Mycorrhizal functions in the forest floor

菌根共生是森林生态系统植物-土壤反馈和碳循环的核心组成部分。然而，尽管已知两种主要的菌根组合类型对凋落物分解和土壤有机质形成的影响是不同的，但这是否也影响了它们对森林地面作为栖息地的偏好仍未得到解决。我们推测，在营养贫乏的冷林或暖林中，菌根真菌更依赖于FF碳(C)，因为较少的光合作用产物被产生并投资到真菌共生体中。结果表明，林场内菌根真菌群落的多样性增加。在中温条件下，当菌根真菌对养分有效性的限制强于对宿主C供应的限制时，两种主要菌根联合类型的反应导致了不同的优势：丛枝菌根真菌在低磷条件下优势明显，而外生菌根真菌在富磷条件下优势明显。我们的目标是在一项横断面研究中，通过分析菌根群落组成和活性对温度升高和无机磷限制的响应，以成熟的欧洲山毛榉(Fagus sylvatica L.，ECM宿主)森林与梧桐枫(Acer PassoPlaanus L.，AM宿主)混合的方式来验证这些预测。为了实现我们项目的目标，我们将结合功能性状分析、同位素分馏分析、13C和15N标记实验、胞外酶分析以及对FF和矿物土壤中菌根真菌群落的下一代测序。这个项目将加深我们对山毛榉混交林森林中菌根真菌生态的理解和预测，因为山毛榉混交林越来越多地暴露在气温上升和磷限制之下。

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.