Emergent Vegetation Cover Research Articles

Improving Inference Within Freshwater Community Studies: Accounting for Variable Detection Rates of Amphibians and Fish.

Research into freshwater communities often aims to link patterns of species distribution in ponds with underlying biotic factors. However, errors with species detection (e.g. false negatives) may underestimate distribution and bias assessments of community structure. Occupancy models that account for imperfect detection offer a solution to this problem. Here, we used three methods (call/visual encounter surveys, dip-netting and newt trapping) to survey amphibians and fish (potential amphibian predators) at 100 ponds in an urbanised landscape in Hungary over one breeding season. We estimated species detection probabilities for amphibians (all life stages combined) and fish using occupancy models to gain insight into amphibian-fish relationships and other survey-specific variables. We detected nine amphibian and 20 fish species. There were relatively low but variable estimated probabilities of detection for amphibians (mean: 0.320, 95% Bayesian credible interval: 0.142-0.598), with three species having detection rates < 0.1. Probabilities of detection peaked in the middle of the breeding season and increased with survey effort. Detection probabilities of five species were negatively associated with the detection of fish at a pond, while there were positive relationships between detection and emergent vegetation cover. We found no substantial differences in detection rates among the three survey methods. The probability of detecting fish was much higher than for amphibians (0.588, 0.503-0.717) but was lower at ponds with high emergent vegetation where amphibian detection was higher. Our results underscore the importance of accounting for the imperfect detection of both response organisms and potentially interacting species in aquatic community studies. We recommend applying multi-species occupancy models to enable inference for both common and rare species at ponds in landscapes subjected to human disturbances.

Urban oasis? Abundant dice snake (Natrix tessellata) populations along artificial lakeside habitats in urban landscapes

ContextHuman-induced landscape modification, such as urbanization, creates new environments that can have adverse effects on flora and fauna, posing threats to biodiversity. Understanding how reptiles respond to urbanization is crucial, especially in light of their ongoing population declines.ObjectivesWe examined the influence of landscape-scale and local-scale urbanization features on the abundance of an aquatic snake species. Our investigation focused on dice snakes (Natrix tessellata) inhabiting a lake with a heavily urbanized shoreline.MethodsWe conducted visual encounter surveys at 25 study sites during the activity period of dice snakes around Lake Balaton in Hungary. We measured both landscape-scale and local-scale variables, including urban land use cover, vegetation cover, road cover, distance of main roads and city size, emergent vegetation cover and the area of artificial rock and concrete shoreline protection structures. We analysed snake survey data using N-mixture models to estimate abundance and examine relationships with landscape-scale and local-scale variables.ResultsUrban land use cover, road cover, the proximity of main roads and the extent of artificial rock and concrete shoreline protection structures positively affected the abundance of snakes. These findings imply that urban habitats may offer new ecological opportunities for dice snakes.ConclusionsThe findings of this study indicate that both landscape-scale and local-scale human-induced landscape modifications may have a positive impact on the abundance of urban snakes. Taken together, our findings suggest that urbanization is a complex phenomenon, affecting species at different levels and with subtle effects.

Wetland nitrogen removal from agricultural runoff in a changing climate

Wetlands in agricultural areas mitigate eutrophication by intercepting nutrient transports from land to sea. The role of wetlands for nutrient removal may become even more important in the future because of the expected increase in agricultural runoff due to climate change. Because denitrification is temperature dependent, wetland nitrogen (N) removal usually peaks during the warm summer. However, climate change scenarios for the northern temperate zone predict decreased summer and increased winter flows. Future wetlands may therefore shift towards lower hydraulic loading rate and N load during summer. We hypothesised that low summer N loads would decrease annual wetland N removal and tested this by examining 1.5–3 years of continuous N removal data from created agricultural wetlands in two regions in southern Sweden (East and West) during different periods. West wetlands showed relatively stable hydraulic loads throughout the year, whereas East wetlands had pronounced no-flow periods during summer. We compared East and West wetlands and tested the effects of several variables (e.g., N concentration, N load, hydraulic load, depth, vegetation cover, hydraulic shape) on annual absolute and relative N removal. We found no difference in annual N removal between East and West wetlands, even though summer N loads were lower in East than in West wetlands. A possible explanation is that stagnant water conditions in East wetlands suppressed decomposition of organic matter during summer, making more organic matter available for denitrification during winter. Absolute N removal in all wetlands was best explained by N load and hydraulic shape, whereas relative N removal was best explained by emergent vegetation cover and hydraulic shape. This study highlights the importance of design and location of agricultural wetlands for high N removal, and we conclude that wetlands in a future climate may remove N from agricultural runoff as efficiently as today.

