No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Impacts of artificial drainage on amphibian breeding sites in hemiboreal forests
Abstract
Artificial drainage is widely used to increase timber production and improve its quality in northern boreal and temperate forests, but its impact on biodiversity remains largely unexplored. Amphibians are particularly dependent on forest wetland qualities to complete their complex life cycles. We explored the supply of water bodies, their occupancy by amphibians, and persistence during the larval period comparatively in drained and natural forest plots in two years in Estonia. The water bodies in drained plots were more abundant but less diverse and of generally lower quality than in natural plots; however, the drainage ditches were favoured by newts. In the dry spring of 2009, water bodies were used more frequently in natural than in drained plots, while in the typical spring of 2010, several natural depressions appeared in drained plots and the frequency of use of water bodies did not differ between natural and drained plots. However, most natural depressions used for breeding in drained plots dried out before tadpole metamorphosis; such drying was not observed in natural plots. Thus, by profoundly changing natural hydrology, intensive large-scale forest drainage reduces the variety of water bodies and the quantity and quality of amphibian breeding sites. Moreover, we suspect that, at least in some years, temporary water bodies in drained areas function as ecological traps for amphibians. We suggest that, where possible, intact wet-forest areas with remaining natural hydrology should stay undrained. In areas already drained, breeding sites for amphibians can be provided by creating depression-like enlargements to some ditches.
... In northern afforested wetlands, amphibian habitat mosaics degrade when naturally patchy sun-exposed areas become uniform forests and ditches remain the only breeding sites prone to overgrowth by rank vegetation (Remm et al., , 2018Soomets et al., 2017). Specifically, lowering of the water table for timber production eliminates fish-free temporary water-bodies that are highquality breeding sites (Petranka et al., 2007;Suislepp et al., 2011). ...
... The target species are collectively known as 'brown frogs': moor frog (Rana arvalis), also listed in the Annex IV of the EU Habitats Directive, and common frog (R. temporaria). Both species are widespread in mires and forested wetlands in Estonia; they have been previously used to describe drainage impacts (e.g., Suislepp et al., 2011;Remm et al., 2018) and habitat improvement after small-scale clearing of overgrown ditch banks (Soomets et al., 2017). Elsewhere, a few studies have demonstrated that drain-blocked pools provide new favourable breeding sites for amphibians (Dibner et al., 2014;Beadle et al., 2015). ...
... Secondly, despite the general water-level increases, there was only limited development of temporary wetlands and pools on the forest floor that are typical of undrained wetland forests (Suislepp et al., 2011;Remm et al., 2015). The pools mostly formed in front of ditch dams (sometimes locally flooding the immediate surroundings), especially at the edges of bogs. ...
... The fragmentation and isolation of the remaining ponds causes problems for amphibian population connectivity (for a review see Cushman 2006), mainly affecting the dispersal of juveniles (Rothermel 2004;Preisser et al. 2000). Also in Estonia the conditions of amphibian habitats, including small freshwater bodies, have degraded during the 20th century due to not only the changes in land use and the intensification of agriculture and drainage, but also by the abandonment of small-scale farming and the subsequent forestation of landscapes (Rannap et al. 2007;Suislepp et al. 2011;Rannap et al. 2015;Remm et al. 2015). These changes have caused a decrease in and range constriction of several amphibian species, including the common spadefoot toad (Pelobates fuscus) and the northern crested newt (Triturus cristatus). ...
... We assessed altogether 25 aquatic and terrestrial features for each pond and its surroundings (Table 1), considering potentially important characteristics for larvae and adult amphibians (Nyström et al. 2002;Gustafson et al. 2011;Suislepp et al. 2011;Rannap et al. 2012Rannap et al. , 2013Rannap et al. , 2015Denoël et al. 2013). In order to determine the distance to the closest pond with the target species, we used previous survey data Soomets et al. 2016) and the orthophotos of The Estonian Land Board and Estonian base map. ...
... Moreover, our results testified to the importance of natural ponds for common species. Rana temporaria and R. arvalis, the two Boreal Palearctic anurans occurring often in mire and forest habitats (Elmberg 1993;Suislepp et al. 2011;Remm et al. 2015Remm et al. , 2018, were found more often in natural water bodies than in constructed ponds. Thus, our study supports previous amphibian surveys, showing that a niche position is of decisive importance for rare species (Rannap et al. 2009b). ...
Ponds—small, isolated freshwater bodies—have vanished in large numbers during the last decades. Despite such great loss, the number of natural small water bodies has still remained quite high in Estonia. Nevertheless, many pond-related species, including amphibians such as the northern crested newt Triturus cristatus and the common spadefoot toad Pelobates fuscus—are in decline in Estonia, suggesting that the conditions of extant natural ponds might not be optimal. However, these conditions have never been examined. To halt the decline of these two pond-breeding species, more than 400 ponds have been constructed or restored from 2004 to 2014 in Estonia. In this study we compared 85 natural and 85 constructed ponds (which were created or restored especially for T. cristatus and/or P. fuscus) to find out: (i) what the main differences are between natural ponds and ponds specially created for threatened species; (ii) whether natural ponds provide breeding conditions for local amphibians; (iii) given the decline of T. cristatus and P. fuscus, what are the characteristics lacking in natural ponds, due to which they are not providing quality breeding habitats for these species. Whereas the constructed ponds were located in open habitats with mineral soils, the natural ponds were mainly in mires and forests, being thus more shaded. Amphibian diversity was higher in the constructed ponds and was positively related to the depth of the pond, the clarity of the water, the presence of slanting slopes, the absence of fish and the presence of nearby fields. T. cristatus preferred constructed ponds for reproduction, while the breeding site selection of P. fuscus was determined mainly by terrestrial habitat characteristics. Importantly, when the threatened species were removed from the sample, the diversity of common amphibians did not differ between natural and constructed ponds, suggesting that in our study sites natural water bodies act still as breeding sites for common species, but not for threatened ones. We conclude that pond construction is an important tool to halt the decline of threatened species, even in landscapes where natural ponds are still preserved.
... In drained commercial forests natural pools and streams have been largely replaced with ditches (Remm et al., 2015b;Suislepp et al., 2011). Periodic ditch maintenance is done to keep the ground water table low (Ahti and Päivänen, 1997). ...
... Studies have also found that amphibians may find these ditches, as well as other novel anthropogenic water bodies, attractive (Johnson et al., 2016;Remm et al., 2015b). Some mitigation measures for wetland biodiversity (e.g., construction of pools and enlargement of ditches) may also be applicable in drained commercial forests (Suislepp et al., 2011;Rosenvald et al., 2014); though, the efficiency of these measures need further testing (Remm et al., 2015a). ...
... This suggests that minimizing the destruction of pools during forest management and cleaning ditches provides opportunities to mitigate the negative effects of drainage on amphibians. However, ditches and pools in drained areas are reported to dry frequently before tadpole metamorphosis, essentially functioning as ecological traps (DiMauro and Hunter, 2002;Suislepp et al., 2011). Our results show that water depth is further decreased by ditch cleaning both in ditches and pools, which increases the probability of desiccation, especially in years with low precipitations. ...
Forest drainage has led to the loss of a considerable number of wetlands, especially in the northern hemisphere. In order to find ways to mitigate the loss of biodiversity in drained forests, we investigated two distinct conservation measures: (i) leaving drained peatlands for natural succession, i.e. protecting without active restoration, and (ii) constructing a variety of mitigation pools during ditch maintenance work in commercial forests. We tested the effectiveness of these conservation approaches for wetland biota, selecting brown frogs (Rana arvalis, R. temporaria) as our focal species. We found that ditches do not substitute natural floods as breeding habitats for brown frogs in protected peatlands. One of the main reasons was the reduction of sun exposure due to drainage-induced forest growth. However, secondary wetlands formed on ditches impounded by Eurasian beaver (Castor fiber) offered high quality reproduction sites for brown frogs. In commercial forests, the number of natural pools decreased due to ditch maintenance work, but the colonisation rate of brown frogs increased in cleaned ditches. The reproduction site selection of the two frog species differed – R. arvalis bred mainly in natural and constructed pools, while R. temporaria bred more frequently in ditches. Among mitigation pools, those with a shallow littoral zone were primarily used for breeding. Thus, the conservation measures are effective only if certain key assumptions are met. The success could stand on the considering of the habitat requirements of target species before creating mitigation habitats or presence of a restoration agent (like beaver) in protected sites modified by human activities.
... In wet years when meadows are heavily flooded, higher ground may also become vital for ground-nesting birds (Jongbloed, 2005). For common frogs, the preferred temporary ponds for breeding may emerge only in wet years (Suislepp, Rannap, & Lõhmus, 2011) and on larger meadows with varying microtopography. ...
... Milsom, Hart, Parkin, & Peel, 2002;Leito et al., 2014) and amphibians (Beebee, Denton, & Buckley, 1996), particularly in years of average precipitation. Sun-exposed depressions, floods and pools with shallow rapidly warming water are essential breeding sites for amphibians, including brown frogs (Hartel et al., 2010;Suislepp et al., 2011;Rannap et al., 2012), but they also constitute important feeding areas for breeding waders (Ausden, Sutherland, & James, 2001;Devereux, McKeever, Benton, & Whittingham, 2004). Wet features offer soft sediments, which are easily penetrable to the bills of probing waders (Milsom et al., 2002;Smart, Gill, Sutherland, & Watkinson, 2006) and provide a supply of aquatic invertebrates − an important food source for adults and chicks, the importance of which increases as the season progresses (Milsom et al., 2002;Ausden, Rowlands, Sutherland, & James, 2003). ...
... Moreover, in the year with average precipitation (2013), breeding success of brown frogs also depended on the length of the ditch network, highlighting the importance of ditches as incubation sites for tadpoles in drained wetlands. However, ditches may still shorten the hydroperiod of natural floods and depressions, making them potential ecological traps for amphibian larvae (Suislepp et al., 2011). ...
Wet grasslands provide unique habitats for several taxa and offer multiple ecosystem services. Their degradation is therefore of increasing concern in many parts of the world. Baltic coastal meadows, which host diverse plant and bird communities and provide an essential breeding ground for amphibians, belong to the most threatened habitat types in Europe. In spite of the EU agri-environmental schemes, the threatened wader and toad populations, characteristic to these meadows, have not recovered, suggesting that the management efforts are failing to provide sufficiently high habitat quality for these species. In this paper we report the results of a large-scale survey determining the factors that influence the patterns of breeding habitat selection of four Charadriiform bird species on 24 coastal meadows in Estonia. We also examined whether the habitat conditions required by the threatened waders would benefit breeding amphibians and meadow plants and whether the threatened waders might act as focal species for managing coastal meadow biodiversity. In total, we analysed 23 landscape-variables, applying co-inertia analysis to discover common multivariate patterns in coastal meadow characteristics, breeding waders, plants and amphibians. We demonstrated that large (≥100 ha) and wide (mean width ≥200 m) meadows with extensive grazing, high water-table and no woody vegetation provide favourable breeding conditions for waders of conservation concern, but at the same time also support other Charadriiform birds, larger amphibian populations, and more diverse plant communities. Meadow management should therefore be targeted at threatened waders, especially Baltic dunlin, which could be considered as a focal species, and focus on the establishment of large and wide meadow areas with extensive grazing.
... Such drained wetlands develop into novel ecosystems with no natural analogues -homogeneous forests with a dense network of open ditches Remm et al., 2013). The main change for freshwater organisms is that the natural diversity of sun-exposed water-bodies is largely replaced by shady linear ditch corridors, and the residual natural depressions become vulnerable to summer drying due to lowered groundwater levels (Suislepp et al., 2011). ...
... Blaustein and Wake, 1995;DuRant and Hopkins, 2008;Wyman, 1998). In principle, several amphibian species can inhabit drained timberproduction landscapes (Homyack et al., 2014;Remm et al., 2015), but the populations may not be viable in the long term without mitigation or restoration measures (Suislepp et al., 2011). Studies on such restoration of freshwater habitats in drained forests are lacking worldwide (Ilmonen et al., 2013), and the whole evidence base for conservation management of these novel landscapes is insufficient (Bernes et al., 2015;Lõhmus et al., 2015). ...
... About 25% of all Estonian forest land is currently affected by artificial draining systems (Torim and Sults, 2005), and the 20th century transition from forest-wetland mosaics to densely stocked, ditched, and harvested forests is arguably one of the most fundamental recent landscape-changes of the country (Ilomets, 2005;Remm et al., 2015). Brown frogs prefer to breed in sun-exposed water bodies (Dibner et al., 2014;Hartel et al., 2010), and drainage has a double impact on them by transforming the water bodies and increasing the shade (Suislepp et al., 2011). Here, we focus on the role of shade. ...
Forestry drainage has transformed extensive North-European wetlands to homogeneous forests with a dense network of open ditches. In such drained wetlands, small sun-exposed temporary water-bodies – a favoured breeding habitat for amphibians – are replaced by linear ditch corridors that become increasingly shaded by woody vegetation. We explored whether simple removal of woody vegetation from ditch corridors can increase the habitat quality for two frog species, Rana arvalis and R. temporaria, in a drained pine-wetland landscape in Estonia. Such practice is compatible with the forestry purposes of maintaining the ditches and access to the area. In a before–after–control–impact (BACI) experimental design, the mean shade above cleaned ditches decreased from 66% to 35% and appeared to be the main reason for a dramatic increase in frog breeding in the next spring. The change increased numbers of both species and was based on colonization of the ditches from the surrounding landscape. We suggest that keeping forest ditches exposed to the sun may mitigate the overall negative drainage impact on wetland species at least in the short term, and brown frogs could be used as focal species to guide these practices. In the longer term, however, such systems may not be viable without stable source populations in protected or restored wetland patches.
