Altered Habitat Conditions Research Articles

Micro-habitat features determine oviposition site selection in High Brown and Dark Green Fritillaries

The survival of butterfly populations depends on successful oviposition strategies. The limited mobility of early life stages requires females to select sites that reflect larval requirements. However, as land use and climate changes are altering habitat conditions and micro-climate, some species may adapt ovipositing strategies and flourish while others, with narrow niche requirements, may be unable to respond. Oviposition site selection and micro-habitat niche is examined for two closely related butterfly species—the specialist High Brown Fritillary (Fabriciana adippe) and relative generalist Dark Green Fritillary (Speyeria aglaja) through field observations of egg-laying females and analysis of micro-habitat characteristics. A total of 104 oviposition behaviour observations across both species were recorded in 69 1 m2 quadrats, with the habitat characteristics compared to randomly selected quadrats in the same area. Results show that higher host plant density was a positively significant factor for oviposition site selection only for the High Brown Fritillary. Moreover, the cover of live Bracken (Pteridium aquilinum) and grass were important for site selection in both species, with High Brown Fritillaries tolerating less live Bracken and grass cover than Dark Green Fritillaries. This confirms the more specific requirements and narrower micro-habitat niche of the High Brown Fritillary, which appears to be more sensitive to micro-habitat cooling.Implications for insect conservationThe management of Bracken mosaic habitats for these two species should aim to supress grass growth and maintain Bracken density within limits, by opening the Bracken canopy on a rotation through grazing or manual cutting, ensuring a continuous supply of suitable micro-habitat.

Bryophytes and vascular plants on peat extraction sites - which factors influence their growth?

Peat extraction leads to the formation of areas with altered habitat conditions in comparison to natural peatlands. Restoration of the peat-formation process in these areas is very difficult and requires the creation of suitable conditions for the growth of peatland species. The aim of the study was to analyse the habitat requirements of bryophytes and vascular plants growing on sites of peat extraction (30 and 40 years after extraction was terminated) and to determine whether the water level influences the growth conditions of plants directly or indirectly through changes in the peat physical, hydraulic and chemical properties. Analysing all factors together revealed that the average water level had a decisive influence on bryophytes, but a statistically significant increase in the percentage of variation explained was obtained by taking into account other parameters as well (proportion of macropores, carbon content, and pH). In the case of vascular plants the analysis showed that the water table coefficient included the effects of all of the other factors analysed, and taking them into account did not increase the percentage of variation explained. The two groups of plants use different resources of the environment.

Canada Warbler response to vegetation structure on regenerating seismic lines

Seismic lines have an extensive footprint in Canada's western boreal forest that alter habitat conditions for many species. Seismic lines exist within a range of seral states due to changing practices and regulations related to operational needs. Forest regeneration is often hindered on seismic lines as they are frequently repurposed for recreational or alternative industrial uses. The Canada Warbler (<em>Cardellina canadensis</em>) is a Neotropical migrant songbird that relies on Canada's boreal region for breeding habitat. As a species at risk both federally (Threatened) and provincially within Alberta (Sensitive), their response to seismic lines has been a significant gap in our understanding of human impacts on the boreal breeding grounds. We used playback surveys along seismic lines within Canada Warbler habitat to identify individual territories. Arrays of autonomous recording units (ARU) were deployed to conduct acoustic source localization (ASL) and map the locations of territorial singing events. Canada Warblers avoided seismic lines with little to no woody vegetation but were more likely to be observed near seismic lines when shrub cover on the line increased. Canada Warblers used the seismic line and the edge environment but did not select for the line when compared to its availability. Use was more evenly distributed across the seismic line as shrub density on the line increased. However, even the most overgrown seismic lines were still perceived as a feature and influenced Canada Warbler space use and behavior. For Canada Warblers, ensuring that seismic lines in old-growth deciduous forests are allowed to recover by reducing reuse of lines should mitigate population level impacts, but more work is needed to assess how population dynamics are influenced by seismic lines and other energy sector disturbances.

Differences in Life History Traits in Rural vs. Urban Populations of a Specialist Ground Beetle, Carabus convexus.

