Tilia americana leaf senescence phenology:FAB 1 : Forests and Biodiversity Experiment - High density diversity

A forest biodiversity experiment (FAB) focused on trees of our region investigates the consequences of multiple dimensions of tree diversity for soil, food webs, plant communities and ecosystems. FAB is designed to unravel effects of three forms of biological diversity: species richness (SR), functional diversity (FD), and phylogenetic diversity (PD). We define FD as the representation of multiple traits of leaves, roots, seeds, and the whole organism that are correlated with species positions along gradients of resource supply, growth, and decomposition. PD is the representation of evolutionary lineages measured as the genetic distances between species. While PD and FD are often correlated, convergent evolution and adaptive differentiation can decouple them. When functional traits that drive specific ecosystem functions are not phylogenetically conserved, PD and FD may give contrasting predictions. SR, PD, and FD are not independent, and we posit that PD may help explain SR effects, and FD may help explain both PD and SR effects. Thus FAB is designed to examine the separate and combined effects of all three components of diversity for multiple ecosystem functions and to distinguish between ???sampling??? and ???complementarity??? effects of biodiversity. Due to the long lag between planting tree seedlings and determining effects of tree composition and diversity on ecosystem functioning, fewer experiments have been established to elucidate the role of biodiversity in the functioning of forest ecosystems than grassland experiments. FAB will contribute to this gap and is a member of the IDENT and TreeDiv network of forest biodiversity experiments (www.treedivnet.ugent.be). Hypotheses: 1. PD, FD, and SR will all contribute to increased productivity, stability, and diversity of other trophic levels (herbivores, predators, parasitoids, soil microbes, soil flora and fauna) as well as to greater soil C sequestration. 2. Because PD incorporates both the number of species and measurement of their evolutionary divergence, PD will explain more of the variation in ecosystem productivity and stability than SR. Similarly, among-species FD will explain more variation in these ecosystem functions than SR or PD. 3. Plant assemblages of similar SR but comprised of increasingly divergent PD or FD will show increasing divergence in ecosystem functions. 4. Species with functional traits not yet present in a plot will more easily invade than species with traits similar to the established species. The FAB single species plots will allow us to test hypotheses about the importance of plant functional traits in influencing ecosystem properties (e.g., NPP, soil C, N mineralization) and plant-associated microbial communities. For example, we expect that plant species that increase concentrations of polyvalent soil cations (e.g., because of unique base cation chemistry or because of effects on soil acidity that influence Al and Fe solubility) will promote soil C stabilization through mineral-organic matter interactions and the formation of microaggregates that protect soil C from decomposition.一项聚焦于本区域林木的森林生物多样性实验（Forest Biodiversity Experiment, FAB），旨在探究树木多样性多维度特征对土壤、食物网、植物群落及生态系统的影响。FAB的核心设计目标为阐明三类生物多样性的生态效应：物种丰富度（Species Richness, SR）、功能多样性（Functional Diversity, FD）与系统发育多样性（Phylogenetic Diversity, PD）。 我们将功能多样性（FD）定义为：与物种沿资源供给、生长及分解梯度的分布位置相关的叶片、根系、种子及整株生物体的多重性状表征。系统发育多样性（PD）则定义为以物种间遗传距离为度量指标的演化世系表征。尽管PD与FD通常存在相关性，但趋同演化与适应性分化可使二者解耦。当驱动特定生态系统功能的功能性状不具有系统发育保守性时，PD与FD可能会给出相悖的预测结果。SR、PD与FD三者并非相互独立，本研究推测PD或可解释SR的生态效应，而FD或可同时解释PD与SR的生态效应。因此，FAB的设计旨在探究三类多样性组分对多种生态系统功能的单独与联合效应，并区分生物多样性的“取样效应”与“互补效应”。 由于从栽植林木幼苗到明确林木组成与多样性对生态系统功能的影响之间存在较长时滞，相较于草地生态系统实验，阐明生物多样性在森林生态系统功能中作用的相关实验较为匮乏。FAB将填补这一研究空白，且隶属于森林生物多样性实验网络IDENT与TreeDiv（www.treedivnet.ugent.be）。 研究假设： 1. PD、FD与SR均将提升其他营养级（植食动物、捕食者、寄生性天敌、土壤微生物、土壤动植物区系）的生产力、稳定性与多样性，同时增强土壤碳固存能力。 2. 由于PD同时涵盖物种数量与物种演化分化程度的度量，其对生态系统生产力与稳定性变异的解释力将强于SR。同理，物种间功能差异对上述生态系统功能变异的解释力也将强于SR或PD。 3. 物种丰富度（SR）相似但系统发育多样性（PD）或功能多样性（FD）逐步升高的植物群落，其生态系统功能将呈现逐步增强的分异。 4. 相较于性状与已定植物种相似的物种，携带当前样地未出现的功能性状的物种更易成功入侵。 FAB设置的单物种种样地，将使我们能够检验关于植物功能性状对生态系统属性（如净初级生产力（NPP）、土壤碳、氮矿化）及植物关联微生物群落的重要性的相关假设。例如，我们推测，可提升多价土壤阳离子浓度的植物物种（如因独特的碱基阳离子化学特征，或通过改变土壤酸度影响铝与铁的溶解度），将通过矿质-有机质相互作用及形成保护土壤碳免受分解的微团聚体，促进土壤碳固存。