Abstract
AbstractLand‐use intensification can reduce soil carbon stocks and changes microbial community biodiversity and functionality. However, there is a lack of consensus on whether management consistently affects microbial biodiversity across geographic scales, and how this relates to altered soil function. From a regulatory and monitoring perspective, there is a need to identify functionally relevant indicators of land use in order to evaluate the progress of soil restoration approaches. We performed a landscape‐scale survey of unimproved calcareous grasslands paired with local arable contrasts, and assessed the consistency of responses in a variety of soil, biotic and functional measures. In addition, adjacent grasslands undergoing restoration were assessed to identify soil microbial indicators of recovery. Organic matter content was consistently larger in grasslands than in arable fields, and increased with time in the restoring sites. Molecular comparisons of grassland versus arable soils revealed numerous bacterial, archaeal and fungal indicators, with more representatives of Ca. Xiphinematobacter, DA101, Bradyrhizobium, Rhodoplanes, Mycobacteria and Mortierella in old grassland soils, whereas Nitrososphaera, Sporosarcina and Alternaria infectoria were more abundant in arable soils. Extracellular enzymatic responses were more variable, with none of the eight investigated enzymes being consistent indicators of grassland or arable soils. Correlation analyses, incorporating the molecular and enzymatic responses across all surveyed soils, revealed that molecular indicators were more strongly correlated with soil organic matter increases with restoration of arable soils. Our results highlight that microbial taxa are among the most sensitive indicators of soil restoration, and we identify consistent responses of specific taxa to management across geographic scales. This discovery will be important for both the instigation and monitoring of soil restoration.Highlights Soil microbes are key drivers of soil ecosystem services and are affected by management Calcareous grassland exhibited abundant Verrucomicrobia; cropping increased Nitrososphaera These taxa responded to SOM increases with grassland restoration, more so than enzymes and fungi Microbes provide consistent, site‐independent indicators for calcareous grassland soil function restoration
Highlights
Microorganisms play a major role in delivering soil ecosystem services, including nutrient cycling, soil aggregate stability, plant productivity and biodiversity (Fierer, 2017; Kallenbach, Grandy, & Frey, 2016)
Our results highlight that microbial taxa are among the most sensitive indicators of soil restoration, and we identify consistent responses of specific taxa to management across geographic scales
Past research has identified that microbial biomass and activity is reduced under intensive arable management, and it is thought that intensification leads to a general reduction in fungi compared to bacteria (Emmerling, Udelhoven, & Schröder, 2001; Lauber, Strickland, Bradford, & Fierer, 2008; Nunes et al, 2012; Potthoff et al, 2006)
Summary
Microorganisms play a major role in delivering soil ecosystem services, including nutrient cycling, soil aggregate stability, plant productivity and biodiversity (Fierer, 2017; Kallenbach, Grandy, & Frey, 2016). Bacteria in particular, are primarily structured along gradients of pH (Griffiths et al, 2011), land-use-driven change in other edaphic properties can often obfuscate direct relationships between intensification, SOM and microbial taxa (Lauber et al, 2008; Thomson et al, 2015). It is, likely that constraining contrasts to land-use comparisons of soils of similar pH may help identify specific indicators relating to SOM and the lack of disturbance from cultivation. The performance of microbial indicators will be contrasted with enzymatic functional measures to test the utility of such metrics for informing on soil status under a restoration context
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