Mycorrhizal functions in the forest floor

点击翻译按钮获取中文摘要

The mycorrhizal symbiosis is a central component of plant-soil feedbacks and carbon 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 (FF) as a habitat. We hypothesize that mycorrhizal fungi are more dependent on FF carbon (C) in cold or warm nutrient-poor forest stands, since less photosynthates are produced and invested into the fungal symbiont. As a result, the diversity of the mycorrhizal fungal community in the FF increases. At intermediate temperature, when mycorrhizal fungi are stronger limited by nutrient availability than by host C supply, the response of the two major mycorrhizal association type leads to diverging superiority: Arbuscular mycorrhizal fungi are superior in P-poor FFs and ectomycorrhizal fungi in P-rich FFs. We aim to test these predictions in a transect study with mature European beech (Fagus sylvatica L., ECM host) forests admixed with sycamore maple (Acer pseudoplatanus L., AM host) by analyzing the response of the mycorrhizal community composition and activity to rising temperature and inorganic P limitation. To achieve the objectives of our project, we will combine functional trait analyses, isotopic fractionation analysis, a 13C- and 15N-labeling experiment, and extracellular enzyme analyses with next generation sequencing of the mycorrhizal fungal community in the FF and mineral soil. This project will refine our understanding and prediction of the ecology of mycorrhizal fungi in the FF of mixed beech forests, which are increasingly exposed to rising temperature and P limitation.