全球变化背景下天山西部雪岭云杉径向生长和水分利用效率对气候要素的响应

Response of Tree-ring Growth and Intrinsic Water-use Efficiency to Climate Elements in the Western Tianshan Mountains under Global Change

全球气候变暖和大气CO_(2)浓度(Ca)急剧上升已成为不争的事实,并对森林生态系统有着深远的影响,全面理解森林生态系统对全球变化的响应至关重要。中亚干旱区特有树种雪岭云杉(Picea schrenkiana Fisch. et Mey)树轮稳定碳同位素(δ^(13)C)和水分利用效率(iWUE)对气候变暖和大气CO2浓度急剧上升的响应缺乏研究。本研究利用天山西部伊犁河流域的雪岭云杉树轮样本,使用树木年代学方法和树轮稳定碳同位素技术,建立树轮宽度年表、稳定碳同位素(δ^(13)C)以及内禀水分利用效率(iWUE)序列,分析了树轮δ13C和iWUE的长期变化特征,探讨了树轮δ13C和iWUE对气候的响应规律以及iWUE与树轮宽度的关系。结果表明,主要的气候因子并没有强烈地限制树木径向生长;夏季平均气温对树轮δ^(13)C分馏有重要影响,iWUE的长期变化受到全球Ca增加和升温趋势影响,但直接影响iWUE年际变化的主要因素是饱和水汽压亏缺(VPD)。全球升温和Ca增加导致了iWUE的持续升高,但并没有导致雪岭云杉树木径向生长的明显增加。

Global warming and the sharp rise in atmospheric CO_(2) concentration have become an indisputable fact and have a profound impact on forest ecosystem.A comprehensive understanding on the responses of forest ecosystem to global change is essential.The growth response of Schrenk spruce(Picea schrenkiana Fisch.et Mey),an endemic tree species in the Central Asian arid region,to the climate change and the rising in atmospheric CO_(2) concentration are lacking.In this study,the Schrenk spruce tree-ring samples from the Ili River Basin were used to establish the tree ring width chronology,stable carbon isotope(δ^(13)C)series and intrinsic water-use efficiency series(iwue).The long-term changes of the δ^(13)C and iWUE and their responses to climate change were analyzed.Meanwhile,the relationship between iWUE and the radial growth of trees was discussed.The results showed that the long-term changes of the iWUE were affected by atmospheric CO_(2) concentration(Ca)increase and warming trends,but the main factor that directly affected the inter-annual changes of iWUE was vapor pressure deficit(VPD).The increase of the iWUE had no direct effect on the radial growth of trees.Global warming and Ca increase led to a continuous increase in intrinsic water use efficiency series,but didn’t cause obvious increase on the radial growth of Schrenk spruce.