青藏高原植被秋季物候变化及其对区域碳循环的影响机制研究

Vegetation phenology is one of the key source of information for mapping, managing, and monitoring the terrestrial ecosystem form local to global scales. Changes in vegetation phenology reflect the biosphere’s dynamic response to climate change. The Tibetan Plateau (TP) acts as environmental and ecological barrier for China. The ecosystems of TP are fragile and instable due to its unique geographical conditions. Thus TP is one of the most sensitive regions to climate change. Therefore, the dynamic changes of vegetation phenology on the TP and their response to climate change have become the focus in recent years. However, the spring phenology of TP has been widely discussed in previous studies, while the autumn phenology has not been well documented. This project will use different methods to retrieve autumn phenology of TP based on multi-source remote sensing data. Independent validation using in-situ observations will also be conducted, with the objective to derive improved algorithms for autumn phenology retrieve. Then we will systematically analyze the temporal and spatial variations of the autumn phenology on the TP and its influencing factors, and clarify the response mechanism and adaptation strategies of the autumn phenology to climate change. Furthermore, we will analyze the relationships between autumn phenology and vegetation productivity, and attempt to understand the phenological changes of the TP and its effects on the carbon cycle. This work is of great significance in protecting the environment of the TP and creating adaptation strategies for dealing with global climate changes.

植被物候是研究植被生态系统变化的关键参数之一，也是气候变化最直接、最敏感的指示器。青藏高原是我国重要的生态安全屏障，但由于独特的地理条件，使其生态环境十分脆弱，对气候变化极为敏感。因此，青藏高原植被物候的动态变化及其对气候变化的响应成为近年来研究者们关注的焦点问题。然而，目前的研究主要集中在春季物候期，关于秋季物候的研究较为缺乏。项目将基于多源遥感数据反演青藏高原植被的秋季物候期，并利用地面观测资料进行独立验证，对比不同方法的可靠性和差异性，获取高精度的秋季物候产品。在此基础上，系统分析青藏高原秋季物候的时空变化规律及其影响因素，阐明秋季物候期对气候变化的响应机制及适应对策；同时，详细探讨高原秋季物候变化对植被生产力年际变化的影响，全面理解青藏高原物候变化及其对生态系统碳循环的作用。从而为青藏高原长期生态环境保护和应对全球变化制定适应对策提供科学的依据。

植被物候是研究植被生态系统变化的关键参数之一，也是气候变化最直接、最敏感的指示器。青藏高原是我国重要的生态安全屏障，但由于独特的地理条件，使其生态环境十分脆弱，对气候变化极为敏感。因此，青藏高原植被物候的动态变化及其对气候变化的响应成为近年来研究者们关注的焦点问题。本项目基于遥感数据研究了青藏高原植被物候变化及其影响因素，取得了如下成果：1）利用长时间序列NDVI数据集，分别采用动态阈值法、逻辑斯蒂函数和双逻辑斯蒂函数法提取了青藏高原植被物候期，生成了长时间序列青藏高原植被物候产品；2）发现1982–2018年期间青藏高原植被生长开始期（SOS）与结束期（EOS）存在显著正相关关系，增温和降水也有利于推迟EOS，太阳辐射的作用范围最小，且以负为主，这些影响在很大程度上受到当地气候条件的调节，SOS对EOS的主导作用在高寒草原和高山稀疏植被明显，而温度对灌丛的作用更大；3）揭示了降水频率对青藏高原植被生长峰值的控制作用，发现在控制降水频率后，降水量对NDVImax的作用显著下降。相关研究成果对于深入了解青藏高原植被物候变化及其对气候变化的响应具有重要意义，可为青藏高原长期生态环境保护和应对全球变化制定适应对策提供科学依据。