Bridging Spatial Scales Using Phenological Measurements To Improve Understanding of Springtime Atmosphere-Biosphere Interactions

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BCS-0649380Mark D SchwartzUniversity of Wisconsin-MilwaukeeEnhancing accuracy of flux estimates at large scales is a critical part of improving understanding of the interactions between global climate change and land surface processes. Current approaches assume that estimates of extremely small areas are representative of larger regions. The timing of leaf flush and subsequent expansion (phenology) during spring, which in tree species is highly sensitive to climate change, in turn has a profound impact on lower atmospheric energy-mass exchange across the landscape. However, spatial variations in the timing of spring phenology at the community level have not been systematically measured and analyzed. If large, these variations may reflect gradients in plant growth during spring leaf development that could foster systematic errors in seasonal fluxes of equal or greater magnitude than those during the height of the growing season. Thus, phenological data collected in a spatially explicit manner offer considerable opportunities for gauging landscape-level spatial variations crucial for accurate scaling-up of flux measurements to larger areas or downscaling regional-scale atmospheric circulation models. In this project, spatial variability of spring phenological data will be measured and analyzed at the community level, and then compared to the microenvironment and remote sensing measurements. The detailed spatially concentrated phenological measurements and spatial analyses that proceed from this study will lay the foundation for future work that explicitly links phenological variations with plant physiological responses. The spatially concentrated phenological measures produced by this study will provide concurrent remote sensing studies being conducted at the study site with a record of spring plant development and growth that contains vastly more information about species differences, spatial variability, and precise event timing that has typically been recorded in the past. These measures will present new opportunities for comparison and validation of the satellite-derived measures, and may lead to consideration of adoption of similar phenological monitoring schemes at additional sites. Overall, the results of this project will also contribute to better understanding of the impacts of climate change on the biosphere, which will increase knowledge of potential future changes, and may allow for better planning relative to societal impacts.This project will address issues that are significant for advancement across the fields of climatology, plant physiological ecology, and remote sensing. Phenological (onset of spring plant growth) variability in space and time has not been previously recorded over a large area nor combined with supporting measurements. Understanding spatial patterns of spring plant phenological development (and the processes that drive them) may be the key knowledge needed to improve larger area estimates of the flow of water vapor and carbon dioxide derived from moderate resolution remote sensing data. The results will contribute to broader understanding of landscape variability, atmosphere-biosphere interactions, and produce measurements that are necessary to accurately scale-up measurements to larger areas.