The forest floor as a habitat for mycorrhizae across temperature and P availability gradients.

The mycorrhizal symbiosis is a central component of plant-soil feedbacks and carbon (C) cycles of forest ecosystems. Yet even though it is known that the two major mycorrhizal association types influence litter decomposition and soil organic matter formation differently, it remains unresolved whether this also influences their preference for the forest floor as a habitat. We aimed to test such preference in mature European beech (Fagus sylvatica L., ECM host) forests admixed with sycamore maple (Acer pseudoplatanus L., AM host) by measuring extracellular enzyme activities in the forest floor and mineral soil of twelve study sites located across gradients of rising temperature and inorganic phosphorus (P) limitation. Sampling took place in the forest floor and at 0-5 cm, 5-10 cm and 10-20 cm soil depth in the proximity of beech and maple trees, respectively, and the activity of recalcitrant C and organic P and nitrogen (N) degrading enzymes were analyzed. In our presentation we will discuss whether our results support the hypotheses that (i) mycorrhizal fungi are more dependent on forest floor C in nutrient-poor forest stands and (ii) arbuscular mycorrhizal fungi are superior in P-poor forest floors and ectomycorrhizal fungi in P-rich forest floors.