DuckeFungi_ASV_dist_ID_function_20220825.xlsx

High tree species diversity in tropical rain forests and rainfall seasonality contribute to large spatio-temporal variability in available resources for soil microbial communities. How the contribution of deterministic vs. stochastic processes to the assembly of these communities varies in space and time remains yet to be quantified so that soil microbial community responses to climate change may be projected.To address this knowledge gap, we characterised the spatio-temporal composition of soil fungal communities from the plot to the stand scales in a topographically homogeneous area in a tropical rain forest in central Amazonia. Doing so, we excluded obvious environmental gradients so as not to mask the detectability of potential mechanisms of community assembly linked to the intrinsic tree diversity of tropical rain forests. We then related fungal communities to seasonal patterns and spatial variability in geographic and soil characteristics.Soil fungal communities showed a greater turnover in space than in time. The relative contribution of stochastic and deterministic processes to community assembly was related to season, with stochastic processes, including potential dispersal limitation and ecological drift dominating in the rainy season, and deterministic processes, such as speciesselection dominating in the dry season. The results indicate that seasonality is likely to be related to the temporary accumulation of tree species-specific litter during the litterfall peak in the dry season, could define a deterministic environment that fades away after the start of the rainy season.Our study highlights the importance of spatial heterogeneity in the absence of environmental gradients and its relationship with seasonal patterns that modulate spatial heterogeneity and contribute to environmental determinism vs. stochasticity for fungal community assembly in tropical rain forests. This baseline may serve for assessing deviations in community patterns caused by changes in biotic interactions with above-ground vegetation, such as those resulting from shifts in taxonomical/functional composition of trees driven by climate change.

热带雨林极高的树木物种多样性与降雨季节性，共同造就了土壤微生物群落可利用资源的显著时空变异。目前，确定性过程与随机过程对这类群落构建的相对贡献如何随空间和时间发生变化，仍有待量化，而该量化工作将助力土壤微生物群落对气候变化响应的预测研究。为填补这一认知空白，我们以亚马孙中部热带雨林内一处地形均质区域为研究对象，对从样地到林分尺度的土壤真菌群落时空组成进行了表征。通过该实验设计，我们规避了显著环境梯度的干扰，以免掩盖与热带雨林固有树木多样性相关的群落构建潜在机制的可检测性。随后，我们将真菌群落特征与地理及土壤属性的季节动态和空间变异进行了关联分析。研究结果显示，土壤真菌群落的空间周转速率高于时间周转速率。群落构建过程中随机与确定性过程的相对贡献与季节密切相关：在雨季，包括潜在扩散限制和生态漂变在内的随机过程占据主导；而在旱季，则是以物种筛选为代表的确定性过程占据优势。本研究结果表明，季节性或与旱季凋落物峰值期树木物种特异性凋落物的临时积累相关，这类积累可形成确定性环境，且该环境会在雨季开始后逐渐消散。本研究强调了无显著环境梯度条件下空间异质性的重要性，及其与季节动态的关联——后者可调控空间异质性，并对热带雨林真菌群落构建过程中的环境确定性与随机性施加调控作用。本研究构建的基准数据集，可用于评估由地上植被生物交互作用变化所引发的群落模式偏离情况，例如气候变化驱动的树木分类/功能组成转变所带来的交互作用变化。