solutions that resolve these conflicts.
The Millennium Ecosystem Assessment has stimulated
much interest in the linkages between the state of ecosystems
and human well-being, and resulted in a number of
international and national initiatives. For example, the
UK National Ecosystem Assessment (UKNEA) is being
widely discussed in research and land use policy communities,
and has already influenced domestic policy (UK
National Ecosystem Assessment 2011). The philosophy of
ecosystem services is thought by many ecologists to be a
good thing, leading to an expectation that their preferred
landscapes or habitats will be conserved and that new
resources will emerge to underpin and secure wider environmental
benefits. Others are interested in particular
markets that might develop the opportunities for new
business enterprises and the new funding that might make
land management more profitable.
Our practitioners’ view stems from involvement in British
forestry and in particular in the application of ecological
research to the policy, planning and management of
woodlands and forests. In the practitioner world, we
inhabit, a common question is:
How does the framework of ecosystem services compare
with the prevailing one of sustainable forest management?
Or, more prosaically, as a senior forest manager
recently put it: What the heck is it all about?
We reflect on the common ground and consider possible
consequences for forestry and sustainable forest management
of incorporating an ecosystem services approach.
Our first perspective is that there is confusion around
terminology and concepts. Many discussants appear to
miss the subtle differences and use concepts from ecosystem
services framework, an ecosystem approach, and sustainable
forest management seamlessly and interchangeably. As
a basis for our perspective, we start, therefore, with brief
definitions. The ecosystem approach is considered to be ‘a
strategy for the integrated management of land, water and
living resources that promotes conservation and sustainable
use in an equitable way’ (Secretariat of the Convention on
Biological Diversity (CBD) 2004). The Ministerial Conference
on the Protection of Forests in Europe (MCPFE)
adopted a definition for sustainable forest management as
‘The stewardship and use of forests and forest lands in a way,
and at a rate, that maintains their biodiversity, productivity,
regeneration capacity, vitality, and their potential to fulfil,
now and in the future, relevant ecological, economic and
social functions, at local, national and global levels, and that
does not cause damage to other ecosystems’ (Helsinki Ministerial
Conference 1993). The UKNEA suggested that ‘Ecosystem
services are the benefits provided by ecosystems that
contribute to making human life possible and worth living’
and that ‘The adoption of an ecosystems approach yields a
requirement for an evidence base on ecosystem change and
ecosystem service provision to inform decision-making’. Furthermore,
the UKNEA sees change in ecosystems as a
result of direct and indirect drivers and that, by understanding
the important contribution to human well-being, a variety
of societal responses may be adopted which lead to
further change and possible improvements in ecosystems
and their services. It is this operationalising of ecosystem
services through the establishment of values and identification
of societal responses which we consider as the ecosystem
services framework. As a basis for our perspective, we
now summarise sustainable forest management, making
selective observations using the language of ecosystem
The health of managed and wild honeybee colonies appears to have declined substantially in Europe and the United States over the last decade. Sustainability of honeybee colonies is important not only for honey production, but also for pollination of crops and wild plants alongside other insect pollinators. A combination of causal factors, including parasites, pathogens, land use changes and pesticide usage, are cited as responsible for the increased colony mortality.
However, despite detailed knowledge of the behaviour of honeybees and their colonies, there are no suitable tools to explore the resilience mechanisms of this complex system under stress. Empirically testing all combinations of stressors in a systematic fashion is not feasible. We therefore suggest a cross-level systems approach, based on mechanistic modelling, to investigate the impacts of (and interactions between) colony and land management.
We review existing honeybee models that are relevant to examining the effects of different stressors on colony growth and survival. Most of these models describe honeybee colony dynamics, foraging behaviour or honeybee – varroa mite – virus interactions.
We found that many, but not all, processes within honeybee colonies, epidemiology and foraging are well understood and described in the models, but there is no model that couples in-hive dynamics and pathology with foraging dynamics in realistic landscapes.
Synthesis and applications. We describe how a new integrated model could be built to simulate multifactorial impacts on the honeybee colony system, using building blocks from the reviewed models. The development of such a tool would not only highlight empirical research priorities but also provide an important forecasting tool for policy makers and beekeepers, and we list examples of relevant applications to bee disease and landscape management decisions.
Rats have reached about 80% of the world's islands and are among the most successful invasive mammals. Rats are opportunistic predators that are notorious for their impact on a variety of animal and plant species. However, little documented evidence on the complexities of these interactions is available.In our study, we assessed the impact of black rats Rattus rattus introduced on a small uninhabited island with a relatively simple ecosystem, Surprise Island, New Caledonia. We also compared the diet of R. rattus in the presence and absence of breeding seabirds, assessing the dietary compensation for this potentially important food source. From 2002 to 2005, we used live trapping studies combined with stable isotope analysis and conventional diet analyses (direct observations, gut and faecal contents) to characterize the diet of rats.Our results suggest a heavy predatory impact on seabirds, which could constitute as much as 24% of the rat diet. Moreover, in the absence of birds, rats compensated marginally by preying more heavily on other components of their diet but mostly acquired a new resource. They shifted their diet by preying heavily upon another endangered species, the hatchlings of sea turtles Chelonia mydas, which could constitute the main resource in the diet of R. rattus in those periods. Abundance, body condition and distribution of the rats were consistent with heavy predation upon this additional resource.Synthesis and applications. In island ecosystems invasive rats prey mainly upon seabird eggs and chicks, thereby threatening their populations. Although rats are certainly capable of surviving on terrestrial foods outside the seabird nesting season, their ability to prey upon ephemeral but abundant resources, such as hatchling sea turtles, may contribute to maintaining their populations. This may explain their success on Surprise Island, an ecosystem of extreme conditions, and suggests that biologists and managers working with threatened species should be aware of the possibility of temporary diet shifts by introduced rodents that may cause unexpected heavy predation on these species. This dietary shift from one endangered taxa to another has major implications for the conservation of seabirds and sea turtles world-wide and more generally for the biodiversity of invaded insular communities.