... We focus on the effects of ditching, which has been extensively used to increase timber yield and accessibility (Paavilainen and Päivänen 1995). Although previous studies explored the habitat value of waterbodies situated downstream of drainage objects (Jutila et al. 1998, Vuori et al. 1998), the aquatic habitats within forest drainage networks have remained almost unexplored (but see Suislepp et al. 2011). Ditching generally shortens the hydroperiod of natural lentic TWBs (Suislepp et al. 2011) and dredges and straightens natural streams. ...
... Although previous studies explored the habitat value of waterbodies situated downstream of drainage objects (Jutila et al. 1998, Vuori et al. 1998), the aquatic habitats within forest drainage networks have remained almost unexplored (but see Suislepp et al. 2011). Ditching generally shortens the hydroperiod of natural lentic TWBs (Suislepp et al. 2011) and dredges and straightens natural streams. Along with the changing forest structure (Minkkinen et al. 1999, Remm et al. 2013), additional long-term changes are expected given shifts in temperature regimes and base substrate. ...
... We expect that the TWB-promoting effect of clear cutting (due to decreased transpiration and interception by canopy cover) is weaker on drier soils that lack soil water. We then exemplify the integrative effects of forest management on habitat quality of TWBs using the common brown frog (Rana temporaria) and the moor frog (R. arvalis), which are typical amphibian species in hemiboreal forests (Suislepp et al. 2011), as indicator species. Amphibians are characteristic inhabitants of TWBs (Bedford et al. 2001), contribute significantly to the biomass of forest fauna (Burton and Likens 1975, Wyman 1998), are food for predators (Blaustein and Wake 1995), and are themselves keystone predators of invertebrates (Davic and Welsh 2004, DuRant and Hopkins 2008). ...
Temporary freshwater bodies are important as wildlife habitats and in biomass cycling, but their quantity and characteristics in relation to forest management are poorly documented. We surveyed small waterbodies in Estonian forest landscapes, along randomly placed transects in forests and non-forested fens. The area of natural puddles and floods varied by nearly two orders of magnitude among habitat types. The main effect of drainage and clear cutting was the conversion of waterbody types: natural ones were partly replaced by ditches and wheel-rut puddles, respectively. Using the common brown frog and the moor frog as indicator species revealed that anthropogenic changes are not necessarily detrimental: the frogs preferred to breed in anthropogenic waterbodies in open areas (i.e., clear cuts). Mitigation of forestry effects on the biota of temporary waterbodies should combine restoration (allowing flooding in selected areas; restoring streams) and compensatory measures (excavating ponds; retaining wheel-rut puddles in key sites).
... Biodiversity responses to forest drainage are apparently complex and result from various interacting changes in abiotic and biotic conditions. Aquatic biota respond rapidly to: increased amounts of solid sediments downstream of the drainage system [17,18,19]; reduced abundance, size, and diversity of natural bodies of water in the drained area [20]; and the appearance of ditches as a novel habitat (e.g. [21,20,22] ,). ...
... Aquatic biota respond rapidly to: increased amounts of solid sediments downstream of the drainage system [17,18,19]; reduced abundance, size, and diversity of natural bodies of water in the drained area [20]; and the appearance of ditches as a novel habitat (e.g. [21,20,22] ,). In the case of non-aquatic biota, shortterm and long-term impacts differ. ...
... (4) Among vascular understory plants and snails, we detected no forest-preferring SPEC and no indicator species of old-growth swamp forests, but drainage modified their assemblage composition (except in snails in old growth;Table 3). In snails, the loss of small bodies of water and seasonal floods [20] may be responsible for the reduction of some species (water snails, Pisidium clams, Succineidae, Cochlicopa nitens, Zonitoides nitidus; see [87]) and the pronounced drainage influence in mature stands corresponds to changes in treelayer (see below). The latter effect was probably both litter and understory-mediated, given that detritivorous species dominated in the samples. ...
Artificial drainage (ditching) is widely used to increase timber yield in northern forests. When the drainage systems are maintained, their environmental impacts are likely to accumulate over time and along accompanying management, notably after logging when new forest develops on decayed peat. Our study provides the first comprehensive documentation of long-term ditching impacts on terrestrial and arboreal biodiversity by comparing natural alder swamps and second-generation drained forests that have evolved from such swamps in Estonia. We explored species composition of four potentially drainage-sensitive taxonomic groups (vascular plants, bryophytes, lichens, and snails), abundance of species of conservation concern, and their relationships with stand structure in two-ha plots representing four management types (ranging from old growth to clearcut). We found that drainage affected plot-scale species richness only weakly but it profoundly changed assemblage composition. Bryophytes and lichens were the taxonomic groups that were most sensitive both to drainage and timber-harvesting; in closed stands they responded to changed microhabitat structure, notably impoverished tree diversity and dead-wood supply. As a result, natural old-growth plots were the most species-rich and hosted several specific species of conservation concern. Because the most influential structural changes are slow, drainage impacts may be long hidden. The results also indicated that even very old drained stands do not provide quality habitats for old-growth species of drier forest types. However, drained forests hosted many threatened species that were less site type specific, including early-successional vascular plants and snails on clearcuts and retention cuts, and bryophytes and lichens of successional and old forests. We conclude that three types of specific science-based management tools are needed to mitigate ditching effects on forest biodiversity: (i) silvicultural techniques to maintain stand structural complexity; (ii) context-dependent spatial analysis and planning of drained landscapes; and (iii) lists of focal species to monitor and guide ditching practices.
... Additionally, constructed wetlands (CWs) have been established to mitigate the impact of diffuse pollution, reduce nutrient runoff from arable land and improve the quality of surface waters (Koskiaho and Puustinen, 2005;Kasak et al., 2018). Although open ditches can provide breeding habitat for some amphibians (Maes et al., 2008;Mitchell, 2016), many species prefer natural wetlands (e.g., depressions, flooded areas, shallow temporary lakes and beaver ponds) as reproduction sites (Griffiths, 1997;Suislepp et al., 2011;Rannap et al., 2015;Remm et al., 2018). CWs, which are designed to mitigate water pollution in agricultural landscapes often resemble natural wetlands with shallow margins and abundant vegetation (Koskiaho and Puustinen, 2005), thus having a potential to play a multi-functional role encompassing water treatment and biodiversity (Hansson et al., 2005;Becerra-Jurado et al., 2012). ...
... It is known that northern crested newt and common spadefoot toad avoid such landscapes (Skei et al., 2006;Gustafson et al., 2011;Rannap et al., 2012Rannap et al., , 2015, whereas common toad, common frog and pool frog are known to be species with higher tolerances of intensively used agricultural land (Loman and Lardner, 2006). Vända CWs were particularly favorable for the common frog and moor frog, species which prefer shallow natural-like wetlands to ditches and artificial pools (Suislepp et al., 2011;Magnus and Rannap, 2019), and cannot successfully reproduce in water bodies with fish (Hartel et al., 2007;Tiberti et al., 2019). As demonstrated previously, the common frog and moor frog favor breeding sites, such as beaver floods and depressions, with plentiful of shallow rapidly warming water (Vehkioja and Nummi, 2015;Wahlroos et al., 2015;Remm et al., 2018) and a high concentration of dissolved oxygen (Costa, 1967). ...
Constructed wetlands are used as an effective measure to improve water quality and reduce nutrient runoff from agriculture. However, their role as alternative breeding sites for different amphibian species is rarely explored. We studied amphibians' colonization and breeding success in two in-stream free surface water wetlands in intensively managed agricultural landscape in southeastern Estonia. Additionally, the sedimentation pond and a nearby farm pond were observed. The observations started a year after the establishment of the constructed wetlands in 2015 and lasted for four years. In Vända constructed wetlands, breeding of five amphibian species were observed, all of which were common to the area: smooth newt (Lissotriton vulgaris L.), common toad (Bufo bufo L.), common frog (Rana temporaria L.), moor frog (Rana arvalis Nilsson) and pool frog (Pelophylax lessonae Camerano). Threatened species, such as the common spadefoot toad (Pelobates fuscus Wagler) or the northern crested newt (Triturus cristatus Laur.), also present in this region, were not found in the study sites. Unlike the sedimentation and farm ponds, constructed wetlands with their shallow rapidly warming water and absence of fish, provided breeding habitat for amphibians, especially for common frog and moor frog. In addition, chemical analyses of the water showed that nutrient concentration in the surface water was relatively low, which should not impair the reproduction of amphibians, at least in the short-term.
... For instance, only a subset of stream fish assemblages can be found in ditches (Rosenvald et al., 2014). Ditch network also shortens the hydroperiod of nearby pools so that they may become ecological traps for amphibians (Suislepp et al., 2011) and may support overall less aquatic invertebrate taxa compared to natural pools or even ditches (Remm et al., 2013;Vaikre et al., 2015). For some (semi-)aquatic taxa, anthropogenic waterbodies (e.g. ...
... The aims of this study were threefold: (i) to explore the differences of aquatic macroinvertebrate assemblages in ditches and pools in drained plots (hereafter remnant pools) and pools in undrained plots (hereafter natural pools) before DNM; (ii) to find whether DNM has an impact on macroinvertebrates in ditches and remnant pools and what environmental factors govern the changes; (iii) to examine the opportunities to mitigate the potential negative effect of DNM by excavating ponds and ditch enlargements. We hypothesise that (H1a) remnant pools have lost some of their biodiversity due to hydrological modifications and isolation caused by drainage (Suislepp et al., 2011); and in addition to functional differences (H1b) have also distinct taxonomical assemblages compared to ditches and natural pools. (H2a) as DNM has a similar effect as the first time drainage on site hydrology (Finér et al., 2018), some loss in remnant pools and associated macroinvertebrate diversity is expected; but (H2b) pioneer communities in ditches establish fairly quickly (Jeffries, 2010;Williams et al., 2008) and (H2c) this is manly facilitated by the recovery of macrophytes. ...
One of the main factors causing biodiversity loss in wetlands is drainage, nevertheless, even drained areas may provide habitat for aquatic fauna in the form of drainage ditches. Assemblages in ditches are regularly disturbed by ditch maintenance, but the extent of these disturbances and mitigation possibilities are poorly documented. We conducted an experimental study in three commercially managed forest plots in eastern Estonia, aiming to find out how ditch network maintenance (DNM) affects the diversity and assemblages of aquatic macroinvertebrates in ditches and remnant pools, and whether this effect can be alleviated by constructing mitigation waterbodies. For comparison we also collected data from natural pools in three undrained forest plots. Before DNM, ditches supported greater number of higher taxa compared to remnant and natural pools and more strictly aquatic taxa, whereas natural pools in undrained plots supported more Trichoptera shredders. After DNM, the diversity in remnant pools decreased. Moreover, majority of the pools dried out, which resulted in further reduction of the richness and abundance of macroinvertebrates. In ditches the diversity dropped immediately after DNM, but recovered in two to three years. Nevertheless, plot-scale richness and abundance did not completely recover. Assemblage shift in ditches took place right after DNM and remained distinct after the four year survey period. Mitigation pools provided habitat for several taxa (especially Odonata) uncommon in other waterbodies in drained and undrained plots. Our results show that DNM in forests substantially impoverishes habitat availability and reduces the abundance and diversity of aquatic macroinvertebrates. We recommend retaining uncleaned sections in ditches and constructing mitigation pools as tools for supporting wetland biodiversity in drained forests.
... Although forestry drainage does not unambiguously decrease the habitat availability for aquatic organisms, it shortens the hydroperiod of natural pools Suislepp et al. 2011) and partly replaces natural water bodies with linear ditch networks . Ditches have relatively longer hydroperiod and connectivity adds the possibility to escape from local drying. ...
... Ditches and pools had distinctly different feeding group compositionscrapers, filterers (and less contrastingly shredders) were aggregated to ditches and gatherers to pools. This supports our hypothesis that the longer hydroperiod of ditches Suislepp et al. 2011) favors feeding groups that rely on autochthonously produced recourses. Surprisingly, water depth did not explain this difference, and thus is not a good proxy for the length of hydroperiod in such small water bodies. ...
Artificially drained commercial forests are hydrologically novel ecosystems, where the array of aquatic habitats consists of ditches and remnant pools. In general the network of ditches has been found to have longer hydroperiod, the knowledge, however, about aquatic invertebrates in this system is scarce. We examined which environmental factors are impacting the biomass and abundance of functional feeding groups. Scrapers and shredders were aggregated to ditches and gatherers to pools. Filterers’ distribution pattern suggested that the function of filtering is carried out by different taxa in pools and ditches. Ditches were rather more suitable for feeding groups that rely on autochthonous resources. Acidity was a major driver of functional community composition, for example, one of the causes for higher scraper frequency in ditches. Predators exhibited greater quantities in extensive macrophyte cover regardless of water body type. Our results suggest that the trophic organization in ditches and pools is different because habitat factors select the feeding groups directly through food resources, but also because of the environmental filter on the other biological traits of the organisms. To support complex ecosystems with several trophic levels also in commercial forests, we suggest to avoid destroying macrophyte rich pools and ditches during silvicultural management.
