Richness of arbuscular mycorrhizal fungi increases with ecosystem degradation of temperate eucalypt woodlands

Abstract

PurposeDegraded ecosystems can be maintained by abiotic and biotic legacies long after initial disturbances, preventing recovery. These legacies can include changes in arbuscular mycorrhizal fungi (AMF). To inform potential restoration pathways, we aimed to elucidate differences in AMF between intact and degraded ecosystems, their responses to modified soils, and interactions with invasive plants.MethodsWe used a state-and-transition framework to characterise AMF communities, native and exotic plant cover, and soil physicochemical properties across little-modified reference states and degraded states, which were carbon (C) and nitrogen (N) -depleted, intermediate, and CN-enriched, in temperate eucalypt woodlands of south-eastern Australia.ResultsMost ground-layer states differed significantly in their AMF communities, with the CN-enriched states being most distinct. All states had unique taxa and characteristic indicator taxa, but intermediate and CN-enriched states harboured four-to-five times more indicator taxa than the reference state. Consistent with this, richness of AMF was higher in the intermediate and CN-enriched states than in reference states, driven by higher richness of Archaeosporaceae, Diversisporaceae, Glomeraceae, and Paraglomeraceae. Pathway analysis indicated that differences in AMF communities among states were strongly related to differences in native:exotic plant cover ratio, mediated by soil organic matter and nutrients.ConclusionOur results indicate that ecosystem degradation is associated with both loss of AMF taxa and introduction of ‘weedy’ AMF, which in turn potentially contribute to maintenance of degraded ecosystems. We argue that our state-and-transition approach to characterising AMF communities improved our understanding of the different pathways of degradation, elucidating possible constraints to ecosystem recovery.