A trait-based approach to unlock the secrets of fungal soil aggregation mechanisms

土壤团聚是一个重要的生态系统过程。然而，导致土壤团聚体的精确、直接机制，特别是土壤生物性状的影响尚不清楚。在本研究的框架内，我们将揭示土壤团聚体的机制（分别为土壤团聚体的形成和稳定）以及腐殖真菌功能多样性的影响。我们将测试三个假设：(i)真菌特征包含系统发育信号，（ii）真菌特征决定真菌形成和稳定聚集体的能力，（iii）真菌对性状距离的增加将导致互补性增加，从而提高土壤聚集反应。我们将在一组30个真菌分离株（腐殖真菌）上测试我们的假设，这些真菌分离株经过系统发育表征和t-RFLP分离优化，均来自一个草原生态系统。作为第一步，我们将收集与土壤团聚体形成和稳定有关的12个选定性状的数据。这些数据将用于评估是否密切相关的物种有更多相似的性状组合比更多的系统发育上遥远的物种。下一步，将分析30个分离株形成和稳定土壤团聚体的能力；这些聚合能力数据将与相应的特征相关联，以评估它们对两个聚合过程的重要性。在最后一步，我们将在成对组合的物种组合中测试性状距离对土壤聚集的影响。获得的数据将揭示土壤聚集背后的机制和腐殖真菌在这个多维相互作用框架中的作用；从而为土壤团聚体研究做出重要贡献。另一方面，这个项目将强调基于性状的方法对真菌的有用性。

Soil aggregation is a major ecosystem process. However, the precise, direct mechanisms leading to soil aggregates and in particular the impact of soil organism traits remain unclear. In the framework of this proposal and the resulting studies, we will unravel the mechanisms of soil aggregation (separately for soil aggregate formation and stabilization) and the impact of functional diversity of saprobic fungi. We will test the three hypotheses that (i) fungal traits contain a phylogenetic signal, (ii) fungal traits determine the ability of fungi to form and stabilize aggregates and (iii) increasing trait distance in pairs of fungi will lead to increased complementarity and thus greater soil aggregation responses. We will test our hypotheses on a set of 30 fungal isolates (saprobic fungi) that were optimized for phylogenetic representation and t-RFLP separation, all isolated from one grassland ecosystem. As a first step, we will gather data for 12 selected traits related to soil aggregate formation and stabilization. These data will be used to evaluate if closely related species have more similar trait combinations than more phylogenetically distant species. In the next step, the 30 isolates will be analyzed for their ability to form and stabilize soil aggregates; these aggregation ability data will be correlated with the corresponding traits to evaluate their importance for the two aggregation processes. In the final step, we will test in pair-wise assembled species combination the impact of trait distance on soil aggregation. The data obtained will shed new light on the mechanisms behind soil aggregation and the role of saprobic fungi in this multidimensional interaction framework; thus we will make an important contribution to soil aggregation research. On the other hand, this project will highlight the usefulness of trait-based approaches with fungi in general.