... The climate is severe and often unpredictable, which produces additional challenges for wetland conservation. Furthermore, nearly 14 million hectares of wetlands have been drained for forestry in northern Europe (Paavilainen and Päivänen 1995;Suislepp et al. 2011). Finland alone has drained more than 5.5 million hectares of wetlands and forests (Peltomaa 2007), most of them during the last 50 years. ...
... Finland alone has drained more than 5.5 million hectares of wetlands and forests (Peltomaa 2007), most of them during the last 50 years. Ditches drain excess surface water, which influences the quality and processes of aquatic ecosystems, resulting in reduced wetland diversity (Suislepp et al. 2011). ...
To be presented, with the permission of the Faculty of Agriculture and Forestry of the University of Helsinki, for public criticism in lecture room 3 (Latokartanonkaari 7) on June 10th 2016, at 12 o'clock noon.
... Changes in forest waterbodies inside the network of ditches are, however, less known. Although ditch digging may increase the overall number of waterbodies in drained forests, it has been shown that as a result, natural temporal waterbodies (nTWB) become nearly absent and the hydroperiod of the extant ones shortens (Suislepp et al., 2011). In addition to purposely excavated ditches, forest management activities can also result in accidental creation of various aquatic habitats (e.g., wheel rut pools), which in fact can be beneficial for aquatic biota (Armitage et al., 2012). ...
... It appears that, even though drainage reduces the number (Table 1; Suislepp et al., 2011) and area (Remm et al., 2015) of natural waterbodies in drained forest landscapes, macroinvertebrates' taxon richness at waterbody scale has not suffered from this, at least in lentic waterbodies. One of the reasons could be that a large proportion of invertebrates inhabiting temporary waterbodies are not remarkably sensitive to habitat modifications, e.g., changed hydroperiod (Neckles et al., 1990). ...
Since the twentieth century, freshwater ecosystems have been extensively drained. Despite the magnitude of artificial drainage, its impact on freshwater biodiversity, especially on small forest waterbodies, is still poorly known. We examined macroinvertebrate taxon richness and assemblages in forest landscapes, comparing natural temporary waterbodies situated in drained and undrained areas, ditches, and wheel rut pools. We aimed to determine macroinvertebrates that are characteristic to these waterbodies, the impact of forest drainage on them, and the functioning of ditches as an alternative habitat for aquatic macroinvertebrates. Altogether 181 waterbodies within six landscape regions were surveyed, identifying 171 macroinvertebrate taxa. Taxa accumulation curves pooling all the regions indicated that natural waterbodies situated in drained areas harbored less invertebrate taxa than other waterbody types. Thus drainage has effect at supraregional scale. At the waterbody scale, however, we did not detect substantial forest drainage effect on taxon richness or assemblages. Ordering of the waterbody types by richness differed between landscape regions, suggesting that macroinvertebrates are largely dependent on landscape characteristics. Since neither total and mean richness nor assemblages did not differ significantly between natural temporary waterbodies and drainage ditches, the latter could be considered as an alternative habitat for invertebrates at least in semi-naturally managed forests.
... It is roughly estimated that 21%-27% of the world's reptiles are threatened ( Kuybida et al., 2019 ;Di Marco, 2022 ). In the context of climate change, many species face additional challenges such as habitat destruction due to anthropogenic impacts, including fragmentation and cultivation of landscapes, particularly deforestation and drainage of wetlands ( Cochard, 2011 ;Suislepp et al., 2011 ). Such changes affect the preferable climatic conditions essential for reptiles of the Palearctic: seasonal temperature changes (e.g., winter temperature drops enable activity pause, correct development of sex cells and proper breeding behavior), daily temperature changes (enabling basking and resting periods), suitable temperature and moisture regimes needed for proper egg incubation, sufficient habitat humidity providing appropriate water, nutrients, food and hides ( Araujo et al., 2006;Böhm et al., 2013;Mantyka-Pringle et al., 2012 ). ...
Reptile fauna should be considered a conservation objective, especially in respect of the impacts of climate change on their distribution and range’s dynamics. Investigating the environmental drivers of reptile species richness and identifying their suitable habitats is a fundamental prerequisite to setting efficient long-term conservation
measures. This study focused on geographical patterns and estimations of species richness for herpetofauna widely spread Z. vivipara, N. natrix, V. berus, A. colchica , and protected in Latvia C. austriaca, E. orbicularis , L. agilis inhabiting northern (model territory Latvia) and southern (model territory Ukraine) part of their European range. The ultimate goal was to designate a conservation network that will meet long-term goals for survival of the target species in the context of climate change. We used stacked species distribution models for creating maps depicting the distribution of species richness under current and future (by 2050) climates for marginal reptile populations. Using cluster analysis, we showed that this herpeto-complex can be divided into “widespread species ” and “forest
species ”. For all forest species we predicted a climate-driven reduction in their distribution range both North (Latvia) and South (Ukraine). The most vulnerable populations of “forest species ” tend to be located in the South of their range, as a consequence of northward shifts by 2050. By 2050 the greatest reduction in range is predicted for currently widely spread Z. vivipara (by 1.4 times) and V. berus (by 2.2 times). In terms of designing an effective protected-area network, these results permit to identify priority conservation areas where the full ensemble of selected reptile species can be found, and confirms the relevance of abiotic multi-factor GIS-modelling for achieving this goal.
... Wet grasslands constitute an important element of rangeland communities around the world. It has been proven that grazing wet meadows increases plant species richness (Joyce and Wade, 1998;Otfinowski and Coffey, 2022); and promotes favorable breeding sites for amphibians (Bos et al., 2002;Wolters et al., 2005;Brunside et al., 2007;Piha et al., 2007;Rannap et al., 2007;Roche et al., 2012), and birds (Ausden et al., 2001;Milsom et al., 2002;Ausden et al., 2003;Devereux et al., 2004;Hartel et al., 2010;Suislepp et al., 2011), including species of conservation concern. ...
Agriculturally used meadows are habitats whose biodiversity depends on anthropogenic disturbances such as fertilization or mowing. Intensified agricultural practices (too frequent mowing, use of mineral fertilizers and insecticides) lead to declines in the abundance and species diversity of the biota inhabiting them. The intensification of agricultural production in north-eastern Poland relates primarily to the increase in cattle numbers and the intensification of grassland management, but many areas were included in Natura 2000 network. Our study was aimed at indicating the impact of diverse use of meadows on the species richness and diversity of invertebrates, amphibians, and birds in the grasslands of Narew river valley, Special Bird Protection Area, where the intensification of grassland use was noted in the last decades, and part of the meadows was included in the agri-environmental program. The agri-environmental program is a very good tool for the protection of grassland biotic diversity. The highest taxonomic richness and diversity of the studied animal groups were found in meadows included in these programs with extensive use, while the lowest was in the over- and intensively used meadows fertilized with mineral fertilizers and liquid manure. Only the meadows in the agri-environment program were inhabited by the fire-bellied toad and the tree frog - amphibians from Annex IV of the Habitats Directive. The number of breeding bird species globally threatened (IUCN Red List), listed in Annex I of the EU Birds Directive, and with negative population trend in Europe (SPEC1-3) was highest in meadows included in EU conservation programs. The main factors reducing biotic diversity in the grassland of flooded river valley were the high number of grassland mowing per season, intensive fertilization, especially with liquid manure, the great distance of meadows to the river, low soil humidity, and low share of shrubs and trees in the meadows border zone.
... Factors contributing to amphibian decline include fungal disease, pollution, land degradation as well as urbanization [14][15][16]. For many amphibian species, increased drainage and the resulting loss of natural water bodies leads to rapid population declines [17][18][19]. Amphibian species richness usually declines with increasing urbanization because anthropogenically altered environments often fail to provide suitable breeding sites as well as terrestrial habitats [15]. However, urban parks for example can provide an oasis for specialized amphibian species and contribute to amphibian conservation [16,20]. ...
Urban areas are increasing worldwide, which poses threats to animal wildlife. However, in certain cases cities can provide refuges for endangered animals. The European green toad (Bufotes viridis) is one of such examples, which is known from cities throughout their distribution. In contrast, considerable areas of their former (primary) habitats have been degraded. The primary habitats of this species include steppes and wild river floodplains, both characterized by dynamic changes and the presence of open areas. We used available green toad observation data (2007–2020) to model the effects of land-use types on occurrence probability in the city of Vienna. Forest and densely populated areas were highly significantly negatively associated with green toad presence, while transformation/construction site areas showed a strong positive effect. Such occurrence pattern might be characteristic for early succession species, which depend on stochastic environmental disturbances (e.g., droughts and floods) in their primary habitats. We argue that urban landscape planning should appreciate the potential ecological value of open land in cities which is either in a transition phase or a permanent ‘wasteland’. Ecological managing of such landscape could vastly increase urban biodiversity.
... A similar gap appears in ecosystem coverage regarding the management of small freshwater bodies, notably headwater streams in forests. Again, there is well-established literature on the indicator value of many aquatic or semi-aquatic taxa, including suggestions to use some invertebrates, fish, amphibians, or birds as broader management targets (e.g., [95][96][97]). Relevant spatial models are, however, rare and tend to focus solely on the species' indicator value (e.g., [98]) or its conservation perspectives (e.g., [99]). ...
A fundamental problem of sustainability is how to reduce the double complexity of ecological and social systems into simple operational terms. We highlight that the conservation concept of focal species (selected species sensitive to a set of anthropogenic threats to their habitat) links multiple issues of ecological sustainability, and their habitat models can provide a practical tool for solving these issues. A review of the literature shows that most spatial modeling of focal species focuses on vertebrates, lacks the aspect of aquatic and soil habitats, and has been slow in the uptake by actual management planning. We elaborate on a deductive modeling approach that first generalizes the main influential dimensions of habitat change (threats), which are then parameterized as habitat quality estimates for focal species. If built on theoretical understanding and properly scaled, the maps produced with such models can cost-effectively describe the dynamics of ecological qualities across forest landscapes, help set conservation priorities, and reflect on management plans and practices. The models also serve as ecological hypotheses on biodiversity and landscape function. We illustrate this approach based on recent additions to the forest reserve network in Estonia, which addressed the insufficient protection of productive forest types. For this purpose, mostly former production forests that may require restoration were set aside. We distinguished seven major habitat dimensions and their representative taxa in these forests and depicted each dimension as a practical stand-scale decision tree of habitat quality. The model outcomes implied that popular stand-structural targets of active forest restoration would recover passively in reasonable time in these areas, while a critically degraded condition (loss of old trees of characteristic species) required management beyond reserve borders. Another hidden issue revealed was that only a few stands of consistently low habitat quality concentrated in the landscape to allow cost-efficient restoration planning. We conclude that useful habitat models for sustainable forest management have to balance single-species realism with stakeholder expectations of meaningful targets and scales. Addressing such social aspects through the focal species concept could accelerate the adoption of biodiversity distribution modeling in forestry.
... In comparison, the other "brown frog" (Rana) species, R.arvalis, had a much higher detectability (WDP of 0.78 and coverage by MAFD estimates of 0.86) due to its less variable calling activity according to time of day 20 and smaller effect from decline in calling activity during the breeding season (data from the present study). Apart from detectability issues, a possible source for the underestimation of R.temporaria population could be the omission of waterbodies that were not visible on orthophoto maps, such as periodically water-filled relief depressions in forests, where R.temporaria is the most common breeding amphibian species 28 . ...
Audial surveys of anuran amphibians (frogs, toads and similar) are cost-effective and allow for the coverage of large areas, but they are usually regarded as unsuitable for population size estimations due to imperfect detection. Our study demonstrated a method for obtaining minimum adult population size estimates from vocalising anuran counts by using sex ratios, life history and vocalising behaviour parameters from other studies. We collected data from 2016 to 2018 for seven taxa on 65 plots (each 25 km²) representing the entirety of Latvia. Among taxa, average breeding waterbody audible detection probabilities ranged from 0.56 to 0.88 per plot, minimum adult frog density (MAFD) estimates were from 12.0 to 51.7 individuals per km², but the estimated fraction of population covered by MAFD varied from 57 to 86%. The least accurate density estimates were in taxa with brief calling activity and quiet mating calls (Rana temporaria), and in taxa with a calling activity dependent on the numbers of males in a pond (Bufo bufo). Our study suggests that lek-breeders would be more suitable than explosive-breeding taxa for minimum population size estimates from audial data. The use of MAFD allowed for coarse minimum population size estimates for the entire country from the audial monitoring data, these ranged from 3.7 ± 0.5 thousand (Bombina bombina) to 1.64 ± 0.47 million (B.bufo) adults.
... An increasing number of studies show that forest microhabitats such as road edges, wood piles or drainage ditches can increase the diversity of various groups of organisms, including vascular plants and amphibians (Lugo and Gucinski, 2000;Suislepp et al., 2011;Zielińska et al., 2016). It has been found that the presence of forest roads and patches of thinned stands favours some bird species (Hagar et al., 2004;Šálek et al., 2010). ...
... Amphibians are the group with the highest proportion of species threatened with extinction (Stuart et al. 2004;Beebee and Griffiths 2005) mainly due to habitat destruction, disturbance, and fragmentation (Mendelson et al. 2006;Wake and Vredenburg 2008;Sodhi et al. 2008;Ochoa-Ochoa et al. 2009;Ducatez and Shine 2017) but also due to other factors like wetland draining, introduction of exotic species, over-exploitation, climate change, UV-B radiation, chemical contaminants and emerging infectious diseases (Carey and Alexander 2003;Daszak et al. 2003;Hirner and Cox 2007;Pearson and Goater 2009;Suislepp et al. 2011). All these factors could work synergistically increasing amphibian populations' declines. ...
