To understand the impact of precipitation pattern of the East Asian monsoon climate in the ecosystem carbon balance at the KoFlux site, located in the deciduous broadleaved forest of Gwangneung, Korea, we investigated the forest net ecosystem productivity (NEP) based on a biometric method for three years (2013–2015). Here, NEP was estimated at the plot scale as the annual difference between the net primary productivity (NPP; the sum of wood biomass production [WBP] and litterfall) and soil respiration (SR) released after trenching treatment. Further, we integrated and analyzed the temporal variability of carbon balance in relation to climatic factors using observations (including the net ecosystem exchange [NEE] as measured by the eddy covariance technique) found in the research literature published for the same site since the early 2000s.
Results/Conclusions
The summer rainy spell or Korean “changma” of 2013 was similar to normal changma in which rainfall is heavy, intensive, and long-lasting. The changma rainfall in 2014 and 2015 made up 50% of 2013, however, and it was uniformly distributed in 2014 but more concentrated in 2015 resulting in drought in the late spring and early autumn. Wood biomass production increased significantly in 2015 with the high soil moisture of early spring and short and intensive changma charateiristics, whereas litterfall production was similar yearly. Soil respiration tended to increase with soil moisture over the course of the study based on the range of low soil moisture due to the drought; thus, the annual SR was lower in 2014 and 2015 than in 2013. Therefore, NEP in 2015 was greatest among the study years and furthermore greatest in consideration of a ≈20-year long term data set for this site (-0.7 to 2.5 Mg C/ha/yr). As a result of correlation analyses between previous NEPs and climatic factors, it was concluded that ecosystem carbon was released or absorbed depending on whether the frequency and intensity of precipitation in the summer or spring and autumn.