Control of animal-born diseases is a major challenge faced by applied ecologists and public health managers. To improve cost-effectiveness, the effort required to control such pathogens needs to be predicted as accurately as possible. In this context, we reviewed the anti-rabies vaccination schemes applied around the world during the past 25 years.
We contrasted predictions from classic approaches based on theoretical population ecology (which governs rabies control to date) with a newly developed individual-based model. Our spatially explicit approach allowed for the reproduction of pattern formation emerging from a pathogen's spread through its host population.
We suggest that a much lower management effort could eliminate the disease than that currently in operation. This is supported by empirical evidence from historic field data. Adapting control measures to the new prediction would save one-third of resources in future control programmes.
The reason for the lower prediction is the spatial structure formed by spreading infections in spatially arranged host populations. It is not the result of technical differences between models.
Synthesis and applications. For diseases predominantly transmitted by neighbourhood interaction, our findings suggest that the emergence of spatial structures facilitates eradication. This may have substantial implications for the cost-effectiveness of existing disease management schemes, and suggests that when planning management strategies consideration must be given to methods that reflect the spatial nature of the pathogen–host system.
Knowledge of infection reservoir dynamics is critical for effective disease control, but identifying reservoirs of multi-host pathogens is challenging. Here, we synthesize several lines of evidence to investigate rabies reservoirs in complex carnivore communities of the Serengeti ecological region in northwest Tanzania, where the disease has been confirmed in 12 carnivore species.Long-term monitoring data suggest that rabies persists in high-density domestic dog Canis familiaris populations (> 11 dogs km(-2)) and occurs less frequently in lower-density (< 5 dogs km(-2)) populations and only sporadically in wild carnivores.Genetic data show that a single rabies virus variant belonging to the group of southern Africa canid-associated viruses (Africa 1b) circulates among a range of species, with no evidence of species-specific virus-host associations.Within-species transmission was more frequently inferred from high-resolution epidemiological data than between-species transmission. Incidence patterns indicate that spill-over of rabies from domestic dog populations sometimes initiates short-lived chains of transmission in other carnivores.Synthesis and applications. The balance of evidence suggests that the reservoir of rabies in the Serengeti ecosystem is a complex multi-host community where domestic dogs are the only population essential for persistence, although other carnivores contribute to the reservoir as non-maintenance populations. Control programmes that target domestic dog populations should therefore have the greatest impact on reducing the risk of infection in all other species including humans, livestock and endangered wildlife populations, but transmission in other species may increase the level of vaccination coverage in domestic dog populations necessary to eliminate rabies.
1. Planning for conservation success requires identifying effective and efficient monitoring strategies but multiple types of uncertainty affect the accuracy and precision of wildlife abundance estimates. Observation uncertainty, a consequence of sampling effort and design as well as the process of observation, is still understudied, with little attention given to the multiple potential sources of error involved. To establish error minimization priorities and maximize monitoring efficiency, the direction and magnitude of multiple sources of uncertainty must be considered.
2. Using monitoring of two contrasting ungulate species in the Serengeti ecosystem as a case study, we developed a ‘virtual ecologist’ framework within which we carried out simulated tests of different monitoring strategies for different types of species. We investigated which components of monitoring should be prioritized to increase survey accuracy and precision and explored the robustness of population estimates under different budgetary scenarios.
3. The relative importance of each process affecting precision and accuracy varied according to the survey technique and biological characteristics of the species. While survey precision was mainly affected by population characteristics and sampling effort, the accuracy of the survey was greatly affected by observer effects, such as juvenile and herd detectability.
Synthesis and applications. Monitoring efficiency is of the utmost importance for conservation, especially in the context of limited budgets and other priorities. We provide insights into the likely effect of different types of observation and process error on population estimates for savanna ungulates, and more generally present a framework for evaluating monitoring programmes in a virtual environment. In highly aggregated species, the main focus should be on survey precision; sampling effort should be defined according to wildlife spatial distribution. For random or slightly aggregated species, accuracy is the key factor; this is most sensitive to observer effects which should be minimized by training and calibration by observer.
This study shows how data from very different disciplines can be combined to address questions relevant to contemporary conservation and understanding. This novel, interdisciplinary approach provides new insights into the role of economic factors as a driver of biodiversity loss in the uplands. Biodiversity levels have varied considerably over 400 years, partly as a function of land management, suggesting that establishing baselines or "natural" target levels for biodiversity is likely to be problematic. Changes in livestock grazing pressures brought about by changes in prices had statistically significant effects on estimated plant diversity, as did land abandonment. This suggests that longterm management of upland areas for the conservation of diversity should focus on grazing pressures as a key policy attribute. Another policy implication is that drastic cuts in grazing pressures - such as might occur under current reforms of the Common Agricultural Policy - can have adverse biodiversity con sequences.
