天然林草对干旱事件的响应机制与韧性评价

干旱影响陆地生态系统结构与功能，威胁区域生态系统安全。天然植被对干旱响应机制认识的不足，以及植被对干旱的韧性量化评价方法的缺乏，限制了气候变化背景下生态系统管理措施的科学制定。本项目以京津冀地区干旱事件频发的滦河上游为研究区，以室内控制实验、野外原型观测实验、数值模拟、遥感与地理信息技术为关键支撑，通过长系列干旱事件与天然林草演变的历史重建，确定正常水分条件下植被长势参数基线；明确干旱时段内对植被长势产生明显影响的干旱等级，并针对一年生和多年生植被，揭示干旱后期对后一个物候期或物候循环周期植被总体长势的影响，剖析天然林草对干旱事件的响应机制；从干旱时段内抵抗力和干旱后期恢复力两个方面对典型类型天然林草对干旱事件的韧性进行量化测度，进而提出区域尺度植被对干旱事件韧性的综合评价方法，实现干旱干扰条件下植被韧性的空间区划。通过本项目研究，将为滦河流域干旱应对和水源涵养提供科学依据和方法支撑。

Drought affects the structure and function of terrestrial ecosystems and threatens the regional ecosystem security. Insufficient understanding of response mechanisms of natural vegetation to drought and the lack of quantitative evaluation method for assessing the vegetation resilience to drought, which limit the scientific formulation of ecosystem management measures under climate change. The project takes the upper reaches of Luanhe River basin as study area, which is frequently affected by drought events in the Beijing-Tianjin-Hebei region. The study will be carried out with key support of indoor control experiment, field prototype observation experiments, numerical simulation, remote sensing and geoinformatics. Through the historical reconstruction of long series of drought events and the evolution of natural forest and grassland, the baseline of vegetation growth parameters under normal water condition was identified. The drought grade that significantly affects vegetation growth during dry period was defined clearly. In addition, for annual and perennial vegetation, the impact of the later period of drought on the overall vegetation growth in the next phenological period or phenological cycle was revealed, and then response mechanism of natural forest and grassland to drought events was also analyzed. The quantitative measure of vegetation resilience to drought events was implemented from two aspects: the resistance in the drought period and resilience in the later period of drought. Finally, a comprehensive evaluation method of vegetation resilience to drought events on the regional scale would be proposed to realize the spatial division of vegetation resilience under the condition of drought interference. The research is expected to provide scientific basis and technical support for the drought response and water conservation in the Luanhe River basin.