Mexico is one of the most diverse countries that is losing a large amount of forest due to land use change, these data put Mexico in fourth place for global deforestation rate, therefore, Mexico occupies the first place in number of endangered species in the world with 665 endangered species. It is important to study amphibians because they are among the most threatened vertebrates on Earth and their populations are rapidly declining worldwide due primarily to the loss and degradation of their natural habitats. Pseudoeurycea robertsi is a micro-endemic and critically endangered Plethodontid salamander from the Nevado de Toluca Volcano and to date almost nothing is known about its natural history therefore, we survey fourteen sites of the Nevado de Toluca Volcano a mountain that is part of the Trans-Mexican Volcanic Belt, Mexico. We carry out the most exhaustive sampling scheme of this species throughout the Nevado de Toluca Volcano to know the number of individuals and the microhabitat features associated with the presence of P. robertsi . Likewise, we carry out a morphometric study and coloration measurements of P. robertsi individuals and we determine the potential distribution of P. robertsi and the other 3 species of pletodontids present in the NTV using ecological niche modeling and to determine the most important habitat features associated with the presence of salamander species, as well as to know the niche overlap among salamander species. This information will help raise conservation strategies for this micro-endemic and critically endangered salamander.
... What is the operational 'safe distance' in terms of biodiversity for ditch maintenance and reconstruction in fens and forested wetlands? Knowledge base Although broad vegetation changes near ditches in wet forests and open wetlands have been described (e.g., Paal et al. 2016), specific impacts on species of conservation concern (e.g., Suislepp et al. 2011) and impacts of ditch reconstruction should be further explored. A study, which demonstrated that ditch reconstruction dries out adjacent natural pools, also found that, at least for amphibians, such habitat loss can be partly mitigated by constructing artificial pools with shallow littoral zone (Remm et al. 2018). ...
Conservation scientists often lack explicit understanding of the knowledge problems faced in practical conservation, which can be resolved through communication between the scientists and the managers. Focusing on cost-effectiveness of such communication, we planned and implemented a rapid research gap prioritization procedure for the main stakeholder groups in conservation management and policy (‘managers’) in Estonia. The procedure required each research gap to be explicitly linked with its expected application and comprised three steps: (i) preparatory work of the managers to list their main knowledge gaps; (ii) a seminar for representatives of all the main manager groups to sort out the potentially most influential research topics at the national scale; (iii) analysis and synopsis writing of the top-voted topics. Researchers provided the methodology, facilitated the procedure, helped to translate practical problems into research topics and checked the topics for existing research. The paper describes the 13 high-priority research topics, which were distinguished among more than 60 topics listed. Land-use planning decisions (notably in forests) were most frequently perceived to lack critical knowledge, while only two priority topics were listed for political decision-making (both in agricultural policy). The priority topics proposed for wetland conservation focused on management techniques to mitigate artificial drainage. Our experience was that, through direct two-way communication between managers and researchers, the perceived knowledge gaps in conservation can be rapidly and transparently formulated as research topics. However, the managers’ views tend to focus on short-term effects of conservation, and a different procedure may be needed for researchers who might vision for longer and less predictable future.
... Amphibians are the group with the highest proportion of species threatened with extinction (Stuart et al. 2004;Beebee and Griffiths 2005) mainly due to habitat destruction, disturbance, and fragmentation (Mendelson et al. 2006;Wake and Vredenburg 2008;Sodhi et al. 2008;Ochoa-Ochoa et al. 2009;Ducatez and Shine 2017) but also due to other factors like wetland draining, introduction of exotic species, over-exploitation, climate change, UV-B radiation, chemical contaminants and emerging infectious diseases (Carey and Alexander 2003;Daszak et al. 2003;Hirner and Cox 2007;Pearson and Goater 2009;Suislepp et al. 2011). All these factors could work synergistically increasing amphibian populations' declines. ...
Land use changes are threatening the maintenance of biodiversity. Genetic diversity is one of the main indicators of biological diversity and is highly important as it shapes the capability of populations to respond to environmental changes. We studied eleven populations of Pseudoeurycea robertsi, a micro-endemic and critically endangered species from the Nevado de Toluca Volcano, a mountain that is part of the Trans-Mexican Volcanic Belt, Mexico. We sequenced the mitochondrial cytochrome b gene from 71 individuals and genotyped 9 microsatellites from 150 individuals. Our results based on the cytochrome b showed two divergent lineages, with moderate levels of genetic diversity and a recently historical demographic expansion. Microsatellite-based results indicated low levels of heterozygosity for all populations and few alleles per locus, as compared with other mole salamander species. We identified two genetically differentiated subpopulations with a significant level of genetic structure. These results provide fundamental data for the development of management plans and conservation efforts for this critically endangered species.
... Critical to lentic organisms, climate change also alters precipitation patterns, which are key in the predictability and variability of water cycling and storage (Williams et al., 2015;Smith et al., 2018). For animals such as aquatic insects and amphibians, with complex life histories that require movement between aquatic and terrestrial habitats, this variation can determine the success of individual development and survival (Robson et al., 2011;Suislepp et al., 2011;Cayuela et al., 2016). ...
Changing patterns of precipitation and drought will dramatically influence the distribution and persistence of lentic habitats. Pond-breeding amphibians can often respond to changes in habitat by plastically shifting behavioral and developmental trait response. However, fitness tradeoffs inherent in life history strategies can carry over to impact development, behavior, and fitness in later life stages. In this experiment, we investigated carryover effects of hydroperiod permanence on the movement behavior of newly-metamorphosed juvenile Northern Red-legged Frogs (Rana aurora). Frogs were raised through metamorphosis in mesocosms under either permanent or ephemeral hydroperiod conditions. After metamorphosis, individuals were removed from the mesocosms, measured, uniquely tagged with elastomer, and moved to holding terrariums. Movement behavior was quantified under two terrain conditions: a physiologically-taxing, dry runway treatment, or a control, moist runway treatment. Individuals were given 30 min to move down the 1 × 20m enclosed structure before distance was measured. We applied a hurdle model to examine two distinct components of movement behavior: (1) the probability of moving away from the start location, and (2) movement distance. We found that hydroperiod condition had an indirect carryover effect on movement via the relationship between individual size and the propensity to move. Individuals from ephemeral mesocosm conditions metamorphosed at a smaller size but showed increased growth rates as compared to individuals from permanent hydroperiod conditions. Individual snout-vent length and runway condition (moist or dry) were significant predictors of both aspects of movement behavior. Larger individuals were more likely to move down the runway and able to move a farther distance than smaller individuals. In addition to the influence of size, dry runway conditions reduced the probability of individuals moving from the start location, but increased the distance traveled relative to the moist runway. The demonstrated cumulative impact of stressors suggests the importance of addressing direct, indirect, and carryover effects of stressors throughout ontogeny.
... Ditches are common features in the range of R. pretiosa and were installed to drain wetlands and convey irrigation and other flows, but how they are used by R. pretiosa, other amphibians, and their predators is not well understood. Two studies of other frog species reported use of ditches by adults but not for breeding (Mazerolle, 2005;Suislepp et al., 2011). Neither study compared movements in ditched and unditched sites. ...
Many amphibians use multiple habitats across seasons. Information on seasonal habitat use, movement between seasonal habitat types, and habitats that may be particularly valuable is important to conservation and management. We used radio-telemetry to study late-season movement and habitat use by Oregon Spotted Frog (Rana pretiosa) at nine sites from four populations along the Cascade Mountains in Oregon. Movement rates declined with date and were the lowest at the end of tracking in December and January. Frogs across our sites used vegetated shallows in late summer and early fall. In fall, frogs used a range of habitat types, and at several sites moved to distinctive habitats such as springs, interstices in lava rock, and semi-terrestrial beaver channels. Distance between first and last tracking location was <250 m for 84.5% (49/58) of frogs, ranged up to 1145 m, and was greater for frogs in ditch habitats than those not in ditches. Distinctive features like springs or semi-terrestrial retreats can host multiple frogs and may represent particularly valuable wintering habitat for R. pretiosa in some sites in their Oregon range.
... Neben der Anzahl Feuchtgebiete (Rückgang von 4 341 auf 708) ist auch deren durchschnittliche Fläche von 3,2 ha auf 1,7 ha geschrumpft. Abzugsgräben als Drainagesystem gibt es auch in Wäldern, was einen stark negativen Einfluss auf die vorkommenden Amphibien hat (Suislepp et al. 2011). ...
The length of the hydroperiod varies among ponds. Temporary ponds dry at regular or irregular intervals. Pond drying reduces the abundance of predators in the ponds. Occurrence and abundance of predators determine which amphibian species can persist in a pond because some species cannot form viable populations in permanent (or temporary) ponds. Even though pond drying may cause the loss of entire cohorts of amphibians, most amphibian species prefer temporary ponds. Amphibians evolved ecological strategies that enable them to compensate for the loss of cohorts of larvae. In most years, amphibians have higher reproductive success in temporary than permanent ponds. Landscape change led to a greater loss of temporary than permanent ponds. Temporary ponds are often not recognized as part of the natural gradient in hydroperiod length and are often not viewed as valuable for conservation. Here, we argue why we believe that successful amphibian conservation can only be achieved through the restoration and construction of temporary ponds. A case study shows that a metapopulation of treefrogs (Hyla arborea) increased after the construction of temporary ponds.
... Neben der Anzahl Feuchtgebiete (Rückgang von 4 341 auf 708) ist auch deren durchschnittliche Fläche von 3,2 ha auf 1,7 ha geschrumpft. Abzugsgräben als Drainagesystem gibt es auch in Wäldern, was einen stark negativen Einfluss auf die vorkommenden Amphibien hat (Suislepp et al. 2011). ...
Gewässertypen unterscheiden sich in der Dauer der Wasserführung. Temporäre Gewässer
zeichnen sich dadurch aus, dass sie regelmäßig oder ab und zu austrocknen.
Das Austrocknen eines Gewässers reduziert die Anzahl Fressfeinde im Gewässer. Das
Vorkommen und die Abundanz der Prädatoren bestimmen, welche Amphibienarten im
Gewässer leben können. Manche Arten können in permanenten Gewässern keine lebensfähigen
Populationen aufbauen und andere wiederum nicht in temporären Gewässern.
Auch wenn das Austrocknen eines Gewässers zum Verlust einer Larvenkohorte führen
kann, so bevorzugen die meisten Amphibienarten dennoch temporäre Gewässer. Amphibien
verfügen über verschiedene ökologische Strategien, um den Verlust von Larvenkohorten
kompensieren zu können. In der Regel ist der Fortpflanzungserfolg in temporären
Gewässern höher als in permanenten Gewässern. Temporäre Gewässer sind in
stärkerem Maß verloren gegangen als permanente Gewässer. Sie werden oft gar nicht
mehr als Gewässer und geschweige denn als wertvoll erkannt; dies erschwert ihren
Schutz. Wir vertreten die Ansicht und belegen durch eine Fallstudie, dass temporäre
Gewässer für einen erfolgreichen Amphibienschutz unbedingt notwendig sind.
... Mit der gross angelegten Entwässerung der Landschaft mittels Gräben und Drainageröhren gingen auf der ganzen Landesfläche Tausende von Kleingewässern verloren [60]. Klein-und Kleinstgewässer bieten spezifische Lebensbedingungen für Amphibien und für eine charakteristische und artenreiche Flora und Fauna [61]. ...
35 wissenschaftliche Institutionen (Universitäten und ETH, Forschungsanstalten und Fachhochschulen, Datenzentren zur Schweizer Flora und Fauna, Naturmuseen, Botanische Gärten und Zoos) unter der Federführung des Forum Biodiversität Schweiz legen mit diesem Bericht die Zahlen zum Zustand der Biodiversität in 2014 in der Schweiz vor.
Die Analyse der 43 Fachpersonen zeigt: Die Anstrengungen der letzten Jahrzehnte für die Erhaltung unserer biologischen Vielfalt haben zwar Wirkung erzielt; sie konnten aber mit den anhaltenden oder gar weiter zunehmenden Bedrohungen nicht Schritt halten.
Sollen Biodiversität und Ökosystemleistungen erhalten bleiben, müssen alle Gesellschaftsbereiche aktiv werden. Politik, Wirtschaft, Bund, Kantone, Gemeinden und Privathaushalte haben es in der Hand, die Natur als wertvolles Kapital zu bewahren.
Small freshwater bodies (streams, pools, ponds, ditches) are biodiversity hotspots that are vulnerable to hydrological modification of landscapes. The impacts of landscape-scale modifications are difficult to study because multiple processes combine (loss, creation and modification of waterbodies and their surroundings). For an insight, we sampled sensitive insect orders (Ephemeroptera, Plecoptera, Trichoptera, Odonata) in small waterbodies in naturally comparable more and less drained forested catchments in Estonia. We asked how the landscape-scale species richness, abundance and assemblage composition are formed by contributions of different waterbodies. The mean abundances and assemblages were similar, but overall species richness was higher in more drained landscapes, primarily due to added man-made ponds (with distinct assemblages) and the heterogeneous surroundings of waterbodies. Ditches did not host specialist species and could not compensate for the loss of natural waterbodies. Natural pools supported the fewest species, but at a comparable mean abundance with the other waterbody types. The results indicate that a mid-term landscape-scale impact of forestry drainage on freshwater biota depends on which waterbodies and how abundantly are added and retained. To better regulate hydrological interventions, it is necessary to develop such regionally observed patterns into a functional understanding of long-term effects across different landscapes.
