Effects of forest type and environmental factors on forest carbon use efficiency assessed using MODIS and FIA data across the eastern USA
We tested two questions. First, whether MODIS CUE is constant or whether it varies by forest type, climate, and geographic factors across the eastern USA. Second, whether those results occur when field-based NPP data are employed. We used MODIS model-based estimates of GPP and NPP, and forest inventory and anlaysis (FIA) field-based estimates of NPP data. We calculated two estimates of CUE for forest in 390 km2 hexagons: (1) MODIS CUE as MODIS NPP divided by MODIS GPP and (2) F/M Z CUE as the standardized difference between FIA NPP and MODIS GPP.
MODIS CUE and F/M Z CUE both varied similarly and significantly in relation to forest type, and climatic and geographic factors, strongly supporting a variable rather than a constant CUE. The CUE was significantly higher in deciduous than in mixed and evergreen forests. Regression models indicated that CUE decreased with increases in temperature and precipitation and increased with latitude and altitude. The similar trends in MODIS CUE and F/M Z CUE support the use of the more easily obtained MODIS CUE.
Document Type: Research Article
Affiliations: 1: Department of Earth Sciences, University of Memphis, Memphis, TN, 38152, USA 2: Department of Geography, University at Buffalo, The State University of New York, Buffalo, NY, 14261, USA
Publication date: December 10, 2013