Summary • Toxicant-resistance is a potential, or very real, problem with many pest-control programmes world-wide. However, apart from rodents, pesticide-resistance has not been well documented in vertebrates. We assessed the potential impact of developing resistance to 1080 in rabbit populations with differing levels of historical exposure to 1080-baiting programmes in south-western Australia. • The sensitivity to 1080 of three out of the four populations of rabbits Oryctolagus cuniculus examined had decreased significantly since Australian rabbits were last tested over 25 years ago. The lethal dose50 (LD50) values for these populations, as determined from formal toxicity trials, ranged from 0·744 to 1·019 mg pure 1080 kg−1, and were significantly greater (P 50 range 0·34–0·46 mg pure 1080 kg−1). The LD50 value for the fourth population (0·584 mg pure 1080 kg−1), which has had the least exposure to 1080, did not differ from that reported previously (P > 0·05). • The lethal dose99 (LD99) values for the four rabbit populations tested ranged from 1·181 to 1·666 mg pure 1080 kg−1, and suggested that, theoretically, all rabbits should be killed during routine baiting campaigns provided that there is no loss of active ingredient from the bait. In reality, the efficacy of 1080 poison bait laid in trails for controlling free-ranging rabbits was reduced in those populations where rabbits had decreased sensitivity to 1080. Mean reductions in rabbit numbers 7–9 days after trail baiting of resistant and sensitive populations ranged from 51·2% to 65·2%, and from 76·4% to 76·5%, respectively. • These findings suggest that genetic resistance to 1080 is developing in at least some populations of Australian rabbits. This has world-wide implications for agricultural protection and wildlife conservation programmes that rely on a 1080-baiting strategy for reducing the impact of vertebrate pests.
Summary • Hybridization seems possible for many crop species after pollen transfer from crops to wild relatives in the surrounding vegetation. Subsequent introgression of crop-specific traits into wild relatives could lead to invasive introgressants. This process has become a public concern following the introduction of genetically modified (GM) crops. Until now, few studies have used demographic vital rates to compare the performance of hybrids with their wild relatives. • We created second-generation (S1 and BC1) hybrids between the non-transgenic crop Lactuca sativa and its entirely cross-fertile wild relative Lactuca serriola. Seeds of parents and hybrids were individually sown in field plots at three different locations. Next to germination and survival, we measured a range of single fitness components and morphological traits. We also compared observed phenotypes to phenotypes theoretically expected, according to different inheritance scenarios. • Phenotypes of both hybrid classes resembled L. serriola closely, and more than theoretically expected. However, demographic vital rates, i.e. germination and survival of hybrids were much higher than in L. serriola. • Our results indicate that hybrids between crop and wild Lactuca are phenotypically indistinguishable from the wild relative and thus will largely remain unnoticed when they occur. However, these hybrids could potentially become invasive because of substantial differences in vital rates and seeds returned per seed sown. • Synthesis and applications. A comparative study on single fitness components, such as seed production, alone would not have revealed the performance advantage of crop–wild hybrids in Lactuca. Therefore, studying demographic vital rates of hybrids and back-crosses to test for long-term consequences of hybridization should be part of any risk assessment of GM crops. Demographic vital rates are also important for the development of predictive modelling tools that can be employed to test the individual- and population-level consequences of new-to-add traits. Journal of Applied Ecology (2005) doi: 10.1111/j.1365-2664.2005.01086.x
1. Freshwater fish are a potentially important link in the transfer of radionuclides from polluted ecosystems to people. A pulsed contamination event such as the Chernobyl fallout in 1986 is a challenge to the prediction of radioactivity in biota, because activity concentrations of radionuclides can change dynamically among populations during an initial equilibration phase. This was demonstrated from time-series of ¹³⁷caesium (Cs) in fish from three Swedish lakes (1986–2000, eight species, > 7600 individuals). In addition, we used these data to test hypotheses about the influence of fish size and trophic level on the temporal patterns of ¹³⁷Cs.
Summary • Chemical effects on organisms are typically assessed using individual-level endpoints or sometimes population growth rate (PGR), but such measurements are generally made at low population densities. In contrast most natural populations are subject to density dependence and fluctuate around the environmental carrying capacity as a result of individual competition for resources. As ecotoxicology aims to make reliable population projections of chemical impacts in the field, an understanding of how high-density or resource-limited populations respond to environmental chemicals is essential. • Our objective was to determine the joint effects of population density and chemical stress on the life history and PGR of an important ecotoxicological indicator species, Chironomus riparius, under controlled laboratory conditions. Populations were fed the same ration but initiated at different densities and exposed to a solvent control and three concentrations of 14C-cypermethrin in a sediment–water test system for 67 days at 20 ± 1 °C. • Density had a negative effect on all the measured life-history traits, and PGR declined with increasing density in the controls. Exposure to 14C-cypermethrin had a direct negative effect on juvenile survival, presumably within the first 24 h because the chemical rapidly dissipated from the water column. Reductions in the initial larval densities resulted in an increase in the available resources for the survivors. Subsequently, exposed populations emerged sooner and started producing offspring earlier than the controls. 14C-cypermethrin had no effect on estimated fecundity and adult body weight but interacted with density to reduce the time to first emergence and first reproduction. As a result, PGR increased with cypermethrin concentration when populations were initiated at high densities. • Synthesis and applications. The results showed that the effects of 14C-cypermethrin were buffered at high density, so that the joint effects of density and chemical stress on PGR were less than additive. Low levels of chemical stressors may increase carrying capacity by reducing juvenile competition for resources. More and perhaps fitter adults may be produced, similar to the effects of predators and culling; however, toxicant exposure may result in survivors that are less tolerant to changing conditions. If less than additive effects are typical in the field, standard regulatory tests carried out at low density may overestimate the effects of environmental chemicals. Further studies over a wide range of chemical stressors and organisms with contrasting life histories are needed to make general recommendations. Journal of Applied Ecology (2003) 40, 1049–1059
1. Evaluating the effectiveness of stream restoration is often challenging because of the lack of pre-treatment data, narrow focus on physicochemical measures and insufficient post-restoration monitoring. Even when these fundamental elements are present, quantifying restoration success is difficult because of the challenges associated with distinguishing treatment effects from seasonal variation, episodic events and long-term climatic changes.
