Estimation of Net Ecosystem Exchange (NEE) in South Korea

A method has been developed to estimate net ecosystem exchange (NEE) over South Korea at 8-km resolution. In this method, gross primary production (GPP) is estimated from model simulation and ecosystem respirations are estimated using empirical formulations developed in South Korea. The mSPA (modified Soil Plant Atmosphere) model has been used for simulation of GPP. The model is a process based model with two-canopy layer and use a 30min integration scheme to implement a leaf-level photosynthesis. The ratio of rice paddy field to crop area has been used to consider the reduction of soil respiration over rice paddy field. Two key driving variables, leaf area index and land cover type are derived from satellite measurements of Moderate Resolution Imaging Spectroradiometer (MODIS). Hourly observed meteorological data at 70 stations have been used as input data. The model outputs are compared with ground plot data measured at two KoFlux sites (Haenam and Kwangrung) to ensure that no significant systematic biases are created. Also spatial distribution of model GPP are compared with that of MODIS GPP and comparison results are discussed. The spatial distributions of estimated GPP, ecosystem respiration and NEE are presented and uncertainties of estimates are discussed.