Net Ecosystem Exchange of Carbon Dioxide of an Apple Orchard in South Korea.

Carbon dioxide (CO₂) gases concentration in atmosphere has been growing since preindustrial times. By sequestering a large amount of atmospheric carbon (C), terrestrial ecosystems are thought to offer a mitigation strategy for reducing global warming. Woody agro-ecosystems such as fruit tree are among the least quantified and most uncertain elements in the terrestrial carbon cycle. In this study, CO₂ and energy fluxes were measured by the eddy covariance method on a 15-year old apple orchard of South Korea in 2006. Environmental parameters (net radiation, precipitation, etc.) were measured along with fluxes. The topography of the flux site is flat and homogeneous covered with apple trees. Micrometeorological fetch is more than 1km depending on the prevailing wind direction. Apple tree (Malus domestica Borkh., variety Fuji) was 15 year old and the average pruned tree height was 4m. The results showed that during late June, the ability to sequestrate C was significant at an apple orchard ecosystem and it reached on the peak of -6.5 g C m^-2 d^-1. We found that in the apple orchard, the daily average of net ecosystem exchange of CO₂ (NEE) and cumulative NEE on a yearly basis were -1.1 g C m^-2 and -396.9 g C m^-2, respectively. These results reveal that there is high carbon sequestration in the apple orchard of South Korea, which is the same magnitude with respect to that of a natural forested ecosystem of the same biome rank (temperate-humid deciduous forest). But, the largest differences with respect to forests are in the allocation pattern and in the fate of produced biomass. The carbon sequestered from the atmosphere is largely allocated to production of fruit, and organic material (leaves, fine root litter, pruned wood and early fruit falls) contributing to the detritus cycle is also included largely. Only a little is attributable to standing biomass increment, while this net primary production (NPP) component is generally the largest in forests. So, NPP and allocation pattern of C in apple orchard need to be assessed by biometric and continuous soil chamber measurements.