Functional role of ectomycorrhizae on drought resistance and recovery of beech and spruce

在之前的资助期内，我们在克兰茨堡森林（TEE）进行了3次夏季干旱的通流排除试验，发现外生菌根（ECM）群落的结构和功能在逐渐发生变化。干旱对云杉ECM群落的影响岩溶。但仅在连续3年干旱后，对森林Fagus sylvatica （L.）的ECM作用较强。干旱频率的增加降低了重要细根和ECM群落多样性，但对水解酶活性没有影响。即使在极端限水条件下，混合树龄对ECM多样性和细根活力也有积极影响。干旱条件下长距离型ECM的相对增加和带腐养电位的EA的不增加支持了目前关于干旱条件下树木C-限制的概念。ECM多样性和功能的实际综合结果表明，相关性取决于特定干旱环境下树种的反应，随单/混合相互作用带和土壤深度的变化而变化。这种对ECM存活的高度环境依赖性需要进一步澄清。因此，这项后续建议的一个主要目标是更好地将地上和地下过程与抗旱和恢复联系起来。因此，植物生态生理学家和菌根生态学家的联合建议旨在将山毛榉和云杉的地上干旱反应与干旱下地下碳供应的差异以及重新浇水后的汇联系起来。在不同土壤来源（沿巴伐利亚降水梯度的湿润和干燥地点）的不同适应的ECM群落背景下进行了植物激素实验，同时，克兰茨堡森林TEE的独特条件代表了成年森林树木的相关情景。这些实验中的碳标签将允许定量地解决碳汇分配问题。为此，我们将评估ECM在干旱和重新浇水后的反应性，特别是混合物对ECM群落干旱影响衰减的影响。这将与干旱和随后在不同适应土壤中不同种内和种间生长的山毛榉和云杉的树木敏感性和资源通量（碳、水、氮）有关。我们评估了植物的结构、生理和生化参数，并使用稳定同位素标记（13C, 15N, D2O）。结合功能参数对ECM群落结构进行分析。重点将放在与植物根部与真菌的碳关系有关的参数（转化酶/淀粉酶活性，非结构烃（NSC）的组成）。该提案的预期结果是澄清1)土壤对树木干旱响应的影响，2)混合物对树种及其ECM群落干旱反应的影响，以及3)山毛榉和云杉在重新浇水后干旱恢复的差异。

In the previous funding term, we found structure and functions of ectomycorrhizal (ECM) communities of to be gradually changed during three summer droughts imposed in a throughfall exclusion experiment at Kranzberg Forest (TEE). Drought effects on ECM communities of Picea abies (L.) Karst. were stronger than on ECM of Fagus sylvatica (L.) but only after three repeated drought years. Increasing drought frequency reduced vital fine roots and ECM community diversity, but not hydrolytic enzyme activities. Tree mixture positively influenced ECM diversity and fine root vitality even under extreme water limitation. A relative increase in long-distance type ECM and no increase of EA with saprotrophic potential under drought support current concepts that question C- limitation in trees upon drought. The actual synthesis of results on ECM diversity and functions suggests correlations to vary depending on a given context of drought specific tree species reactions varying with monospecific/mixed interaction zone and soil depth. This high context dependency for survival of ECM requires further clarification. Therefore, a major objective in this follow up proposal is to better link above- and belowground processes upon drought resistance and recovery. Therefore this joint proposal of plant ecophysiologist and mycorrhizal ecologist aims to connect the rather contrasting above-ground drought responses of beech and spruce with below-ground differences in C supply under drought and to sinks upon re-watering. A phytotrone experiment is performed in the context of differently adapted ECM communities from different soil origins (moist vs. dry sites along a Bavarian precipitation gradient), and in parallel the unique conditions of the Kranzberg Forest TEE represents a relevant scenario on adult forest trees. 13C labeling in these experiments will allow addressing quantitatively C-allocation to sinks. For this purpose we will assess reactivity of ECM under drought and upon re-watering particularly the effect of mixture on attenuation of drought impact on ECM communities. This will be connected with tree sensitivity of and resource fluxes (C, H2O, N) among intra- and interspecifically grown beech and spruce under drought and subsequent recovery in differently adapted soils. We assess plant structural, physiological, biochemical parameters and use stable isotope labelling (13C, 15N, D2O). ECM community structure will be analyzed combined with functional parameters. A focus will be on parameters related to carbon relations of plant roots with fungi (invertase/amylase activity, composition of non-structural hydrocarbons (NSC)). The expected outcome of the proposal is clarification of 1) soil impact on drought response of trees, 2) effects of mixture upon drought reactions of tree species and their ECM communities, and 3) differences in drought recovery of beech and spruce upon re-watering.