新疆地区植被对多时间尺度干旱的响应研究

Different Time-scale Responses of Vegetation to the SPEI Drought Index in Xinjiang

新疆是中国干旱区的主体,区域内生态承载能力和植被覆盖率较低,受干旱影响突出。以标准化降水蒸散指数(Standard Precipitation Evapotranspiration Index,SPEI)表征干旱状况,以归一化植被指数(Normalized Difference Vegetation Index,NDVI)表征植被状况,系统研究了1982—2015年新疆不同气候区、不同土地利用类型下,植被对多时间尺度干旱事件的响应及其时滞效应。结果表明:(1)新疆NDVI表现出北疆大于南疆、山区大于平原的总体分布特征。NDVI高值区集中在天山南北坡、阿尔泰山山脉,低值区分布于塔里木盆地边缘及昆仑山脉北缘,NDVI值普遍低于0.20。(2)北疆西部、西北部山区,NDVI主要表现出与较长时滞(12~24个月)SPEI的高相关性(R_(max)>0.6),而南疆植被NDVI普遍与短时滞(1~6个月)SPEI呈较小相关性(R_(max)<0.4);(3)不同植被类型对干旱的敏感性存在差异。林地与长时间尺度(SPEI时间尺度中位数为11)SPEI相关性较大(相关系数中位数为0.49);农作物对干旱的敏感性最低,但在人为活动干扰下其时滞尺度的离散程度最大。(4)对于不同气候区,半干旱气候区内植被对较长时期的干旱具有最高的敏感性;湿润区NDVI与SPEI相关性最小,极端干旱区干旱对植被影响的时滞性最短(SPEI时间尺度中位数为5)。

As the main body of arid zone in China,the coverage fraction and carrying capacity of vegetation are low in Xinjiang,which are prominently affected by drought.Based on the Normalized Difference Vegetation Index(NDVI)which represents the growth condition of vegetation and Standard Precipitation Evapotranspiration Index(SPEI)data from 1982 to 2015 in Xinjiang,multi time-scale responses of vegetation changes relative to meteorological drought in different regions and vegetation types were comprehensive examined.The results indicated that:(1)The distribution of NDVI in Xinjiang was largely showed that NDVI of northern Xinjiang was larger than that of the southern Xinjiang,and NDVI of the mountains was larger than that of the plains.Higher NDVI areas were concentrated on the north and south slopes of the Tianshan Mountains and the Altay Mountains,while lower NDVI areas were located on the edge of the Tarim Basin and the northern edge of the Kunlun Mountains.(2)In the western and northwestern mountainous regions of the Northern Xinjiang,NDVI mainly showed higher correlation(R_(max)>0.6)with longer lag time SPEI(12-24 months),while NDVI in most of the vegetation areas of southern Xinjiang showed lower correlation(R_(max)<0.4)with shorter lag time SPEI(1-6months).(3)There were differences in the sensitivity of different vegetation types to drought.Forests were more correlated with long time scale SPEI(The median of timescales of SPEI is 11).Crops were the least sensitive to drought,but had the greatest dispersion of time lag scales under anthropogenic disturbances.(4)For different climatic zones,vegetation in semi-arid climatic zones had the highest sensitivity to longer periods of drought.NDVI was the least correlated with SPEI in humid areas,while the time lag of drought effects on vegetation was the shortest(The median of timescales of SPEI is 5)in extreme drought areas.