Gross primary production, ecosystem respiration and net ecosystem exchange in Asian rice paddy: an eddy covariance-based approach

Carbon dioxide (CO2) exchange between the terrestrial ecosystems and the atmosphere is one of the major processes affecting atmospheric CO2 concentration. In various ecosystems in the world long-term observations of CO2 exchange have been made for assessing the role of terrestrial ecosystems in the present-day global CO2 budget and to predict its changes in the future climatic scenario. The eddy covariance (EC) system can provide a measure of net ecosystem exchange (NEE), which can be partitioned into gross primary production (GPP) and ecosystem respiration (RE) using mathematical modelling approach helpful for characterization of ecosystem carbon budgets. The EC technique for measuring CO2, water vapour and energy fluxes between the biosphere and the atmosphere is widely used in various regional networks. Presently, more than 400 EC sites are operational worldwide measuring carbon exchange in different biomes and climatic conditions at high temporal resolution. Rice paddy fields are widespread in monsoon Asia and the carbon exchange between paddy fields and the atmosphere is greatly influenced by cultivation and field management practices. In this review, an attempt has been made to summarize NEE, GPP and RE with the help of EC system in Asian rice paddies focusing on CO2 exchange between the biosphere and the atmosphere.