Functional Role of Mycorrhiza in the Competition for Water and Nitrogen

山毛榉树与不同种类的外生菌根真菌形成共生关系。据推测，这些真菌形成了特征群落，适应了当时的环境条件，改善了对宿主树的氮和水的供应。为了验证这一假设，将对不同氮暴露和干旱条件下山毛榉林中菌根丰度和物种组成进行表征，并通过使用网袋和稳定氮同位素测量不同田间试验处理下根、菌丝和菌根的氮吸收来确定菌根在氮营养中的作用。菌根群落对山毛榉氮和水供应变化的响应将在植物栽培室和温室的受控条件下进行测试。为了比较菌根对山毛榉氮营养和水分供应的作用，将在根室和菌丝室分离的生长箱中研究非菌根山毛榉和菌根山毛榉的供氮和水分状况。

Beech trees form symbiotic associations with different species of ectomycorrhizal fungi. It is hypothetised that these fungi form characteristic communities, adapted to the prevailing environmental conditions improving the supply of nitrogen and water to the host tree. To test this hypothesis, mycorrhizal abundance and species composition in beech forests differing in nitrogen exposition and drought will be characterised and the role of mycorrhiza in nitrogen nutrition will be determined by measuring N-uptake of roots, hyphae and mycorrhizae using mesh bags and stable nitrogen isotopes under different field-experimental treatments. Shifts in mycorrhizal communities in response to changes in nitrogen and water supply to beech will be tested under controlled conditions in phytotrons and glasshouses. To the test the function of mycorrhizae for nitrogen nutrition and water supply to beech in comparison with other microorganisms, N-supply and water status of non-mycorrhizal and mycorrhizal beech will be investigated in growth boxes with separated root and hyphal compartments.