Recent Advances In The Understanding Of Ecosystem Processes At Eddy Covariance Co2 Flux Sites In East Asian Forest Ecosystems: A Review

To elucidate the dynamic features of carbon sequestration in ecosystems under changing climates and various disturbance regimes, researchers must understand key ecosystem processes, such as carbon allocation and partitioning, organic matter decomposition, and nutrient cycles, as well as plant functional traits. Here, we reviewed the existing literature and conducted meta-analyses using available datasets from eddy covariance CO2 flux sites in East Asia to clarify these ecosystem processes and attributes. Since the establishment of AsiaFlux in 1999, the number of flux tower sites has grown to 110 sites, spanning a large geographic extent in East Asia and covering diverse ecosystems embedded in large climatic gradients. Early publications relating to AsiaFlux described CO2 fluxes from single sites, but over the last 20 years more ecosystem processes and attributes have been included in the study sites' research programs. Among other advances, researchers have quantified the plant functional traits related to photosynthesis or ecosystem-scale gross primary production and thus demonstrated that CO2 fluxes are controlled by plant traits; this quantification provides a basis for building ecosystem models. Additional means of understanding the carbon fluxes and pools of these ecosystems have been provided by biometric measurements beneath eddy covariance flux towers, partly on the basis of traditional forestry practices and the measurements of component carbon fluxes, such as respiratory fluxes and litter decomposition rates. Through meta-analyses, we demonstrate good correlations between these fluxes and mention the characteristics of carbon cycle processes in Asian forest ecosystems. By investigating nitrogen biogeochemical cycles at the flux sites, studies have shown that carbon fluxes are also controlled by nitrogen availability. The future success and progress of AsiaFlux could be promoted by further collaborations between this research community and other networks, such as long-term ecological research (LTER) networks, and the development of open databases.