Conservation prioritization through combined approach of umbrella species selection, occupancy estimation, habitat suitability and connectivity analysis of kingfisher: A study from an internationally important wetland complex (Ramsar site) in India

Assessment of occupancy status, as well as projection of suitable habitats and connectivity of wetland indicator species, and thereby identification of potential conservation umbrella and projection of conservation priority areas are often considered important for wetland conservation. Kingfishers are wetland indicators and suffer from habitat degradation due to world-wide destruction of wetlands. Therefore, they can be considered potential candidates for conservation intervention. The present knowledge about the spatial distribution of suitable areas and habitat connectivity of kingfishers at a landscape level is non-existent. We conducted extensive surveys and recorded four kingfisher species in East Kolkata Wetlands (EKW; Ramsar site No. 1208; ∼125 km2). The occupancy estimates were highest for White-throated kingfisher (Halcyon smyrnensis, WTK), followed by common kingfisher (Alcedo atthis, CK), stork-billed kingfisher (Pelargopsis capensis, SBK) and lowest for pied kingfisher (Ceryle rudis, PK). WTK has the highest amount of suitable areas followed by CK, PK and SBK. The spatial overlap of suitable habitats showed that SBK is the potential umbrella species and therefore provides conservation benefits to other kingfisher species and eventually to the EKW. In addition to water areas, emergent vegetation, crop lands and tree cover are other important habitats for kingfishers. The connectivity analyses revealed that suitable habitats were disjunct and are under various anthropogenic threats. Therefore, we need to protect suitable habitats and connectivity between them. Finally, we identified conservation priority areas. Conservation intervention on these high priority zones will not only be beneficial for kingfishers, but also for other avifauna having similar resource requirements as well as the wetland parse.

A functional definition to distinguish ponds from lakes and wetlands

Ponds are often identified by their small size and shallow depths, but the lack of a universal evidence-based definition hampers science and weakens legal protection. Here, we compile existing pond definitions, compare ecosystem metrics (e.g., metabolism, nutrient concentrations, and gas fluxes) among ponds, wetlands, and lakes, and propose an evidence-based pond definition. Compiled definitions often mentioned surface area and depth, but were largely qualitative and variable. Government legislation rarely defined ponds, despite commonly using the term. Ponds, as defined in published studies, varied in origin and hydroperiod and were often distinct from lakes and wetlands in water chemistry. We also compared how ecosystem metrics related to three variables often seen in waterbody definitions: waterbody size, maximum depth, and emergent vegetation cover. Most ecosystem metrics (e.g., water chemistry, gas fluxes, and metabolism) exhibited nonlinear relationships with these variables, with average threshold changes at 3.7 ± 1.8 ha (median: 1.5 ha) in surface area, 5.8 ± 2.5 m (median: 5.2 m) in depth, and 13.4 ± 6.3% (median: 8.2%) emergent vegetation cover. We use this evidence and prior definitions to define ponds as waterbodies that are small (< 5 ha), shallow (< 5 m), with < 30% emergent vegetation and we highlight areas for further study near these boundaries. This definition will inform the science, policy, and management of globally abundant and ecologically significant pond ecosystems.

