Abstract：
Picea schrenkiana is the dominant tree species in Ili River Basin located in the western Tianshan Mountains of Xinjiang. We investigated the growth decline characteristics of P. schrenkiana at different altitudes (1800, 2300 and 2800 m) based on tree-ring index (TRI) and percentage growth change (GC), aiming to understand the growth response of P. schrenkiana to drought events at different altitudes and the impacts of altitude on tree growth decline in this region. The results showed that P. schrenkiana experienced multiple decline events at low-altitude (1800 m). TRI and GC identified inconsistent occurrence time of the decline events. The variations of TRI indicated that P. schrenkiana at low-altitude experienced two large-scale declines during 1927-1933 and 2017-2014, respectively. The variations of GC identified four decline events, including 1891-1893, 1924-1926, 1973-1975, and 2004-2009. The radial growth of P. schrenkiana across altitudes from low to high was significantly affected by the Palmer drought severity index (PDSI) of the previous growing season. The impact of current PDSI on P. schrenkiana during the growing season initially enhanced but later decreased with increasing altitude. In the extreme drought year 1917, the magnitude of growth decline increased with altitude. At low-altitude (1800 m), the TRI was 0.65, which was 35% lower than the normal level. At mid-altitude (2300 m) and high-altitude (2800 m), it was 0.56 and 0.54, respectively, being 40% lower than the average level. The drought event in 1917 had a 2-year legacy effect on the growth of P. schrenkiana at all the altitudes, with the TRI in 1920 recovered to exceeding 0.9, being close to the normal level. The impact of altitude on drought-induced forest decline was significant. Tree growth in low-altitude areas was more vulnerable to drought events due to the relatively poorer water and temperature conditions at low-altitude, which could lead to multiple large-scale decline events. In mid- and high-altitude areas, where hydrothermal conditions were more favorable, trees could experience even more severe decline during extreme droughts.
本文以新疆天山西部伊犁河流域优势树种雪岭云杉为对象,采用树轮指数(TRI)和生长变化百分率(GC)的方法研究不同海拔(1800、2300和2800 m)雪岭云杉的衰退特征,分析不同海拔雪岭云杉生长对干旱事件的响应差异,揭示该地区海拔对树木生长衰退的影响。结果表明: 低海拔(1800 m)雪岭云杉呈现多次衰退,但树轮指数法和生长变化百分率法判定的衰退时间存在差异。树轮指数表明,低海拔雪岭云杉在1927—1933、2007—2014年期间出现了2次的持续大规模衰退;生长变化百分率表明,低海拔雪岭云杉在1891—1893、1924—1926、1973—1975、2004—2009年期间出现了4次生长衰退。上一年生长季帕尔默干旱指数(PDSI)显著影响不同海拔雪岭云杉径向生长。随着海拔上升,当年生长季PDSI对雪岭云杉径向生长的作用呈现先显著增强再减弱的趋势。在极端干旱年份(1917年),雪岭云杉生长衰退程度随海拔增加呈现增强趋势,低海拔处(1800 m)树轮指数为0.65,比平均水平低35%,而中(2300 m)、高(2800 m)海拔则分别为0.56和0.54,显著低于平均水平40%。1917年的干旱事件对不同海拔雪岭云杉生长均存在2年的遗产效应,1920年树轮指数达到0.9以上,接近正常水平。海拔因素对干旱导致的森林衰退具有重要影响,分布在水热条件相对较差的低海拔处的树木生长更易受到干旱事件的抑制作用,进而引发了次数多、规模大的衰退事件。但在面对极端干旱时,水热条件较好的中、高海拔处的树木也会出现更大程度的衰退事件。.
本文以新疆天山西部伊犁河流域优势树种雪岭云杉为对象,采用树轮指数(TRI)和生长变化百分率(GC)的方法研究不同海拔(1800、2300和2800 m)雪岭云杉的衰退特征,分析不同海拔雪岭云杉生长对干旱事件的响应差异,揭示该地区海拔对树木生长衰退的影响。结果表明: 低海拔(1800 m)雪岭云杉呈现多次衰退,但树轮指数法和生长变化百分率法判定的衰退时间存在差异。树轮指数表明,低海拔雪岭云杉在1927—1933、2007—2014年期间出现了2次的持续大规模衰退;生长变化百分率表明,低海拔雪岭云杉在1891—1893、1924—1926、1973—1975、2004—2009年期间出现了4次生长衰退。上一年生长季帕尔默干旱指数(PDSI)显著影响不同海拔雪岭云杉径向生长。随着海拔上升,当年生长季PDSI对雪岭云杉径向生长的作用呈现先显著增强再减弱的趋势。在极端干旱年份(1917年),雪岭云杉生长衰退程度随海拔增加呈现增强趋势,低海拔处(1800 m)树轮指数为0.65,比平均水平低35%,而中(2300 m)、高(2800 m)海拔则分别为0.56和0.54,显著低于平均水平40%。1917年的干旱事件对不同海拔雪岭云杉生长均存在2年的遗产效应,1920年树轮指数达到0.9以上,接近正常水平。海拔因素对干旱导致的森林衰退具有重要影响,分布在水热条件相对较差的低海拔处的树木生长更易受到干旱事件的抑制作用,进而引发了次数多、规模大的衰退事件。但在面对极端干旱时,水热条件较好的中、高海拔处的树木也会出现更大程度的衰退事件。.
摘要：
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