HR: 14:40h
AN: B53D-04    [Abstracts]
TI: Integrating ground observations of phenology with remotely sensed measurements: A 2007 growing season experiment at Sevilleta LTER
AU: * Bradley, B
EM: bethanyb@princeton.edu
AF: Princeton University, Woodrow Wilson School, Princeton, NJ 08544, United States
AU: Wetherill, K
EM: karen@sevilleta.unm.edu
AF: University of New Mexico, Department of Biology, Albuquerque, NM 87131, United States
AU: Vanderbilt, K
EM: vanderbi@sevilleta.unm.edu
AF: University of New Mexico, Department of Biology, Albuquerque, NM 87131, United States
AU: Nickeson, J
EM: jaime.e.nickeson@nasa.gov
AF: Innovim, Goddard Space Flight Center, Greenbelt, MD 20771, United States
AB: The use of satellites to monitor land surface phenology is important for understanding local and regional ecosystem variability, identifying change over time, and potentially predicting ecosystem response to short and long-term changes in climate. However, the relationship between how phenology is expressed on the ground and how it is interpreted from satellites is poorly understood because phenological stages do not always correspond well to changes in spectral reflectance. Rather than focusing on phenological stages (e.g., first leaf, first flower), the ground measurements in this study focus on changes in ecosystem greenness during the 2007 growing season. We collected bi-monthly measurements of community greenness in two perennial grasslands at the Sevilleta National Wildlife Refuge in central New Mexico, a Long Term Ecological Research (LTER) site. One site is dominated by blue grama grass (Bouteloua gracilis); the other is dominated by black grama grass (Bouteloua eriopoda). Grama grasses grow during the summer/fall time period, with onset of greenness typically occurring mid-July and peak greenness occurring in September. Bi-monthly ground measurements were collected from July 2, 2007 – October 4, 2007 within systematically arrayed 30x30 cm quadrats. Within each quadrat, we recorded percent green cover (grass or forb), percent non- photosynthetic cover, and percent soil. A nadir oriented digital photograph was also taken of each quadrat, from which a greenness index was calculated. Field sampling was timed within two days of an ASTER satellite image acquisition. Here, we compare three greenness measurements from ground sampling, digital photography, and ASTER satellite imagery for the 2007 growing season. We show the degree of correlation between the three measurements through time and draw inferences about how satellite imagery can be used to assess ecosystem phenology. This study is an important first step in furthering the linkage between remotely sensed phenologies and community-level ecosystem phenologies.
DE: 0438 Diel, seasonal, and annual cycles (4227)
DE: 0439 Ecosystems, structure and dynamics (4815)
DE: 0476 Plant ecology (1851)
DE: 0480 Remote sensing
SC: Biogeosciences [B]
MN: 2007 Fall Meeting