Secretive marsh bird habitat relationships at mid‐continent spring migration stopover sites

AbstractDespite several secretive marsh bird (SMB) species being listed as critically imperiled throughout the mid‐continent of North America, limited information on SMB distribution and habitat use within primary migratory corridors results in uncertainty on contributions of wetlands in mid‐latitude states toward their annual cycle needs. Our objectives were to quantify temporal patterns of SMB wetland occupancy during spring migration at a mid‐latitude state and evaluate the relationships between SMB colonization probability and water‐level management practices, and the resulting habitat conditions during spring migration. We conducted a 2‐year, dynamic occupancy study (2013–2014) that included 6 rounds of repeated call‐back surveys to detect the presence of 5 SMB species (i.e., Virginia rail [Rallus limicola], sora [Porzana carolina], king rail [R. elegans], least bittern [Ixobrychus exilis], and American bittern [Botaurus lentiginosus]) during spring (Apr–Jun) on 107 wetlands across 8 conservation areas and 4 national wildlife refuges throughout Missouri, USA. We detected sora most frequently, followed by least bittern, American bittern, Virginia rail, and king rail. Coefficient estimates indicated colonization probability for all species was positively associated with emergent vegetation cover and negatively associated with amount of open water. Open water was the only variable in the best supported model explaining American bittern site colonization, to which they were negatively associated. Virginia rail colonization had a strong positive association with vegetation height, whereas least bittern and sora site colonization were influenced positively by water depth and agriculture, respectively. Based on the habitat associations within and among SMB species identified in this study, wetland managers can tailor management strategies to optimize spring migration habitat for single‐ or multi‐species objectives.

Identifying Translocation Sites for a Climate Relict Population of Finescale Dace

AbstractTranslocation is a management strategy that seeks to address threats to fish and wildlife populations by establishing new populations in ecologically suitable areas. Populations of Finescale Dace Chrosomus neogaeus in the Great Plains may benefit from translocation, as they exhibit a climate relict natural history that has led to a disjunct distribution and minimal dispersal opportunities. We assessed the translocation suitability of sites for Finescale Dace in the Belle Fourche River basin, Wyoming–South Dakota, using a ranking approach for output from multiple analyses. We used multivariate analysis to evaluate dissimilarity in fish occurrence and habitat between sites with and without Finescale Dace in contemporary surveys (2018–2019; n = 68). We further evaluated the capacity for sites to support Finescale Dace under base case and future climate change scenarios using the predicted probability of occurrence (P) from species distribution models (SDMs) fitted with basinwide fish occurrence data from surveys conducted in 2008–2019 (n = 124) and spatially continuous environmental variables, including forecasted stream temperature scenarios. Sites with Finescale Dace tended to occur close to standing waterbodies, contained emergent vegetation cover, and did not exhibit large overlap in species‐space with either native or nonnative species. Predicted P of Finescale Dace exhibited nonlinear relationships with mean August stream temperature, channel slope, and base flow index. The amount of suitable habitat (i.e., high predicted P) declined with forecasted stream warming scenarios in the SDMs. This study highlights the utility of using field observations, historical data, and forecasted climate change scenarios to assess translocation site suitability and inform management of at‐risk native fish populations, and the results may be transferable to other populations with limited data or restricted distributions.

Hot, wet and rare: modelling the occupancy dynamics of the narrowly distributed Dixie Valley toad

