内蒙古植被春季返青期和秋季枯黄期的气候敏感性研究

Climate sensitivity of the start of the growing season in spring and the end of the growing season in autumn for vegetation in Inner Mongolia

春季返青期和秋季枯黄期是植被生长过程中两个重要的物候指标,其变化对气候,尤其对温度敏感性的大小及其差异十分不清楚。利用2001-2019年MODIS NDVI和气象数据,在气象台站和像元尺度上分别计算内蒙古植被春季返青期和秋季枯黄期,并以生长度日(GDD)和冷却度日(CDD)为影响返青期和枯黄期的温度指标,研究两个物候指标对气候敏感性的空间格局及其大小。结果表明,2001-2019年内蒙古植被返青期主要集中在第110~135 d,整体呈提前趋势(2.6 d·10 a^(-1));枯黄期主要集中在第260~280 d,整体呈微弱的推迟趋势(0.7 d·10a^(-1))。返青期对GDD和枯黄期对CDD的敏感性主要以负敏感性为主,分别占研究区总面积的68.1%和56%。从两个物候指标对降水的敏感性看,植被物候对降水敏感性主要以正敏感为主。气象台站尺度的研究结果总体与像元尺度的研究结果基本一致。在气象台站尺度上对比显示有65%的站点枯黄期对温度的敏感性大于返青期,94%的站点返青期对降水的敏感性大于枯黄期,在气候不断变化的条件下,敏感性的研究可促进生态系统可持续管理的能力,对物候模拟以及生态系统气候的评估具有重要参考价值。

The start of growing season(SOS)in spring and the end of growing season(EOS)in autumn are regarded as two important phenological indicators of vegetation growth.However,the sensitivity of these indicators to changes in climate,especially temperature,as well as their differences remain unclear.In this study,MODIS NDVI and meteorological data from 2001 to 2019 were used to calculate the SOS in spring and the EOS in autumn of vegetation in Inner Mongolia at meteorological station-and pixel-scales.In these analyses,the numbers of growing degree-days(GDD)and cooling degree-days(CDD;i.e.DD with mean temperature below the base temperature)were used as temperature indicators that affect the SOS and EOS.These analyses revealed spatial patterns of SOS and EOS and their sensitivity to climate change.It was found that,from 2001 to 2019,the SOS for vegetation in Inner Mongolia usually occurred around d 110-135(where Jan 1st=d 1),and was progressively earlier with time(2.6 d·10 a^(-1)).The EOS usually occurred around d 260-280,and showed a weak trend towards later occurrence(0.7 d·10 a^(-1)).In 68.1%of the study area the SOS was advanced by GDD accumulation in the period immediately prior and similarly in 56%of the study area EOS was advanced by CDD accumulation in the period immediately prior.Both SOS and EOS were sensitive to precipitation,and the response was mainly positive(i.e.a delay of SOS or EOS).The results at the meteorological station-scale were basically consistent with those at the pixel-scale.At the meteorological station-scale,the temperature sensitivity of 65%stations was greater at the EOS than at the SOS,and the precipitation sensitivity of 94%stations was greater at the SOS than at the EOS.In the context of climate change,the results of studies on sensitivity are useful for devising sustainable ecosystem management strategies,and have important reference value for phenological simulations and ecosystem climate assessments.