1982-2013年内蒙古地区植被物候对干旱变化的响应

气候变化引起的植被物候变化正在大幅度改变生态系统，研究植被物候对干旱的响应对保护内蒙古的生态系统具有重要意义。根据1：100万植被区划，把内蒙古划分为8个植被分区，利用多时间尺度气象标准化降水蒸散指数（SPEI）和NDVI3g时序数据所反演的物候指标，分析内蒙古植被物候的时空变化及其对干旱的响应规律。结果显示：1）在1982年至2013年间，内蒙古植被受到不同时间尺度下干旱的高度控制，尤其是时间尺度干旱的影响（SPEI-3）；2）对于整个研究区，生长季开始（SOS）呈提前趋势，生长季结束（EOS）呈延后趋势，生长季长度（LOS）呈延长趋势，像元比例分别为63.79%、59.77%和62.83%；3）内蒙古除荒漠植被类型地区外，同年春季和夏季初期干旱对SOS均具有延迟作用，同年秋季干旱对EOS均具有延迟作用 ；4） 不同植被类型对干旱强度指数的响应程度存在差异，响应程度集中在-10d/0.1-10d/0.1（例如，1d/0.1表示干旱强度指数每增大0.1，会导致物候指数延迟1 d，而-1d/0.1表示干旱强度指数每增大0.1，会导致物候指数提前1 d）。

Response of vegetation phenology to drought in Inner Mongolia from 1982 to 2013

Under warning climate, vegetation phenology changes dramatically, which significantly alter ecological process. The response of vegetation phenology to drought is a crucial issue to understand vegetation response to climate change. In this study, we analyzed the spatial and temporal pattern of the vegetation phenology response to drought. Vegetation phenology metrics were extracted from AVHRR NDVI3g time-series during 1982-2013. Drought was defined by multiple time-scale Standard Precipitation-Evaporation index (SPEI). Results showed that: 1) during1982-2013, vegetation phenology was highly controlled by drought on different time scales and by effects of seasonal drought (3 month time-scale SPEI) in particular; 2) the starting of the growing season (SOS) was earlier than before; the ending of the growing season (EOS) was delayed than before; the length of the growing season (LOS) was lengthening; the changing rate of SOS, EOS and LOS was respectively 63.79%, 59.77% and 62.83%; 3) except desert vegetation, spring and early summer drought of the same year all had the effect of inhibiting the SOS of other vegetation types regions, e.g., drought delays SOS, and the autumn drought of the same year all had the effect of inhibiting the EOS of other vegetation types regions; 4) there are differences in the responses of different vegetation types to the drought intensity index, the response levels are concentrated in -10d/0.1 -10d/0.1, e.g. 1d/0.1 indicates that each increase in the drought intensity index of 0.1 will cause a delay of 1 day in the phenology metrics, -1d/0.1 indicates that each increase in the drought intensity index of 0.1 will cause a advance of 1 day in the phenology metrics.