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Depressional wetlands are highly vulnerable to changes in land surface temperature and rainfall but little is known about their responses to future climate change. This study assessed the variation in edaphic factors between wetlands and along their littoral gradients to detect the boundary between the endorheic wetlands and upland zones. A sample of 202 paired measurements of three edaphic factors were collected (Soil Moisture Content – SMC-g/g, Bulk Density – BD-g/cm 3 and Salinity as Electrical Conductivity – EC-dS/m) in 10 m plots along 14 belt transects in eight representative wetlands in the Mpumalanga Lake District, South Africa. In general, there were significant differences between the eight wetlands for SMC and BD but not for EC.SMC and BD generally showed negative trends along the littoral gradients. The trends occurred over short distances, ranging from 30 to 70 m, reflecting the extent of the wetlands. Understanding of the spatial variation of edaphic factors helps in the management and monitoring of depressional wetlands under a changing climate. In addition, the study showed that the current wetland buffer zone stipulated in local legislation was too narrow and recommended that this be extended to 100 m.

This study focuses on comparing the driving ecological factors and community diversity of fen vegetation from the plain part of the South Ural region with those of the mountain fen vegetation, previously described by us (Ivchenko and Znamenskiy Russian Journal of Ecology 47:453–459, 2016), by means of vegetation data clustering and gradient analysis. The indicator values by several authors (H Ellenberg, E Landolt, LG Ramensky, DN Tsyganov) and WorldClim bioclimatic variables were used to determine the ecological meaning of the gradients. We found that the main gradient for both plain and mountain fen vegetation is the “poor-rich fen” gradient, which depends on local substrate chemical composition. The second gradient is associated with moisture, which tends to increase consistently both from mountains towards plains and across plains from peneplain towards West Siberian Lowland. The moisture gradient proved to be unrelated to precipitation, which increase linearly from plains towards mountains. The community diversity in the mountain part is higher than in the plain part. The fen vegetation of plains and mountains overlap in ordination space but a half of the types described for mountain fen vegetation do not occur on plains, while two types of plain fen vegetation from the West Siberian Lowland are absent on mountains.

Seasonal ponds are common throughout forested regions of the north central United States. These wetlands typically flood due to snow-melt and spring precipitation, then dry by mid-summer. Periodic drying produces unique fishless habitats with robust populations of aquatic invertebrates. A basin’s physical/chemical features, the absence of vertebrate predation, and especially the duration of seasonal flooding, have long been viewed as the major structuring influences on these communities, but previous studies have shown only limited effects of environmental variables on pond invertebrates. Applying ordination methods to data from weekly collections of invertebrates during 2008–2009, we tested influences of site-level environmental gradients on the presence and relative abundance of aquatic invertebrate communities in 16 seasonal ponds in a forested region of north central Minnesota, USA. We assessed invertebrate community patterns in relation to pond size and depth, soil nutrients, canopy closure, hydroperiod, and predominant groundwater function (recharge, discharge, or flow-through). Patterns in pond invertebrate community composition were consistently related to pond depth, overhead canopy closure, and hydroperiod. Site-level hydrologic function showed weak relationships to seasonal patterns of invertebrate abundance. Although physical features of ponds had only modest influence on presence and abundance of invertebrates, weekly sampling improved models relating environmental variables to pond invertebrates.

During 1999–2005, we studied aquatic invertebrate communities in 24 small, seasonally flooded wetlands (seasonal ponds) in aspen (Populus spp.)-dominated landscapes in north central Minnesota, USA. Sites were chosen from 2 different landforms, with 6, 6, and 12 wetlands selected from stands estimated to have been harvested 10–34 (young age), 35–58 (mid-age), and 59+ (old age) years before onset of the study, respectively. Of 12 ponds in the old age group, six were clear-cut during the winter of 2000–2001. Direct gradient analysis indicated that invertebrate communities were influenced by canopy openness, total phosphorus, total alkalinity, maximum depth, and hydroperiod, although relationships were complex, with no single environmental variable explaining > 9.3% of invertebrate variance. Invertebrate taxon richness was negatively correlated with stand age and was also lower during the period following tree removal. However, taxon richness declined to a lesser extent in harvested old age stands relative to unharvested controls during the post-harvest time period. Our results indicated the presence of weak relationships between invertebrate communities and environmental characteristics of seasonal ponds and adjacent uplands. Innovative research strategies are needed because adaptations of aquatic invertebrates may limit interpretation of responses to natural and anthropogenic gradients in these habitats.

Pattern and zonation of peatland vegetation are regulated by environmental gradients, as well as by effects of biomass and competitive exclusion on distribution of species richness. The interplay of these factors has not been closely examined in calcareous prairie fens, which are isolated, species rich, calcareous peatlands in the Prairie Peninsula region of North America. We used multivariate analyses to classify vegetation and to quantify species richness in relation to substrate conditions and vegetation structure in a 23-ha calcareous prairie fen in northeast Illinois, USA. Plant assemblages formed a floristic continuum across sedge meadow, graminoid fen, calcareous seep, marl flat, and spring run vegetation, with complete dissimilarity between spring run and sedge meadow. These vegetation zones corresponded to gradients of decreasing organic content and cation exchange capacity, and increasing pH, Na, Mg, and total Ca concentrations, which reach extremes in spring run and marl flats. Species richness was unimodal across the fen gradient, fitting an expected model of low richness in vegetation either with large biomass (as shown by low light penetration in tall sedge meadow) or with environmentally harsh conditions and low biomass (shown by high light penetration in short marl flat and spring run vegetation). These biotic and abiotic factors, as well as hydrology, mediate vegetation pattern across the fen.

Species composition in floodplain vegetation is often related to initial floristics, succession, and disturbances such as flooding and herbivory. However, on a braided, cobble-bedded river with contrasting sediment facies, much of the composition of understory vegetation within a cottonwood forest was related to edaphic factors controlled by stream-deposit stratigraphy. Large shifts in understory species composition were more related to soil texture and water availability than deposit age or hydroperiod. Finer-textured and thicker overbank deposits had greater water availability and supported mesic species, while sites with coarse sediments to the surface supported only xeric species. A strong gradient of site moisture corresponded to a gradient in species composition. Soil water potential (Ψs) indicated by pre-dawn xylem water potential (XWPPD) in a shallow-rooted grass reached −4.2 MPa on xeric-species sites in mid-summer; on mesic-species sites, XWPPD was always greater than −1.5 MPa for the s...

The autecology of several peatland plant species has been studied on a wide variety of gradients that include elevation relative to the water table, surface water chemistry, mire margin to mire expanse, shade, and climate. The accuracy with which species’ realized niches are defined and the ability to predict community structure as conditions change along gradients vary considerably between studies. Many studies have quantified species niche dimensions along individual gradients, and although they have the ability to predict species abundance and distribution, they do not account for synergistic effects between gradients. Other methods analyze two gradients simultaneously producing rectangles and ellipsoids, but these methods have limited predictive ability. A variety of ordination techniques are often used to analyze species preferences along several gradients simultaneously. However, with the exception of Detrended Canonical Correspondence Analysis, these methods have limited predictive ability because gradients are defined as ordination axes and it is difficult to analyze each gradient individually. Species response surfaces calculated along several gradients simultaneously offer a more accurate definition of species’ realized niche dimensions. Response surfaces can be used to predict baseline community structure along several gradients, but they do not integrate such biotic factors as competition and succession, as well as such disturbances as fire, pollution, and peat harvesting.