2. We report results of one of the most comprehensive and continuous records of physical, chemical and biological data available to assess restoration success for a stream ecosystem in North America. Over a 17 year period we measured seasonal and annual changes in metal concentrations, physicochemical characteristics, macroinvertebrate communities, and brown trout Salmo trutta populations in the Arkansas River, a metal-contaminated stream in Colorado, USA.
3. Although we observed significant improvements in water quality after treatment, the effectiveness of restoration varied temporally, spatially and among biological response variables. The fastest recovery was observed at stations where restoration eliminated point sources of metal contamination. Recovery of macroinvertebrates was significantly delayed at some stations because of residual sediment contamination and because extreme seasonal and episodic variation in metal concentrations prevented recolonization by sensitive species.
4. Synthesis and applications. Because recovery trajectories after the removal of a stressor are often complex or nonlinear, long-term studies are necessary to assess restoration success within the context of episodic events and changes in regional climate. The observed variation in recovery among chemical and biological endpoints highlights the importance of developing objective criteria to assess restoration success. Although the rapid response of macroinvertebrates to reduced metal concentrations is encouraging, we have previously demonstrated that benthic communities from the Arkansas River remained susceptible to other novel anthropogenic stressors. We suggest that the resistance or resilience of benthic macroinvertebrate communities to novel stressors may be effective indicators of restoration success that can account for the non-additive (e.g. synergistic) nature of compound perturbations.
SUMMARY1This paper describes the effectiveness of a range of bracken* control and heathland restoration treatments, in factorial combination, on heath development over an 18-year period. Control treatments included cutting once and twice yearly between 1978 and 1996; spraying the herbicide asulam at the recommended rate (4.4kg a.i. ha-1) in two treatments, 1978 and 1978 plus 1979, each followed by repeat doses in 1984 and 1990; and spraying asulam followed by cutting once yearly. Calluna* seeds were added to half the plots to aid heathland establishment. After 6 years the experiment was split and bracken control was continued/re-applied on half the plots and stopped on the remainder. The effects of all treatments on the cover of colonizing species between 1986 and 1996 is described.2Twenty-five species were recorded in the 10 years, but some were present only for a very short time. Initially Calluna establishment was good in some treatments, especially where Calluna seed was added and bracken was controlled; cutting bracken twice yearly was most effective. Other plots developed either a grass heath flora dominated by Agrostis capillaris, Deschampsia flexuosa, Dicranum scoparium, Festuca ovina and Rumex acetosella, or were dominated by either Culamagrostis epigejos or Curex arenaria. Some plots were invaded by Betuln spp.; mortality was high but some survived to overtop the bracken by 1996.3In 1990 and 1991 there was considerable mortality of Rumex acetosella and Calluna, respectively, almost certainly as a direct effect of the weather; these 2 years were the hottest and driest during the experimental period. The grass heath species showed distinct spatial effects during colonization, and tended to have a greater cover where bracken control was continued. Bracken litter was maintained at a low cover where treatment was continued, but increased to near untreated levels within 10 years, except where bracken was cut twice yearly. The cut twice yearly plots started from a lower level, but litter cover was still increasing at the end of the experimental period.4A major influence on the vegetation development was the increasing numbers of rabbits which occurred during the course of the experiment. Rabbits had invaded all treatments by 1996 and increased the amount of bare ground in many treatments. Rabbit activity was greatest where the bracken control was increased.5The original objectives of the restoration scheme ‘to restore a Calluna heathland’ have not been met, as the Calluna died. However, a reasonable Breck grass heath flora developed in many plots, which is a better community from a conservation viewpoint than dense bracken.6The implications for the restoration of heathland on dense bracken communities is discussed and an integrated management approach is suggested.
This paper examines the effectiveness of a range of bracken control and heathland restoration treatments on bracken performance over an 18-year period on a Calluna health in Breckland, UK. Initial treatments were a combination of cutting and spraying with asulam, with and without sowing Calluna seeds. After 6 years a further treatment was added, with the bracken treatments being either continued/reapplied or discontinued.
Seeding with Calluna had no long-term effect on bracken levels recorded under any bracken control treatment.
No treatment eradicated bracken completely, although all achieved some control. Asulam was the most effective treatment in the 2 years after application, but bracken recovered rapidly thereafter. Bracken frond biomass was reduced to c. 6% of untreated levels after 18 years by cutting once yearly, irrespective of whether combined with an initial asulam application or not, but to 3% by cutting twice yearly. Re-applications of asulam produced similar responses to the initial application, with a rapid decrease followed by recovery.
