Seed and seedling traits as related to plant diversity and community assembly in grasslands at different land-use intensity

种子建群是植物生活史中的一个重要的种群学过程，它影响着植物种群的持续性和稳定性，影响着植物群落的组装过程。近年来，基于特质的方法越来越多地被用来理解社区组装过程的机制及其与生态系统功能的关系。然而，大多数研究都集中在成年植物的地上和地下性状，而种子和幼苗的性状在基于性状的生态学中受到的关注要少得多。因此，本项目的主要目标是描述生物多样性探索站草原中多个物种的种子和早期生活史特征，并将这些特征与土地利用对草原多样性和群落组装过程的影响联系起来。将解决以下具体目标：（1）形态和化学种子性状将进行分析，发芽和幼苗性状进行测量，出现在150个实验区的生物多样性勘探站在标准化条件下，在一个共同的花园实验中的多个草地物种。(2)环境条件的影响，这是相关的草地土地利用强度，即凋落物的存在和施肥，发芽和幼苗性状将通过操纵这些因素在第二个共同花园实验的所有物种，这将用于种子添加实验中的新的多草地土地利用实验。(3)短期影响的实验减少土地利用强度的物种丰富度和密度的活种子库的顶部土壤中的网站包括在新的多草地土地利用实验将被量化，有助于变量有关的人口储存作为一个重要方面，在解释植物多样性和组成的草原群落的变化，以减少土地利用强度。(4)最后，我们将使用种子和幼苗性状的数据，结合生物多样性探索站的其他数据，来测试不同土地利用强度的草地中植物物种的发生和丰度与种子再生特征的关系，测试当土地利用强度降低或增加种子时，种子和幼苗性状对群落组装过程的作用，以及种子和幼苗性状多样性的度量如何与成年植物的性状多样性相关。总之，该项目将有助于将基于特征的生态学扩展到人口统计学的角度，方法是将成年植物以外的生活史阶段的植物特征纳入其中，这些特征特别脆弱，因此可能对了解群落组装过程和维持草原植物多样性至关重要。

Establishment from seeds is a key demographic process in the life-history of plant species, which influences the persistence and stability of plant populations and processes of community assembly. In recent years, trait-based approaches are increasingly used to understand the mechanisms underlying processes of community assembly and its relationships to ecosystem functioning. However, most studies have focused on above- and belowground traits of adult plants, while traits of seeds and seedlings have received much less attention in trait-based ecology. Therefore, this project has the major goal to characterize seed and early life-history traits of multiple species occurring in the grasslands of the Biodiversity Exploratories and relate these traits to land-use effects on grassland diversity and processes of community assembly. The following specific objectives will be addressed: (1) Morphological and chemical seed traits will be analyzed and germination and seedling traits will be measured for multiple grassland species that occur in the 150 experimental plots of the Biodiversity Exploratories under standardized conditions in a common garden experiment. (2) The effects of environmental conditions, which are related to land-use intensity of grasslands, i.e. litter presence and fertilization, on germination and seedling traits will be measured by manipulating these factors in a second common garden experiment for all species, which will be used for the seed addition experiment in the new multi-grassland land-use experiment. (3) The short-term effects of experimental reduction of land-use intensity on species richness and density of the viable seed bank in the top soil of the sites included in the new multi-grassland land-use experiment will be quantified to contribute variables related to demographic storage as an important aspect in explaining shifts in plant diversity and composition of the grassland communities in response to reduced land-use intensity. (4) Finally, we will use data on seed and seedling traits, in combination with other data from the Biodiversity Exploratories, to test how the occurrence and abundance of plant species in grassland of different land-use intensity relates to traits characterizing regeneration from seeds, to test for the role of seed and seedling traits for community assembly processes when land-use intensity is reduced or seeds are added, and how measures of diversity of seed and seedling traits relate to trait diversity of adult plants. In summary, the project will contribute to an extension of trait-based ecology to a demographic perspective by incorporating plant traits of life-history stages other than adult plants, which are particularly vulnerable and might therefore be essential to understand processes of community assembly and the maintenance of grassland plant diversity.