树轮多指标记录的天山地区极端气候干旱事件及驱动机制和对树木生长的影响

The Tianshan mountains, which is located in the arid region, are vulnerable to extreme drought, and are more vulnerable to extreme droughts under climate warming in the future. Therefore, understanding the variability and mechanism of extreme drought events and its influences on the regional tree-growth are very urgent in arid areas, which will befit for regional ecological construction and implement of "One Road One belt" development strategy. However, there are a few studies on extreme drought events in Tianshan mountains. The influence of extreme drought on tree-growth is poorly understood. This study intends to adopt multi-proxies from tree rings (tree-ring width, density, and stable isotopes) combining with intra-annual stable carbon and oxygen isotopes and process models, to detect mechanism among extreme drought event and stable isotope records. Then, we will explore the long-term changes and mechanisms of the extreme drought events through the statistical method and meteorological methods. We will adopt the tree-ring width and stable carbon isotope indicating tree-growth and long-term intrinsic water-use-efficiency (iWUE) to detect the influences of extreme drought events on tree-growth and iWUE. This project will provide the scientific data for the study of regional climate change and decision data for the development of ecological civilization in the “One Road One Belt” development strategy.

位于干旱区的天山地区容易受到端气候干旱的影响，且在未来气候增暖背景下该区域更易于遭受极端气候干旱的威胁。因此，理解天山地区极端气候干旱事件变化规律及机制，明确极端气候干旱事件对于区域树木生长的影响机制显得十分迫切，对于区域生态文明建设和“一带一路”发展战略具有重要的意义。然而，目前对天山地区极端气候干旱事件的研究相对较少。本研究拟采用树轮多代用指标(宽度、密度和同位素）为手段，结合高分辨率树轮稳定碳氧同位素和树轮过程模型，进行极端干旱事件研究，明确树轮稳定氧同位素对极端气候干旱事件记录的机理；结合统计手段研究长时间尺度上极端干旱的发生，以树轮宽度和稳定碳同位素指示树木生长和长期水分利用变化，揭示天山地区过去极端气候干旱事件发生的规律及其驱动因子和机制，明确极端气候干旱事件对于树木生长和长期水分利用效率的影响。该研究为干旱区极端气候研究提供科学认知，也为“一路一带”生态文明建设提供决策数据。

项目利用树轮多指标（宽度、碳氧稳定同位素）结合高分辨率树轮稳定碳氧同位素理解区域极端干湿变化及其影响。项目利用高分辨率树轮稳定碳氧同位素理解极端干旱和湿润状况下，高分辨率树轮稳定碳氧同位素的变化特征，将实测结果和树轮同位素模型模拟结果进行比较，揭示其反映的树木生理响应的差异。基于此，揭示出树轮不同部分反映的气候信号和源水氧同位素信号的差异机理，并进行区域过去115年水分干旱和大气干旱变化的重建和比较研究。同时项目研究中还发现不同年龄树木碳氧同位素存在气候响应差异，将不同年龄树轮稳定碳氧同位素组合能够较好地揭示区域气候变化信号，进一步揭示区域极端干湿变化信号，不同年龄树木树轮稳定碳氧同位素组合能够有效地克服“气候分异”。以上研究将有助于理解碳氧稳定同位素记录区域极端干旱的机理，有助于评价极端干旱对树木生理变化的响应和影响。