江河源区四十多年来干湿变化分析

江河源区的干湿变化关系到流域水源涵养功能和生态安全。利用Holdridge可能蒸散率(PER)对江河源区18个站点1961-2002年的气象资料进行了计算。结果表明,在时间序列上,PER始终处于波动变化中, 前19年的趋势线基本上高于后23年的趋势线,多数地区自20世纪80年代中期缓慢波动上升;在空间上体现为从东南向西北干燥度逐渐增加,干湿变化的幅度亦增加。根据江河源区PER大小、变化趋势及变幅,可将源区分为西北部、中部和东南部3组;在变化过程中,西北部和东南部干湿差异有缩小的趋势。根据Holdridge模型模拟、NPP 估算、AVHRR／NDVI计算和土地覆盖变化等相关研究可知,这种干湿变化还未对植被分布产生质的影响,但可以影响植被覆盖度和净第一性生产量。

Dry and wet climatic changes in recent decades in the source regions of Yangtze,Yellow and Lantcang Rivers

Dry and wet climatic changes in the source regions of Yangtze ,Yellow and Lantsang Rivers have great effect on function of conservation water and ecological security. Holdridge PER of 1961-2002 on 18 weather observations were calculated. Results show that PER fluctuates all the time. The trend line of the early 19 years is higher than that of the following 23 years. Most places have turned dry slightly since middle 1980 s. As for its spatial distribution,the aridity and the change range gets higher from southeast to northwest. Research area can be divided into 3 groups based on PER and its change range. The gap of aridity between southeast and northwest has narrowed during 42 years' change process. Based on the simulation by Holdridge model,the calculation of NPP and AVHRR/NDVI,along with the research of land use and cover change,this kind of change can affect the net primary productivity and vegetation coverage without much change in vegetation distribution.