改进Biome-BGC模型模拟哈佛森林地区水、碳通量

Simulation of water and carbon fluxes in Harvard forest area by using improved Biome-BGC model

Biome-BGC模型通过耦合植被、土壤与大气间的水分与CO2交换过程,实现植被生产力的模拟,但土壤水平衡模块的不够完善,导致在长时间无降水情况下植被生产力模拟存在较大误差。针对这一问题,本文对Biome-BGC模型中土壤水分胁迫气孔导度方程、蒸散计算公式及土壤水分流失过程等3方面进行了改进和调整,利用改进的Biome-BGC模型模拟美国哈佛森林地区蒸散、植被生产力,并与地面通量观测值进行了比较。结果表明,改进后模拟精度有明显的提高,蒸散、植被生态系统生产力(NEE)与观测值间的决定系数分别由0.483和0.658提高到0.617和0.813,蒸散逐年均方根误差平均下降了48.7%,NEE逐年误差平方和平均下降了39.8%。改进后的模型模拟结果更接近观测值。

Using Biome-BGC model can simulate vegetation productivity through the coupling of water and CO2 exchange processes between vegetation, soil and atmosphere, but the soil water balance module is not perfect enough, leading to a large deviation between simulated and observed values under condition of a long time no precipitation. Aiming at this problem, this paper improved and adjusted the equation of stomatal conductance stressed by soil water, the calcula- tion formula of evapotranspiration, and the process of soil water loss in Biome-BGC model. Using this improved model, the evapotranspiration and vegetation productivity in Harvard Forest area were simulated, and compared with field observations. The accuracy of simulated results by the improved model enhanced obviously, with the evapotranspiration R2 between simulated and observed values increased from 0. 483 to 0. 617, NEE R2 increased from 0. 658 to 0. 813, root mean square error （RMSE） of annual evapotranspiration decreased averagely by 48.7% , and annual sum squared error （ASSE） of NEE decreased averagely by 39.8%, which suggested that the simulated results by using the improved model were more close to the observed results.