Dung fungi as an indicator of large herbivore dynamics in peatlands

Abstract

Coprophilous fungal spores (CFS) have gained prominence in paleoecology as a proxy for large herbivore dynamics. Dung availability is one of several factors that influences spore abundance so it is unclear how closely CFS levels track herbivore biomass. This uncertainty is particularly relevant in peat- and moorland, where grazing impacts are a recurring topic in paleoecology and source of tension in environmental management, and where the method has yet to be tested. The current study used three ecological and conservation grazing experiments in UK peat- and moorland to study modern and recent historic relationships between grazing treatment and the abundance of three key CFS types and three pollen disturbance indicators. A total of 78 surface samples and 2 short peat cores were analyzed. Dispersal distances are estimated to range from <10 m to tens of meters, based on significantly lower CFS abundance in exclosed than grazed plots at two sites, and similar CFS trends over the last century in short peats cores located 80 m apart at the third site. The CFS signal thus represents activity in the surrounding landscape, despite predominantly local dispersal. CFS abundance does not correspond with animal biomass when compared across the three sites, however, and pollen disturbance indicators in the peat cores matched recent historic grazing records more consistently than CFS abundance. Potential reasons for these mismatches are discussed. Quantitative inferences about large herbivore abundance from CFS in peatlands should therefore be made with caution and recommendations are made for further testing of the method.