Simple SummaryUrbanization is an important driver of global change, with negative consequences for biodiversity. Specialist species living in isolated urban forest fragments may be the most impacted by urbanization-driven environmental modifications. We compared various life history parameters of a forest specialist ground beetle in its original forest habitat and in urban forest fragments. Abundance was more than five times higher in the rural forest stands than in the urban forest fragments. We found no significant differences in body size or condition between the rural and urban individuals of either sex. Despite higher temperatures in urban habitats, the beginning of the reproductive period did not start earlier in the urban than the rural habitat. The number of ripe eggs was significantly higher in urban than rural females. The urban environmental conditions, however, seemed to cause high mortality of the immature stages, preventing the growth of urban populations.Urbanization is increasing worldwide and causes substantial changes in environmental parameters, generating various kinds of stress on arthropods, with several harmful consequences. We examined a forest specialist ground beetle, Carabus convexus, in forested habitats to evaluate the changes in four important life history traits between rural and urban populations. Analyzing beetles from the overwintered cohort in their first breeding season, we found no significant differences in body length or body mass between the rural and urban individuals. Body condition, judged by fat reserve scores, was similarly poor in both habitats, indicating that beetles were not able to accumulate substantial fat reserves at either habitat. Females with ripe eggs in their ovaries were first captured at the same time in both areas. The number of ripe eggs, however, was significantly higher in females of the low-density urban population (6.13 eggs/female) than in those of the high-density rural population (4.14 eggs/female), indicating density-dependent fecundity. Altered environmental and habitat conditions by urbanization, however, seemed to cause high mortality during egg hatching and/or larval development, preventing the growth of the urban population to the level of rural one.

Morphological divergence, tail loss, and predation risk in urban lizards

Urbanisation changes the structure of natural habitats and alters trophic interactions, pressuring urban species to adjust and adapt. Unlike behavioural shifts that tend to be more flexible, morphological characteristics in vertebrates are less plastic and changes may come at a greater cost. We explored the hypothesis that morphological characteristics in a tropical agamid lizard Psammophilus dorsalis are not only selected to suit altered habitat conditions in urbanised areas but reflect predation risk in urban habitats. In addition, we explored differences in tail loss in both sexes from urban and rural habitats. First, we find that predation risk did not differ between urban and rural habitats, but differed between sexes. Conspicuous courtship-coloured male lizards were more likely to be attacked compared to cryptically-coloured female lizards. Next, we find that P. dorsalis differed in key morphological characteristics, with greater urban-rural differences in males than females. Urban lizards had shorter proximal limb elements, longer 4th digits and greater body mass than rural lizards; and among males, urban lizards had significantly larger head sizes and longer distal limb elements than rural lizards. Finally, we find that the rates of tail loss differed between habitats and sexes, with urban male lizards having greater rates of tail loss than rural males and all females. Inter-sexual difference in tail loss was consistent with the difference in predation risk between sexes, but tail loss differences between urban and rural habitats could not be explained by predation risk. In sum, we find that adaptations to novel urban environments are not exclusively driven by a single promoter (e.g. predation risk) but are influenced by multiple selection pressures with associated fitness costs, such as tail loss.

The use of sentinel logs to assess host shifts in early beetle colonisers of deadwood under climate‐ and forestry‐induced tree species substitutions

Abstract Global change scenarios project drastic modifications in tree species range and an increase in exotic tree plantations. Subsequent tree species substitutions may alter habitat conditions for biodiversity. We measured substitutability between tree species for early deadwood colonisers, through a sentinel log approach, i.e. through the experimental exposure of paired down deadwood (DDW) pieces to native beetles in native stands. We compared two native/substitute tree species pairs: one conifer pair composed of a rapidly expanding exotic species (Douglas fir) and a declining native species (silver fir), and one deciduous pair composed of two native species, one expanding (sessile oak) and one retreating (beech) at the regional scale. The effects of expanding exotic and native trees on beetle communities were not in line with expectations. Species assemblages in Douglas fir DDW were indistinguishable from those in native silver fir DDW and did not contain fewer species. Assemblages were not more generalist on average in substitutes than in substituted trees: we did not note any decrease in species richness of functional groups to the detriment of specialist species. Moreover, species richness and abundance were higher in substitute oak than in native beech DDW, confirming that species from the regional pool were able to colonise oak, even though it is a minor tree species at the regional level. Large‐scale monitoring schemes including multi‐taxon, multi‐year and multiple native/substitute pairs would further our knowledge of the generic effects of tree species substitution on biodiversity and ecosystem functioning.