Where bracken control was stopped after 6 years there was an increase in bracken in all treatments compared to where control was continued/reapplied. However, even after 12 years of remission, frond biomass was lower than that of untreated bracken in most treatments. Where cutting was applied twice yearly for 6 years and then allowed to recover for 12 years, the frond biomass was still less than 40% of untreated values.
The response of bracken to asulam was compared to predictions from published models and a reasonable fit was obtained, although the sensitivity of one such model to the efficacy of the initial bracken reduction was noted.
The implications of these results for both long-term bracken control and the monitoring of bracken stocks are discussed.
1. This paper examines the effectiveness of a range of bracken control and heathland restoration treatments on bracken performance over an 18-year period on a Calluna heath in Breckland, UK. Initial treatments were a combination of cutting and spraying with asulam, with and without sowing Calluna seeds. After 6 years a further treatment was added, with the bracken treatments being either continued/reapplied or discontinued. 2. Seeding with Calluna had no long-term effect on bracken levels recorded under any bracken control treatment. 3. No treatment eradicated bracken completely, although all achieved some control. Asulam was the most effective treatment in the 2 years after application, but bracken recovered rapidly thereafter. Bracken frond biomass was reduced to c. 6% of untreated levels after 18 years by cutting once yearly, irrespective of whether combined with an initial asulam application or not, but to 3% by cutting twice yearly. Re-applications of asulam produced similar responses to the initial application, with a rapid decrease followed by recovery, 4. Where bracken control was stopped after 6 years there was an increase in bracken in all treatments compared to where control was continued/reapplied. However, even after 12 years of remission, frond biomass was lower than that of untreated bracken in most treatments. Where cutting was applied twice yearly for 6 years and then allowed to recover for 12 years, the frond biomass was still less than 40% of untreated values. 5. The response of bracken to asulam was compared to predictions from published models and a reasonable fit was obtained, although the sensitivity of one such model to the efficacy of the initial bracken reduction was noted. 6. The implications of these results for both long-term bracken control and the monitoring of bracken stocks are discussed.
1. There has been a surge of interest in the effects of modern agriculture on biodiversity but studies of farmland flora have lacked continuity and historical context. Here we present the results of 38 years of annual monitoring of the weed flora of cereal crops on the Sussex Downs.
2. This study investigates the long-term changes in abundance of 214 weed species, two subspecies and one forma found in the cereal fields of a 62-km2 area of the Sussex Downs. Species occurrence and weed abundance were recorded annually in June from 1970 to 2005 inclusive. Stubbles were surveyed in 1968, 1971, 2004 and 2005.
3. Annual archaeophytes and perennial natives predominated and the community belonged to the Papaver rhoeas–Silene noctiflora association (OV16) of the UK National Vegetation Classification.
4. Overall, 97% of fields were treated with herbicides prior to sampling, reducing dicotyledonous weed abundance by 64% and taxon occurrence by 52%. From 1970 to 2005 there was no trend in overall abundance of dicotyledons, although monocotyledons decreased by 13% relative to the early 1970s.
5. Of 66 taxa monitored from 1970 to 2005, 18 increased, 38 rose and fell (or vice versa) and 10 showed no trend. Annuals increased until the early 1980s, when many were not susceptible to herbicides, before levelling off or declining slightly as the efficacy of herbicides expanded.
6. Perennial dicotyledons increased steadily throughout the study. This latter change was due to the loss of traditional leys, not to changes in herbicide efficacy.
7. Ninety-two species of dicotyledons were found on stubbles, with no significant overall change in occurrence from 1968–1971 to 2004–2005. In both stubbles and crops, species uncommon at the start have tended to increase whereas common species have tended to decrease.
8. Combining this study with earlier records, we estimate that 16 weed species have been lost from the study area and 15 gained. Before 1970, the loss rate of archaeophytes and the gain rate of neophytes were both higher than for other species. Most species lost were historically uncommon whereas many of the species gained are now common.
9. Synthesis and applications. The soil seed bank remains sufficient to enable a rapid restoration of the pre-herbicide flora where needed for wildlife conservation purposes, without ‘enhancement’, i.e. seeding. The means to do this are available through the UK’s agri-environment ‘in-field measures’, but these are very unpopular with farmers. Incentives need to be much improved to ensure the future conservation of the traditional arable flora.
1. Estimating temporal trends in animal abundance is central to ecology and conservation, but obtaining useful trend estimates is challenging when animal detection rates vary across surveys (e.g. because of differences in observers or conditions). Methods exist for obtaining abundance estimates using capture–recapture and distance sampling protocols, but only recently have some of these been extended to allow direct estimation of abundance trends when detection rates vary. Extensions to distance sampling for >2 surveys have not yet been demonstrated.
1Wild birds are commonly observed in private residential gardens in Great Britain. However, little is known about how their use of this significant and increasingly important habitat is changing and how such changes relate to their population status.2Trends in the use of private residential gardens by wild birds in Great Britain were investigated using weekly bird records from 18 300 gardens over 8 years.3We showed that the use of this habitat is seasonal and cyclic, with the timing and regularity of its periodicity variable between species.4We evaluated the significance of the underlying trends in the cyclic reporting rates. Eighteen species showed clear trends, the three with the most negative year term parameter estimates being ‘red-listed’ as high conservation concern.5Examining correlations with national scale survey data suggested that garden reporting rates are related to general population trends in a number of species, including several of conservation importance. Other species exhibit important differences between national and garden trends.6Synthesis and applications. Our analysis demonstrates ecologically meaningful trends and provides novel insights into seasonal cycles of habitat exploitation, using relatively simple and cost-effectively collected data. This will lead to greater understanding of the relationships between gardens and general bird populations and of the times of year at which garden habitats are most important for birds. We have demonstrated the practicality and productivity of ‘citizen science’ in this context, and provided new information on the status of some birds of conservation concern.
