Determining the mechanisms controlling the changes of wet and dry conditions will improve our understanding of climate change over the past hundred years, which is of great significance to the study of climate and environmental changes in the arid regions of Central Asia. Forest trees are ecologically significant in the local environment, and therefore the tree ring analysis can provide a clear record of regional historical climate. This study analyzed the correlation between the tree ring width chronology of Juniperus turkestanica Komarov and the standardized precipitation evapotranspiration index (SPEI) in Northwest Tajikistan, based on 56 tree ring samples collected from Shahristan in the Pamir region. Climate data including precipitation, temperature and the SPEI were downloaded from the Climate Research Unit (CRU) TS 4.00. The COFECHA program was used for cross-dating, and the ARSTAN program was used to remove the growth trend of the tree itself and the influence of non-climatic factors on the growth of the trees. A significant correlation was found between the radial growth of J. turkestanica trees and the monthly mean SPEI of February–April. The monthly mean SPEI sequence of February–April during the period of 1895–2016 was reconstructed, and the reconstruction equation explained 42.5% of the variance. During the past 122 a (1895–2016), the study area has experienced three wetter periods (precipitation above average): 1901–1919, 1945–1983 and 1995–2010, and four drier periods (precipitation below average): 1895–1900, 1920–1944, 1984–1994 and 2011–2016. The spatial correlation analysis revealed that the monthly mean SPEI reconstruction sequence of February–April could be used to characterize the large-scale dry-wet variations in Northwest Tajikistan during the period of 1895–2016. This study could provide comparative data for validating the projections of climate models and scientific basis for managing water resources in Tajikistan in the context of climate change.

中文翻译：

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自公元 1895 年以来塔吉克斯坦西北部基于树木年轮的干旱变化

确定干湿条件变化的调控机制，将增进我们对近百年来气候变化的认识，对研究中亚干旱地区气候与环境变化具有重要意义。林木在当地环境中具有重要的生态意义，因此年轮分析可以提供区域历史气候的清晰记录。本研究基于从帕米尔地区沙赫里斯坦采集的 56 个年轮样本，分析了杜松树年轮宽度年表与塔吉克斯坦西北部标准化降水蒸散指数 (SPEI) 之间的相关性。包括降水、温度和 SPEI 在内的气候数据是从气候研究单位 (CRU) TS 4.00 下载的。使用COFECHA程序进行交叉测年，使用ARSTAN程序去除树木本身的生长趋势和非气候因素对树木生长的影响。发现 J. turkestanica 树的径向生长与 2 月至 4 月的月平均 SPEI 之间存在显着相关性。重建了1895-2016年2-4月的月平均SPEI序列，重建方程解释了42.5%的方差。在过去的 122 a（1895-2016）中，研究区经历了三个湿润期（降水量高于平均水平）：1901-1919、1945-1983 和 1995-2010，以及四个干燥期（降水量低于平均水平）：1895-1900 , 1920–1944, 1984–1994 和 2011–2016。空间相关性分析表明，2-4月的月平均SPEI重建序列可用于表征1895-2016年塔吉克斯坦西北部大尺度干湿变化。该研究可为验证气候模型的预测和塔吉克斯坦在气候变化背景下管理水资源的科学基础提供比较数据。