Land-use effects on plant regeneration strategies in grasslands and their relation to community assembly

成功繁殖的能力对植物种群的持续和稳定以及群落聚集过程至关重要。植物繁殖策略在依赖种子生产或无性系繁殖方面有所不同。在以多年生草本植物为主的温带草原上，几乎所有的植物都是通过有性繁殖的种子进行繁殖，并辅以无性繁殖。然而，温带草原土地利用变化对植物更新策略的影响尚不清楚。因此，本项目的主要目标是通过生物多样性实验站联合多站点草地实验（土地利用强度降低实验（REX）、土地利用实验（LUX）），在群落水平上表征土地利用对植物更新策略的影响。具体目标如下：首先，我们将对地下芽库进行取样，以评估总密度和组成（不同类型的芽库），其中包括所有可能用于营养再生的芽。其次，我们将估计植物群落的生殖产量（即种子产量和种子雨），这是植物种子再生的潜在资源。第三，确定表层土壤种子库的密度、物种丰富度和组成，这是种子再生的人口统计储存的重要组成部分。通过结合这些测量，我们将收集不同植物更新策略和人口存储的数据，从而量化土地利用变化对不同植物更新策略的影响，这些数据很少被并行研究。利用这些数据，我们将评估可活土壤种子库和地下芽库随土地利用强度变化的变化在多大程度上类似于地上植被多样性和组成的变化，以及这些变化如何依赖于以前土地利用强度的差异、土地利用的各个组成部分（割草、放牧、施肥）的变化以及不同地点之间的环境差异。此外，我们将测试土地利用强度的变化如何影响不同植物再生策略之间以及与生长相关的植物性状之间的相关性和/或权衡。拟议的项目将扩展基于性状的方法，纳入植物再生性状，这些性状可以共同或单独地作为种群增长或丰度的关键决定因素，从而有助于更全面地了解土地利用变化后植物群落的组装过程。

The capacity to successfully reproduce is vitally for the persistence and stability of plant populations and processes of community assembly. Plant reproduction strategies differ in their reliance on seed production or clonal reproduction. In temperate grasslands, which are dominated by perennial herbaceous plant species, almost all plant species reproduce by sexually produced seeds often complemented by clonal (asexual) reproduction. However, it is not well studied how changes in land use of temperate grasslands affect plant regeneration strategies. Therefore, this project has the major goal to characterize land-use effects on plant regeneration strategies at the community level in the Joint multi-site grassland experiments (Reduced Land-use Intensity Experiment (REX), Land-use Experiment (LUX)) of the Biodiversity Exploratories. The following specific objectives will be addressed: First, we will sample the belowground bud bank to assess the total density and composition (different bud bank types), which consists of all buds that can potentially be used for vegetative regeneration. Second, we will estimate the reproductive output (i.e. seed production and seed rain) of the plant communities, which is potentially available for plant regeneration from seeds. Third, we will determine the density, species richness and composition of the viable soil seed bank in the top soil, which is an important component of demographic storage for regeneration from seeds. By combining these measurements, we will collect data on different plant regeneration strategies and demographic storage, which are rarely studied in parallel, and thereby quantify effects of changes in land use on different plant regeneration strategies. Using these data we will evaluate to what extent changes in the viable soil seed bank and the belowground bud bank in response to changes in land-use intensity resemble shifts in the diversity and composition of the aboveground vegetation and how these changes depend on differences in previous land-use intensity, changes in the individual components of land use (mowing, grazing, fertilization) and environmental differences between sites. Moreover, we will test how changes in land-use intensity affect correlations and/or trade-offs of different plant regeneration strategies with each other and with growth-related plant traits. The proposed project will extend trait-based approaches by incorporating plant regeneration traits, which can jointly or independently act as key determinants of population growth or abundance, and thereby contribute to a more comprehensive understanding of plant community assembly processes after changes in land use.