Summary • The presence of commensal rodents was assessed in the 1996 English House Condition Survey (EHCS). Logistic regression techniques were used to identify the key factors that might determine the susceptibility of dwellings to infestation. • The overall percentages of dwellings that were infested, weighted to allow for the more intensive sampling used in certain categories of dwellings, were 1·83% for mice Mus domesticus, 0·23% for rats Rattus norvegicus living indoors and 1·60% for rats living outdoors. These figures excluded vacant properties, properties with some commercial use, and purpose-built flats, as these groups showed different patterns of infestation and were therefore excluded from the logistic regressions. • The prevalence of both rats and mice was significantly greater for dwellings where pets or livestock were kept in the garden. • Dwellings classed as unfit for human habitation were more likely to be infested with mice. • Dwellings in areas of low-density housing had a significantly higher prevalence of both rat and mouse infestation. This probably reflects the general suitability of the rural environment for commensal rodents. • Older properties had a relatively high prevalence of rats. This may be because their mature gardens provided suitable habitats for colonization. Once other confounding factors were taken into account, the age of the property did not influence the rate of infestation by mice. • Dwellings in areas with substantial problems, such as dereliction, litter, vacant properties and unkempt gardens, had a significantly higher prevalence of rats and mice. • This study reveals the value of applied ecological techniques, including logistic regression of presence–absence data, in understanding the distribution of commensal rodents in relation to dwellings, with the prospect of more effective management practices being developed as a consequence.
1. We investigated the effects of forest fragmentation on American martens (Martes americana Rhoads) by evaluating differences in marten capture rates (excluding recaptures) in 18 study sites with different levels of fragmentation resulting from timber harvest clearcuts and natural openings. We focused on low levels of fragmentation, where forest connectivity was maintained and non-forest cover ranged from 2% to 42%.
2. Martens appeared to respond negatively to low levels of habitat fragmentation, based on the significant decrease in capture rates within the series of increasingly fragmented landscapes. Martens were nearly absent from landscapes having > 25% non-forest cover, even though forest connectivity was still present.
3. Marten capture rates were negatively correlated with increasing proximity of open areas and increasing extent of high-contrast edges. Forested landscapes appeared unsuitable for martens when the average nearest-neighbour distance between open (non-forested) patches was <100 m. In these landscapes, the proximity of open areas created strips of forest edge and eliminated nearly all forest interior.
4. Small mammal densities were significantly higher in clearcuts than in forests, but marten captures were not correlated with prey abundance or biomass associated with clearcuts.
5. Conservation efforts for the marten must consider not only the structural aspects of mature forests, but the landscape pattern in which the forest occurs. We recommend that the combination of timber harvests and natural openings comprise <25% of landscapes ≥9 km2 in size.
6. The spatial pattern of open areas is important as well, because small, dispersed openings result in less forest interior habitat than one large opening at the same percentage of fragmentation. Progressive cutting from a single patch would retain the largest amount of interior forest habitat.
The Natura 2000 Network will consist of sites designated by the Member States of the European Union, under the Habitats and Birds Directives. Many of these sites need an appropriate management to maintain a favourable conservation status; this will often be based on low-intensity agricultural practices. Out of the 198 listed habitat types of the Habitats Directive, 28 (14%) could be threatened by the abandonment of low-intensity agricultural practices. The paper gives a comparative outlook over some situations in Europe, after an introduction to the framework set by the European Commission and the Council of Europe.
1. To encourage more project assessment and reporting of restoration outcomes, Palmer et al. (2005) propose five criteria for assessing the ecological success of river restoration. They also suggest that these criteria should help to clarify which activities should qualify for ecological restoration funding and facilitate consistency about what constitutes an ecologically successful restoration project. 2. We critique the five criteria and agree they all merit inclusion in an assessment of successful river restoration. However, the practical application of measuring self-sustainability (resilience) following restoration is potentially problematic and an explicit timeframe is needed to evaluate the results of the restoration. 3. A sixth criterion is proposed that encourages specific hypotheses and/or a conceptual model of the ecological mechanisms by which the proposed activities will achieve their target. This would enhance our understanding of the mechanisms at play for successful river restoration, and provide a more powerful deductive framework likely to lead to appropriate practices that can be applied across rivers. To explore the potential practical applicability of these six criteria, we applied them to a recently published example of river restoration to ascertain its ecological success. 4. Synthesis and applications. We agree with the criteria proposed by Palmer et al. (2005), although the problems of measuring resilience and defining a timeline for recovery should be addressed. We suggest strengthening the deductive framework of restoration projects by formulating some sort of conceptual model. This step could involve scientists, and be a useful way of involving science more explicitly in restoration activities. Agreed-upon criteria for successful restoration will greatly facilitate evaluation of river ecosystem recovery at the critical broader scales where our knowledge is still limited.
