摘要
对中国东北样带植被生物量的时空变化进行了计算机模拟。模型以12种植被类型的绿色和非绿色生物量以及3层土壤水分为其状态变量。模拟绿色生物量被转成AVHRR归一化植被指数(NDVI),并与1986～1990年观测到的植被指数进行了比较。大气CO_2浓度、气温和降水被用作样带对全球变化响应研究的3个基本驱动变量。模型中还包括了降水和气温改变对日照百分率、相对湿度、辐射及土壤水分和植物生长的影响。CO_2取当前浓度或加倍,降水取当前水平或增加20％,气温取当前水平或增加4℃。三个驱动变量各取2种不同的水平意味着8种不同的驱动变量组合方案,对每一方案,将模型运行至平衡(或稳态)。模拟结果说明:样带自然植被生物量和生产力对温度上升和CO_2浓度加倍非常敏感。在当前CO_2浓度条件下,温度上升4℃导致的蒸散增加可使全样带自然植被的平均生物量和生产力分别下降32.1％和41.9％。相比之下,20％降水增量将导致样带自然植被平均生物量和生产力上升8.1％和13.4％。而在当前气候条件下,CO_2浓度加倍则可使全样带平均生物量和生产量分别上升12.2％和17.1％。由于CO_2浓度和降水增加的正向效应和温度增加的负向效应的相互抵消作用,CO_2 浓度加倍、气温上升4℃、降水增加20％的综合交互作用将使全样带生物量和生产力均?
A remote sensing driven dynamic simulation model was developed for terrestrial ecosystems . The model was encoded in C language under the environment of SPAMOD, a spatial simulation tool developed under MS Windows. The model was applied to Northeast China Transect to simulate the dynamics of green and non-green biomass of 12 vegetation categories as well as soil water of 3 layers. The green biomass was converted to normalized difference vegetation index (NDVI) of AVHRR remote sensing, and compared with the observed NDVI from 1986 to 1990. The model was also compared with ground measurements of biomass and productivity along the transect. Ambient CO2 concentration, monthly mean air temperature and monthly precipitation were regarded as the three basic driving variables for global change study. The model also included the effects of temperature and precipitation on sunshine fraction, relative humidity, radiation, soil water and eventually plant growth. For each CO2 and climatic scenario, the model was run for an equilibrium solution. The results indicated that the natural vegetation of the transect was very sensitive to variation of temperature and CO2 concentration. With CO2 remained unchanged and temperature increased by 4C , the induced increase in evapotranspiration could reduce the average biomass and net primary productivity (NPP) over the whole transect by 32.1% and 41.9% respectively. In contrast, a 20% increase in precipitation alone could lead to an increase of the average biomass and NPP by 8.1 % and 13.4% respectively. Under the present climatic conditions, CO2 doubling could increase the average biomass and NPP by 12.2% and 17.1% respectively. Because of compensation between the positive effects of CO2 and precipitation increase and the negative effect of temperature increase, a comprehensive interaction among CO2 doubling, a 20% increase of precipitation and a 4C increase of temperature altogether can lead to approximately a 2% reduction in the biomass and NPP of the natural vegetation over the whole transect.
基金
国家自然科学基金(No.39393004)
