青藏高原植被物候变化及其生物量响应机制研究

Global warming has been causing worldwide plant phenological transitions and has a significant impact on plant biomass. The Tibet Plateau located in the central part of the troposphere in the mid-latitude westerlies, is one of the most critical and sensitive regions in the earth ecosystem. Thus, the plateau's unique geographical conditions create a strong environmental gradient. The resulting spatial heterogeneity in terrain and meteorological conditions may lead to diverse phenological responses to warming cross the plateau, which are different from the global universal phenological variation. In this study, the long-term changes in the plant phenology over the Tibet Plateau were examined and plant biomass response mechanisms were studied by analyzing satellite-inversion plant phenology information and biomass information over the past three decades. Firstly, using phenological inversion models we identified proxy metrics for phenological transitions from the time series of normalized difference vegetation index (NDVI), leaf area index (LAI) and land surface temperature (LST).Secondly, using the Dynamic Land Ecosystem Model (DLEM), to improve the model's algorithm and calibrate parameters according to field measures, we calculate the inter-annual biomass for different vegetation types, and analyze the mechanisms of biomass response to phenological change under different eco-environmental background. Finally, we examine and simulate spatial patterns and temporal patterns of plant phenology and biomass over past the three decades, to identify how the productivity will respond to future phonological shifts resulting from ongoing climate change, and to analyze its impacts on the regional C/N cycle. Thus we can provide the scientific basis for the long-term eco-environmental protection and response measures for global change impacts on the Tibet Plateau.

全球气温变暖引起的植被物候响应会对其生物量产生重大影响。青藏高原作为全球变化的敏感区域，由于气候因子分布所独有的地带性和非地带性，植被物候随经纬度和海拔高度有推移性，表现出明显不确定性，有别于全球普遍物候变化规律。本项目通过对青藏高原主要植被类型开展包括物候、生物量以及气候监测，基于遥感技术研究该区域植被近30 年物候变化及其生物量的响应机制。具体为基于多平台对地观测数据，通过长时间序列、多平台遥感数据协同精准处理，反演过去30年时序植被物候信息并对比分析其变化的时空特征；而后应用DLEM模型并改进模型算法，估算近30年主要植被类型的年际生物量，分析不同植被类型、生态区划下植被生物量变化对物候变化的响应机制，阐明青藏高原植被物候近期演变的驱动机制，并对其进行数值模拟，预测植被物候的未来情景，分析其对区域C/N循环的影响。从而为青藏高原长期生态环境保护及应对全球变化制定适应对策提供科学依据。

全球气温变暖引起的植被物候响应会对其生物量产生重大影响。青藏高原作为全球变化的敏感区域，由于气候因子分布所独有的地带性和非地带性，植被物候随经纬度和海拔高度有推移性，表现出明显不确定性，有别于全球普遍物候变化规律。因此，本项目通过对青藏高原主要植被类型开展包括物候、生物量以及气候环境的监测，基于遥感技术研究了该区域植被近30 年物候变化及其生物量的响应机制，具体内容包括基于多平台对地观测数据，通过长时间序列、多平台遥感数据协同精准处理，反演过去30年时序植被物候信息并对比分析其变化的时空特征；估算近30年主要植被类型的年际生物量，分析不同植被类型、生态区划下植被生物量变化对物候变化的响应机制，阐明青藏高原植被物候近期演变的驱动机制，并对其进行数值模拟。研究结果表明，青藏高原大部分区域近30年植被物候表现为返青期提前，落叶期退后，植被的生长期延长，植被生产力也有显著增加。同时，在不同生态地理单元，植被生产力响应植被物候变化表现为不同的响应方式。其中，温度、降水在植被生产力对物候变化的多样性响应方面起了不同的作用。