植被物候是生态系统对气候变化反馈的重要感应器,研究青藏高原高寒草地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。本研究选取2001 -2015年MODIS植被指数(vegetation index, VI)16 d最大值合成产品MOD13A1,以TIMESAT 3.2平台为基础,采用阈值法提取青藏高原高寒草地植被物候期,包括返青期(start of growth season, SOG)、枯黄期(end of growth season, EOG)和生长季长度(length of growth season, LOG),分析青藏高原高寒草地2001-2015年植被物候时空变化及其驱动力。结果表明,1)随着水热条件的差异,青藏高原由东南向西北,返青期逐渐推迟,从儒略日第110天推迟到第170天;枯黄期逐渐提前,从儒略日第300天提前到第260天;生长季长度逐渐缩短,由170 d逐渐缩短为100 d。不同草地类型的物候期表现出明显的差异。2)青藏高原高寒草地植被物候年际变化中返青期呈提前趋势,枯黄期也呈提前趋势,整体上,生长季长度呈增长趋势。 3)海拔是影响青藏高原高寒草地类型物候空间分布异质性的主要因素。在3 500 m以下,植被物候随海拔变化的波动较大,没有明显的规律;在3 500-5 000 m,物候与海拔的关系密切,随着海拔升高,不同草地类型的返青期逐渐推迟,枯黄期逐渐提前,生长期长度也逐渐缩短。
英文摘要:
Vegetation phenology is an important sensor for ecosystem feedbacks on climate change. The study of phenological changes of alpine grassland vegetation on the Tibetan Plateau is of great scientific significance, to reveal the response mechanisms of alpine ecosystems to global climate change. In this study, we selected the 16-day maximum synthetic product MOD13A1 of the MODIS Vegetation Index (VI) from 2001 to 2015. Based on the TIMESAT 3.2 platform, the threshold method was used to extract the vegetation phenological period of the alpine grassland on the Tibetan Plateau, including the start of growth season (SOG), end of growth season (EOG), and length of growth season (LOG). We analyzed the temporal and spatial variations of the vegetation phenology and its driving forces in an alpine grassland of the Tibetan Plateau from 2001 to 2015. The conclusions are summarized as follows: 1) From southeast to northwest, with the deterioration of water and heat conditions and the uplift of topography, the SOG became gradually more delayed, from the 110 days to 170 days. The EOG became gradually more advanced, from the 300 days to 260 days. Finally, the LOG became gradually shorter, from the 300 days to 260 days. However, major differences were noted for the different grassland types. 2) The interannual variation of alpine grasslands showed a tendency for the SOG and EOG to advance, but the LOG increased on the Tibetan Plateau. 3) Altitude is the main factor that affects the phenological heterogeneity of the different grassland types on the Qinghai-Tibet Plateau. Phenology is closely related to altitude between 3 500 m and 5 000 m. With increasing elevation, the SOG of different grassland types became gradually more delayed, the EOG became gradually more advanced, and the LOG became gradually shorter. However, below 3 500 m, the alpine grassland phenology fluctuated greatly with elevation, with no obvious regularity.