Contrasting spatial patterns and ecological attributes of soil bacterial and archaeal taxa across a landscape

Abstract

Even though recent studies have clarified the influence and hierarchy of environmental filters on bacterial community structure, those constraining bacterial populations variations remain unclear. In consequence, our ability to understand to ecological attributes of soil bacteria and to predict microbial community response to environmental stress is therefore limited. Here, we characterized the bacterial community composition and the various bacterial taxonomic groups constituting the community across an agricultural landscape of 12 km2, by using a 215 × 215 m systematic grid representing 278 sites to precisely decipher their spatial distribution and drivers at this scale. The bacterial and Archaeal community composition was characterized by applying 16S rRNA gene pyrosequencing directly to soil DNA from samples. Geostatistics tools were used to reveal the heterogeneous distribution of bacterial composition at this scale. Soil physical parameters and land management explained a significant amount of variation, suggesting that environmental selection is the major process shaping bacterial composition. All taxa systematically displayed also a heterogeneous and particular distribution patterns. Different relative influences of soil characteristics, land use and space were observed, depending on the taxa, implying that selection and spatial processes might be differentially but not exclusively involved for each bacterial phylum. Soil pH was a major factor determining the distribution of most of the bacterial taxa and especially the most important factor explaining the spatial patterns of α-Proteobacteria and Planctomycetes. Soil texture, organic carbon content and quality were more specific to a few number of taxa (e.g., β-Proteobacteria and Chlorobi). Land management also influenced the distribution of bacterial taxa across the landscape and revealed different type of response to cropping intensity (positive, negative, neutral or hump-backed relationships) according to phyla. Altogether, this study provided valuable clues about the ecological behavior of soil bacterial and archaeal taxa at an agricultural landscape scale and could be useful for developing sustainable strategies of land management.

Tillage intensity and pasture in rotation effectively shape soil microbial communities at a landscape scale

“…More precisely, soil organic carbon content and quality ( C : N ratio) were the main determinants of the microbial biomass. This observation is in accordance with the results of Constancias, Saby, et al., ; Constancias, Terrat, et al., also obtained at a landscape scale. The soil organic matter content and its recalcitrance to degradation were also related to the abundance of microorganisms in field experiments or at a wider scale (De Boer et al., ).…”

“…In this way, our study confirmed the importance of soil properties as drivers of microbial communities (Constancias, Saby, et al., ; Constancias, Terrat, et al., ). Similar results have been obtained at national (Dequiedt et al., ; Griffiths et al., ) and continental scales (Fierer & Jackson, ).…”

“…In addition, visual comparison of the different maps evidenced that the location of the hot and low spots was different for each microbial parameter and suggested that these variations were related to soil characteristics (as represented by soil types above). Altogether, these observations lead to conclude that various environmental factors drive microbial biomass and diversity as previoulsy observed at the landscape scale (Constancias, Saby, et al., ; Constancias, Terrat, et al., .…”

“…Besides, the landscape is a relevant scale for cropland management by farmers and for the implementation of agricultural strategies by decision‐makers. Some studies dealt with the agricultural landscape scale but evaluated basic land management categories such as forests versus grasslands versus croplands (e.g., Constancias, Saby, et al., ; Constancias, Terrat, et al., ). We now need to quantitatively integrate the range of farm systems variation and identify those farming practices which have the most impact.…”

“…We now need to quantitatively integrate the range of farm systems variation and identify those farming practices which have the most impact. Moreover, studies at landscape scale often focused on the bacterial community (e.g., Constancias, Saby, et al., ; Constancias, Terrat, et al., ; Landa et al., ). However, the fungal community also has a major role in agroecosystem functioning and needs to be addressed (De Boer, Folman, Summerbell, & Boddy, ).…”