Response of dung beetle assemblages to grazing intensity in two distinct bioclimatic contexts

Given the impact of livestock on ecosystems worldwide, it is necessary to understand the effects of grazing practices on biodiversity in order to improve the sustainability of pasture management practices. In a pasture, spatio-temporal variability in livestock activity results in a heterogeneous distribution of defoliation, trampling and excreta. To date, fine-scale analyses of grazing intensity have been rare, and the geographical extent of the studies often limited. In this study, we addressed this gap by analysing the influence of contrasting intra-pasture grazing intensity on the structure and composition of dung beetle assemblages. To do this, we studied a three-level grazing intensity gradient in two distinct bioclimatic contexts, a Mediterranean steppe and the Alps, which also allowed us to determine if dung beetle responses to grazing intensity are related to bioclimatic conditions. The observed dung beetle responses showed an imprint of the bioclimatic context and the local pasture conditions, and species composition and relative abundance showed strong variations along the grazing intensity gradient in both study areas. Species assemblages from the most and least grazed parts of pastures differed strongly. By altering habitat conditions, changing dung availability and modifying competitive interactions, fine-scale heterogeneity in grazing intensity led to substantial variations in the abundance of dung beetle nesting guilds. In both study areas an increase in grazing intensity was detrimental to the largest species and the soil-digging species (which bury dung in underground nests), whereas dung-dwelling species (which reproduce inside dung pads) were favoured. We discuss the combined use of nesting guilds and body mass as potential features to generalize the application of dung beetles as indicators of grazing practices.

Carnivore community response to anthropogenic landscape change: species-specificity foils generalizations

Human exploitation of landscapes result in widespread species range loss and spatial community redistribution. Reduced species occupancy for large ranging terrestrial carnivore communities in disturbed or fragmented landscapes is a common outcome but the underlying mechanisms are ambiguous and the complexity of interacting mechanisms often under-appreciated. To examine for similarity in spatial responses of carnivores to human-mediated landscape disturbance, we hypothesize common mechanism(s) to manifest at the community-level. To then incorporate a competitive surface, we evaluate the relative role interspecific interactions may play, where some species are benefited by altered habitat conditions. We deployed camera-trap arrays across a systematic grid-based study design to quantify carnivore occurrence. We tested hypotheses to understand spatial patterns of carnivore occurrence, in relation to biophysical and anthropogenic landscape factors, using multivariate analysis and species distribution models under an information-theoretic approach. Differential response was found within the carnivore community, with some species occurring more frequently in disturbed landscapes while others displayed landscape scale avoidance of more highly disturbed areas. Interspecific interactions played an additive role to human-mediated response by some carnivores—suggesting generalist, human-adapted species, exaggerate interference interactions for other more sensitive species. Generalizable patterns are highly sought as clues to consistent mechanisms effecting changes to spatial distributions, but evidence weighs heavily in favour of species-specificity in responses implicating mechanisms that likewise vary for each species. Our findings underscore the value of a trait-based and community-level approach to understanding and managing the effects of anthropogenic land-use change on vertebrate biodiversity.

