沁河流域蒸散时空分异对植被生长期动态的响应

Focusing on evapotranspiration observation, simulation and temporal-spatial variations, this project aims to study the response of evapotranspiration changes to vegetation growing season dynamics under globle change. The Qinhe Basin located in the warm temperate zone of North China is taken as the study area. Soil evaporation and vegetation transpiration are plan to be observed in-situ at the zonal deciduous broad-leaved forest. Then the inter-annual variations in evapotranspiration will be analyzed. Based on the multi-sources data from in-situ measurements, remote sensing and field investigation, the Lund-Potsdam-Jena model will be optimized using data-model assimilation technique, to improve the simulation of seasonal changes in evapotranspiration. And evapotranspiration will be validated using basin water balance equation as well. Moreover, the onset, offset and length of growing season will be identified according to several inversion algorithms based on remote sensing leaf area index series. Next, the temporal and spatial variations of evapotranspiration and growing season will be analyzed during the period 2001-2015. Furthermore, the contribution of growing season dynamics to changes in annual and seasonal evapotranspiration will be clarified. Based on the analysis, the response of changes in evapotranspiration and its components to vegetation growing season dynamics will be clarified. This project is valuable to better understand the interaction and feedback mechanisms between climate and vegetation, as well as the impact of global change on terrestrial ecosystem and its adaptation. It also provides scientific basis for ecosystem management and basin water resources plan.

本项目以蒸散观测、模拟和时空分异为主线，从全球变化下植被生长期动态的角度，研究蒸散时空分异对生长期动态的响应。以华北暖温带沁河中上游流域为研究区，通过在地带性落叶阔叶林开展土壤蒸发和植被蒸腾定位连续观测，明晰蒸散的年内变化规律。综合定位观测、植被遥感和野外调查等多源数据，利用数据-模型同化技术，改进优化LPJ植被动态模型以提高对蒸散季节变化的模拟能力，并利用流域水量平衡对结果进行检验。同时基于遥感叶面积指数时序资料，采用多种植被生长期反演算法，识别划分植被生长期起止点。基于此，系统深入地分析2001年以来研究区蒸散和植被生长期的时空变化特征，明确植被生长期动态在年和不同季节蒸散变化中的作用，揭示蒸散及其各分量变化对植被生长期动态的响应与区域差异。研究有助于深入理解气候和陆表系统的相互作用和反馈机制，以及全球变化对生态系统的影响与适应，并为生态系统管理和流域水资源规划等提供科学依据。

陆面蒸散是水循环和能量循环的重要环节，也是连接土壤-植被-大气系统的关键纽带，在全球变化背景下，蒸散对气候变化与植被动态的响应是当前研究前沿和热点问题之一。本项目针对陆面蒸散的时空分异特征及其对植被生长期动态的响应开展研究。重点研究利用植被遥感数据，结合沁河流域典型地带性落叶阔叶林生态系统野外调查及土壤水分与物候观测资料，识别过去30年来植被物候生长季时空变化特征及其对水热要素的响应，发现在增暖背景下沁河流域植被生长季呈显著增加延长趋势（7.62d/10yr，p<0.01）。通过研究遥感卫星GRACE数据与水量平衡模型方法，以及LPJ动态植被模型改进优化的蒸散模拟方法，揭示了研究区过去不同尺度蒸散变化趋势。利用蒸散和物候长时序变化，进一步分析了过去30年来蒸散变化过程对物候生长期动态的响应，发现总体上沁河流域实际蒸散的减少趋势主要受降水量变化的影响，特别是植被生长季起始日提前与结束日推后的蒸散增加效应受4月和10月同期降水量波动影响而减弱，揭示了沁河流域实际蒸散对气候和植被变化的复杂非线性响应特征。研究有助于深入理解气候和陆表系统的相互作用和反馈机制，以及全球变化对生态系统的影响与适应，并为生态系统管理和流域水资源规划等提供科学依据。项目执行过程共发表研究论文12篇，其中SCI收录论文9篇（第1标注5篇）。