Fire versus water: ecosystem boundaries in tropical forest landscapes

了解气候、干扰和植被之间的相互作用以及人类活动如何改变热带生物群落中的这些关系是一个具有全球影响的重大挑战。在接下来的五年里，我的研究计划将确定气候变化，土壤性质，火灾和植被结构和功能之间的关键反馈在季节性干旱热带森林（SDTF）。我们将解决以下短期目标：1）量化气候变异性和土地利用对SDTF景观中火灾状况的影响，2）确定火灾，土壤条件和植被结构之间的关键反馈和植被类型之间的边界功能。 我们将通过跨多个空间尺度的研究来实现这些目标，从全球分析到个别叶子。我们的大部分工作将在柬埔寨北方进行，那里的落叶龙脑香林类似于热带草原，经常燃烧，与干燥的常绿森林形成斑斑驳驳的景观马赛克和突然的边界。我们将使用这个系统作为一个模型来了解火灾活动的人为和生物物理驱动因素，火灾，土壤特性和植被之间的反馈，并探索植物物种用水策略和火灾敏感性之间的关系。 为了实现目标1，我们将使用遥感技术来描述所有SDTF的火灾状况，以及柬埔寨北方的区域火灾状况，以探索形成SDTF火灾状况的因素。为了实现目标2，我们将进行实地研究，以描述环境，森林结构和动态以及森林类型之间的植物策略的变化。测量功能性状相关的用水策略和火灾的脆弱性，沿着与土壤特性和火灾历史的数据，将使我们能够推断哪些环境因素发挥最强的过滤器，在何种程度上火有利于特定的用水策略。我们还将使用激光雷达来表征森林结构，并将森林结构的变化与景观尺度上的火灾历史联系起来。热带森林结构和功能的变化对碳储存和生物多样性有很大影响，但很难预测，部分原因是对控制生态系统之间边界的过程不完全了解。全球对森林-稀树草原边界的研究排除了东南亚的生态系统，限制了普遍性。通过量化东南亚生态系统中气候，火灾和植被之间的反馈，我的研究计划将有助于解决一些这种不确定性。我们的研究将对保护和森林管理有重要的应用，我们与柬埔寨森林管理局的合作将确保我们的工作直接影响当地的政策和管理指导方针。拟议的研究将培训至少8名HQP，包括3名博士，2名硕士和3名本科生，并将产生至少10篇同行评审的出版物。

Understanding the interactions between climate, disturbance, and vegetation and the ways human activities modify these relationships in tropical biomes is a major challenge with global implications. Over the next five years, my research program will identify key feedbacks between climate variability, soil properties, fire, and vegetation structure and function in seasonally dry tropical forests (SDTF). We will address the following short-term objectives: 1) Quantify the influence of climate variability and land use on fire regimes in SDTF landscapes and 2) identify key feedbacks between fire, soil conditions, and vegetation structure and function at boundaries between vegetation types. We will address these objectives with studies across multiple spatial scales, ranging from global analyses to individual leaves. Much of our work will take place in northern Cambodia, where deciduous dipterocarp forests, which resemble savanna and frequently burn, form patchy landscape mosaics and abrupt boundaries with dry evergreen forests. We will use this system as a model to understand anthropogenic and biophysical drivers of fire activity, feedbacks between fire, soil characteristics, and vegetation, and to explore relationships between plant species water-use strategies and fire sensitivity. To address Objective 1, we will use remote sensing to characterize fire regimes across all SDTF, and regionally within northern Cambodia, to explore factors that shape SDTF fire regimes. To address Objective 2, we will conduct field research to characterize variation in environment, forest structure and dynamics, and plant strategies across forest types. Measurements of functional traits related to water-use strategies and vulnerability to fire, along with data on soil characteristics and fire history will allow us to infer which environmental factors exert the strongest filters and to what degree fire favors particular water-use strategies. We will also use LiDAR to characterize forest structure, and link variation in forest structure to fire history at the landscape scale. Changes in tropical forest structure and function have large implications for carbon storage and biodiversity, but are difficult to predict, in part due to incomplete understanding of the processes that govern the boundaries between ecosystems. Global studies of forest-savanna boundaries have excluded southeast Asian ecosystems, limiting generality. By quantifying feedbacks between climate, fire, and vegetation in southeast Asian ecosystems, my research program will help resolve some of this uncertainty. Our research will have important applications for conservation and forest management, and our engagement with Cambodia's Forest Administration will ensure that our work directly affects local policy and management guidelines. The proposed research will train at least 8 HQPs, including 3 PhDs, 2 MScs, and 3 undergraduates, and will result in at least 10 peer reviewed publications.