Dissertation Research: Balancing the influence of biological and architectural diversity on rainforest productivity along an elevation gradient in Hawaii

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Tropical forests cover more than 12% of surface area and contain 50% of sequestered carbon on land, and are important contributors to the global carbon cycle. The carbon dynamics of tropical forests are dependent on climatic conditions, such as cloud coverage, solar radiation, and temperature. At short time scales, i.e. within a year, climate influences forest productivity directly by controlling rates of photosynthesis and respiration. Over longer periods, climate changes may alter forest 3D structure and composition, but this is difficult to determine because large areas of forest are needed to assess this, and collection of field data can be problematical. Thus, studying the spatial and temporal interactions among forest structure, composition and carbon dynamics requires new methods. This study utilizes a new airborne imaging system, LiDAR (Light Detection and Ranging), which measures properties of scattered light, and hyperspectral imaging, which provides information using a vast portion of the electromagnetic spectrum, to develop detailed 3D maps of forest structure. Microclimate and leaf physiology data will be collected simultaneously to develop and validate a high-resolution 3D model of forest photosynthesis. By using a study transect comprising three km2 of tropical forest situated along an elevation gradient, it will be possible to quantify effects of forest structure, composition and climatic differences on forest photosynthesis and productivity at scales not before feasible. This project will develop a new tool for large-scale and cost-effective monitoring of forest carbon dynamics. The researcher also plans to develop a video presentation on this subject for use at the high-school and undergraduate level.