In Lower Austria’s Waldviertel region, artificial drainage ditches were constructed in the last century in order to use peatlands for forestry, agriculture, and peat extraction. By now, many of these peatlands are part of the Natura 2000 network and therefore gradually undergo restoration measures, which aim to rewet the peatlands. For this, the ditches are blocked with wooden dams, leading to a water runback, which in turn fills the ditches and peat pools. Such artificial water bodies generally depict secondary habitats for many species. Here, we investigated the amphibian fauna in four restored peatlands in the Waldviertel region and measured abiotic factors of the aquatic habitats to answer the question whether blocked ditches and peat pools are valuable secondary habitats for amphibians. We characterized the microhabitats of amphibians based on various structures and vegetation. Additionally, this study provides a basic assessment of reptile species in the investigated peatlands. During our assessment, we observed 1520 individuals of eight amphibian species, 64 individuals of four reptile species, and characterized 12 different microhabitats. Despite the low pH values of 3.2–4.2, four amphibian species and amphibian spawn were detected in Schwarzes Moos. Our results indicate that peat pools, drainage ditches, and open moorlands are potential habitats for amphibians and reptiles, making their conservation and management an important factor in the protection of amphibian and reptile species.
A rapid loss of species and habitats is occurring globally. Amphibians and wetlands are important components of this overall decline. Wetlands in the boreal region are frequently constructed by damming activities of an ecosystem engineer, the beaver (Castor sp.). The authors investigated the anuran fauna in ten such ‘beaver ponds’, ten ‘non-beaver ponds’ and eight temporary ponds in Finland. All three anuran species present in the region occupied the beaver ponds, including a species absent (the moor Frog Rana arvalis Nilsson, 1842) in natural waters (non-beaver ponds and temporary ponds). Moor frogs obviously benefitted from pond construction and removal of trees by beavers leading to a plentitude of shallow water and a wide belt of emergent vegetation. The results show that beavers offer high-quality habitats for anurans and facilitate the occurrence of moor frogs. It is suggested that these ecosystem engineers could be used in ecosystem restoration. The beaver clearly represents a species that promotes amphibian conservation
A fundamental goal of wetland restoration is to reinstate pre-disturbance hydrological conditions to degraded landscapes, facilitating recolonization by native species and the production of resilient, functional ecosystems. To evaluate restoration success, baseline conditions need to be determined and a reference target needs to be established that will serve as an ecological blueprint in the restoration process. During the summer wet seasons of 2010 and 2011, we used automated recording units to monitor a community of calling anuran amphibians in the Picayune Strand State Forest of Southwest Florida, USA. This area is undergoing hydrological restoration as part of the Comprehensive Everglades Restoration Plan. We compared occurrence of anurans at sites in the restoration area, to nearby locations in relatively undisturbed habitat (reference sites). We assessed the utility of the latter as restoration targets, using a hierarchical model of community species occupancy to estimate the probability of occurrence of anurans in restoration and reference locations. We detected 14 species, 13 of which were significantly more likely to occur in reference areas. All 14 species were estimated by our model to occur at these sites but, across both years, only 8-13 species were estimated to occur at restoration sites. The composition and structure of these habitats within and adjacent to the Picayune Strand State Forest indicate that they are suitable targets for habitat restoration, as measured by amphibian occurrence and species richness. These areas are important sources for recolonization of anuran amphibians as the hydrologically degraded Picayune Strand undergoes restoration to mitigate the effects of overdrainage and habitat loss.
Conservation of charismatic vertebrates in modern landscapes often includes habitat engineering, which is well supported by the public but lacks a consideration of wider conservation consequences. We analysed a pond management project for an introduced island population of captive-bred, Critically Endangered European mink
Mustela lutreola
. Ponds were excavated near watercourses in hydrologically impoverished forests to support the main prey of the mink (brown frogs
Rana temporaria
and
Rana arvalis
). A comparison of these ponds with other, natural, water bodies revealed that the (re)constructed ponds could reduce food shortages for the mink. Moreover, the ponds provided habitat for macroinvertebrates that were uncommon in the managed forests in the study area, including some species of conservation concern. The cost-effectiveness of the management of charismatic species can be increased by explicitly including wider conservation targets at both the planning and assessment stages.
Artificial drainage of forested wetlands to increase timber production has profoundly altered the hydrology of North-European landscapes during the 20th century. Nowadays, drainage ditches and small dredged streams can comprise most fluvial water bodies there, but the resulting ecological effects are poorly documented. In the current study, we explored, using fish as an indicator group, consequences of the transformation of natural stream networks to a mixture of natural and artificial watercourses. We asked whether the transformation results in impoverishment, enrichment or re-assembling of the communities both at watercourse and the landscape scales. We sampled fish in 98 sites in five well-forested regions in Estonia where ditches formed 83–92%, dredged streams 4–7%, and natural streams 3–10% of the total length of small watercourses. Based on a total of 6370 individual fish of 20 species, we found that, compared to natural streams, ditches had an impoverished fauna at both scales and both in terms of species richness and assemblage composition. Only natural streams hosted characteristic species (with Barbatula barbatula, Lampetra planeri and Lota lota emerging as significant indicators), while dredged streams had intermediate assemblages. The habitat factors explaining those drainage-related differences included a reduced flow velocity, loss of stream channel variability, less transparent water, and abundant aquatic vegetation. Hence, for stream-dwelling fish, drained forest landscapes represent degraded habitats rather than novel ecosystems, which contrasts with the transformation of terrestrial assemblages. Future studies should address whether that reflects the situation for whole aquatic assemblages, and how is the functioning of the hydrological systems affected. We suggest that the critical management issues for environmental mitigation of ditching effects on fish include basin scale spatial planning, protecting of the remaining natural streams, and rehabilitation of ditch channels in flat landscapes lacking beavers.
Koskiniemi, J. 1998. Adverse impact of forestry on fish and fisheries in stream environments of the Isojoki basin, western Finland. Boreal Env. Res. 3: 395–404. ISSN 1239-6095 The effects of forestry on fish and fisheries were studied in the Isojoki basin, western Finland. The most abundant fish species in the study area, brown trout (Salmo trutta L.), was found in 27 of 50 brooks studied. Enzyme electrophoresis revealed at least five genetically differentiated stocks of brown trout in the brooks. Regression analysis indi-cated that the population density of brown trout was positively dependent on the abun-dance of pools, stony bottom material (2 to < 10 cm in diameter), undercut banks in the streams, and water pH, while the abundance of ditches in the catchment area and shad-ing by the tree canopy affected the density negatively. Incubation experiments showed that sedimentation with mineral and humus material impaired the survival of trout eggs in the rapids. The results suggest that dredging of brooks and increased soil erosion due to drainage may threaten the reproduction and genetic diversity of trout stocks in the brooks and main river.
The aim of this overview paper is to analyse the inclusion and use of the ecosystem services concept in scientific studies of degraded peatlands and peatland restoration. Publications indexed by the Institute of Science Information (ISI) Web of Science (WoS) from 1980 to October 2009 were analysed. Word combinations relevant to peatland ecosystem services in the title, keywords and abstract were used. We followed the division of ecosystem services into four categories: supporting, regulating, provisioning and cultural, as provided by the Millennium Ecosystem Assessment (2005). The analysis indicated that the concept of ecosystem services is not referred to explicitly in ISI WoS studies on peatland restoration. The interpretation of the content identified using search phrases related to various beneficial functions of peatlands showed that they mainly include information on regulating and supporting ecosystem services critical to sustaining vital ecosystem functions that deliver benefits to people. There are only a few articles addressing provisioning and cultural ecosystem services. One of the key issues concerning the effect of peatland restoration in the provisioning of ecosystem services is the balance of greenhouse gases and their role in global climate regulation.
Extinctions are normal biological phenomena. Both mass extinctions in geological time and local extinctions in ecological time are well documented, but rates of extinction have increased in recent years—especially in vertebrates, including amphibians—as illustrated by recent reports of their population declines and range reductions. We suggest that long-term population data are necessary for rigorously evaluating the significance of the amphibian declines. Due to the physiological constraints, relatively low mobility, and site fidelity of amphibians, we suggest that many amphibian populations may be unable to recolonize areas after local extinction.
Las extinciones son un fenómeno biológico normal. Extinciones en masa en una escala temporal geológica y extinciones locales en una escala temporal ecológica, están bien documentadas, pero en años recientes las tasas de exinción han incrementado, especialmente en vertebrados, incluyendo a los anfibios tal como ha sido ejemplificado en reportes recientes sobre la declinación de su población y la reducción de su área de distribución. Nosotros sugerimos que datos poblacionales a largo plozo son necesarios para evaluar rigurosamente la significancia de la declinación en anfibios. Nosotros sugerimos que muchas de las poblaciones de anfibios son incapaces de recolonizar áreas después de extinciones locales debido a las restricciones fisiológicas, la relativamente baja movilidad y la filopatría de los anfibios.
Mosquitoes (Culex pipiens L., 1758) are important vectors for diseases of both wildlife and humans. Understanding how natural factors influence mosquito abundance may provide insights into the ecology of various diseases, as well as solutions to controlling disease vectors. One of the natural factors regulating mosquito distributions and population sizes is predation. A poorly understood source of natural mosquito predation is amphibians. We determined the mosquito consumption capability of two amphibians, adult Red-spotted Newts (Notophthalmus viridescens viridescens (Rafinesque, 1820)) and larval Mole Salamanders (Ambystoma talpoideum (Holbrook, 1838)). We also compared mosquito consumption of eastern mosquitofish (Gambusia holbrooki Girard, 1859), a known predator of mosquitoes, and A. talpoideum. Both salamander species were capable of consuming large numbers of mosquito larvae per day (least-square means 1SE = 439 20 and 316 35 mosquitoes/day consumed by A. talpoideum and N.v.viridescens, respectively). In A. talpoideum, mosquito consumption scaled with body size, with the largest individual (4.4g) ingesting 902 mosquitoes in 1day. Gambusia holbrooki consumed 3.5 more mosquitoes during a 24h feeding trial than similar-sized A. talpoideum. Our findings suggest that amphibians could have a substantial impact on mosquito larvae abundance, especially considering that amphibians can reach densities of up to 500000 individuals/ha. Furthermore, we hypothesize that introduction of G. holbrooki could reduce abundances of native mosquito predators (e.g., salamanders) indirectly, through competition for invertebrate prey.
Salamanders are cryptic and, though largely unrecognized as such, extremely abundant vertebrates in a variety of primarily forest and grassland environ-ments, where they regulate food webs and contribute to ecosystem resilience-resistance (= stability) in several ways: (a) As mid-level vertebrate predators, they provide direct and indirect biotic control of species diversity and ecosystem processes along grazer and detritus pathways; (b) via their migrations, they connect energy and matter between aquatic and terrestrial landscapes; (c) through association with underground burrow systems, they contribute to soil dynamics; and (d) they supply high-quality and slowly available stores of energy and nutrients for tertiary consumers throughout ecological succession. Salamanders also can provide an important service to humans through their use as cost-effective and readily quantifiable metrics of ecosystem health and integrity. The diverse ecological roles of salamanders in natural areas underscore the importance of their conservation.
Baltic coastal meadows are among the most threatened habitats in Europe, with most residual habitat being in Estonia and Sweden. We quantitatively related the changes in this habitat type in Estonia to the history of a key inhabitant — the natterjack toad (Bufo calamita Laur.). Between the 1930s and 2000s, 67% of 52 local populations of the toad disappeared; in coastal meadows, the decline was 91%. Since the 1980s, coastal grasslands have lost their value as the main habitat for the species, and occupation of secondary habitats has not balanced the disappearance of primary habitat. According to aerial photographs from 1950–51, 1970–71,
and 1996–2000, 60%–83% of the coastal meadow habitats in Estonia were lost by 2000, and the toad became extinct in more than 80% of its historical habitat. The survival of local populations was related to the sizes of managed meadows and sandy areas — larger initial areas were related to better survival, probably due to larger population size. Extinction rates exceeded habitat loss rates during advanced stages of habitat loss after 1970, probably due to the additive effects of habitat fragmentation and the disappearance of critical habitat components. Hence, habitat restoration for natterjack toads should focus on large meadow areas, and should be initiated prior to advance habitat loss. Currently, however, meadow populations of the toad in Estonia are unlikely to persist without artificial re-establishment of populations.
We examined larval anuran assemblages at 12 temporary wetlands occurring on the MacArthur Agro-Ecology Research center (MAERC)
in southcentral Florida. MAERC is an active cattle ranch, and the wetlands on the site are heavily influenced by an extensive
series of ditches that drain the landscape. Ditching has resulted in a change from a historically extensive marsh system to
a series of isolated wetlands surrounded by upland habitats. Because a majority of anurans in Florida breed exclusively or
facultatively in wetlands whose drying regime excludes fish, we were interested in determining the value of these modified
wetlands as breeding sites. We examined the effect of wetland size and hydrology on anuran use, and compared breeding activity
across three summers that varied greatly in rainfall pattern. We sampled tadpoles from May 93 to August 93 and from May 94
to September 95. A total of 3678 tadpoles from 11 species was collected. Rana utricularia was the most abundant species and the only species found in every wetland Species richness was related positively to wetland
size (r=0.65, p=0.023) but not hydroperiod (r=0.03, p=0.93). Tadpole abundance was not related to wetland size (r=0.35, p=0.29)
nor hydroperiod (r=0.40, p=0.22). Annual variation in rainfall resulted in significant changes in species composition. A drought
during 1993 resulted in no breeding. A high water table in the spring of 1995 resulted in localized flooding in early summer
on part of the ranch. Wetlands in these areas were exposed to spillover of water from ditches containing fishes. Wetlands
so impacted showed significant changes in species composition from the previous year (x2=1008, p < 0.0001), whereas wetlands that were not impacted did not differ in composition. The wetlands at MAERC provide dynamic
habitats that offer varying breeding opportunities that are highly dependent on meteorological conditions.
