Patel, NR, Dadhwal, VK, Saha, SK, Garg, A, Sharma, N (2010). Evaluation of MODIS data potential to infer water stress for wheat NPP estimation. TROPICAL ECOLOGY, 51(1), 93-105.
The present, study carried out in Haryana, explores potential of MODIS data for scaling constant light use efficiency (epsilon(star)) for computing the net primary productivity (NPP) of wheat crop following Monteith's concept. We compared three scaling approaches epsilon(star) in time and space by using three different MODIS derived surface wetness indices, i.e. vegetation temperature condition index (VTCI), water deficit index (WDI) and land surface wetness index (LSWI). The approach using MODIS observations allows estimation of temporal evolution and geographical distribution of NPP of wheat in Haryana. High levels of seasonal NPP in wheat were observed in northern districts of Kaithal, Kurushretra and Fatehabad compared to districts in southern and western Haryana. Among three water stress scalars, the seasonal NPP simulated with LUE (LSWI) was higher in the magnitude (950-1200 g DM m(-2)) and mean NPP (1030 g DM m(-2)). Further, simulated NPP of wheat with LUE (LSWI) had good agreement with observed crop NPP of wheat (R-2=0.39, RMSE=64.9 g DM m(-2)) compared to simulated NPP with LUE (VTCI) and LUE (WDI). Statistical analysis revealed that the dynamics and magnitude of absorbed photosynthetically active radiation (APAR) over wheat growing season mainly determined the spatio-temporal dynamics of NPP. The LUE estimates from LWSI were within range of experimental LUE of wheat but did not show significant differences that cause variability in NPP.