Supplementary material to Micro-environmental variation of soil microbial biodiversity differs across land use types – implications for field sampling designs

Abstract

Background and Aims: Soil microbial biodiversity is the driving force behind several soil processes and is highly affected by land use change. The development of soil quality indicators based on microbial biodiversity is growing, mainly focusing on macro-environmental factors (soil type, climate, biomes). However, little is known about how these communities vary within micro-environmental gradients (soil depth, spatial distance) across different land uses, which is critical for designing field sampling protocols. Our objective was to assess how soil microbial communities changed with soil depth and spatial distance after land use conversion in Patagonia, Argentina. Methods: A state-and-transition model was used as a reference framework entailing native forest, horticulture and grassland soils. We sampled soils in four spatial distances (from 0.1 to 70 m) and four depths (within 0-40 cm) and combined 16S rRNA gene sequencing, DNA quantification and soil chemical characterization to explore micro environmental variation in microbial biomass, α-diversity, β-diversity, and microbial communities' assembly processes. Results: Depth and spatial distance had differential effects on microbial biodiversity within different land uses. Microbial biomass was most sensitive to depth, α-diversity to spatial distance, and b-diversity to both depth and spatial distance. Deterministic processes dominate microbial communities' assembly along depth in all land uses, which is a promising result for developing soil quality indicators based on microbial biodiversity. Conclusions: Overall, our results suggest that a homogeneous sampling effort does not necessarily capture the same soil microbial variability across different land uses; hence, design adjustments should be needed.