Effects of disturbance, seed addition and land-use intensity on plant community assembly and ecosystem functions in grasslands (ESCAPE II)

拟议的EASH II项目侧重于植物群落(重新)组装，涉及一系列不同的生态系统功能、土地利用强度和植物多样性。特别强调了这些功能和关系在干扰后的弹性，以及实验上增加的植物多样性对两者的影响。因此，我们将继续对新建立的种子添加和干扰实验SADE进行监测，同时对所有150个实验地和实验植物群落(中游植物)进行补充分析。在当前阶段，并与植物学核心项目密切合作，我们成功地安装了这一大规模实验，现在将作为一个独特的实验平台，联合研究生物多样性探索草原中生物多样性的功能作用。首先，结果表明，干扰后播种区的植物多样性显着增加，表明这些处理在克服扩散和微场地限制方面是成功的。我们的初步工作还揭示了植物多样性对生态系统功能的显著影响；例如，植物生物量中13C和15N的同位素丰度表明，在EP水平上，植物多样性水平较高的植物对干旱的敏感性降低，养分利用更全面。此外，我们还发现，在受干扰的沙地土壤中，氮素向下迁移增加，特别是在高施肥强度下。在一个小型草皮试验中，由于施肥和干旱胁迫的交互作用，氮素损失也增加了。这一增长反过来又被更高的植物多样性所减缓。在下一阶段，我们将使用和维持Sade实验，其中植物多样性的增加现在变得越来越可用，以机械地评估植物多样性在广泛的生态系统过程中的功能作用。具体来说，我们将监测植被轨迹，评估种子雨的影响，分析植物生物量中13C和15N的同位素丰度以及数量和质量，量化养分保留和凋落物分解。我们的主要假设是：(1)植物多样性对不同生态系统的功能及其在干扰后的恢复力有积极的影响；(2)土地利用强度和/或其单一成分对这些功能有很强的直接和间接影响(通过植物多样性的调节)；(3)群落(重新)组装和干扰后生态系统功能的恢复取决于当地种子雨的功能丰富度。与目前阶段一样，我们将接管萨德地块活动的协调，并将鼓励合作和综合。

The proposed project ESCAPE II focuses on plant community (re-)assembly in relation to a range of different ecosystem functions, land-use intensity and plant diversity. A special emphasis is given to the resilience of these functions and relationships after disturbance and to effects of experimentally increased plant diversity on both. Therefore, we will continue the monitoring of the newly established seed addition and disturbance experiment SADE in combination with complementing analyses on all 150 Experimental Plots and on experimental plant communities (mesocosms). During the current phase and in close cooperation with the Botany core project, we successfully installed this large-scale experiment, which will now serve as a unique experimental platform for joint research on the functional role of biodiversity within the grasslands of Biodiversity Exploratories. First results already showed significantly higher plant diversity in seeded plots after disturbance indicating that these treatments were successful in overcoming dispersal and microsite limitation. Our preliminary work also revealed pronounced effects of plant diversity on ecosystem functioning; e.g. isotopic abundances of 13C and 15N in plant biomass indicated reduced sensitivity towards drought and more complete nutrient use at higher levels of plant diversity on EP level. Further, we found increased downwards relocation of N on soils of disturbed SADE plots, especially under high fertilization intensity. In a small-scale sod experiment, N losses also increased due to the interaction of fertilization and drought stress. This increase was in turn moderated by higher plant diversity. During the next phase, we will use and maintain the SADE experiment, where the increase in plant diversity now becomes increasingly available, to mechanistically assess the functional role of plant diversity on a wide range of ecosystem processes. In detail, we will monitor vegetation trajectories, assess effects of seed rain, analyse 13C and 15N isotopic abundances in and the quantity and quality of plant biomass, quantify nutrient retention and litter decomposition. In a complementary mesocosm experiment, we will specifically address the mechanism of nutrient partitioning among plant species in interdependency with plant diversity, fertilization intensity and climate (drought).Our main hypotheses are that i) plant diversity has a positive effect on different ecosystem functions and their resilience after disturbance; ii) land-use intensity and/or its single components have strong direct and indirect effects on these functions (mediated by plant diversity); iii) community (re-) assembly and the recovery of ecosystem functions after disturbance depends on the functional richness of the local seed rain. As in the current phase, we will take over the coordination of activities on the SADE plots and will encourage collaboration and synthesis.