Summary • The authors of ‘Standards for ecologically successful restoration’ ( Palmer et al. 2005 ) are commended for clearly articulating and discussing the nuances of establishing ecological standards in river restoration practice. We agree that there is a need for better and more thoughtful standards to elevate the practice of river restoration to a science of restoration. As practitioners of fluvial restoration, and students of the sciences of geomorphology, hydrology, ecology and plant sciences, we offer our experiences and observations, noting that the desire to achieve ecologically effective project outcomes is not new. We agree that there are valid questions regarding the application of the term ‘restoration’ to projects with minimal ecological benefits. • We also concur that guiding image development is critical to project success. However, we note that well-intentioned projects often drift from having initially sound restoration objectives to ultimately providing reduced ecological benefit. Our observations suggest that this phenomenon can be attributed to risk aversion and the progressive incorporation of rigid engineered elements. We term this project hardening, where natural channel boundary evolution and change (deformability) is progressively sacrificed. This artificially constrains natural fluvial dynamics and associated ecological function. • We agree that meaningful pre- and post-monitoring programmes are essential to understanding project success. We encourage the academic community to make relevant data sets available to facilitate the evolution of restoration science. It is appropriate for sponsoring agencies to require the collection of these data. • Synthesis and applications. As practitioners we suggest that more interaction with ecologists and the larger academic community is necessary so that practical experience is communicated and integrated into the emerging science of restoration. While this interaction will advance the common goal of implementing more ecologically effective projects, we also note that project participants outside the scientific community must also appreciate the challenges a project faces in meeting higher standards. These challenges are not insignificant and include convincing project sponsors, practitioners and regulators of the need for standards in project generation, implementation and monitoring on a project-by-project basis. Journal of Applied Ecology (2005) 42, 223–227 doi: 10.1111/j.1365-2664.2005.01021.x
1. In a recent paper, Caut, Angulo & Courchamp (2008, Functional Ecology, 22, 255) experimentally measured isotope discrimination factors for rats Rattus rattus. In their study, values for their discrimination factors spanned a much larger range than previously reported in the literature and were found to be negatively related to the stable isotope composition of the diet that the rats were fed.
2. In a subsequent meta-analysis, Caut, Angulo & Courchamp (2009, Journal of Applied Ecology, 46, 443) confirmed the trends they had found in their previous study and pointed to a method for obtaining adequate values for discrimination factors when they could not be measured experimentally.
3.Synthesis and applications. We argue that the discrimination factors determined by Caut et al. (2008) were an artefact of experimental design. We also argue that the reported linear relationships between the stable isotope composition of the diet and isotope discrimination factors in their follow-up meta-analyses (Caut et al. 2009) do not reflect relevant trends that can be extrapolated to the field and that the method they proposed for obtaining adequate values for discrimination factors should be used with considerable care.
1. Eradication of a single pest species from a multiply invaded island system may have unpredicted and detrimental impacts. Bergstrom et al. (2009) describe damage to vegetation following an increase in the number of rabbits on Macquarie Island. They propose that the increase in rabbit numbers was caused solely by eradication of cats.
2. However, their modelling is flawed and their conclusion that cats were controlling rabbit numbers is unsupported. We suggest the increase was because of some combination of four factors: reduced releases of Myxoma virus, abundant food after 20 years of vegetation recovery, release from cat predation and climate variability.
3. Recent high numbers of rabbits on Macquarie Island are not unprecedented; vegetation has been damaged in the past but has recovered. Rabbit numbers appear to be in decline again in the absence of both cats and Myxoma releases, suggesting that other factors can contribute to regulation of rabbit numbers in this system.
4. We do not agree with the implication that pest management could have been better integrated. Eradication techniques for rodents and rabbits on an island the size of Macquarie were unavailable when cat eradication was deemed necessary. The benefits to seabirds of cat eradication have been rapid. Our analysis further highlights the complexity of multiply invaded island ecosystems.
1. The management of non-indigenous species is not without its complications. In Bergstrom et al.’s (2009) study, we demonstrated that feral cats Felis catus on sub-Antarctic Macquarie Island were exerting top-down control on the feral rabbit Oryctolagus cuniculus population, and that the eradication of the cats led to a substantial increase in rabbit numbers and an associated trophic cascade.
2. Dowding et al. (2009) claim our modelling was flawed for various reasons, but primarily that a reduction in the application of the rabbit control agent, Myxoma virus, coinciding with cat removal, was a major driver of rabbit population release.
3. We explore this proposition (as well as others) by examining rates of Myxoma viral release between 1991 and 2006 (with an attenuation factor for the years, 2003–2006) in association with presence/absence of cats against two estimates of rabbit population size. Myxoma viral release was a significant factor in the lower estimates of rabbit population, but the effect was small, and was not significant for higher rabbit population estimates. By contrast, the presence or absence of cats remained highly significant for both estimates.
4.Synthesis and applications. We re-affirm our position that top-down control of rabbit numbers by cats, prior to their eradication, was occurring on Macquarie Island. Nonetheless, we agree with Dowding et al. (2009) that systems with multiple invasive species represent complex situations that require careful scrutiny. Such scrutiny should occur in advance of, during, and following management interventions.
