Application of the land surface temperature from MODIS in the estimation of gross primary productivity for a subtropical pinus plantation in southern China

In this study, the land surface temperature (LST) from Moderate Resolution Imaging Spectroradiometer (MODIS) sensor which was chosen as one scalar temperature directly modifying light use efficiency (LUE), together with the 8-day composited MODIS data and the site measurements of photosynthetically active radiation (PAR) of a subtropical evergreen coniferous forest ecosystem in southern China during 2005-2006 are used to estimate the seasonal variations of gross primary production (GPP) with the Production Efficiency Model (PEM). To investigate the possibility of LST instead of atmospheric temperature (T_a) in the PEM model to estimate the GPP values, the LST predicted GPP (GPP_LST) and T_a predicted GPP (GPP_air) are used to compare the GPP values observed from eddy covariance measurements (GPP_obs). It was found that the coefficient of determination of the fitted exponential equations between the GPP_obs and the T_a(r² = 0.89) was slightly higher than that between the GPP_obs and the LST(r² = 0.80), and both variables could explain above 80 % variations of the GPP_obs in this area. Both the GPP_LST and GPP_air agreed well with the observed GPP_obs.There was a very strong linear relation between GPP_LST and GPP_air (r² = 0.99), and they both were highly correlated with the GPP_obs (r² = 0.91 and 0.91, respectively). The annual total GPP_LST and GPP_air values (1630.6 and 1598.6 g C m^-2 for 2005; 1740.2 and 1660.8 g C m^-2 for 2006, respectively) were slightly lower than the GPP_obs (1646.8 and 1867.4 g C m^-2, respectively), and the error of the predicted GPP from LST (0.98% and 6.8% for 2005 and 2006, respectively) was smaller than the predicted GPP from T_a (2.9% and 11.1% for 2005 and 2006, respectivel- - y) for the whole year data. These results demonstrate that the LST can be potentially used to estimate GPP instead of T_a.