Environmental drivers of the distribution of nitrogen functional genes at a watershed scale

Abstract

To date only few studies have dealt with the biogeography of microbial communities at large spatial scales, despite the importance of such information to understand and simulate ecosystem functioning. Herein, we describe the biogeographic patterns of microorganisms involved in nitrogen (N)-cycling (diazotrophs, ammonia oxidizers, denitrifiers) as well as the environmental factors shaping these patterns across the Koiliaris Critical Zone Observatory, a typical Mediterranean watershed. Our findings revealed that a proportion of variance ranging from 40 to 80% of functional genes abundance could be explained by the environmental variables monitored, with pH, soil texture, total organic carbon and potential nitrification rate being identified as the most important drivers. The spatial autocorrelation of N-functional genes ranged from 0.2 to 6.2 km and prediction maps, generated by cokriging, revealed distinct patterns of functional genes. The inclusion of functional genes in statistical modeling substantially improved the proportion of variance explained by the models, a result possibly due to the strong relationships that were identified among microbial groups. Significant relationships were set between functional groups, which were further mediated by land use (natural versus agricultural lands). These relationships, in combination with the environmental variables, allow us to provide insights regarding the ecological preferences of N-functional groups and among them the recently identified clade II of nitrous oxide reducers.

Soil Temperature Dynamics Modulate N2O Flux Response to Multiple Nitrogen Additions in an Alpine Steppe

“…Thereby, we may expect that pH had little impact on the AOA responses to N additions in the current study. In addition, changes in soil moisture may influence nitrification‐related microbial growth (Tsiknia et al, ). It has been reported that N addition might cause soil water depletion owing to increased plant growth and leaf transpiration (Xia et al, ; Zhang et al, ) and decreased soil water content might constrain microbial growth.…”

Global biogeography of microbial nitrogen-cycling traits in soil

“…We hypothesized that the taxa responsible for each pathway would vary greatly by habitat type, because the habitat would select for specialized taxa. We further predicted that soil pH-previously identified as an important driver of soil composition (25,26)-would also influence compositional variation within microorganisms encoding N-cycling traits.…”

Local Environmental Factors Drive Divergent Grassland Soil Bacterial Communities in the Western Swiss Alps

“…Most authors have studied soil grassland bacterial diversity on a single or a few mountain transects, notably to emphasize the elevation factor in mountain ecosystems (3)(4)(5)(6)(7)(8). However, alpine studies that span an important horizontal surface area, along with the vertical elevation gradient, are much fewer, despite that mountain ecosystems are composed of a large spectrum of different topographic, climatic, soil physical, and chemical conditions, interspersed with a wide range of microclimates occupied by varied vegetation and animal populations (2,(9)(10)(11)(12).…”