Effects of woody species diversity and composition on individual plant growth and demography

对光的竞争被广泛认为是决定植物生长的关键因素。在木本植物中，树冠、树枝和树叶的水平特征都有助于光收集效率，从而促进生长。虽然这些特征在个体乔木和灌木中的表达受到遗传和机械方面的限制，但个体有能力在一定阈值内表现出对当地非生物和生物条件的可塑性反应。因此，树冠功能性状(CFT)表现出种间和种内的变异，特别是个体乔木和灌木的树冠尺寸和结构对当地邻居的相互作用反应敏感。然而，为了详细解释树冠的空间发展，需要关于单个树枝的信息，因为树冠扩展的过程取决于树枝和树枝人口的空间发展。在第三阶段，这个子项目将继续研究物种丰富度对地上植物生长和树枝人口统计的影响，以检验在样地水平上的多样性效应是当地社区水平多样性效应的总体结果的假设。具体目标是(I)分析乔木和灌木物种丰富度(关于样地和局部多样性水平)对个体乔木和灌木生长和物种间死亡的影响，(Ii)根据增长率和分支人口统计来量化当地邻居之间的相互作用，并测试多样性是否会减少竞争，以及(Iii)调查物种丰富度如何影响CFT的种间和种内变异性。在主要实验(包括BEFmod实验中的树木，设置在所有VIP的小块上)和比较研究地块中，将继续使用常规方法和3D地面激光扫描对单个乔木和灌木及其当地邻居的建筑特征(茎、冠、枝)进行重复测量。将测量或计算一系列变量，例如树干直径、树高、树干细长、树冠底部高度、树冠长度、树冠直径、树冠投影面积、相对生长率和树冠效率(单位树冠投影面积的年平均生物量增长)。这些变量与物种丰富度(解释变量)和当地立地条件(作为协变量；包括通过生态景观方法确定的所有变量)有关。此外，与SP3一起，这个子项目将使用SP2，特别是SP3测量的一整套性状进行合成工作。SP3提供的重要数据将是对关键性状对多样性水平的可塑性的分析，以及群落加权平均值以及功能和系统发育多样性模式的计算。

Competition for light is broadly recognised as a key factor determining plant growth. In woody species, crown, branch and leaf level traits all contribute to light harvesting efficiency, and thus growth. Although there are genetic and mechanical constraints to the expression of these traits in individual trees and shrubs, individuals have the ability to show plastic responses within certain thresholds as a reaction to local abiotic and biotic conditions. As a result, crown functional traits (CFT) show inter- and intraspecific variability.In particular, crown dimensions and architecture of individual trees and shrubs are known to respond sensitively to local neighbourhood interactions. However, to explain the spatial development of crowns in detail, information on single branches is needed, since the process of crown expansion depends on the spatial development of branches and branch demography.In the third stage this subproject will continue to address the influence of species richness on aboveground plant growth and branch demography at the individual and local neighbourhood level to test the hypothesis that the diversity effect at the plot level is the overall result of the diversity effects at the local neighbourhood level.Specific objectives are (i) to analyse the impact of tree and shrub species richness (regarding both the plot and local diversity level) on individual tree and shrub growth and mortality within and among species, (ii) to quantify local neighbour interactions in terms of growth rates and branch demography and to test whether diversity reduces competition, and (iii) to investigate how inter- and intraspecific variability of CFTs is affected by species richness. Repeated measurements of architectural traits (stem, crown, branches) of individual trees and shrubs and their local neighbours by both, conventional methods and 3D terrestrial laser scanning, will be continued in the Main Experiment (including the trees of the BEFmod experiment, set up on subplots on all VIPs) and the Comparative Study Plots. A wide range of variables will be measured or calculated, such as stem diameter, tree height, stem slenderness, crown base height, crown length, crown diameter, crown projection area, relative growth rate and crown efficiency (mean annual biomass growth per unit of crown projection area).These variables are then related to species richness (explanatory variable) and local site conditions (as covariables; including all variables determined by the ecoscape approach). In addition, jointly with SP3 this subproject will use the whole suite of traits, which have been measured by SP2 and in particular by SP3, for synthesis work. Important data provided by SP3 will be the analyses of the plasticity of key traits as a response to diversity levels, and the calculation of community weighted means as well as of functional and phylogenetic diversity patterns.