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.

长期以来，生态学家一直强调气候是决定大尺度生态系统动态的主要因素，但气候和植被之间的关系并不总是确定的。 在植被-环境反馈显著的地方（例如，在热带稀树草原），预测对气候的反应可能特别困难。 最近的研究表明，火灾的反馈可能使稀树草原比它们的分布完全由气候决定的情况更加普遍;因此，稀树草原和森林对全球变化的反应可能是剧烈的，突然的，难以预测。 然而，现有的工作并没有解释为什么稀树草原与稀树草原和森林与森林在空间上聚集-这种模式表明，空间过程也可能在决定生态系统对气候的反应方面发挥作用。 在这里，研究人员将考虑热带稀树草原和森林之间的空间相互作用对它们的分布以及它们对过去和未来气候和土地利用变化的潜在响应的影响。研究人员确定了三个假设来解释热带稀树草原和森林的空间聚集：H1）稀树草原和森林是交错分布，初始条件下空间结构（作为过去气候的结果）决定了它们的分布，H2）稀树草原和森林是交错的，但稀树草原内的空间过程（例如，火蔓延）导致空间结构化分布，和/或H3）稀树草原和森林之间最近邻的相互作用改变了它们在长时间尺度上的分布，影响了它们的长期稳定性。 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解开这些过程。 研究结果将使研究小组能够对全球热带稀树草原和森林的过去和未来分布做出明智的理论和经验预测。 拟议的工作也将产生新的数学结果。理论的，空间随机模型的可能结果包括a）稀树草原和森林共存的景观，B）森林排斥稀树草原，c）稀树草原排斥森林，或d）生物群落稀树草原/森林优势的替代稳定状态。 最后的结果在均匀空间随机模型中是不可能的，其中获胜的生物群落由生物群落边界的移动方向决定（即，前面），但最接近于真实的生物群系分布。空间随机模型结果将与使用理论和模拟建模的观测结果相一致。