Different Stages of Aquatic Vegetation Succession Driven by Environmental Disturbance in the Last 38 Years

In recent years, investigating the trend of aquatic plant diversity in response to different disturbance events has received increasing interest. However, there is limited knowledge of the different stages of aquatic vegetation succession over a long period in eutrophic lakes. In this study, we analyzed aquatic plant species richness and its relation to the physical and chemical characteristics of water in Chenghai Lake for the period of 1980–2018. This study shows that the richness and distribution of aquatic vegetation in Chenghai Lake are related to chlorophyll-a concentration, dissolved nutrients, base cations, and micronutrients. The results show that the long-term succession of aquatic plants in this lake classified in different stages: (I) A peak in species richness occurred at an intermediate stage that lasted from 1980 to 1992, and this was caused by more aquatic species being able to coexist since the competition for resources was lower; (II) after 26 years of secondary succession (1992–2018), the diversity and distribution area of aquatic plants gradually declined because pioneer species or human activities may have altered habitat conditions to render habitats less beneficial to pioneer species and more suitable for new aquatic plant species. Thus, species diversity and growth performance of aquatic plants in their communities may be useful indicators of Chenghai Lake’s trophic status, especially during the transition period from a mesotrophic lake to a eutrophic one.

Possible causes for the decline in Adélie Penguin population numbers at anvers island, Western antarctic Peninsula

The impacts of climate change are evident even at the most remote places on the planet. This is especially apparent on the isolated Western Antarctic Peninsula (WAP). Anvers island, located on the WAP, has historically had low humidity and extremely low temperatures. Also, regular seasonality maintains equilibrium within the entire system, from which organisms evolved to match these climate patterns. However, recent studies on climate trends in the WAP show disturbances in the regularity of the seasons. Vaughan et al., [1], observed a warming rate during the winter months from 1991 to 2008 that was more intense than along any other studied location globally. Rising temperatures limit sea ice duration as melting occurs earlier. This warming event is altering habitat conditions, thus disrupting entire trophic systems from primary producers to top predators like Adelie penguins [2].

Recent drought and tree mortality effects on the avian community in southern Sierra Nevada: a glimpse of the future?

Birds respond rapidly to changes in both habitat and climate conditions and thus are good indicators of the ecological effects of a changing climate, which may include warmer temperatures, changing habitat conditions, and increased frequency and magnitude of extreme events like drought. We investigated how a widespread tree mortality event concurrent with a severe drought influenced the avian community of the Sierra Nevada mountain range in California. We assessed and compared the separate effects of climate stresses and altered habitat conditions on the avian community and used this information to evaluate the changes that are likely to occur in the near future. We built tree mortality maps from freely available Landsat imagery with Google Earth Engine. We analyzed avian point counts from 2010 to 2016 in the southern Sierra Nevada, to model temperature, water deficit, and tree mortality effects on the abundances of 45 bird species, and then used these models to project abundances into the future based on three climate projections. A large portion of the avian community, 47%, had a positive relationship with temperature increase, compared to 20% that responded negatively. More species (36%) declined with drier conditions than increased (29%). More species declined in response to high tree mortality (36%) than increased (9%). A preponderance of species adapted to colder temperatures (higher elevation) had negative responses to high tree mortality and water deficit, but positive responses to increasing temperature. We projected the highest total bird abundances in the future under the warmest climate scenario that we considered, but habitat modification (e.g., tree mortality) and water deficit could offset the positive influence of temperature for many species. As other studies have shown, climate warming may lead to substantial but idiosyncratic effects on wildlife species that could result in community composition shifts. We conclude that future climate conditions may not have a universally negative effect on biodiversity in the Sierra Nevada, but probable vegetation changes and increased likelihood of extreme events such as drought should be incorporated into climate-smart forest and wildlife management decisions.

Adaptive Features of the Leaf of &amp;lt;i&amp;gt;Juno vicaria&amp;lt;/i&amp;gt; (Vved.) T. Hall &amp;amp; Seisums in Different Ecological Conditions of Uzbekistan

The anatomical structure of the leaf of the Central Asian endemic species of Juno vicaria, growing in two different ecological conditions (Baysun Mountains of Surkhandary region and Tashkent Botanical Garden of Uzbekistan) was analyzed and diagnostic signs were determined. Also identified are adaptive mesomorphic and xeromorphic signs from an environmental point of view. A species that grows in natural habitat is dominated by more xeromorphic signs: a thickened outer wall of the epidermis; numerous epidermal, spongy cells; submerged stomata; small, multi-row sclerenchymal and collenchymal cells, which indicate a more xeromorphic and adaptability, as well as the wide distribution of this species to the natural growing conditions. In a species growing under the conditions of introduction of the Tashkent Botanical Garden, more mesomorphic features predominate: thin-walled, large, few epidermal, spongy cells; not immersed stomata; large non multi-row sclerenchymal and collenchymal cells, which show that the species is adapted to altered habitat conditions.

