Quantifying Climate Influence on Net Ecosystem Exchange in Lowland Tropical Rice: A Five-Year Eddy Covariance Study

A five-year study on net ecosystem exchange (NEE) to assess the impact of climatic drivers on inter-annual variability (IAV) was conducted using eddy covariance measurements in a lowland tropical rice–rice system. The IAV of carbon dioxide fluxes in two crop growing phases, i.e., dry and wet seasons along with fallow periods, was analyzed. The gross primary productivity (GPP) flux builds up during the crop growing season with corresponding increase in ecosystem respiration (RE) during the study period. Annual cumulative value of NEE was negative (sink) in both the crop growing seasons. The variability of climate drivers and changes in the ecosystem responses to drivers revealed a large intra-annual as well as inter-annual variability of net ecosystem fluxes. The NEE was correlated with different meteorological variables such as photosynthetically active radiation (PAR), precipitation, air temperature and soil temperature. The anomalies of NEE, GPP and RE were observed to be less in 2017 and 2018, which may be due to lower temperature anomalies recorded in these years. This work improves further understanding of biological mechanisms which are involved in the variation of climatological variables to improve our ability to predict future IAV of NEE.