Context Small population sizes and no possibility of metapopulation rescue put narrowly distributed endemic species under elevated risk of extinction from anthropogenic change. Desert spring wetlands host many endemic species that require aquatic habitat and are isolated by the surrounding xeric terrestrial habitat. Aims We sought to model the occupancy dynamics of the Dixie Valley toad (Anaxyrus williamsi), a recently described species endemic to a small desert spring wetland complex in Nevada, USA. Methods We divided the species’ range into 20 m × 20 m cells and surveyed for Dixie Valley toads at 60 cells during six primary periods from 2018 to 2021, following an occupancy study design. We analysed our survey data by using a multi-state dynamic occupancy model to estimate the probability of adult occurrence, colonisation, site survival, and larval occurrence and the relationship of each to environmental covariates. Key results The detection probabilities of adult and larval toads were affected by survey length and time of day. Adult Dixie Valley toads were widely distributed, with detections in 75% of surveyed cells at some point during the 3-year study, whereas larvae were observed only in 20% of cells during the study. Dixie Valley toad larvae were more likely to occur in cells far from spring heads with a high coverage of surface water, low emergent vegetation cover, and water temperatures between 20°C and 28°C. Adult toads were more likely to occur in cells with a greater coverage of surface water and water depth &gt;10 cm. Cells with more emergent vegetation cover and surface water were more likely to be colonised by adult toads. Conclusions Our results showed that Dixie Valley toads are highly dependent on surface water in both spring and autumn. Adults and larvae require different environmental conditions, with larvae occurring farther from spring heads and in fewer cells. Implications Disturbances to the hydrology of the desert spring wetlands in Dixie Valley could threaten the persistence of this narrowly distributed toad.

Mechanistic understanding of the pollutant removal and transformation processes in the constructed wetland system.

Constructed wetland systems (CWs) are biologically and physically engineered systems to mimic the natural wetlands which can potentially treat the wastewater from the various point and nonpoint sources of pollution. The present study aims to review the various mechanisms involved in the different types of CWs for wastewater treatment and to elucidate their role in the effective functioning of the CWs. Several physical, chemical, and biological processes substantially influence the pollutant removal efficiency of CWs. Plants species Phragmites australis, Typha latifolia, and Typha angustifolia are most widely used in CWs. The rate of nitrogen (N) removal is significantly affected by emergent vegetation cover and type of CWs. Hybrid CWs (HCWS) removal efficiency for nutrients, metals, pesticides, and other pollutants is higher than a single constructed wetland. The contaminant removal efficiency of the vertical subsurface flow constructed wetlands (VSSFCW) commonly used for the treatment of domestic and municipal wastewater ranges between 31% and 99%. Biochar/zeolite addition as substrate material further enhances the wastewater treatment of CWs. Innovative components (substrate materials, plant species) and factors (design parameters, climatic conditions) sustaining the long-term sink of the pollutants, such as nutrients and heavy metals in the CWs should be further investigated in the future. PRACTITIONER POINTS: Constructed wetland systems (CWs) are efficient natural treatment system for on-site contaminants removal from wastewater. Denitrification, nitrification, microbial and plant uptake, sedimentation and adsorption are crucial pollutant removal mechanisms. Phragmites australis, Typha latifolia, and Typha angustifolia are widely used emergent plants in constructed wetlands. Hydraulic retention time (HRT), water flow regimes, substrate, plant, and microbial biomass substantially affect CWs treatment performance.

Multi‐Species Occupancy Modeling Provides Novel Insights into Amphibian Metacommunity Structure and Wetland Restoration

A fundamental goal of community ecology is to understand species-habitat relationships and how they shape metacommunity structure. Recent advances in occupancy modeling enable habitat relationships to be assessed for both common and rare species within metacommunities using multi-species occupancy models (MSOM). These models account for imperfect species detection and offer considerable advantages over other analytical tools commonly used for community analyses under the elements of metacommunity structure (EMS) framework. Here, we demonstrate that MSOM can be used to infer habitat relationships and test metacommunity theory, using amphibians. Repeated frog surveys were undertaken at 55 wetland sites in southeastern Australia. We detected 11 frog species from three families (Limnodynastidae, Myobatrachidae, and Pelodryadidae). The rarest species was detected at only one site whereas the most common species was detected at 42 sites (naive occupancy rate 0.02-0.76). Two models were assessed representing two competing hypotheses; the best-supported model included the covariates distance to the nearest site (connectivity), wetland area, presence of the non-native eastern mosquitofish (Gambusia holbrooki), proportion cover of emergent vegetation, an interaction term between Gambusia and emergent vegetation cover, and the proportion canopy cover over a site. Hydroperiod played no detectable role in metacommunity structure. We found species-habitat relationships that fit with current metacommunity theory: occupancy increased with wetland area and connectivity. There was a strong negative relationship between occupancy and the presence of predatory Gambusia, and a positive interaction between Gambusia and emergent vegetation. The presence of canopy cover strongly increased occupancy for several tree frog species, highlighting the importance of terrestrial habitat for amphibian community structure. We demonstrated how responses by amphibians to environmental covariates at the species level can be linked to occupancy patterns at the metacommunity scale. Our results have clear management implications: wetland restoration projects for amphibians and likely other taxa should maximize wetland area and connectivity, establish partial canopy cover, and eradicate Gambusia or provide aquatic vegetation to mitigate the impact of this non-native fish. We strongly advocate the use of MSOM to elucidate the habitat drivers behind animal occupancy patterns and to derive unbiased occupancy estimates for monitoring programs.