Influence of debris flows on macroinvertebrate diversity and assemblage structure

The middle catchment of the Nu River is highly susceptible to debris flows. Differences in flow and substratum conditions among mainstem reaches correlate with debris flow depositions from lateral tributaries. We studied the impacts of debris flows on macroinvertebrates, especially responses in their diversity and assemblage structure to habitat modification at 22 sites in three habitats: barrier lakes and debris dams, formed by debris flow deposits barring the river, and unaffected mainstem sections. Unaffected mainstem sites supported the most diverse macroinvertebrate assemblage, with mean taxon richness, density and biomass 1.4, 1.1, and 23.6 times higher than those of debris dam sites, and 2.1, 4.2, and 7.4 times higher than those of barrier lake sites, respectively. Variance analysis revealed significant differences in diversity indices, and both taxonomic and functional feeding group composition among habitats. Although barrier lakes and debris dams had lower taxon richness, the two affected habitats contributed 17 and 16 exclusive taxa, respectively, to total taxon richness. Redundancy analysis identified habitats could be characterized by water temperature, electrical conductivity, flow velocity, and median particle size of substratum type. Significant differences in flow velocity and substratum median particle size among habitats were attributed to debris flows. Distinct assemblages within barrier lakes were associated with fine sediments. By altering habitat conditions, debris flows affect macroinvertebrate assemblages, reducing diversity locally in affected reaches, contributing to variation in diversity and assemblage structure throughout the catchment. Three genera (Cricotopus sp., Pseudocloeon sp. and Monodiamesa sp.) are proposed as potential indicator taxa for unaffected mainstem, debris dam and barrier lake habitats, respectively.

Human development and climate affect hibernation in a large carnivore with implications for human–carnivore conflicts

Abstract Expanding human development and climate change are dramatically altering habitat conditions for wildlife. While the initial response of wildlife to changing environmental conditions is typically a shift in behaviour, little is known about the effects of these stressors on hibernation behaviour, an important life‐history trait that can subsequently affect animal physiology, demography, interspecific interactions and human‐wildlife interactions. Given future trajectories of land use and climate change, it is important that wildlife professionals understand how animals that hibernate are adapting to altered landscape conditions so that management activities can be appropriately tailored. We investigated the influence of human development and weather on hibernation in black bears (Ursus americanus), a species of high management concern, whose behaviour is strongly tied to natural food availability, anthropogenic foods around development and variation in annual weather conditions. Using GPS collar data from 131 den events of adult female bears (n = 51), we employed fine‐scale, animal‐specific habitat information to evaluate the relative and cumulative influence of natural food availability, anthropogenic food and weather on the start, duration and end of hibernation. We found that weather and food availability (both natural and human) additively shaped black bear hibernation behaviour. Of the habitat variables we examined, warmer temperatures were most strongly associated with denning chronology, reducing the duration of hibernation and expediting emergence in the spring. Bears appeared to respond to natural and anthropogenic foods similarly, as more natural foods, and greater use of human foods around development, both postponed hibernation in the fall and decreased its duration. Synthesis and applications. Warmer temperatures and use of anthropogenic food subsides additively reduced black bear hibernation, suggesting that future changes in climate and land use may further alter bear behaviour and increase the length of their active season. We speculate that longer active periods for bears will result in subsequent increases in human–bear conflicts and human‐caused bear mortalities. These metrics are commonly used by wildlife agencies to index trends in bear populations, but have the potential to be misleading when bear behaviour dynamically adapts to changing environmental conditions, and should be substituted with reliable demographic methods.

