Disentangling the fundamental underpinning of soil biological resilience
The ability of soils to continue to function under stress or perturbations – their resilience – is key to sustaining many of the ecosystem services which flow from them. However, the factors supporting soil resilience (and indeed its definition) remain obscure and this is further complicated by the fact that soils are multi-functional. Many of these functions are inextricably linked to the soil microbial community and as such the response of this community will have a strong influence on the resistance and resilience of soil functioning in general, and in relation to microbially-mediated processes in particular. In this study, we are starting to untangle the linkages between different combinations of intrinsic (i.e. soil-based) and extrinsic (e.g. landscape context, management) factors to elucidate how they collectively determine the resilience of soil respiration to cycles of drying and rewetting, and the extent to which the soil microbiome relates to such resilience. We use model experimental systems based upon high temporal resolution respiration profiles following repeated drying:wetting cycles, in which resilience is determined and modelled, and then contextualised using Bayesian approaches within the soil landscape over 60 soils sampled across England.
An initial exercise in the modelling of factors that drive resilience of a prescribed physical (void ratio) and biological (respiration) soil function was carried out on published data pertaining to 38 English and Scottish soils. This revealed that soil contextual factors (e.g. land use, parent material and soil texture but not soil organic matter) were dominant in determining soil resilience in general, and aspects of the soil microbial community were also pertinent. These models performed well, with an error rate of <3% for each of the resilience measures. It is noteworthy that the main factors considered in the literature as putatively being key to soil resilience/resistance, such as soil organic matter, did not surface as important in the modelling part of this study. Results from the larger set of English soils (60) showed that in general soils are well adapted (resilient) to repeated dry:wet cycles. From the resilience model, we note that that overall change in the functional response of the soil was related to microbial community (P < 0.01) and that the system’s ability to return to its pre-disturbance functional state is related soil total nitrogen content of the soil (P < 0.01) and water holding capacity of the soil (p = 0.03).