Multi-species occupancy modeling provides novel insights into amphibian metacommunity structure and wetland restoration.

A fundamental goal of community ecology is to understand species-habitat relationships and how they shape metacommunity structure. Recent advances in occupancy modeling enable habitat relationships to be assessed for both common and rare species within metacommunities using multi-species occupancy models (MSOM). These models account for imperfect species detection and offer considerable advantages over other analytical tools commonly used for community analyses under the elements of metacommunity structure (EMS) framework. Here, we demonstrate that MSOM can be used to infer habitat relationships and test metacommunity theory, using amphibians. Repeated frog surveys were undertaken at 55 wetland sites in southeastern Australia. We detected 11 frog species from three families (Limnodynastidae, Myobatrachidae, and Pelodryadidae). The rarest species was detected at only one site whereas the most common species was detected at 42 sites (naive occupancy rate 0.02-0.76). Two models were assessed representing two competing hypotheses; the best-supported model included the covariates distance to the nearest site (connectivity), wetland area, presence of the non-native eastern mosquitofish (Gambusia holbrooki), proportion cover of emergent vegetation, an interaction term between Gambusia and emergent vegetation cover, and the proportion canopy cover over a site. Hydroperiod played no detectable role in metacommunity structure. We found species-habitat relationships that fit with current metacommunity theory: occupancy increased with wetland area and connectivity. There was a strong negative relationship between occupancy and the presence of predatory Gambusia, and a positive interaction between Gambusia and emergent vegetation. The presence of canopy cover strongly increased occupancy for several tree frog species, highlighting the importance of terrestrial habitat for amphibian community structure. We demonstrated how responses by amphibians to environmental covariates at the species level can be linked to occupancy patterns at the metacommunity scale. Our results have clear management implications: wetland restoration projects for amphibians and likely other taxa should maximize wetland area and connectivity, establish partial canopy cover, and eradicate Gambusia or provide aquatic vegetation to mitigate the impact of this non-native fish. We strongly advocate the use of MSOM to elucidate the habitat drivers behind animal occupancy patterns and to derive unbiased occupancy estimates for monitoring programs.

Emergent vegetation in Netley-Libau Marsh: Temporal changes (1990–2013) in cover in relation to Lake Winnipeg level and Red River flow

A time-series (1990–2013) of classified vegetation cover maps was produced for Netley-Libau Marsh, a 26,000 ha coastal wetland on Lake Winnipeg, to assess its current status and verify earlier trends of emergent vegetation loss. Open water area in the marsh was measured from late-summer Landsat images for 20 years; three classes of vegetation types (emergents, wet meadows, upland) could also be identified for 12 images covering the same period. Temporal changes in area and distribution of marsh vegetation were related to adjoining Lake Winnipeg water-level and Red River discharge, as well as marsh connectivity and bathymetry. From 1990 to 2002, an increase in open-water areas and decrease in emergent vegetation coincided with rising levels and flows. The year 2003 marked major wetland regeneration and a decrease of open-water area under extremely low water-levels and flows. From 2005 to 2013, open-water area remained consistent, under high but variable levels and flows. A strong negative correlation was found between area of emergent vegetation and mean Red River discharge in the previous June-July. Superimposition of the limit of new emergent vegetation observed in 2003 with depth contours surveyed in 2010 revealed the dynamic nature of marsh bathymetry. Periods of extremely low water as short as one year (2003) induced a marked expansion in emergent vegetation cover that persisted over the next ten years despite higher water-levels. Rather than being gradual, changes in the spatial extent of Netley-Libau Marsh vegetation appeared to proceed by fits and starts, wherein periods of relative stasis were disrupted by major changes in abundance.

