长江流域植被净初级生产力对未来气候变化的响应

研究基于气象观测和B2气候变化情景数据,利用大气-植被相互作用模型(AVIM2)模拟了1981—2000年和2010—2050年两个时段内植被NPP的空间分布格局及其时间变化趋势并分析了其时空变化与气温和降水量的关系。研究表明1981—2000年流域内植被NPP的空间分布大致呈现自西向东、自北向南递增的趋势。未来长江流域气温将整体增加,但各地增温幅度不同。流域降水量有增有减,主要增加区域位于长江源头和上游及中游的江北地区。未来在气温增加幅度较小而降水量增加的区域,如长江源头和上游的青海、西藏、川西及云南的部分地区的植被NPP将增加。在气温增幅较大而降水量减少或者降水量增加不多的区域如长江中游和下游的广大地区植被NPP将减少。从植被类型来看,长江流域大部分森林、郁闭灌丛和农作物的NPP在B2气候变化情景下将减少,每年减少量分别在0~4.5 gC.m-2、0~2 gC.m-2和0~2.5 gC.m-2之间。高寒草甸、草地和稀疏灌丛的NPP将增加,每年增长量介于0~2 gC.m-2之间。

The Impacts of Climate Change on Vegetation Net Primary Productivity of the Yangtze River Basin

The Yangtze River Basin covering the eastern, middle and western economic zones of China contains total 19 provinces, municipalities and autonomous regions. It is the most densely populated and highly developed social and economic region. The total area of the Yangtze River Basin is 1808500 km², accounting for 18.8% of China’s total land area. The future climate change will bring a series of complex impacts on the vegetation of the river basin. Whether these impacts are positive or negative is unknown by now. Vegetation in the Yangtze River Basin has the important function in water and soil conservation, and river runoff adjustment. It is the barrier for maintaining the ecological balance of the entire Yangtze River Basin. Therefore, exploring the response of vegetation in the Yangtze River Basin to the climate change in the future is of great importance. The best indicator for measuring the response of vegetation to climate change is net primary productivity (NPP). Based on the meteorological data during 1981 to 2000 and the B2 scenario of Special Report on Emissions Scenarios (SRES) data during 2010 to 2050, the vegetation NPP in the Yangtze River Basin was predicted by the atmosphere-vegetation interaction model (AVIM2). The relationships between the vegetation NPP and the climate change were analyzed. The results indicate that the spatial pattern of vegetation NPP averaged over 1981 to 2000 shows the increasing trend both from west to east and from north to south. Under B2 climate scenario, the study area will experience an overall increase in temperature, but the increasing rates are various in different areas. The future precipitation change shows regional differences. The areas with increasing precipitation are mainly located in the source region of Yangtze River, upper and northern part of the middle reaches. In the future, vegetation NPP will increase in the source and upper reaches of the Yangtze River which include the most part of Qinghai, Tibet, western Sichuan and Yunnan provinces. These areas will experience precipitation increase and smooth temperature rise. Vegetation NPP will decrease in areas with higher temperature rise and precipitation decrease. These areas scattered in the broad area of the middle and lower reaches of the Yangtze River. In terms of vegetation NPP, NPP for most of the forests, closed shrubs and crops will decrease by 0-4.5 gC·m^-2, 0-2 gC·m^{- 2} and 0-2.5 gC·m^-2, respectively. Vegetation NPP for meadows, grasslands and open shrubs will increase by 0-2 gC· m^-2. In summary, the future B2 climate change scenario will bring a positive effect on the meadows, grasslands and open shrubs and will bring a negative effect on forests, closed shrubs and crops in the Yangtze River Basin.