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、土壤特性、火灾和季节性干燥热带森林(SDTF)植被结构和功能之间的关键反馈。我们将解决以下短期目标：1)量化气候变化和土地利用对SDTF景观火情的影响，2)确定火、土壤条件、植被结构和功能之间在植被类型之间的关键反馈。我们将通过多个空间尺度的研究来解决这些目标，从全球分析到个别树叶。我们的大部分工作将在柬埔寨北部进行，那里类似于稀树草原、经常燃烧的落叶双翅果林形成了斑驳的景观马赛克和与干燥的常绿森林的陡峭边界。我们将利用这个系统作为一个模型，以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，并探索植物物种水分利用策略和火灾敏感性之间的关系。为了解决目标1，我们将使用遥感来描述所有SDTF的火情，以及柬埔寨北部地区的火情，以探索影响SDTF火情的因素。为了实现目标2，我们将进行实地研究，以确定不同森林类型在环境、森林结构和动态以及植物策略方面的变化。测量与水分利用策略和火灾脆弱性有关的功能特征，以及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作用，以及火灾在多大程度上有利于特定的水利用策略。我们还将使用LiDAR来表征森林结构，并在景观尺度上将森林结构的变化与火灾历史联系起来。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，部分原因是对支配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将东南亚生态系统排除在外，限制了一般性。通过量化东南亚生态系统中气候、火和植被之间的反馈，我的研究计划将有助于解决一些不确定性。我们的研究将在保护和森林管理方面有重要的应用，我们与柬埔寨林业局的合作将确保我们的工作直接影响当地政策和管理指导方针。这项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篇同行评议的出版物。

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.