Evaluation of Community Land Model version 3.5-Dynamic Global Vegetation Model over Deciduous Forest in Gwangneung, Korea

The performance of Community Land Model version 3.5 - Dynamic Global Vegetation Model (CLM-DGVM) was evaluated through a comparison with the observation over temperate deciduous forest in Gwangneung, Korea. Influence of plant phenology, composition of plant functional type, and climate variability on carbon exchanges was also examined through sensitivity test. To get equilibrium carbon storage, the model was run for 400 years driven by the observed atmospheric data at the deciduous forest of the year 2006. We run the model for 2006 with the equilibrium carbon storage at Gwangneung forest and compared the model output with the observation. A comparison of leaf area index (LAI) between the model and observation indicated that the simulated phenology poorly represented the timing of budburst, leaf-fall, and evolution of LAI. Senescence of the phenology was delayed about four weeks and the simulated maximum LAI (of 5.8 ㎡m-²) was greater than the observed value (of 4.5 ㎡m-²). The overestimated LAI contributed to overestimation of both gross primary productivity (GPP) and ecosystem respiration (R∧e) through increased photosynthesis and foliar autotropic respiration (R∧a), respectively. Despite the discrepancy between the simulated and observed LAI, the simulated tree carbon storage amounts were comparable with the reported values at the site. Change in plant phenology from the simulated to the observed reduced more than six weeks of the plant growth period, resulting in the decreased amount of GPP and R∧e. These values, however, were still higher (~10% of GPP and 40% of R∧e) than the observed values. The effect of change in plant functional type composition (from dominant temperate deciduous forest to the coexistence of temperate deciduous and needle leaf forests) on the estimated amount of GPP and R∧e was marginal. The influence of climate variability on carbon storage amounts was not significant. The simulated inter-annual variation of GPP and R∧e from 1994 to 2003 depended on annual mean air temperature and total radiation but not on precipitation. Other deficiencies of CLM3.5-DGVM have been discussed.