Recovery of arbuscular mycorrhizal fungi root colonization after severe anthropogenic disturbance: four species assessed in old-growth Mediterranean grassland

Abstract

Arbuscular mycorrhizal fungi (AMF) interact continuously with vegetation and soil, and thus shape the dynamics of plant communities. Yet the recovery of AMF after severe anthropogenic disturbance such as cultivation has rarely been assessed. Here, to determine whether AMF root colonization recovers after such disturbance, we compared AMF root colonization in abandoned fields last cultivated 2, 35 and 150 years ago in the La Crau area (south-eastern France) with that of a grassland several thousands of years old (considered as the reference ecosystem). We measured AMF root colonization of four species (Carthamus lanatus, Carduus pycnocephalus, Brachypodium distachyon and Bromus madritensis) and performed surveys of plant communities and soil chemical properties. AMF root colonization was still significantly lower 35 years after disturbance for one species (B. distachyon) and two years after disturbance for one species (B. madritensis). The main soil chemical properties (soil pH, phosphorus and potassium content) were similar to the reference ecosystem 35 years after disturbance. Average vegetation height and cover recovered after 35 years whereas species richness recovered only on the field abandoned for 150 years. Vegetation composition and structure did not recover in any of the abandoned fields. Our results suggest that recovery of AMF root colonization is very low after a severe anthropogenic disturbance, despite the recovery of soil chemical properties.