50年长江源区域植被净初级生产力及其影响因素变化特征

基于长江源区1959—2008年月平均气温、最高气温、最低气温、相对湿度、降水量、风速和日照时数等气候要素资料,应用修订的Thornthwaite Memorial模型计算了50年植被净初级生产力,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年间,研究区年降水量呈增加趋势,降水量变化曲线线性拟合倾向率每10年为5.685~13.047 mm,春夏季增幅较大;年平均气温呈极显著上升趋势,气温变化曲线线性拟合倾向率每10年在0.240~0.248℃之间,增温率以秋冬季最大;最大蒸散呈增加趋势,年最大蒸散变化曲线线性拟合倾向率每10年在5.073~5.366 mm,春季增幅最大;地表湿润指数也呈增加趋势,年地表湿润指数变化曲线线性拟合倾向率每10年为0.013~0.020,冬季增幅最大,在10年周期时间频率附近,出现了6~8个干湿交替期,20世纪90年代之后为偏湿期,在低频区,1998—2005年有偏干振荡;近50年年NPP变化呈显著上升趋势,NPP变化曲线线性拟合倾向率每10年在97.901~197.01 kg.hm-2之间,2001—2008年NPP较高。影响长江源区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。

Change feature of net primary productivity of natural vegetation and its impact factors over the source region of the Yangtze River in recent 50 years

Based on climatic observational data of monthly average temperature,maximum temperature,minimum temperature,relative humidity,precipitation,wind speed and sunshine duration in the source region of the Yangtze River in 1959-2008,the net primary productivity（NPP） of natural vegetation was computed by using revised Thornthwaite Memorial Model.The inter-annual change and the seasonal difference of NPP were analyzed,and the impact climatic factors for the change trend of NPP were discussed.The main results were as follows： In the period of 1959-2008,the annual precipitation in this region had an increasing trend,with a linear fitting rate of the annual precipitation change curves being 5.685~13.047 mm？（10a）-1,higher increasing rate appeared in spring and summer;while the annual temperature as well displayed an ascending trend,with a linear fitting rate of the annual temperature change curves being 0.240~0.248 ℃？（10 a）-1,higner ascending rate appeared in autumn and winter;likewise,the annual maximum evapotranspiration（ET0） displayed an ascending trend,with a linear fitting rate of the annual ET0 change curves being 5.073~5.366 mm？（10a）-1,the rate of increasing appeared higher in spring;the surface humid index too displayed an ascending trend,with a linear fitting rate of the surface humid index change curves being 0.013~0.020（10 a）-1,the rate of increasing appeared higher in winter.6~8 climatic periods of Dry-wet alternation happened in 10a period of Temporal frequency,which were the light wet stages since 1990s,while the light dry stages appeared in 1998-2005 at a low frequency.The annual NPP in this region had a significant increasing trend,with a linear fitting rate of the annual NPP change curves being 97.901~197.01 kg·hm-2·（10 a）-1,the NPP appeared in 2001-2008.The main factors which influence the NPP were precipitation,the maximum evapotranspiration and the average minimum temperature.