Fire versus water: ecosystem boundaries in tropical forest landscapes

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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. *****