内蒙古中部荒漠草原I_(NDV)时空变化及其对气候的响应特征

Temporal and spatial variation and responses of I_(NDV) to climatic variables in desert steppe of the middle Inner Mongolia

利用内蒙古中部荒漠草原区2011—2015年的I_(NDV)和降水等资料,分析了研究区I_(NDV)时空变化特征及I_(NDV)对降水和气温的响应特征.结果表明,研究区I_(NDV)在2012年达到5年中的最高水平,2013—2015年则呈下降趋势.从空间范围来看,研究区由西向东、由北向南表现出I_(NDV)逐渐增高的趋势.相对于气温因子,降水量对研究区I_(NDV)变化起到关键作用,降水量南多北少是研究区I_(NDV)南北差异的主要原因.南部地区利用地下水进行农田灌溉,加剧了I_(NDV)的空间差异.植被返青时期(5月初)的降水对全年I_(NDV)的提升至关重要,而7—9月降水量变化对I_(NDV)的影响明显减弱.除个别雨量充沛的年份以外,研究区北部在每年7—8月反而出现了年内I_(NDV)的较低值,这主要是由于冬季冰雪融水有助于植被返青,但春末及夏季少雨、高温的条件不利于植被发育甚至存活.研究区北部受人类影响较小的荒漠草原区I_(NDV)对降水量波动的敏感性强于研究区南部.

The I NDV spatial-temporal variation and its response to precipitation and air temperature are analyzed using the newest GIMMS I NDV 3g.v1 and meteorology data from 2011 to 2015 in the study area.The results show that the average I NDV values reached its maximum in 2012 and then decreased gradually over the next three years.The spatial variation characteristic of I NDV is in an increasing trend from north to south and from west to east in our study area.Compared to air temperature,the precipitation is the key factor that affected the I NDV fluctuation.The diminution of precipitation from south to north is the major reason leading to the I NDV variation,and the irrigation with pumping groundwater in the southern part has aggravated this variation.The precipitation in the period of grass regeneration(first half of May)can prominently affect the annual I NDV,but this influence of precipitation from July to September become weaker.The relatively high I NDV in regeneration period is mainly caused by the melt-water from winter and rainfall in spring.The low I NDV values in July and August in northern part of study area result from the high temperature and low precipitation compared with that in the southern part.The sensitivity of I NDV to precipitation is high in the north part of desert steppe,where human activities are relatively weak.