玛曲草原植被ＮＤＶＩ与气候和载畜量变化的关系分析

 利用玛曲草原１９８２－２００５ 年的气候和载畜量及ＮＡＳＳ／ＧＩＭＭＳ 半月合成归一化植被指数（ＮＤＶＩ）遥感数据，分析了ＮＤＶＩ与气候因素和载畜量的年际变化关系，以及植被ＮＤＶＩ对气温和降水的时滞响应。统计了４ 个时间尺度（１～４个月）×４个时滞期（前０～３个月）共１６种组合下，植被ＮＤＶＩ与同期和前期（前１～６个月）气温和降水之间的相关系数。结果表明，春夏季ＮＤＶＩ的年际变化呈显著增加，增幅为０．０１９／１０ａ和０．０２２／１０ａ。季节和年均气温及≥０℃年积温的年际变化呈显著增加，增幅为０．５～０．７℃、０．６℃和１２１．５℃；季节和年降水量的年际变化不显著；夏季气温变化稳定，春、秋季气温和４季降水的年际变化不稳定。春季～秋季和全年各月的ＮＤＶＩ与同期气温呈极显著正相关，相关系数（R）为０．７２～０．９５和０．８７；春季、秋季和冬季及全年各月的ＮＤＶＩ与降水呈极显著正或负相关，R 为０．８４，０．７７，－０．５２及０．８０；每年ＮＤＶＩ的月均值与同期＞０℃ 年积温和家畜数量呈显著正相关，犚为０．６６和０．４５。植被ＮＤＶＩ对当月和前２月降水的累积量（时间尺度为３个月）及对当月和前１月气温（时间尺度为２个月）的响应最强，时间尺度为１～３或１～２个月，时滞期为０个月的同期气温或时滞期为１个月的降水对生长季间ＮＤＶＩ的促进效应大；早期（４月）气温升高促进植物生长，而早期和后期（８－９月）的降水累加及后期高温抑制植物生长。

Study the change of NDVI and climate factors and carrying capacity and their correlation in Maqu County,Gansu

The paper reports on a study conducted in Maqu County located in eastern Tibet Plateau from 1982 to 2005.It was focused on the change of NDVI,climate factors and carrying capacity and their correlation,as well as the time lag effect between NDVI and temperature and precipitation.The correlation coefficients between NDVI and temperature and precipitation over the same period and the effect of including data from a prior period were analyzed under 16 combinations of temperature or precipitation(4 time durations by 4 time lags).The annucal changes of NDVI in spring and summer were significantly increased and their increasing range were 0.019/10 a and 0.022/10 a respectively.The annual change of seasonal and annual temperature as well as annual accumulated temperature above 0℃ were significantly increased over the study period and their increasing range were 0.5-0.7℃,0.6℃ and 121.5℃ respectively.The changes of seasonal and annual precipitation were not significantly different.The change of temperature in summer was steady but in spring and autumn it was variable.So too was the change of precipitation in four seasons.The correlation of monthly NDVI all the year round and the NDVI in spring and autumn in response to temperature at same period were significant positive or negative,and the value of correlation coefficient were 0.84,0.77,-0.52 and 0.80 respectively.The correlation of average monthly NDVI every year in response to annual accumulated temperature above 0℃ and carrying capacity were significant positive,and the value of correlation coefficient were 0.66 and 0.45 respectively.The correlation of NDVI in response to precipitation in the current month and accumulated precipitation in two months prior(time durations: three months) were highly significant,the temperature in the current month and one month prior(time durations: two months) was also highly significant.By taking lag times into account we found significantly high correlations with the NDVI increase during the growing seasons.The increase of temperature in early growth stage(April) promoted vegetation growth.Generally precipitation later in the year had negative effects especially rains late in the growth stage of forage plants(August to September) as did high temperature at this time.