A NEIGHBORHOOD APPROACH TO THE BIOGEOGRAPHY OF PUERTO RICAN TREES

树种的地理分布既反映了自然过程(如地质、气候)，也反映了生物过程(如竞争、草食)。这些因素不是独立起作用的。例如，在低肥力土壤中，树木之间的竞争强度可能会更强。然而，只有几项研究考察了物理因素和生物过程对树木生长和存活的同时影响。这种综合对于预测树种对环境变化的反应至关重要。这在热带森林中是一个关键问题，因为这些生态系统正在经历快速的环境变化，并在调节全球气候方面发挥关键作用。这项研究将开发一种新的分析方法，以表征物理异质性和当地生物相互作用对波多黎各全岛树种生长和生存的联合影响。该岛具有高度的树木多样性，显著的环境和气候梯度，以及大量的现有数据，使这里成为进行这项研究的理想地点。这项研究的结果将为美国农业部林业局适应快速环境变化的几项倡议提供成功的可能性。研究人员与当地组织之间现有的合作将有助于对波多黎各森林的管理和保护产生直接影响。数据将在网上提供，并直接提供给当地管理机构，包括美国林业局和波多黎各自然资源部。研究人员还将在波多黎各的机构组织关于分析方法的研讨会。最后，该项目将培训和雇用一名波多黎各技术员和一名博士后研究员，为STEM劳动力发展做出贡献。范围动态和社区集会反映了区域环境异质性和当地进程的互动影响。然而，对这些相互作用的实证检验却很少见。研究人员将开发一种新的基于功能特征的空间显式邻域方法，以理清环境异质性和生物交互作用对波多黎各各地树木生长和存活的局部影响，同时考虑到个体特征的差异。为此，他们将结合(A)树种范围内的树木特征测量，包括与水分利用策略相关的特征，(B)基于特征的树木生长和存活邻域模型，该模型来自24个测绘地块中收集的数据，以及(C)利用草本植物集合描述相对于区域环境梯度的物种分布的通用联合属性模型。他们将检验以下假设：(1)局部生物相互作用对树木生长和存活的负面影响在对物种最有利的地点最高，促进区域共存；(2)种内性状跨环境梯度变化的空间结构促进了这种共存。这项研究的结果将经验性地检验个体特征变异在调节区域物种共存中的重要性，并检验稳定机制在促进热带森林物种共存和多样性方面的重要性。这项研究将为未来的研究奠定概念基础，这些研究将把当地社区的互动置于生物地理背景下，并改变对调解区域规模森林社区聚集的环境和生物因素的理解。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The geographic distributions of tree species reflects both physical (e.g., geology, climate) and biological processes (e.g., competition, herbivory). These factors do not act independently. For example, the strength of competition among trees may be stronger in low fertility soils. However, only a few studies have examined the simultaneous effects of physical factors and biological processes on tree growth and survival. Such synthesis is central to predicting tree species responses to environmental change. This is a critical issue in tropical forests because these ecosystems are experiencing rapid environmental change and play a key role in regulating global climate. This research will develop a novel analytical approach to characterize the joint effects of physical heterogeneity and local biological interactions on growth and survival of tree species across the island of Puerto Rico. The island has high tree diversity, marked environmental and climate gradients, and an extensive amount of existing data, making this an ideal site for this research. Results from this study will inform the likelihood of success of several USDA Forest Service initiatives to adapt to rapid environmental change. Existing collaborations between the researchers and local organizations will facilitate a direct impact on the management and conservation of Puerto Rican forests. Data will be made available online and provided directly to local management agencies, including the US Forest Service and the Puerto Rico Department of Natural Resources. The researchers also will organize workshops on the analytical methods at Puerto Rican institutions. Finally, the project will train and employ a Puerto Rican technician and a postdoctoral researcher, contributing to STEM workforce development.Range dynamics and community assembly reflect the interactive effects of regional environmental heterogeneity and local processes. Yet empirical examination of these interactions is rare. The researchers will develop a novel functional trait-based, spatially-explicit neighborhood approach to disentangle local effects of environmental heterogeneity and biotic interactions on tree growth and survival across Puerto Rico while accounting for individual trait variation. To do so, they will couple (a) tree trait measurements across species ranges traits, including traits related to water use strategies, (b) trait-based neighborhood models of tree growth and survival derived from data collected in 24 mapped plots, and (c) generalized joint attribute models that characterize species distributions with respect to regional environmental gradients using herbaria collections. They will test the following hypotheses: (1) the negative effect of local biotic interactions on tree growth and survival is highest at the most environmentally favorable sites for a species, fostering regional coexistence; (2) the spatial structure of intraspecific trait variation across environmental gradients fosters such coexistence. Results from this research will empirically examine the importance of individual trait variation in mediating regional species coexistence and test the importance of a stabilizing mechanism in promoting species-coexistence and diversity in tropical forests. The research will lay a conceptual foundation for future studies that place local community interactions within a biogeographic context and transform understanding of the environmental and biotic factors that mediate forest community assembly at regional scales.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.