Remote Sensing of Forest Carbon Accumulation

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Objective: The overall aims of my research are to increase our understanding of the interaction between vegetation pigments, biochemistry and forest stand structure and how remote sensing technologies can be used to estimate properties of forest vegetation at a range of spatial and temporal scales. My research informs terrestrial carbon modelling and species distributions prediction under a changing climate, and through the use of advanced remote sensing technologies, contributes to sustainable forest management and developing conservation priorities.Context: Over the past 6 years my group's research has contributed to an increased awareness that high spectral resolution data can be used to inform models of forest productivity. Key to this approach is estimating light-use efficiency (LUE), which is determined by the most limiting of a number of environmental stresses restraining the photochemical reaction process. We quantify these changes using spectral indices such as the Photochemical Reflectance Index (PRI). My recent key contributions have focused on (i) modeling leaf spectral data acquired from a diverse set of vegetation species and stand structures, (ii) deployment of the AMSPEC III, an in-house, automatic spectra-radiometer system and (iii) an increased awareness of the role forest structure (which influences both inter and intra crown shading) plays on the overall light regime of the forest stand and its impact on the vertical stratification of LUE. Research Questions: Key hypothesis in my proposal will focus on the short and long term temporal variations in the LUE / PRI relationship. In the short term, the role of canopy shading on plant photosynthetic efficiency and over the longer term, the role of other pigments and other leaf processes on vegetation stress. Three research objectives are defined: Since initial research on PRI and LUE we know that PRI is responsive to changes in the xanthophyll cycle at fine time scales, principally driven by the light regime in the canopy. Over weekly to seasonal time scales other vegetation pigments change more slowly. My first objective focuses on these short and long term changes due to the xanthophyll cycle, and seasonally changing pigment pool cycles, respectively. Second, as we have a poor understanding on the vertical distribution of carbon assimilation within a canopy that results from attenuation of sunlight in the lower strata, we will use Light Detection and Ranging data, forest architecture models, and within canopy sensors, to measure and model vertical light regimes linked to the above canopy response. Finally, in addition to understanding photosynthesis through PRI, other approaches exist due to upcoming satellite missions. My final objective is to examine if existing forest physiological models can be modified to incorporate dynamic estimates of LUE from a number of sources or if new model structures are required.