哈萨克斯坦东部西伯利亚落叶松冠层与茎干干旱韧性的影响因素

Factors influencing drought resilience in the canopy and stem of Larix sibirica in eastern Kazakhstan

摘要

【目的】比较西伯利亚落叶松冠层与茎干的干旱适应能力，量化其韧性指标并分析主要影响因素。【方法】在哈萨克斯坦东部斋桑区 2 个不同海拔区域采集树轮宽度样本，建立年表并分析树木径向生长与气候的关系；结合生长和气候异常识别干旱事件，分别计算树轮宽度指数和归一化植被指数的 3 类韧性指标：抵抗力、恢复力和恢复弹力，并利用广义线性模型方法分析冠层韧性与地形、土壤及冠层结构的关系，探究环境因素如何塑造森林的干旱韧性。【结果】（1）高温和干旱是限制生长的主要因素，树轮宽度指数随干旱加剧而整体下降，生长同步性也有所增强。在湿润条件下树木径向生长整体高于平均水平，并且相较于干旱条件，个体间的生长差异明显增大。（2）干旱显著影响了树木的韧性，随着干旱强度增加，西伯利亚落叶松茎干表现出的抵抗力、恢复力和恢复弹力整体减弱。（3）海拔是影响茎干韧性的重要环境梯度，高海拔树木在较凉爽环境的缓冲下，干旱期间的抵抗力较高，并且干旱后恢复力和恢复弹力的表现都高于低海拔树木。土壤容重、冠层高度和海拔分别是冠层抵抗力、恢复力和恢复弹力的主要影响因素。更高的土壤容重削弱了冠层对干旱的抵抗力，但增强了部分区域的恢复力；高大的树木抵抗力较高，但恢复速度较慢；海拔可以解释 55.45% 的恢复弹力变化，随着海拔的升高，恢复弹力迅速提高，当海拔超过 2 044 m 时，冠层能够得到完全恢复；而热量的增加不利于干旱期间维持生长，但有利于干旱后恢复。树木茎干对干旱的敏感性高于冠层，两者韧性差异明显。【结论】树木对干旱的响应受环境条件显著影响，地形、土壤和林分结构在很大程度上塑造了森林韧性。长期冠层观测可有效监测植被生长状态。气候变化的背景下，未来干旱事件的发生频率和强度都可能有所增加，低海拔树木的韧性较低提示未来干旱可能导致森林衰退及物种组成变化的风险。

Abstract

[Objective] To compare the drought adaptive capacity of the canopy and stem of Larix sibirica, to quantify their resilience indices, and to analyze the main driving factors influencing their drought resilience. [Method] Tree-ring width samples were collected from two elevation zones in Zaysan District, East Kazakhstan Region, to develop chronologies and to analyze the relationships between radial growth and climate. Drought events were identified by combining growth anomalies with climatic anomalies. Three drought resilience components: resistance, recovery, and resilience, were calculated separately for the tree-ring width index and the Normalized Difference Vegetation Index. Generalized linear models were then used to examine the relationships of canopy resilience with topography, soil properties, and canopy structure, in order to explore how environmental factors shape forest drought resilience. [Result] (1) High temperature and drought were the main factors limiting growth. The tree-ring width index declined overall with increasing drought intensity, and growth synchrony also increased. Under wet conditions, radial growth remained above the mean level, and inter-individual variability in growth was markedly greater compared to drought conditions. (2) Drought significantly affected tree resilience. As drought intensity increased, the resistance, recovery, and resilience of the stems of Larix sibirica all declined overall. (3) Elevation was an important environmental gradient influencing stem resilience. Buffered by cooler conditions, high-elevation trees showed higher resistance during drought and greater recovery and resilience after drought than low-elevation trees. Soil bulk density, canopy height, and elevation were the major factors influencing canopy resistance, recovery, and resilience, respectively. Higher soil bulk density weakened canopy resistance to drought but enhanced recovery in some areas. Taller trees showed higher resistance but recovered more slowly after drought. Elevation explained 55.45% of the variation in canopy resilience; resilience increased rapidly with elevation, and when elevation exceeded 2 044 m, the canopy was able to recover fully. Greater heat accumulation was unfavorable for maintaining growth during drought but beneficial for post-drought recovery. Stems were more sensitive to drought than canopies, resulting in pronounced differences in resilience between the two. [Conclusion] Tree responses to drought were significantly influenced by environmental conditions, with forest resilience being largely shaped by topography, soil properties, and stand structure. Long-term canopy observations can effectively track vegetation growth status. Under climate change, both the frequency and intensity of future drought events are likely to increase, and the lower resilience of low-elevation trees suggests that future droughts may pose risks of forest decline and shifts in species composition.

关键词

韧性 / 树木年轮 / NDVI / 干旱 / 西伯利亚落叶松

Key words

resilience / tree ring / NDVI / drought / Larix sibirica

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基金资助

新疆维吾尔自治区青年拔尖人才项目(2023TSYCCX0076)

重点实验室建设-新疆维吾尔自治区重点实验室开放课题(2025D04018)

中国气象科学研究院科技发展基金项目(2021KJ034)

新疆维吾尔自治区天山创新团队项目(2025D14004)