Ditches are common in landscapes influenced by agricultural, forestry, and peat mining activities, and their value as corridors
remains unassessed. Pond-breeding amphibians can encounter hostile environments when moving between breeding, summering, or
hibernation sites, and are likely to benefit from the presence of ditches in the landscape. Within a system consisting of
ditch networks in bogs mined for peat in eastern New Brunswick, Canada, I quantified the breeding, survival, and movements
of green frogs (Rana clamitans melanota) in drainage ditches and also surveyed peat fields. Frogs rarely ventured on peat fields and most individuals frequented
drainage ditches containing water, particularly in late summer. Though frogs did not breed in ditches, their survival rate
in ditches was high (88%). Ditches did not hinder frog movements, as frogs moved independently of the current. Results indicate
that drainage ditches containing water enable some movements between habitats isolated by peat mining, in contrast to peat
surfaces, and suggest they function as amphibian movement corridors. Thus, such drainage ditches may mitigate the effects
of peat extraction on amphibian populations. At the very least, these structures provide an alternative to hostile peat surfaces.
This study highlights that small-scale corridors are potentially valuable in population dynamics.
Large-scale restoration of quality habitats is often considered essential for the recovery of threatened pond-breeding amphibians
but only a few successful cases are documented, so far. We describe a landscape-scale restoration project targeted at two
declining species—the crested newt (Triturus cristatus Laur.) and the common spadefoot toad (Pelobates fuscus Wagler)—in six protected areas in southern and southeastern Estonia. The ponds were restored or created in clusters to (i)
increase the density and number of breeding sites at local and landscape levels; (ii) provide adjacent ponds with differing
depths, hydroperiods and littoral zones and (iii) restore an array of wetlands connected to appropriate terrestrial habitat.
In only 3years, where 22 of the 405 existing ponds (5%) were restored and 208 new ponds (51%) created, the number of ponds
occupied by the common spadefoot toad increased 6.5 times. Concerning the crested newt and the moor frog (Rana arvalis Nilsson), the increase was 2.3 and 2.5 times, respectively. The target species had breeding attempts in most of the colonised
ponds—even more frequently than common species. Also, the amphibian species richness was higher in the restored than in the
untreated ponds. The crested newt preferably colonised ponds that had some submerged vegetation and were surrounded by forest
or a mosaic of forest and open habitats. The common spadefoot toad favoured ponds having clear and transparent water. Our
study reveals that habitat restoration for threatened pond-breeding amphibians can rapidly increase their numbers if the restoration
is implemented at the landscape scale, taking into account the habitat requirements of target species and the ecological connectivity
of populations. When the remnant populations are strong enough, translocation of individuals may not be necessary.
Predation is an important mortality factor among larval amphibians. Female amphibians may therefore increase their fitness by choosing predator-free reproductive habitats. We studied whether female common frogs choose their breeding habitat in order to minimize tadpole mortality by fish predation. In a paired experimental design we manipulated twelve freshwater rock-pools by introducing adult threespine sticklebacks in them and compared the numbers of reproducing female frogs and surviving tadpoles with those in twelve unmanipulated pools at close distance. All pools had supported a breeding frog population during the two preceding years. Common frog females did not alter their pool choice after the fish introductions. There was no difference in the number of egg batches laid in manipulated and in control pools. The egg laying pattern did not differ qualitatively from that in the two previous years. Laboratory experiments revealed that threespine sticklebacks prey heavily upon young common frog tadpoles and field investigations indicated significantly lowered tadpole survival in pools with sticklebacks. Thus, common frog females did not choose their reproductive habitat to avoid predation on tadpoles. We discuss site tenacity and intraspecific competition among tadpoles as other possible agents affecting female reproductive habitat choice.
High floods in watercourses are of great interest, because of the potential hazards they pose to people and low-lying land near rivers. In many parts of the world, inundations are common and in northwest Europe there are high discharges almost every year, occasionally with serious consequences. In Sweden, such a major flood occurred in 1985, causing a damburst. Land use in the area was mainly forestry, and fairly extensive clear-felling and drainage were believed to have amplified high discharges following heavy rain. This led to investigation of the hydrological consequences of these forestry activities. Drainage was carried out both as new drainage of virgin peatlands, and as drainage of moist and wet mineral soils, i.e. remedial drainage of clear-felled areas. The investigations were made on small catchments and utilised the calibration period and control basin technique, using linear regression relations. Peatland drainage resulted in reduced high discharges, while drainage of clear-felled areas resulted in increased high discharges, as compared to forested conditions. However, drainage of clear-felled areas partly led to reduced peak flows. A high groundwater level was an important prerequisite for increased discharges. When results from small catchments were applied to larger rivers, the effects of forest drainage were small, i.e. increases were less than 10%.
The first global assessment of amphibians provides new context for the well-publicized phenomenon of amphibian declines. Amphibians
are more threatened and are declining more rapidly than either birds or mammals. Although many declines are due to habitat
loss and overutilization, other, unidentified processes threaten 48% of rapidly declining species and are driving species
most quickly to extinction. Declines are nonrandom in terms of species' ecological preferences, geographic ranges, and taxonomic
associations and are most prevalent among Neotropical montane, stream-associated species. The lack of conservation remedies
for these poorly understood declines means that hundreds of amphibian species now face extinction.
Ecological thresholds are defined as points or zones at which a rapid change occurs from one ecological condition to another. The existence of thresholds in species-habitat relationships has important implications for management, but the lack of concordance across studies and the wide range of methods used make generalizations difficult. We used two different statistical methods to test for the existence of thresholds for both individual species and the whole community, using three newt species as models. Based on a sample of 371 ponds, we found significant thresholds for both landscape configuration and composition. These were for the relationships between distance to forest and occurrence of Triturus alpestris and T. helveticus, and forest and crop cover and T. helveticus. Variability in the location of thresholds observed for the different species in this study caution against their use at the community level. Future studies should be based on the identification and assessment of thresholds for targeted species. Thresholds can be a useful concept from which tools may be developed to focus conservation effort for threatened species and their habitats.
We examined larval anuran assemblages at 12 temporary wetlands occurring on the MacArthur Agro-Ecology Research center (MAERC) in southcentral Florida. MAERC is an active cattle ranch, and the wetlands on the site are heavily influenced by an extensive series of ditches that drain the landscape. Ditching has resulted in a change from a historically extensive marsh system to a series of isolated wetlands surrounded by upland habitats. Because a majority of anurans in Florida breed exclusively or facultatively in wetlands whose drying regime excludes fish, we were interested in determining the value of these modified wetlands as breeding sites. We examined the effect of wetland size and hydrology on anuran use, and compared breeding activity across three summers that varied greatly in rainfall pattern. We sampled tadpoles from May 93 to August 93 and from May 94 to September 95. A total of 3678 tadpoles from 11 species was collected. Rana utricularia was the most abundant species and the only species found in every wetland Species richness was related positively to wetland size (r=0.65, p=0.023) but not hydroperiod (r=0.03, p=0.93). Tadpole abundance was not related to wetland size (r=0.35, p=0.29) nor hydroperiod (r=0.40, p=0.22). Annual variation in rainfall resulted in significant changes in species composition. A drought during 1993 resulted in no breeding. A high water table in the spring of 1995 resulted in localized flooding in early summer on part of the ranch. Wetlands in these areas were exposed to spillover of water from ditches containing fishes. Wetlands so impacted showed significant changes in species composition from the previous year (x2=1008, p < 0.0001), whereas wetlands that were not impacted did not differ in composition. The wetlands at MAERC provide dynamic habitats that offer varying breeding opportunities that are highly dependent on meteorological conditions.
To fit nature into categories is always difficult, especially with complex vegetation. In the northern hemisphere forest vegetation in the temperate zone usually consists of deciduous forests and in the boreal zone often of coniferous forests. In the transition zone there are forests with deciduous trees, coniferous trees and also very often deciduous and coniferous trees mixed (later in this chapter referred to as mixed forests). In the Nordic countries this transition is termed the ‘hemiboreal’ zone (Ahti et al., 1968; see map in chapter 7). In Sweden this zone is about 600 km wide and in the western Soviet Union even wider. Thus, the hemiboreal zone covers large areas. In spite of this its main ecological features are less well understood than those of more southern and northern zones. This is due to intensive exploitation in historic times and the complex dynamics between deciduous and coniferous trees. The separation of natural and man–made factors affecting vegetation dynamics has been especially difficult. In this short presentation of the hemiboreal zone in Sweden the description of some important features and processes must be very brief due to space limitation. I present major landscape changes and their main causes over the last 1000 years. Keystone species, i.e. species whose presence affects the distribution and/or abundance of several other species or whose absence would cause cascading effects throughout a community, are sometimes treated in more detail. Examples of such species are major forest trees and shrubs, common vertebrate predators and herbivores, pollinators and seed dispensers.
Virgin and forest-ameliorated pine bogs were compared when 10 yr had passed since artificial drainage began and 6 yr since the fertilization of the ameliorated bog. In the virgin bog the oribatid community of the hollows was dominated by Limnozetes sphagni, the community of the hummocks by Oppiella nova and Tectocepheus velatus. The typical peatland species had either decreased following the forest-amelioration or had shifted their main microhabitat from the hummocks to the hollows. Their place had been taken by the habitat generalists (eg Oppiella nova) and by species preferring a drier environment (eg Chamobates borealis). The drying of the soil was the main cause of the faunal response observed. Palaeacarus hystricinus, Trhypochthonius nigricans, T. badius and Eupelops acromios are reported for the first time in Finland. -from Author
Vernal-pool breeding amphibians often oviposit in anthropogenic pools formed during industrial forest-management activities, as well as in natural ephemeral pools. We quantified wood frog (Rana sylvatica) and spotted salamander (Ambystoma maculatum) reproductive effort and metamorph emergence, pool hydroperiods and environmental features, and the density of natural and anthropogenic pools across the landscape to compare the reproductive effort and success of amphibians breeding in natural and anthropogenic pools in managed forests in Maine. Numbers of egg masses in anthropogenic and natural pools did not differ for either wood frogs (median number masses/pool = 15 and 14, respectively) or spotted salamanders (13 and 13 masses/pool). Anthropogenic pools outnumbered natural pools on survey transects by a factor of 3.7. Pool area, depth, temperature, solar exposure, and coverage of closed-canopy forest within 100 m influenced amphibian reproductive effort in temporary pools. In a year with typical breeding-season rainfall (1997), anthropogenic pools dried sooner than natural pools (median drying dates: June 17 and July 30, respectively), and extensive larval mortality occurred upon pool drying. During an unusually wet breeding season (1996), the two pool types had similar hydroperiods (median drying dates: August 17 and 28). Metamorphs emerged from natural pools later and at larger size than metamorphs emerging from anthropogenic pools. Anthropogenic pools seem to function as ecological traps for breeding wood frogs in most years, and thus they should be avoided or designed with adequate size, depth, and shading to maintain an adequate hydroperiod.
Of 167 ponds within 700 m of deciduous forest, 56% contained egg clutches of Rana dalmatina (in all 1546) and 55% of all egg-clutches were found in 10% of the ponds. An almost exponential decline in the number of egg-clutches with increasing distance from forest is seen. No relation between pond size and population size was found. Only 16% of the breeding sites were >500 m2 and thus protected by the Nature Conservancy Law. Number of clutches was relatively low in very eutrophicated or very shady ponds. -from Author
Coordinated efforts by ecologists and natural resource managers are necessary to balance the conservation of biological diversity with the potential for sustained economic development. Because some amphibians have suffered world-wide declines during the last 20 years, it is important to consider biologically based management strategies that will preserve local and regional populations. This paper provides a brief overview of potential threats to local and regional populations, the state of knowledge on population and landscape processes, and the critical elements needed for an effective management plan for amphibians. Local population dynamics and ecological connectivity of amphibian metapopulations must be considered in effective management plans. There are 3 critical factors to consider in a management plan (1) the number or density of individuals dispersing from individual wetlands, (2) the diversity of wetlands with regard to hydroperiod, and (3) the probability of dispersal among adjacent wetlands or the rescue and recolonization of local populations. Wetland losses reduce the total number of sites where pond-breeding amphibians can reproduce and recruit juveniles into the breeding population. Loss of small, temporary wetlands (
From the reviews of the First Edition."An interesting, useful, and well-written book on logistic regression models . . . Hosmer and Lemeshow have used very little mathematics, have presented difficult concepts heuristically and through illustrative examples, and have included references."—Choice"Well written, clearly organized, and comprehensive . . . the authors carefully walk the reader through the estimation of interpretation of coefficients from a wide variety of logistic regression models . . . their careful explication of the quantitative re-expression of coefficients from these various models is excellent."—Contemporary Sociology"An extremely well-written book that will certainly prove an invaluable acquisition to the practicing statistician who finds other literature on analysis of discrete data hard to follow or heavily theoretical."—The StatisticianIn this revised and updated edition of their popular book, David Hosmer and Stanley Lemeshow continue to provide an amazingly accessible introduction to the logistic regression model while incorporating advances of the last decade, including a variety of software packages for the analysis of data sets. Hosmer and Lemeshow extend the discussion from biostatistics and epidemiology to cutting-edge applications in data mining and machine learning, guiding readers step-by-step through the use of modeling techniques for dichotomous data in diverse fields. Ample new topics and expanded discussions of existing material are accompanied by a wealth of real-world examples-with extensive data sets available over the Internet.
