基于MODIS产品的生态系统呼吸模型在内蒙古半干旱草原的验证

利用2010—2013年锡林浩特国家气候观象台涡动相关通量观测系统数据以及MODIS产品数据, 验证基于增强型植被指数(EVI)、陆地表面水分指数(LSWI)和地表温度(LST)的生态系统呼吸模型在内蒙古半干旱草原的适应性, 并探讨该遥感生态系统呼吸模型存在的问题。结果表明: 生态系统呼吸模型能较好地模拟夜间生态系统呼吸速率(R_eco)在生长季内和年际间的变化, 模拟值与观测值吻合较好(R²=0.90, RMSE=0.02 mgCO₂/(m²·s)); 夜间R_eco的观测值与EVI_s×W_s (EVI_s和W_s分别是EVI和LSWI对光合作用的影响函数)呈较显著的线性相关(R²=0.63), 与LST 的关系基本上满足L-T方程(R²=0.39); 夜间R_eco在生长季的前、中、后期对EVI_s×W_s和LST的响应不同是造成模型误差的重要原因之一。

A Validation Study of MODIS-Based Ecosystem Respiration Model in a Semi-Arid Grassland of Inner Mongolia

Eddy covariance data from Xilinhaote National Climatological Observatory in Xilin Gol League during growing seasons of 2010—2013 as well as MODIS data were used to validate an ecosystem respiration model based on enhanced vegetation index (EVI), land surface water index (LSWI) and land surface temperature (LST) in a semi-arid grassland of Inner Mongolia. The limitations of this remote sensing respiration model were also discussed. The results indicate that this model can successfully simulate the variations of nocturnal ecosystem respiration (R_eco) in the growing seasons and between different years. The simulated nocturnal R_eco also agreed remarkably with the observed R_eco (R²=0.90, RMSE=0.02 mgCO₂/(m²·s)). Moreover, the observed nocturnal R_eco showed a good linear correlation with EVI_s×W_s (R²=0.63), in which EVI_s and W_s are response functions of EVI and LSWI on photosynthesis, respectively. The response of nocturnal R_eco to LST was also found following the L-T equation (R²=0.39). In addition, the difference between responses of nocturnal Reco to EVI_s×W_s and LST in the early, middle and late stages of the growing season is indicated as one principal source of the deviations of model results.