Phenotypic plasticity in developmental rate is insufficient to offset high tadpole mortality in rapidly drying ponds

AbstractHabitat suitability is strongly regulated by seasonal conditions and stochastic processes, and this is especially important in temporary aquatic systems that contain organisms with complex life cycles. We investigated the potential for phenotypic plasticity in timing of and size at metamorphosis to mitigate effects of altered habitat conditions, specifically shortened hydroperiod (duration of water in ponds) and altered predator‐prey dynamics, in the pond‐breeding boreal chorus frog (Pseudacris maculata). We simulated reduced hydroperiod and concentrated predator cue in the laboratory to understand potential benefits and costs of plasticity. Tadpoles developed faster in response to the combined effects of reduced hydroperiod and increased concentration of predator cue, potentially due to reduced conspecific density. In contrast, there was no effect of reduced hydroperiod or predator cue on size at metamorphosis. Alone, this result suggests that phenotypic plasticity may allow P. maculata to escape the negative effects of rapidly drying ponds. However, tadpole survival was significantly lower in reduced hydroperiod treatments relative to all other treatments, suggesting that even if plasticity acts as a buffer against reduced hydroperiod by facilitating metamorphosis, heightened mortality may offset benefits of this rapid response. Our results add to previous studies of plastic responses in amphibians by disentangling the costs and benefits of plasticity in habitats with multiple, simultaneous stressors. We show that while plasticity may accelerate metamorphosis, similar, heightened levels of mortality are experienced regardless of plasticity. This implies that plasticity may not completely buffer populations against the effects of altered habitat conditions, such as those that occur with climate change or urbanization.

Alteration of physico-chemical and microbial properties in freshwater substrates by burrowing invertebrates

The hyporheic interstitial provides habitat for many different organisms – from bacteria to burrowing invertebrates. Due to their burrowing and sediment reworking behaviour, these ecosystem engineers have the potential to affect hyporheic processes such as respiration and nutrient cycling. However, there is a lack of studies that characterize the interactions between bioturbators, physico-chemical habitat properties and microbial communities in freshwater substrates. In a standardized laboratory experiment, we investigated the effects of three functionally different bioturbators, duck mussels (Anodonta anatina, Linnaeus 1758), mayfly nymphs (Ephemera danica, Müller 1764) and tubificid worms (Tubifex tubifex, Müller 1774), on the physico-chemical conditions and bacterial communities in hyporheic substrates. We hypothesized that different invertebrates distinctly alter habitat conditions and thus microbial community composition, depending on the depth and the manner of burrowing. A. anatina and E. danica caused an increase in interstitial oxygen concentration, whereas strong declines in oxygen concentration and redox potential were detected in the T. tubifex treatment. These effects on physico-chemical habitat properties were even detectable in open water. Mussels and tubificid worms also significantly influenced the composition of bacterial communities in the hyporheic zone. A loss or replacement of bioturbators in stream ecosystems due to anthropogenic habitat alterations is expected to result in shifts in microbial community compositions, with effects on nutrient fluxes, pollutant degradation and benthic food webs. An understanding of the effects of functionally different native and invasive bioturbators is crucial to predict changes in stream ecosystem functioning.

Effects of invasive and indigenous amphipods on physico-chemical and microbial properties in freshwater substrates

Native benthic amphipods play a key role in freshwater ecosystem services such as leaf litter decomposition. The replacement of native by invasive species with different functional traits has the potential to alter hyporheic processes, communities, and food webs. Despite the increasing number of publications on invasive species, there is a lack of studies that compare the effects of native versus invasive amphipods on physico-chemical habitat properties and microbial communities in the substrate. We compared the effects of an indigenous (Gammarus roeseli, Gervais 1835) and an invasive (Dikerogammarus villosus, Sowinsky 1894) amphipod on leaf litter decomposition, as well as on bacterial communities and physico-chemical conditions in freshwater substrata. We hypothesized that the different amphipod species distinctly alter habitat conditions and microbial community composition, depending on functional differences in leaf litter decomposition. We detected strong differences between G. roeseli and D. villosus in the feeding rates on alder leaves, with 11-fold greater decomposition of alder leaves by the native species. Additionally, our study revealed differences in microbial community composition between treatments at the substrate surface, but almost no differences in physico-chemical parameters in the interstitial and open water. These results support the hypothesis that the replacement of indigenous amphipod species by functionally different invasive amphipods can lead to a decrease in leaf litter decomposition and an altered microbial community composition with possible effects on benthic food webs. These effects on ecosystem services should be taken into account when assessing the impacts of invasive species on freshwater habitats.