There were about 2950 salamanders per ha (1770 g/ha wet wt) in the Hubbard Brook Experimental Forest in New Hampshire. The terrestrial species, Plethodon cinereus, accounted for about 93.5% of the total biomass while the streamside species, Desmognathus fuscus, Eurycea bislineata and Gyrinophilus porphyriticus, accounted for the remaining 6.5%. Notophthalmus viridescens was present, but was rare and insignificant in the biomass calculations. The population size of salamanders at Hubbard Brook appears to be stable. The biomass of salamanders is about twice that of birds during the bird's peak (breeding) season and is about equal to the biomass of small mammals.
Impacts of forestry have been described in many studies, with a strong focus on changes in run-off water quality. Biological responses to forest drainage and the efficiency of commonly used water protection methods remain largely unknown, however. We used a six-year replicated before-after-control-impact (BACI) field experiment to assess the effects of forest drainage improvement works (ditch cleaning; digging of supplementary ditches) on water chemistry, sedimentation, brown trout egg mortality and macroinvertebrate community composition in six headwater streams in Northern Finland. Standard water protection methods (ditch break combined with sedimentation pit) were used to reduce fine sediment (
Soil mesofauna community structure was studied in a drainage-succession continuum of peatland sites supporting Scots pine (Pinus sylvestris L.) dominated stands in southern Finland. The numbers of Enchytraeidae, Collembola, Oribatida, Mesostigmata and Prostigmata in an 8-cm-deep surface peat layer were compared among a pristine undrained pine mire site, comparable sites drained for forestry 12, 26 and 60 years earlier, and a 42-year-old drained site re-wetted two years earlier.Drainage and the consequent water-level draw-down clearly increased the numbers of all soil animals studied, the numbers showing highly significant correlation with the water-table level of the sites. On the older drained sites, the populations were generally about ten times higher than on the undrained site; for Collembola, almost 100 times higher. After re-wetting, the numbers dropped abruptly, falling between those of the undrained and the youngest drained site. Oribatida were the most frequently found animals on the sites studied: on the undrained site almost 60% of the total number were these mites, the relative proportion somewhat decreasing along the drainage succession. The proportion of Enchytraeidae also decreased slightly after drainage, whereas that of Collembola clearly increased. Most of the soil fauna was found close to the soil surface. In general, >80% of Collembola, Oribatida, Mesostigmata and Prostigmata, and >60% of Enchytraeidae were found in the topmost 4-cm layer. In the course of the drainage succession, the soil fauna community structure became more similar to that of upland sites with similar tree-stand growth potential.
In S and C Sweden, frequency of occurrence of the woodpecker increased with total area of deciduous woodland; when census areas (200 ha) contained <17 ha, it was 24%, with 17-38 ha it was 62%, and with >38 ha deciduous woodland it was 80%. Latitude had no significant effect, but the species requires larger areas in managed than in natural forests. Occupation of census areas could be predicted with 68% accuracy from the area of nemoral and riparian deciduous woods (positive association with occupation) and the area of mixed coniferous/deciduous (negative association with occupation). The area of nemoral deciduous forest has decreased in Sweden during the second half of this century due to cutting, probably one cause of the decline of the lesser spotted woodpecker. -from Authors
A field study has been made in the relatively narrow sympatric zone of Triturus cristatus and T. marmoratus, in the department Mayenne (France). Ecological data have been analysed. In the sympatric area specific preferences appear to exist: ecological isolation has developed in some areas. Typical T. marmoratus areas are hilly and wooded, provided with many terrestrial hiding-places, while forest pools and springs especially serve as spawning sites. T. cristatus areas are flat and open. Comparison with distribution data of 24 years ago shows expansion of T. cristatus at the expense of T. marmoratus, which presumably is true for the whole sympatric zone. The preferences of the species in combination with changes in environment by human intervention explain the detected changes in distribution. Ecological isolation as a phenomenon in the speciation of both species is discussed.
It is said that the forest industry is the backbone of the national economy in Finland. This was in particular the case in the twentieth century. That is also why the drainage of forests has played an important role in the national forestry policy. The most intensive period of forest drainage started at the beginning of the 1960s and lasted for 20 years. During that period the annual drained area was on average 200 000 ha. This article presents a short overview of the history of forest drainage in Finland in its heyday and also illustrates some current water conservation measures in the drainage of forested areas. Copyright © 2007 John Wiley & Sons, Ltd.On dit que l'industrie de la forêt est l'épine dorsale de l'économie nationale en Finlande. Ce fut en particulier le cas au 20ème siècle. C'est également pourquoi le drainage des forêts a joué un rôle important dans la politique nationale de la sylviculture. La période la plus intensive de ce drainage a commencé dans le début des années 60 et duré les 20 années suivantes. Au cours de cette période la surface drainée annuelle a été en moyenne de 200 000 hectares. Cet article présente une brève vue d'ensemble de l'histoire du drainage des forêts en Finlande à son apogée et illustre également quelques mesures actuelles de conservation de l'eau dans le drainage des régions forestières. Copyright © 2007 John Wiley & Sons, Ltd.
1. Temporary ponds provide rich but unpredictable habitats for amphibians. Frogs, toads and newts have life cycles which are geared to the filling and drying-up of temporary ponds, and have evolved strategies for dealing with desiccation and short-term changes in pond quality. 2. Plasticity in development allows frogs and toads to adjust the rate of larval development according to the risk of pond desiccation. This may be achieved by increasing behavioural thermoregulation so that body temperature is raised in warm, shallow water. 3. As a pond dries up, increased crowding between amphibian larvae may result in increased competition, growth inhibition, and cannibalism. Large larvae may therefore survive at the expense of small larvae, but this may increase the chance of some reproductive success within the population as a whole. Conflicting selection pressures may maintain different breeding strategies within the same population. 4. Despite high fecundity, repeated breeding by adults, and developmental plasticity and cannibalism in larvae, many larval populations still suffer catastrophic mortality each year. Providing catastrophes do not occur more often than once per generation, the population may still persist. Should extinction occur at one pond, immigration of juveniles or adults from a neighbouring pond may ensure population continuity. Networks of ponds are therefore essential to maintain viable, self-adjusting metapopulations into the long-term. © 1997 John Wiley & Sons, Ltd.
1. Forest drainage, including mainly ditching of waterlogged peatlands in order to increase wood growth, has caused substantial changes in the hydrology and water quality of Finnish streams. However, knowledge on the ecological impact of these changes is poor. This paper studies the potential impact of forest drainage, catchment characteristics and habitat factors on the water quality and benthic macroinvertebrates in headwater streams of the River Isojoki, western Finland. An intensive programme of water sampling was carried out at nine study sites, while zoobenthic samples covered a total of 18 streams.2. According to multivariate regression models concentrations of aluminium and suspended solids in stream water at nine study sites increased significantly with increasing forest drainage of the catchment area. Further, drainage intensity contributed significantly to the decrease in minimum values of alkalinity.3. In a Canonical Correspondence Analysis, the variation in macroinvertebrate species distribution and abundance was largely explained by drainage intensity, moss coverage and the concentrations of aluminium and iron in stream water. A significant positive correlation was established between the species richness of benthic macroinvertebrates and the proportional cover of vegetation on the stream bed, whereas a significant negative correlation was found between species richness and sand cover.4. The results suggest that drainage has significantly contributed to the deterioration of water quality and habitat structure, and impoverishment of benthic communities in the headwater streams of the River Isojoki. In order to protect the ecological integrity of such boreal headwater streams, more effective protection schemes in forestry practices and rehabilitation of the adversely affected streams and their catchment areas are needed. © 1998 John Wiley & Sons, Ltd.
The growth and size of the newts, Triturus vulgaris (L.) and T. cristatus (Laurenti) in different parts of Norway (+ Jämtland, Sweden) were studied. Age was estimated from skeletal growth marks, size-frequency histograms and, for the males, from the number of testis lobes.
On average, the T. vulgaris Larvae in central Norway and Jämtland are smaller than those in southeastern Norway, although in good localities, at the same altitude, they are of approximately the same size and complete their development already within 2½–3 months. Larvae living in eutrophic habitats are larger than those in oligotrophic-dystrophic habitats. In bog habitats at similar times of year the T. cristatus larvae from central Norway are about the same size as those from similar habitats in southwestern and southeastern Norway, but somewhat smaller than those from eutrophic ponds in the Oslofjord area.
No significant differences in the mean size of adult T. vulgaris from southeastern Norway and from central Norway were found. The maximum lengths attained were recorded from central Norway, however. In eutrophic habitats T. vulgaris adults BK usually larger than those in oligotrophic/dystrophic habitats.
In southeastern Norway, where growth is rapid, T. vulgaris may become sexually mature when 2+ yr-old, in central Norway usually a year later, in Jämtland. on average, still later, and in their northernmost locality (Vefsn) they probably do not breed until 5+ or 6+ yr-old.
On average, T. cristatus adults from southeastern Norway are slightly larger than those from central Norway, and may become mature at 2+ yr-old. compared with 4 + yr-old, at the earliest, in the latter area. The differences in the growth rates of both larvae and metamorphosed stages, of both species, most probably represent a response to climatic differences, although biotope quality is also an important factor.
The concept of the ecological trap, a low-quality habitat that animals prefer over other available habitats of higher quality, has appeared in the ecological literature irregularly for over 30 years, but the topic has received relatively little attention, and evidence for traps remains largely anecdotal. Recently, however, the ecological trap concept has been the subject of a flurry of theoretical activity that is likely to raise its profile substantially, particularly in conservation biology. Ecological trap theory suggests that, under most circumstances, the presence of a trap in a landscape will drive a local population to extinction. A number of empirical studies, almost all of birds, suggest the existence of traps and demonstrate the difficulties of recognizing them in the field. Evidence for ecological traps has primarily been found in habitats modified by human activities, either directly (e.g., through the mowing of grassland birds' nests) or indirectly (e.g., via human-mediated invasion of exotic species), but some studies suggest that traps may occur even in relatively pristine areas. Taken together, these theoretical and empirical results suggest that traps may be relatively common in rapidly changing landscapes. It is therefore important for conservation biologists to be able to identify traps and differentiate them from sinks. Commonly employed approaches for population modeling, which tend to assume a source-sink framework and do not consider habitat selection explicitly, may introduce faulty assumptions that mask the effects of ecological traps and lead to overly optimistic predictions about population persistence. Given the potentially dire consequences of ecological traps and the accumulating evidence for their existence, greater attention from the community of conservation biologists is warranted. In particular, it is important for conservation biologists and managers to incorporate into conservation planning an explicit understanding of the relationship between habitat selection and habitat quality.
The breeding success of Finnish grouse has been in decline for decades. While it has been shown that fragmentation and modern forestry practices such as clear‐cutting affect the viability of grouse populations, little is known about effects of large‐scale drainage. The drainage network in Finland has increased dramatically during the past decades. By 1988, 6 million ha of bog ecosystems had been drained. This is likely to have had a profound direct and indirect effects on grouse productivity. Because ditches persist in time, large‐scale drainage may therefore have strong potential for affecting the long‐term breeding success of three forest grouse species in Finland.
Using a mixed‐model approach on nation‐wide data, we estimate the effects of drainage on breeding success of three grouse species for the period from 1966 to 1988. The possible additive effect of precipitation is investigated using regional precipitation data. For each species, we compare a set of hypotheses and select the best model(s) according to the Akaike information criterion.
For all species, the model which included the main effects of both ditch density and precipitation outperformed the models with just one of the main effects as well as the interaction model. The effects are restricted to southern and central Finland, where drainage is most intensive.
The effects of drainage are likely to be both direct and indirect, but the mechanisms are less clear. Both bottom‐up, such as decreased availability of insect food, and top‐down effects, such as increased predation risk, may account for indirect effects. Direct effects are likely to involve drowning of chicks.
Synthesis and applications . Bogs are classified as key biotopes by the European Union, and Finland is obliged to maintain their favourable conservation status and to protect typical bog communities. While this goal may be achieved for state‐owned land, restoration of drainage systems on private land continues. Considering the persistence of ditches, new legislation are therefore needed to favour the recovery of former bogs and mires on private land as well as to protect remaining ones.
SUMMARY 1. Floods are an important mechanism of disturbance operating in streams that can markedly influence the abundance and diversity of benthic fauna. In upland streams many studies cite the scouring effects of fine transported sediments as a potential source of disturbance to the biota during spates, but few studies have sought to test this hypothesis critically.
2. Here we used a series of eight artificial streams to test whether high suspended-sediment concentrations influenced the short-term response of benthic invertebrate fauna to increases in flow. In an experiment designed to simulate a small spate, flow and sediment loads were each manipulated to examine their independent and interactive effects. Benthic invertebrates were sampled before and after the manipulation, and drift samples were taken at regular intervals during the experiment. The experiment was repeated twice, once at the end of winter (June, 1998), and once in summer (February, 1999).