Wetland Waterbird Food Resources Increased by Harvesting Invasive Cattails

ABSTRACTThe conservation of many freshwater marsh waterbirds (i.e., waterfowl, shorebirds, wading birds, and secretive marshbirds) in the Laurentian Great Lakes requires managing invasive emergent macrophytes, which degrade waterbird habitat by creating dense, litter‐clogged stands, and excluding plants that produce nutritionally balanced and high‐energy food (seeds, tubers, and submerged aquatic vegetation). The most commonly used management approach in the United States Great Lakes region involves the application of herbicides, which can stimulate waterbird forage plants but does not address the accumulation of plant litter, the underlying cause of plant community diversity loss and habitat degradation. We experimentally evaluated the effects of an alternative approach, harvesting invasive plants and their litter followed by flooding, on plant communities, focusing on the effects of these treatments to increase the abundance of high‐energy wetland plants. At the Shiawassee National Wildlife Refuge in Michigan, USA, we experimentally treated an invasive cattail (Typha × glauca)‐dominated wetland in August and September of 2016, 2017, and 2018, using a randomized block design with 4 blocks and 3 treatments (sediment surface harvest, above ground harvest, and control). We monitored the effects of these treatments on the abundance and dominance of waterbird forage‐producing plants, plant diversity, and plant communities prior to (Jul 2016) and during the summer following each treatment (late Jul or early Aug 2017, 2018, and 2019). Additionally, we used pre‐ and post‐treatment waterbird use‐day data collected at the unit scale and compared values with satellite imagery‐derived land cover changes. Compared to control plots, 3 years of harvesting and flooding significantly increased plant species diversity, increased the abundance of waterbird seed‐ and tuber‐producing plant species by 5 times, and increased annual plant dominance by more than 10 times, while substantially reducing all measures of cattail and its litter. Use‐days increased for total waterbirds, including waterfowl and dabbling ducks, following treatment. Cattail cover decreased and open water and non‐cattail emergent vegetation cover increased. Harvesting invasive plant biomass coupled with flooding promoted a plant community composition and structure beneficial to waterbirds. © 2020 The Wildlife Society.

Marsh bird occupancy of wetlands managed for waterfowl in the Midwestern USA.

Marsh birds (rallids, bitterns, and grebes) depend on emergent wetlands, and habitat loss and degradation are the primary suspected causes for population declines among many marsh bird species. We evaluated the effect of natural wetland characteristics, wetland management practices, and surrounding landscape characteristics on marsh bird occupancy in Illinois during late spring and early summer 2015–2017. We conducted call-back surveys following the North American Standardized Marsh Bird Survey Protocol three times annually at all sites (2015 n = 49, 2016 n = 57, 2017 n = 55). Across all species and groups, detection probability declined 7.1% ± 2.1 each week during the marsh bird survey period. Wetlands managed for waterfowl (ducks, geese, and swans) had greater occupancy than reference wetlands. Marsh bird occupancy increased with greater wetland complexity, intermediate levels of waterfowl management intensity, greater proportions of surface water inundation, and greater proportions of persistent emergent vegetation cover. Wetland management practices that retain surface water during the growing season, encourage perennial emergent plants (e.g., Typha sp.), and increase wetland complexity could be used to provide habitat suitable for waterfowl and marsh birds.