Summary • The European Water Framework Directive (WFD) requires that all natural European waterbodies should be assigned to one of five ecological categories defining the degree to which present-day conditions deviate from those uninfluenced or only negligibly impacted by anthropogenic activities (the reference condition). By 2015, all relevant waterbodies must have obtained ‘good’ ecological quality. • We describe the changes in ecological state in 21 Danish lakes usingad1850 as a benchmark for reference conditions. Sediment samples representing 1850, 1900, 1950 and 2000 were analysed for diatom and cladoceran subfossils. Ecological status since 1850 was evaluated using correspondence analysis and dissimilarity measures to assess assemblage changes, and existing transfer functions were applied to infer changes in total phosphorous concentrations from diatoms (DI-TP) and submerged macrophyte coverage (SUB-COV) and benthi-planktivorous fish catch per unit effort (BP-CPUE) from cladoceran subfossils. • Eighteen lakes underwent significant changes, most markedly during the past 50–100 years, in either or both diatom and cladoceran community structure. Low floristic and faunal alteration was found only in three lakes; these were, however, already nutrient-rich in 1850. • In 1850, most lakes were already characterized by high DI-TP (median of 17 lakes = 86 µg TP L−1), high inferred BP-CPUE and low inferred SUB-COV, and these eutrophic conditions still prevail. In addition, the accumulation rate of sediment and cladoceran subfossils and the pelagic dominance of diatoms and cladocerans have increased. • When applying the thresholds proposed by a recent WFD classification for Danish lakes to the DI-TP values, only one lake could be described as having a ‘good’ ecological state with a concurrent low community change since 1850, limited to the cladoceran community, however. This suggests that this lake alone may serve as a potential reference site. • Synthesis and applications. Our study, demonstrating the potential of a palaeolimnological approach to assess deviations from reference conditions, suggests that Danish reference lakes may be difficult to find, most probably due to the country's long history of cultural impact. Lake managers consequently face great challenges in their endeavour to ensure ‘good’ ecological state by 2015. Therefore, further restrictions on land-use and nutrient loading in lake catchments are needed as is the initiation of restoration activities to improve the ecological state of the lakes.
1. Hydromorphological river restoration usually leads to habitat diversification, but the effects on benthic invertebrates, which are frequently used to assess river ecological status, are minor. We compared the effects of river restoration on morphology and benthic invertebrates by investigating 26 pairs of non-restored and restored sections of rivers in Austria, Czech Republic, Germany, Italy and the Netherlands.
2. Sites were grouped according to (1) region: central Europe vs. southern Europe; (2) river type: mountain vs. lowland rivers; (3) restoration approach: active vs. passive restoration and (4) a combination of these parameters. All sites were sampled according to the same field protocol comprising hydromorphological surveys of river and floodplain mesohabitats, microhabitats at the river bottom and habitat-specific sampling of benthic invertebrates. Restoration effects were compared using Shannon–Wiener Indices (SWIs) of mesohabitats, microhabitats and invertebrate communities. Differences in metric values between non-restored and restored sites were compared for 16 metrics that evaluated hydromorphology and the benthic invertebrate community.
3. Mean SWIs differed for both mesohabitats (1·1 non-restored, 1·7 restored) and microhabitats (1·0 non-restored, 1·3 restored), while SWIs for invertebrate communities were not significantly different (2·4 non-restored, 2·3 restored). Meso- and microhabitat metrics in the restored sections were usually higher compared with the non-restored sections, but the effects on invertebrate metrics were negligible.
4. Measures in southern Europe and mountainous regions yielded larger differences between non-restored and restored sections of rivers. Differences in the meso- and microhabitat metrics were largest for actively restored sections of central European mountain rivers and rivers from southern Europe, followed by passively restored mountain rivers in central Europe. The smallest differences were observed for lowland sites. There was no significant restoration effect on invertebrate metrics in any categories.
5. Synthesis and applications. Restoration measures addressing relatively short river sections (several hundred metres) are successful in terms of improving habitat diversity of the river and its floodplain. Active restoration measures are suitable if short-term changes in hydromorphology are desired. To realize changes in benthic invertebrate community composition, habitat restoration within a small stretch is generally not sufficient. We conclude that restoring habitat on a larger scale, using more comprehensive measures and tackling catchment-wide problems (e.g. water quality, source populations) are required for a recovery of the invertebrate community.
Summary1. As the role of forestry-based options for reducing or mitigating greenhouse gas emissions is debated by policymakers, there is a need to inform the debate by synthesizing existing information on carbon dynamics in tropical forest systems and by applying this information to a range of possible interventions in forestry.2. To investigate the consequences of reductions in logging damage for ecosystem carbon storage, we constructed a model to simulate changes in biomass and carbon pools following logging of primary dipterocarp forests in south-east Asia. We adapted a physiologically driven tree-based model of natural forest gap dynamics (FORMIX) to simulate forest recovery following logging.3. Following selective logging, simulated ecosystem carbon storage declined from prelogging levels (213 Mg C ha−1) to a low of 97 Mg C ha−1, 7 years after logging. Carbon storage in biomass approached prelogging levels about 120 years after logging.4. The relationship between fatal stand damage and ecosystem carbon storage was not linear, with biomass recovery following logging severely limited by 50–60% stand damage.5. Results from simulations suggest that when 20–50% of the stand is killed during logging, replacing persistent forest species with pioneer tree species can reduce the site's potential for carbon storage by 15–26% over 40–60 years.6. Reducing fatal damage from 40% to 20% of the residual stand, as was the case with a pilot project in Malaysia, was associated with an increase of 36 Mg C ha−1 in mean carbon storage over 60 years.7. Efforts to monitor and verify the benefits, either through carbon sequestration in new growth or carbon retention in existing biomass, of offset projects involving tropical forests and natural forest management should focus on above-ground biomass, particularly the large trees. Selection of the most appropriate allometric equations for a site and species is important because of their influence on biomass estimates.