NDVI and a simple model of deciduous forest seasonal dynamics

Satellite derived NDVI for forest stands has been related to leaf area index (LAI) (Remote Sens. Environ. 61 (1997) 229), the fraction of absorbed photosynthetically active radiation (fPAR) (Remote Sens. Environ. 58 (1996) 115; Remote Sens. Environ. 61 (1997) 254) and to CO2 uptake (Tellus 43B (1991) 188) with varying success. NDVI observations reflect leaf density, but are primarily indicators of process rates—photosynthesis and transpiration (Int. J. Remote Sens. 7 (1986) 1395). A simple model was developed of seasonal deciduous forest growth as a function of climate variables, including light intensity, temperature and moisture. The model was parameterized for six deciduous Maryland sites with non-photosynthetic biomass between 2.1 and 58.7 kgC/m2. Model estimates of leaf biomass and gross primary productivity were compared to 1992 and 1993 1-km 10-day composite NDVI from the NOAA advanced very high resolution radiometer (AVHRR) instrument. Significant fluctuations in GPP appear to correlate to temporal variations in NDVI. A linear model relating NDVI to leaf biomass and specific gross primary productivity accounted for 51% of the variation in NDVI with P-values for all coefficients <0.0001. Improvements in field data, more rigorous model treatment of cloud cover, consideration of site heterogeneity and corrections for atmospheric attenuation and satellite view angle might improve the correlation and thus allow use of NDVI for model calibration.