Managing farm ponds as breeding sites for amphibians: key trade-offs in agricultural function and habitat conservation.

Millions of farm ponds have been constructed in agricultural landscapes around the globe. These ponds are built to support a variety of functions, including erosion control, cattle grazing, and recreational fishing, but their role as breeding habitat for amphibians remains poorly understood. We addressed this knowledge gap by studying farm ponds in the eastern Great Plains of the United States, a pond-dense region dominated by agriculture. We used field surveys and occupancy modeling to identify the important biophysical components of amphibian habitat and to assess the species-specific effects of cattle and fish presence on breeding occupancy. We next used a chronosequence to determine whether pond renovation, which often occurs when ponds are about 40yr old, threatens the development of amphibian habitat. Nine amphibian species bred in the farm ponds that we surveyed, and the relationship between breeding occupancy and habitat variables varied by species. We found that the pH conditions associated with amphibian breeding occupancy were significantly more likely to occur in older ponds (>50yr old). Emergent vegetation cover was also associated with increased breeding probability and rarely reached high levels in newer ponds. Since the older ponds with suitable habitat are at an age where renovation is likely needed to restore their agricultural function, this habitat may be at risk. We suggest that conservation of amphibians in farm ponds in the United States will require adopting renovation and management practices that balance the multiple uses of these sites and maintain a mosaic of pond successional states.

Aquatic Insects of Man-Made Habitats: Environmental Factors Determining the Distribution of Caddisflies (Trichoptera), Dragonflies (Odonata), and Beetles (Coleoptera) in Acidic Peat Pools

As degradation of sensitive habitats like Sphagnum L. (Sphagnales: Sphagnaceae) peatbogs is endangering their invertebrate fauna, artificial peat pools may offer peatbog insect fauna a chance of survival. The entomofauna of seven peat pools in a peatbog and its surrounding natural marginal zone in SE Poland was investigated at the level of species, assemblages and faunistic metrics, indicating the key environmental drivers of the insect distribution and their implications for the biodiversity and potential conservation of these habitats. The species composition, specialists, and insect assemblages of the peat pools were linked with the fauna typical of both peatbogs and dystrophic pools with an open water surface. The most specialized fauna was found in the pools with the largest Sphagnum cover: only tyrphobionts, of all the ecological elements, significantly discriminated the fauna of peat pools and the marginal zone. Sphagnum cover was the key structural factor affecting the distribution of all the insects. Additionally, dragonflies were dependent on pH, beetles on temperature, and caddisflies on dissolved oxygen; however, structural factors—apart from Sphagnum cover—pool perimeter and emergent vegetation cover were predominant. Our results show that appropriate management of the structural factors of peat pools, especially Sphagnum cover, and the provision of different successional stages, can enhance biodiversity and help to maintain a valuable specialist fauna. Even along small environmental gradients and in a homogeneous area, the response of insects is highly differentiated. Dragonflies probably best represent the conservation value of the overall invertebrate fauna of Sphagnum bogs.

Lattice Boltzmann method for simulating flows in open-channel with partial emergent rigid vegetation cover

Flows in open-channel with partial emergent rigid vegetation cover are simulated using the lattice Boltzmann method (LBM) described by the 2-D nonlinear shallow water equations. The effect of vegetation is represented with the vegetation roughness coefficient, which is related to the vegetation density, diameter of the vegetation elements and drag coefficient. The model is verified by three numerical tests: flow in a 180° curved open channel with partial vegetation cover at the outer bank, flow in a rectangular channel with a finite patch of vegetation and flow in a rectangular channel with a vegetated bank. Numerical results are compared with the experimental data, and the good agreement proved that the presented model can model the vegetated channel flows correctly.

