近50年黄河源区植被净初级生产力变化特征及其影响因素

Change Feature of Net Primary Productivity of Natural Vegetation and Its Impact Factor in the Source Region of Yellow River in Recent 50 Years

利用1959—2008年黄河源区月平均气温、最高气温、最低气温、相对湿度、降水量、风速和日照百分率等气候要素资料,应用修订的Thornthwaite Memorial模型计算了近50年植被净初级生产力(net primary productivity,NPP),分析其年际和年代际变化特征及其主要气象因子的影响。结果表明,1959—2008年黄河源区年降水量呈增加趋势,其线性拟合倾向率为5.316～11.318mm.(10a)-1,春、夏季增幅较大;年平均气温呈显著上升趋势,其线性拟合倾向率在0.273～0.322℃.(10a)-1之间,增温率以冬季最大;最大蒸散呈增加趋势,年最大蒸散的线性拟合倾向率为5.286～8.026mm.(10a)-1,夏季增幅最大;地表湿润指数也呈增加趋势,年地表湿润指数的线性拟合倾向率为0.011～0.026(10a)-1,冬季增幅最大,在15年时间频率附近出现了5个干湿交替期,20世纪90年代以后为偏湿期,在中高频区,1998—2004年有偏干振荡;近50年年NPP变化呈显著上升趋势,NPP变化的线性拟合倾向率在95.502～190.72kg.hm-2.(10a)-1之间,20世纪80～90年代NPP较高。影响黄河源区NPP变化的主要气候因子是降水量、最大蒸散量和平均最低气温。

Climatic observation data of monthly average temperature,maximum temperature,minimum temperature,relative humidity,precipitation,wind speed and sunshine duration in the source region of Yellow River during 1959-2008,the net primary productivity（NPP） was computed by revised Thornthwaite Memorial Model.The annual and interannual changes of NPP were analyzed and the impact climatic factors of NPP are discussed.The main results are as follows： In 1959-2008,the annual precipitation in this region has a increasing trend and the linear fitting ratio of annual precipitation change was 5.316~11.318 mm·（10 a）-1.The precipitation obviously increased during spring and summer in this areas.The annual temperature shows a ascending trend too.The linear fitting ratio of annual temperature change is 0.273~0.322 ℃·（10 a）-1 and the ratio significantly increased in winter.The annual maximum evapotranspiration（ET0） displayed a ascending trend too,with a linear fitting ratio from 5.286 to 8.026 mm·（10 a）-1 and the rate of increasing obviously appeared in summer.The surface humid index displayed a ascending trend as well as precipitation,but the linear fitting ratio is 0.011~0.026（10 a）-1 and the surface mositure index quickly increased in winter.There are five periods of dry and wet alternations in recent 50 years.Before 1990s,it was a light wet stage,but the light dry stages appeared about high frequency from 1998 to 2004.The annual NPP in this region had a increasing trend.The linear fitting ratio of annual NPP is 95.502~190.72 kg·hm-2·（10 a）-1.The major climatic impact factors of the NPP are the precipitation,maximum evapotranspiration and average minimum temperature in the regions.