The proximity (< 1.5 km) of the two KoFlux tower sites (i.e., Gwangneung coniferous forest site, GCK and deciduous forest site, GDK) provides an excellent opportunity to compare and contrast the carbon sink strength of the two different forests under similar weather and climatic conditions. We applied the resilience framework to better understand the forest carbon dynamics. Resilience is defined as the capacity of the system to absorb disturbances, to be changed, and then to self-organize and still have the same purpose and controls on function and structure. One of the key concepts in resilience approach is adaptive cycles which describe a repeated process of growth, conservation, collapse, and re-organization. The GCK is currently in rapid growth stage with relatively younger (< 96 years) Abies spp., of ~25 m canopy height. On the other hand, GDK has reached the conservation stage, dominated with the climax overstory and understory vegetation such as Quercus spp., (>200 years old) and Carpinus spp., respectively. We hypothesized that the inter-annual variation of ecosystem carbon sink strength would be more stable in GDK with better optimized water use efficiency in comparison to that in GCK. The quantitative measurements of CO2 fluxes by eddy covariance at both GCK and GDK, the analysis of their carbon budget components, and their inter-annual variations from 2007 to 2010 support our hypothesis.