Evidence of ecological critical slowing-down in temperate soils

The resilience of ecological systems is crucially important, particularly in the context of climate change. We present experimental evidence of critical slowing-down arising from perturbation of a key function in a complex ecosystem, exemplified by soil. Different behavioural classes in soil respiratory patterns were detected in response to repeated drying:rewetting cycles. We characterised these as adaptive, resilient, fragile or non-resilient. The latter involved increasing erratic behaviour (i.e. increasing variance), and the propagation of such behaviour (i.e. autocorrelation), interpreted as a critical slowing-down of the observed function. Soil microbial phenotype and land-use were predominantly related to variance and autocorrelation respectively. No relationship was found between biodiversity and resilience, but the ability of a community to be compositionally flexible rather than biodiversity per se appeared to be key to retaining system function. These data were used to map the extent to which soils are close to crossing into alternative stable states at a national scale.