3. Flow increases caused large increases in the number and diversity of drifting animals, and significant declines in the numbers and diversity of organisms found in benthic samples, but these declines were apparently not affected by the addition of fine sediment. The addition of sediment alone had little effect on the fauna. These results were consistent across both experiments.
4. The results suggest that flow increases alone can disturb benthic fauna, and that neither substrate movement nor suspended sediment increases are necessary for floods and spates to disturb the benthic assemblage. However, as argued elsewhere, the effects of flow increases are likely to be contingent upon the presence or absence of local flow refugia, which can allow animals to escape the shear forces that would otherwise remove them from the surface or interstitial areas of the streambed.
Declines in amphibian populations and the loss of some species has spurred research into the causes of declines. Little research has been done on what the loss of amphibian species may mean to ecosystem function. I describe a field experiment where the number of Plethodon cinereus (the red-backed salamander) was manipulated in enclosures buried in the forest floor. I determined the composition of the forest floor invertebrate community and the rate of decomposition of leaf litter in enclosures with and without salamanders over 4.5 months. Salamander predation in enclosures significantly reduced invertebrate numbers compared to control enclosures. Salamander predation also indirectly reduced rate of decomposition by between 11 and 17%. This was probably due to salamanders consuming a significant number of leaf fragmenters (e.g. Coleoptera and Diptera larvae). Predation on leaf litter fragmenters may alter carbon dynamics in forested ecosystems.
Ephemeral or “vernal” pools occur commonly throughout the forest of the northeastern United States and adjacent eastern Canada.
These pools are critical breeding habitat for a number of amphibian species and support a diverse invertebrate community.
The hydroperiod or duration of surface water of vernal pools affects faunal composition and reproduction. We conducted bathymetric
surveys of 34 vernal pools located in central Massachusetts in early spring when the pools were at maximum extent after receiving
snowmelt runoff. With these data, we estimated maximum pool depths, surface areas, perimeters, volumes, and basin profile
coefficients. We calculated relative hydroperiod indices for the pools based on the presence or absence of surface water during
periodic pool visits over the three-year study. The ranges of estimated pool morphological parameters were 0.11–0.94 m for
maximum depth, 68–2941 m2 for maximum surface area, 6–506 m3 for maximum volume, and 30–388 m for maximum perimeter. Basin profile coefficients ranged between 0.60 (convex) and 2.24
(concave), with a median value of 1.02 (straight slope). Maximum pool depth was positively correlated with area and perimeter,
but the correlations were only moderately strong, and there were many shallow pools with large surface areas. Correlations
between basin profile coefficients and other morphological parameters were weak or non-significant. Maximum pool volume was
proportional to the product of area and depth, but the proportionality constant was dependent on the basin profile coefficient.
Relative hydroperiod was weakly correlated with pool morphometry; the strongest relationship was found between hydroperiod
and maximum pool volume. In general terms, pools with a maximum depth greater than 0.5 m, a maximum surface area larger than
1000 m2, or a maximum volume greater than 100 m3 had surface water more than 80% of the times they were visited. In contrast, shallower pools, smaller pools, or pools with
lesser volumes had varying hydroperiods. The weak relationships between pool morphometry and hydroperiod indicate that other
factors, including temporal patterns of precipitation and evapotranspiration and ground-water exchange may have significant
influence on vernal pool hydrology and hydroperiod.
Although regulatory, agencies in the USA typically require 3–5 yr of post-restoration monitoring of biotic responses to wetland
mitigation, many researchers have argued that longer time frames are needed to assess population responses adequately. We
conducted an 8-yr study to examine the demographic responses of the wood frog (Rana sylvatica) and spotted salamander (Ambystoma maculatum) to wetland creation at a mitigation bank in western North Carolina. Our primary goals were to compare juvenile output in
ten reference and ten constructed ponds and to assess the overall change in breeding population size in response to site restoration.
We used annual censuses of egg masses to assess changes in breeding population size and used estimates of larval population
size at hatching and the initiation of metamorphosis to assess embryonic and larval survival. Adults of both species bred
in most constructed ponds within a few months after filling in 1996. Estimated juvenile production from 1996 to 2002 did not
differ significantly between pond types for either species. The percentage of both constructed and reference ponds that produced
juveniles decreased markedly from 1996 to 1998 and remained low through 2002. The decrease in juvenile output was mostly associated
with reduced larval survival rather than increased embryonic mortality across years. Drought and outbreaks of a pathogen (Ranavirus) were the primary causes of low juvenile production from 1998 to 2002. The overall breeding population of R. sylvatica increased markedly in 1999–2000 following a large recruitment of juveniles from constructed ponds in 1996–1997. With the
onset of drought and ranaviral infections, the population declined to levels in 2002 that were at or below 1995 pre-restoration
numbers. Despite site perturbations, the breeding population of A. maculatum remained relatively stable from 1995 to 2002, a phenomenon that may reflect selection for delayed reproduction and iteroparity
in this species. Although we have monitored R. sylvatica and A. maculatum for seven breeding seasons after the creation of seasonal wetlands, we are still uncertain that site restoration will achieve
the goal of increasing breeding populations above pre-restoration levels. Because amphibians have significant population lags
and are sensitive to site perturbations, monitoring that exceeds five years may be required to assess demographic responses
to site restoration adequately.
Under section 401 and section 404 of the Clean Water Act, permission to degrade existing natural wetlands in the USA may be
conditional on restoring or creating ‘replacement’ wetlands. Success of wetland mitigation efforts in adequately replacing
lost wildlife habitats depends on our good understanding of key ecological attributes that affect the structure of wetland
faunal communities. We examined the effects of the presence of predatory fish, shallow vegetated littoral zone, emergent vegetation
cover, wetland age and size on amphibian diversity in 42 replacement wetlands located in the Ohio’s North Central Tillplain
ecoregion. We recorded 13 species of pond-breeding amphibians, and the average local species richness (α-richness) was 4.2±1.7 species per site (range 1–7). There is strong evidence for the positive association between amphibian
species richness and presence of a shallow littoral zone, and the negative association with presence of predatory fish. There
was no evidence for the association between species richness and age, size, amount of forest cover within 200m, nor the amount
of emergent vegetation cover at the study sites. It is estimated that local species richness in wetlands with shallows was
1.76 species higher on average than in wetlands without shallows (95% CI from 0.75 to 2.76). The presence of predatory fish
was associated with an average reduction in species richness by an estimated 1.21 species (95% CI from 0.29 to 2.11). Replacement
wetlands were placed in areas with little or no existing forest cover, and amphibian species associated with forested wetlands
were either rare (eastern newt, spotted salamander) or not present at all (marbled salamander, wood frog). In addition, we
surveyed all replacement wetlands constructed under section 401 in Ohio since 1990, and found that predatory fish were present
in 52.4% of the sites and that shallows were absent from 42.7% of the sites. Our results indicate that current wetland replacement
practices could have a negative effect on the amphibian diversity within our region.
This study investigates factors of importance for tadpoles survival and metamorph production in the common frog Rana temporaria. It also assess the importance of this for the population dynamics of the species. Eighteen ponds were studied for up to 8 years. Data collected each year included: number of spawn clumps deposited, tadpole number and metamorph number. The permanency of the ponds was also recorded each year. Measures were taken of predator density. There was no suggestion of density dependence in the survival of tadpoles. In contrast, the number of spawn clumps deposited per pond area was highest for ponds with high survival. Density of predators (sticklebacks, newts and invertebrates) was negatively correlated to tadpole and metamorph survival. This was true both within (among years) and among ponds. Several of the study ponds dried completely before metamorphosis in some years. However, those ponds also were those with the smallest number of predators and in years with successful metamorphosis, these ponds produced more metamorphs than more permanent ponds. An analysis of the year to year dynamics showed that population size (number of deposited spawn clumps) was correlated to that in the previous year, suggesting a fairly high adult survival, but also on the number of metamorphs emerging two or three years before (corresponding to the age of sexual maturity of the species). It is concluded that the aquatic stage is not strongly limiting in these ponds but conservation efforts should be focused on the terrestrial habitat. Also, the study stresses the value of temporary ponds, despite the fact that recruitment often fails totally in these.
Forest drainage is recognized as a means of improving soil conditions for tree growth, but it may also have environmental impacts. This article presents the 5-y time trend of soil and surface water quality observed in a drainage experiment conducted in a black spruce (Picea mariana (Mill.) BSP) peatland of eastern Québec, Canada, using the paired watershed approach. Nutrient content of peat soil water was enhanced by drainage. The effect was generally proportional to ditch closeness for S and Mg, while increases of N, Na, K and Ca were mainly observed within 5 m of the ditches, even though high levels of K and Ca were occasionally observed at 15-m distance. Drainage increased and sustained summer low flows by 25% through a 80 m3 d−1 increase of base flow on the 8 ha basin. The concentration of suspended sediments significantly increased and exceeded acceptable limits for aquatic organisms only during ditching and during the peak flows of the following weeks. No effect on suspended sediments was detected during the spring following ditching but an increase was observed during a storm 2 y after ditching. Drainage modified the basin outflow temperature fluctuations by lowering the average weekly minimum and increasing the maximum, by 2°C and 7°C, respectively. Water temperature increases to 25°C or more at the outlet of the drained basin were above the preferred range for brook trout. The treatment significantly increased specific conductivity of surface water, which was clearly related to increases in mineral N (NH4+NOx), Ca, Mg, Na and S concentrations. However, conductivity and the increased nutrient concentrations remained within the acceptable criteria for aquatic organisms. Drainage also produced a pH increase of one unit, a result attributed to increased runoff from the upland part of the treated watershed. No effect related to drainage was found for Zn, Fe and Al contents.
Forest drainage, utilizing protective buffer zones, caused clear changes in the habitat structure as well as in the species richness and composition of moss-dwelling invertebrates in a small headwater stream. The aquatic moss Fontinalis dalecarlica was the dominant habitat in the control riffle areas, whereas sand dominated the riffles impacted by forest ditches. The significance of the forest ditches as a source of inorganic material was studied by comparing the quality of both indigenous and transplanted moss habitats. The Fontinalis tufts in the affected sites were silted up and contained a significantly higher average amount of inorganic matter than the mosses in the control site. The species richness of invertebrates within the silted mosses was significantly lower than at the control site. Shredder-feeding stoneflies dominated the moss communities of the control site, whereas Simuliidae dominated the impacted riffles. We suggest that the drainage-induced impoverishment of the benthic communities is due to two combined disturbance factors: (1) deposition of the particles on benthic habitats and (2) particle movement along the surfaces. Further, it is concluded that the present buffer zones and sedimentation ponds are insufficient to protect the biodiversity of streams draining easily eroding lands. In order to protect these vulnerable lotic ecosystems effectively, the most erodible parts of the catchment area should be undrained, and more retentive buffer mechanisms should be utilized in the drainage areas.
Organisms often rely on environmental cues to make behavioral and life-history decisions. However, in environments that have been altered suddenly by humans, formerly reliable cues might no longer be associated with adaptive outcomes. In such cases, organisms can become ‘trapped’ by their evolutionary responses to the cues and experience reduced survival or reproduction. Ecological traps occur when organisms make poor habitat choices based on cues that correlated formerly with habitat quality. Ecological traps are part of a broader phenomenon, evolutionary traps, involving a dissociation between cues that organisms use to make any behavioral or life-history decision and outcomes normally associated with that decision. A trap can lead to extinction if a population falls below a critical size threshold before adaptation to the novel environment occurs. Conservation and management protocols must be designed in light of, rather than in spite of, the behavioral mechanisms and evolutionary history of populations and species to avoid ‘trapping’ them.
We reviewed studies on the biological state of agricultural drainage ditches in the temperate and boreal zones of the Northern Hemisphere. We looked at the relative importance of ditches for farmland biota as compared to that of other habitats, and assessed the degree to which biological communities of ditches contribute to the provisioning of ecosystem services. We evaluated impacts pertaining to replacement of open drains by subsurface drainage, removal of main ditches, rehabilitation of old drainage systems, and maintenance of ditches. Most ditches support species also common elsewhere. Whenever comprehensive surveys were conducted, ditches were shown to provide valuable wet vegetated non-cropped habitats to both aquatic and terrestrial taxa, supply food resources lacking in otherwise dry and intensively managed cropland, and perform connectivity functions within a wider landscape. Regionally ditches were shown to harbour rare species or species not found presently in other farmland habitats. Some functions of drainage ditches, such as regulating water flow and nutrient retention, are likely to depend on the composition and structure of biological communities of ditches, though the issue remains poorly explored. The biggest threat to the quality of ditch networks as ecosystems is presented by a severe runoff from the fields, management in disregard of a habitat value of ditches, and removal of ditches.
We investigated the within-site distribution of Enchytraeidae, Collembola, Oribatida, Mesostigmata and Prostigmata relative to varying water level and substrate quality on pine mire sites forming a drainage succession continuum. Collembolans were most intolerant of wetness, favoring drier locations at all stages of the drainage succession. In general, the effect of water level variation on the within-site distribution of the soil fauna was strongest when the site was at an early stage of either progressive or regressive water level change. When the average water level was below 20 cm, it no longer had a significant effect on the distribution of mites, but still affected that of Enchytraeidae and Collembola. Boron was positively correlated with faunal density in several cases, and thus may be the growth limiting nutrient affecting substrate quality for decomposers in these sites. The overall changes in the soil mesofauna in drained peatlands depicted here show that these peatland forests are converging ecologically on upland forests where decomposition in general is much faster than in pristine peatlands. The change caused by restoration shows how labile these ecosystems are also with respect to the mesofaunal community.