滇西北白马雪山高山松(Pinus densata)径向生长对气候因子的响应

Radial growth response of Pinus densata to climate factors in the Baima Snow Mountain,Northwest Yunnan

滇西北是我国西南地区气候变化最为显著的地区之一,过去几十年来气候呈现快速变暖趋势。高山松(Pinus densata)是该地区主要的针叶树种,研究高山松径向生长对气候因子的响应,有助于深入认识该地区亚高山针叶林对气候变化的适应能力。在滇西北白马雪山1 hm^(2)永久性样地内采集了161棵高山松树木样芯(322个),运用传统树木年轮学原理及方法,建立高山松年轮宽度差值年表,分析年表与样地附近气象站1957—2020年气候因子的相关性。结果表明:1)高山松的径向生长与冬季及春季(前一年11月至当年4月)温度呈正相关关系,与当年5月份最高温度和平均温度呈负相关;2)高山松径向生长与当年4—6月降水量显著正相关,与5月相对湿度呈正相关,与5—8月标准化降水蒸散指数(SPEI6)呈正相关;3)滑动相关分析表明,白马雪山高山松径向生长-气候关系不稳定,冬季温度对高山松生长的限制作用在减弱,说明冬季低温限制在一定程度上解除;而夏秋季温度对高山松径向生长的相关性由弱的负相关转为近年来的显著正相关;对夏季相对湿度和标准化降水蒸散指数的敏感性降低。研究结果可为探讨气候变化下高山松自然林的生长动态提供参考。

Northwest Yunnan is one of regions undergoing significant climate change in southwestern China and has experienced fast warming in the past decades.Pinus densata is a coniferous species that mainly dominates the south-facing slopes in this region.Studying the response of radial growth of P.densata to climate factors is of importance for understanding the adaptation of subalpine coniferous forests to climate change.A total number of 322 cores from 161 trees were collected in one hectare permanent forest plot in the Baima Snow Mountain.Tree ring-width residual chronology was developed by using standard dendrochronology techniques.To determine the key climate factors limiting the radial growth of P.densata,correlation coefficients between ring-width chronology and monthly climate data were calculated during 1957-2020.The results showed that radial growth of P.densata was positively correlated with temperature in winter and spring from November of the previous year to April of the current year.Meanwhile,ring-width index also negatively correlated with the maximum and average temperature in May of the current year.The radial growth of P.densata was positively correlated with precipitation April-May,relative humidity in May,and standardized precipitation-evapotranspiration index(SPEI6)during May-August.Moving correlation analysis revealed an unstable responses of P.densata radial growth to climatic factors.The influences of winter temperature on the growth of P.densata were weakened during the past decades,which implied that to some extent P.densata growth might benefit from regional winter warming.The influence of summer and autumn temperatures on radial growth of P.densata shifted from weakly negative to significantly positive in recent years.Moreover,the sensitivity of the radial growth of P.densata to relative humidity and SPEI6 during summer months were diminished during recent decades.These results can provide a reference for studying the growth dynamics of subalpine pine natural forests under climate change.