Morphological responses of Capoeta gracilis and Alburnoides eichwaldii populations (Cyprinidae) fragmented due to Tarik Dam (Sefidrud River, Caspian Sea basin, Iran)

This study was conducted to evaluate the morphological responses of two different species including Capoeta gracilis and Alburnoides eichwaldii due to construction of the Tarik dam in the Sefidrud River using geometric morphometric technique. For this purpose, a total of 80 specimens of C. gracilis and 60 specimens of A. eichwaldii were collected from upstream and down-stream of dam. The left sides of specimens were photographed and14 and 18 landmark-points were digitized on 2D pictures of and C. gracilis and A. eichwaldii , respectively. The landmark data were submitted to GPA to remove non-shape data, analyzed by discriminate functional analysis and Ttest hotelling. The results showed no differences between the upstream and downstream populations of C. gracilis , but a significant difference found in A. eichwaldii in terms of body shape. The observed differences were related to head, snout, caudal peduncle regions and eye diameter that could be an adaptation to altered habitat and hydrological conditions of upstream and downstream due to damming. Different response of two studied species displayed that fishes can respond in different way to anthropogenic modifications of riverine ecosystem.

The response of δ13C, δ18O and cell anatomy of Larix gmelinii tree rings to differing soil active layer depths

Global warming is most pronounced in high-latitude regions by altering habitat conditions and affecting permafrost degradation, which may significantly influence tree productivity and vegetation changes. In this study, by applying a “space-for-time” approach, we selected three plots of Larix gmelinii forest from a continuous permafrost zone in Siberia with different thermo-hydrological soil regimes and ground cover vegetation with the objective of assessing how tree growth and productivity will change under different stages of permafrost degradation. A tree-ring multi-proxy characterization of mature trees was used to identify shift in ecophysiological responses related to the modified plant-soil system. Variability of tree-ring width (1975–2009), stable isotope ratios (oxygen and carbon, 2000–2009) and xylem structural characteristics (2000–2009) under climatic conditions of particular years indicated that an increased depth of the soil active layer will initially lead to increase of tree productivity. However, due to an expected water use increase through transpiration, the system might progressively shift from a temperature to a moisture-limited environment.

After the burn: factors affecting land snail survival in post-prescribed-burn woodlands

Prescribed burning is commonly used for vegetation management. Whereas effects on vegetation are apparent, effects of these burns on ground-dwelling invertebrates are not. Land snails are especially susceptible to burns. Snail loss occurs directly from burns, but may also occur post-burn because of altered habitat conditions, although post-burn loss has not previously been tested. We used a field experiment to investigate snail survival and factors affecting survival in post-burn habitats. We exposed snails (Discidae: Anguispira alternata) to combinations of intact leaf litter, wood shelters, burned leaf litter, charred wood and ash added to leaf litter, to simulate a variety of post-burn conditions. Half of the replicates were watered every 3 d, which allowed detection of desiccation effects in comparison to ambient water conditions. The on-going drought resulted in high snail mortality. Watering increased survival and, as a consequence, growth. Snail mortality was higher in habitats with burned leaves and/or wood than in unburned habitats. Higher temperatures and rapid initial mortality in burned habitats, and increased survival with watering, indicated that the major cause of post-fire mortality was desiccation, rather than starvation. Contrary to expectations, snails in burned-leaf habitats grew more than snails in unburned habitats, and this greater growth was associated with higher soil pH. Snails surviving fires in burned woodland areas likely have high post-burn mortality. Our experiment highlights the negative impacts of burned woodland habitats on some nontarget organisms and indicates that prescribed burns should be avoided during exceptionally dry conditions.