Soil multifunctionality increases after grazing abandonment in semiarid rangelands

Abstract

Grazing by domestic animals is an economic activity that can alter the ecosystem structure and functioning of drylands. Some rangelands are experiencing a temporary or complete abandonment of grazing, but the effects of these practices on the ecology of drylands are poorly studied. Plant patches are recognized as fertility islands in drylands. Unvegetated inter-patches, far from being lifeless, harbor diverse soil microbial communities, habitually in the form of biocrusts. Here, we determined changes in plant, biocrust, and bare soil cover after grazing cessation over a 63-year period in Patagonian semiarid drylands. We also quantified, at microsite (2.25 m2) and plot (2500 m2) scales, temporal changes in soil multifunctionality by using four specific soil multifunctionality indexes associated with soil carbon, fertility, biogeochemical cycling, and stability. Our results indicate that biocrusts, although with low cover values, colonize new soil areas following grazing cessation, whereas bare soil cover increases at the expense of plants. We found that soil multifunctionality consistently increased with time since grazing cessation at the microsite scale, with biocrusts showing the highest multifunctionality values. We also observed that soil multifunctionality increased over time after grazing cessation at the plot scale, with bare soil and plants being more important than biocrusts due to their greater cover. Overall, our field study shows that the abandonment of grazing leads to a natural recovery of soil functioning in semiarid rangelands, with biocrusts and microbial communities of bare soils playing central roles, but at different spatial scales.