青藏高原植被物候监测及其对气候变化的响应

Vegetation phenology dynamics and its response to climate change on the Tibetan Plateau

研究青藏高原植被物候变化对揭示高寒生态系统对全球气候变化的响应机制具有重要的科学意义。本文选取1982-2005年的GIMMS NDVI遥感数据,采用动态阈值法提取了青藏高原高寒草地的物候信息,包括植被返青期、枯黄期及生长季长度,分析了青藏高原高寒草地植被物候的时空变化及其对气候变化的响应规律。研究结果表明,1)青藏高原植被物候多年均值的空间分布与水热条件密切相关。青藏高原从东南向西北,植被返青期逐渐推迟、枯黄期逐渐提前,生长季长度因受到植被返青和枯黄的影响,呈现逐渐缩短的趋势;2)植被返青期和枯黄期的年际变化整体上呈提前的趋势,生长季长度呈增长趋势;3)高原地区的植被物候易受到海拔的影响,但存在3400m的分界线,在3400m以下,物候随海拔变化的波动较大,而在3400m以上,物候与海拔的关系密切;4)气象因子是不同草地类型植被物候变化的主要影响因素,与降水相比,植被物候期与温度相关程度更高。

We extracted vegetation phenology parameters(start,end and duration of the growing season)using GIMMS NDVI remote sensing data from 1982-2005 from the Tibetan Plateau and analyzed the spatial distribution and inter-annual variation of vegetation phenology in order to explore the mechanisms of the response of phenology to climate change.The spatial distribution of vegetation phenology was closely related to hydrothermal conditions on the Tibetan Plateau.Along a transect running from the southeast to the northwest,the start of the growing season was gradually delayed,the end of growth season advanced while the length of growing season reduced.The inter-annual variability of the start and the end of the growing season tended to increase while that of the growing season length decreased.Elevation plays an important role in the regional heterogeneity of phenology,but a boundary was identified at approximately 3400 maltitude.Below 3400 m phenology fluctuated irregularly with altitude whereas above 3400 mphenology was closely associated with altitude.Based on climate data from meteorological stations,the relationship between vegetation phenology and the key meteorological factors under the different grassland types were analyzed;the results show that temperature is more important to the change of vegetation phenology than precipitation on the Tibetan Plateau.