Collaborative Research: The Role of Spatial Interactions in Determining the Distribution of Savanna and Forest

合作研究：空间相互作用在确定稀树草原和森林分布中的作用

• 批准号: 1615585
• 负责人: Simon Levin
• 金额: $ 11万
• 依托单位: Princeton University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-01 至 2020-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1615585&HistoricalAwards=false
• 关键词: Collaborative; Research; Role; Spatial; Interactions

Ecologists have long emphasized climate as primary factor determining ecosystem dynamics at large scales, but the relationship between climate and vegetation is not always deterministic. Where vegetation-environment feedbacks are significant (e.g., in savannas), predicting responses to climate can be especially difficult. Recent work suggests that feedbacks with fire may make savannas much more common than they would be were their distributions solely determined by climate; as a result, savanna and forest responses to global change may thus be drastic, sudden, and difficult to foresee. However, existing work does not explain why savanna is spatially aggregated with savanna and forest with forest -- a pattern that indicates that spatial processes may also play a role in determining ecosystem responses to climate. Here the investigators will consider the impacts of those spatial interactions between savanna and forest on their distributions and on their potential responses to climate and land-use change, both in the past and into the future.The investigators have identified three hypotheses to explain the spatial aggregation of savanna and forest: H1) that savanna and forest are bistable, and that spatial structure in initial conditions (as a result of past climate) determines their distributions, H2) that savanna and forest are bistable, but that spatial processes within savanna (e.g., fire spread) result in spatially structured distributions, and/or H3) that nearest neighbor interactions between savanna and forest change their distributions on long time scales, impacting their long-term stability. These hypotheses are variously supported in the empirical literature, and existing work has not attempted to disentangle these processes. Results will allow the research team to generate informed theoretical and empirical predictions about the past and future distribution of savanna and forest globally. The proposed work will also generate novel mathematical results. Possible outcomes of theoretical, spatial-stochastic models include a) savanna and forest coexistence in landscapes, b) forest exclusion by savanna, c) savanna exclusion by forest, or d) alternative stable states in biome savanna/forest dominance. The last outcome would be unlikely in a homogeneous spatial stochastic model, where the winning biome is decided by the direction of movement of the biome boundary (i.e., the front), but most closely resembles real biome distributions. Spatial stochastic model results will be reconciled with observations using theoretical and simulation modeling.

生态学家长期以来一直强调气候是决定大尺度生态系统动态的主要因素，但气候与植被之间的关系并不总是确定性的。 在植被-环境反馈显着的地方（例如，在稀树草原中），预测对气候的反应可能特别困难。 最近的研究表明，与仅由气候决定分布的情况相比，火的反馈可能会使稀树草原更加普遍。因此，稀树草原和森林对全球变化的反应可能是剧烈、突然且难以预见的。 然而，现有的工作并没有解释为什么稀树草原在空间上与稀树草原聚合，森林与森林聚合——这种模式表明空间过程也可能在决定生态系统对气候的响应方面发挥作用。 在这里，研究人员将考虑过去和未来稀树草原和森林之间的空间相互作用对其分布及其对气候和土地利用变化的潜在反应的影响。研究人员已经确定了三个假设来解释空间相互作用稀树草原和森林的聚合：H1）稀树草原和森林是双稳态的，初始条件下的空间结构（由于过去的气候）决定了它们的分布，H2）稀树草原和森林是双稳态的，但稀树草原内的空间过程（例如火势蔓延）会导致空间结构化分布，和/或 H3），稀树草原和森林之间的最近邻相互作用会改变它们在长期尺度上的分布，影响它们的长期稳定性。 这些假设在实证文献中得到了不同的支持，现有的工作并没有试图理清这些过程。 研究结果将使研究团队能够对全球稀树草原和森林过去和未来的分布做出明智的理论和实证预测。 拟议的工作还将产生新颖的数学结果。理论空间随机模型的可能结果包括a）稀树草原和森林在景观中共存，b）稀树草原对森林的排斥，c）森林对稀树草原的排斥，或d）生物群落稀树草原/森林优势的替代稳定状态。 在同质空间随机模型中，最后的结果不太可能出现，其中获胜的生物群落由生物群落边界（即前部）的移动方向决定，但最接近真实的生物群落分布。空间随机模型结果将与使用理论和模拟模型的观测结果相一致。