SP1: Microbial root symbionts as drivers of eco-evolutionary dynamics and long- term biodiversity–ecosystem functioning relationships in plant communities

随着时间的推移，生物多样性与生态系统功能（BEF）之间的关系往往变得更加密切。一种可以解释这一现象的机制是植物和土壤生物之间的共同适应，这种适应随着时间的推移而发展，特别是与当今绝大多数植物物种的根共生的丛枝菌根真菌（AMF）。AMF的碳获取严格依赖于植物，植物通过动员和转移土壤中的矿质养分来支持植物。通过这种相互作用，植物物种特有的AMF有助于植物群落之间的资源分配。然而，通过形成共同的菌丝网络，多面手AMF也可以促进资源共享。随着时间的推移，这两种机制都可能导致BEF关系的增加。然而，关于丛枝菌根（AM）共生在植物多样性梯度上的动态，目前还缺乏相关的知识。特别是，AMF多样性和群落聚集对植物多样性的短期和长期响应，以及这些响应在生物多样性对AMF介导的重要生态系统功能的影响中的作用尚不清楚。我们的子项目探讨了(1)生态系统老化是否对应于AM共生真菌和植物伙伴之间的共同适应，以及(2)这种共同适应如何影响AMF专业化和共生联系的强度。此外，我们检验(3)AM共生体对BEF关系的贡献是否取决于土壤历史、植物历史，或两者兼而有之。最后，我们研究了(4)观察到的动态是否仅针对土壤真菌群落及其进一步的功能群中的AMF。子项目将利用耶拿试验中对植物多样性的操纵，主要是实验处理，这些处理解开了植物历史和土壤历史效应与时间相关的共同适应。利用分子方法，我们将评估AMF在散装土壤中的群落结构，并将其与其他真菌群落进行比较。此外，在田间试验和Ecotron试验中，将利用常驻植物的根际和根系来确定共生群落结构、AMF的专一化和菌根化强度。综上所述，本子项目旨在阐明植物和AMF多样性之间的相互作用是否会随着时间的推移而变化，以及由此产生的AM共生体是否在随着时间的推移而加强BEF关系中发挥作用。此外，我们将评估是否由于它们对植物的高度依赖，AMF的行为不同于土壤中其他真菌类群，这些真菌类群可能不太具有植物物种特异性，如腐养菌或寄生虫。

The relationship between biodiversity and ecosystem functioning (BEF) often becomes stronger over time. One mechanism that could explain this observation is a co-adaptation, which develops over time between plants and soil organisms, in particular with arbuscular mycorrhizal fungi (AMF) that live in symbiosis with roots of the vast majority of today’s plant species. Carbon acquisition of AMF strictly depends on plants, which they support by mobilization and transfer of mineral nutrients from soil. Through this interaction, AMF specific to plant species contribute to partitioning of resources among plant communities. However, by forming common mycelial networks, generalist AMF can also facilitate resource sharing. Both mechanisms could contribute to the increase of the BEF relationship over time. Nevertheless, there is a lack of knowledge regarding the dynamics of arbuscular mycorrhizal (AM) symbiosis along plant diversity gradients. In particular, the short- and long-term responses of AMF diversity and community assembly to plant diversity are unclear, as well as the role of these responses in the impact of biodiversity on important AMmediated ecosystem functions. Our subproject explores whether (1) ecosystem aging corresponds to co-adaptation between the fungal and plant partners of AM symbioses, and (2) how this co-adaptation affects AMF specialization and the strength of the symbiotic link. Furthermore, we test (3) whether the contribution of AM symbioses to the BEF relationship is contingent on soil history, plant history, or both. Finally, we investigate (4) whether the observed dynamics are specific to AMF within the soil fungal community and its further functional groups. The subproject will make use of the manipulations of plant diversity in the Jena Experiment, and predominantly, of the experimental treatments, which disentangle time-related co-adaption of plant history and soil history effects. Using molecular methods, we will assess the community structure of AMF in bulk soils and compare it to other fungal communities. In addition, symbiotic community structure, specialization of AMF and mycorrhization intensity will be determined using rhizosphere and roots of resident plant species, both in the Field Experiment and the Ecotron Experiment. Taken together, this subproject aims to elucidate whether the interplay between plant- and AMF diversity changes over time, and whether the resultant AM symbioses play a role in the strengthening BEF relationship over time. In addition, we will assess whether due to their high dependency on plants, AMF behave differently than other fungal groups in the soil that may be less plant species-specific, such as saprotrophs or parasites.