Impacts of elevated temperature on the growth and functioning of decomposer fungi are influenced by grazing collembola

Elevated temperature has potential to influence the biological mechanisms regulating ecosystem–atmosphere carbon exchange. The relationship between warming and heterotrophic microbial respiration remains poorly understood, not least in terms of the differential sensitivity of microbial groups to temperature and the complexity of interactions with other biota. Cord-forming basidiomycete fungi are dominant primary decomposers in temperate woodland. Decomposition rates are determined by the composition of the decomposer community, ecophysiological relationships between these fungi and abiotic variables and interactions with other organisms. Amongst the latter, a major determinant is the balance between mycelial growth and removal by soil invertebrate grazers, which can themselves be affected by elevated temperature. We investigated the impact of elevated temperature on fungal foraging and decomposition of beech (Fagus sylvatica) wood in soil microcosms to which the invertebrate grazers, Folsomia candida and Protophorura armata (Collembola), were added in factorial combinations with five basidiomycete fungi. Species-specific impacts on mycelial development and function resulted from differential sensitivity of fungi to warming and grazing. Temperature impacts on collembola abundance were resource-specific, causing increased grazing pressure by both species, but on different fungi. Grazing often counteracted warming-induced stimulation of mycelial growth, but occasionally amplified the temperature effect, with implications for colonization rates of new resources. High grazing pressure did not prevent increased fungal-mediated decomposition of colonized wood, as fungi utilized more resource-derived energy to maintain explorative growth. Impacts of elevated temperature on decomposition are likely to depend on local composition of the fungal and invertebrate decomposer community