Land-use and land-cover effects on soil microbial community abundance and composition in headwater riparian wetlands

Abstract

Headwater riparian wetlands are relatively small in size but functionally significant as expected "hot spots" of microbial activity in the landscape. Despite their roles as biogeochemical drivers, little is known about how microbial communities in headwater riparian wetlands are affected by surrounding land-uses and land-covers (LULCs). The primary objective of this study was to determine if and how wetland soil microbial abundance and community composition varied as a function of landscape metrics as mediated through on-site edaphic properties. Forty-two soil samples, collected from eight headwater riparian wetlands in the Ridge and Valley Region of central Pennsylvania, were used for phospholipid fatty acid (PLFA) profiling of soil microbial communities. These samples were used to create microbial habitat models describing plot-level relationships between edaphic properties and microbial measures (i.e., microbial biomarker abundances, ratios and composition). Soil organic matter (SOM) content was a strong predictor of microbial biomarker abundances and fungi / bacteria ratios, while soil pH was a strong predictor of microbial composition (i.e., relative abundance of individual fatty acids) and potential microbial stress indices (i.e., cy19:0a/18:1ω7c and cy17:0/16:1ω7c). Soil texture, soil moisture, and litter total nitrogen had smaller, but significant effects in these empirical microbial habitat models. Microbial habitat models were subsequently used to estimate microbial measures for a larger regional headwater riparian wetland dataset (n = 87), where edaphic property information was compiled. Site-average microbial measures were correlated with wetland elevation, and with landscape composition metrics in a landscape assessment area (i.e., 125,664 m 2). Wetland elevation explained high among-site variability in microbial abundance measures, as mediated through SOM content, in headwater riparian wetlands in forested landscapes. However, wetland elevation was confounded by landscape composition, for

Fine‐scale spatial homogenization of microbial habitats: a multivariate index of headwater wetland complex condition

“…Moon et al. () found that 93% of variability in microbial biomass across these sampling blocks could be explained by soil organic matter content and mineral soil clay content (Fig. A).…”

“…To construct our MHIs, we used soil properties that had been previously correlated with microbial biomass and composition from Moon et al. (); in this concurrent study, microbial community composition data were collected at a subset of the 1‐m 2 sampling blocks ( n = 42) across our eight sites using phospholipid fatty acid analysis. Moon et al.…”

“…Panel A displays the interactive relationship between phospholipid fatty acid ( PLFA ) microbial biomass (nmol/g soil) and soil organic matter and clay content, modeled using Moon et al. (). As soil organic matter and clay content increase, there is an increase in the PLFA microbial biomass (refer to the gray‐scale legend).…”

“…Fourth, it is common to assess soil properties individually for mean changes and spatial structure; however, we know that microbial nutrient cycling depends on an array of soil properties that need to be considered simultaneously (i.e., multivariate indices) to understand the overall effects of human disturbance on wetland microbial functioning (Moon et al. ).…”

“…, Moon et al. ), and as such we describe them as microbial habitat indices (i.e., MHIs). We investigate these MHIs in headwater wetland complexes, the dominant wetland type within the upper reaches of the Chesapeake Bay Watershed (first described as complexes by Wardrop et al.…”