Habitat selection and reproductive success of coot Fulica atra on ponds under different fish size and density conditions

Fish may influence habitat selection and reproductive success in waterfowl. We investigated the effects of common carp Cyprinus carpio on breeding coots Fulica atra along a gradient of fish size structure and density, created by separate stocking of age cohorts in ponds in eastern Poland. Coot breeding densities were higher on ponds with low biomass of small-sized, young-of-the-year fish than on ponds with medium- or large-sized fish, stocked at high biomass densities; they also increased with increasing submerged vegetation biomass (an effect correlated with water transparency) and emergent vegetation cover. Densities of nektonic and epibenthic macroinvertebrates and of amphibian larvae were also negatively influenced by fish size/density gradient, while densities of emerging insects were not affected. However, coot breeding success per pair was similar among pond types, while positively related to submerged vegetation, indicating that either plant food abundance was more important than the overall trophic impact of fish or fledgling production was additionally limited by factors other than food. Carp may adversely affect pond habitats of waterfowl both via trophic interactions and through abiotic disturbance of ecosystem processes. In coots, however, the effects can be mitigated by maintenance of abundant emergent vegetation and of submerged macrophytes resistant to fish.

The functional response and resilience in small waterbodies along land-use and environmental gradients.

There is growing recognition of the essential services provided to humanity by functionally intact ecosystems. Freshwater ecosystems are found throughout agricultural and urban landscapes and provide a wide range of ecosystem services, but globally they are also amongst the most vulnerable. In particular, ponds (lentic waters typically less than 2ha), provide natural flood management, sequester carbon and hold significant cultural value. However, to inform their management it is important to understand (1) how functional diversity varies in response to disturbance and (2) the link between biodiversity conservation and ecosystem function. In this study, a meta-analysis of seven separate pond studies from across England and Wales was carried out to explore the effect of urban and agricultural land-use gradients, shading, emergent vegetation, surface area and pH upon groups of functionally similar members of the macroinvertebrate fauna. Functional effect groups were first identified by carrying out a hierarchical cluster analysis using body size, voltinism and feeding habits (18 categories) that are closely related to biogeochemical processes (e.g. nutrient and carbon recycling). Secondly, the influence of the gradients upon effect group membership (functional redundancy-FR) and the breadth of traits available to aid ecosystem recovery (response diversity) was assessed using species counts and functional dispersion (FDis) using 12 response traits. The effect of land-use gradients was unpredictable, whilst there was a negative response in both FR and FDis to shading and positive responses to increases in emergent vegetation cover and surface area. An inconsistent association between FDis and FR suggested that arguments for taxonomic biodiversity conservation to augment ecosystem functioning are too simplistic. Thus, a deeper understanding of the response of functional diversity to disturbance could have greater impact with decision-makers who may relate better to the loss of ecosystem function in response to environmental degradation than species loss alone.

Sedimentation and resuspension modelling in free water surface constructed wetlands

Eutrophication is a widespread problem that is being tackled from many perspectives and the recently applied technology of constructed wetlands is being used in the treatment of eutrophic water. However, process-based models to simulate their performance are scarce, so in this work a mechanistic model was developed to simulate the removal of total suspended solids, phytoplankton and total phosphorus in free water surface constructed wetlands treating eutrophic water. The model represents the influence of the main factors of the biotope and biota on these water quality variables, and particular attention is paid to resuspension produced by wind and by avifauna. Likewise, the effect of emergent vegetation cover in sedimentation, resuspension and phytoplankton growth is included. Phytoplankton is considered to store phosphorus internally in order to use it when growing, and the contribution of phytoplankton concentration to the suspended solids budget is included. The software AQUASIM was used to calibrate and validate the model in two full-scale constructed wetlands treating eutrophic water from Lake l′Albufera de València (Spain) for three years. The simulated data and field measurements showed satisfactory adjustments for the three studied variables. The budgets obtained for each variable reveal that sedimentation and resuspension are the main processes in total suspended solids performance. Sedimentation of organic particulate phosphorus is the most important process in total phosphorus removal. The sum of the effect of resuspension by avifauna and by wind increases by more than 50% the quantity of solids that enters the water column. The model reveals that simulating the effects of the emergent vegetation cover and resuspension is crucial for representing the performance of the studied variables.