不同生境中多树种生长对干旱胁迫的敏感性评价——以德国萨克森州为例

Assessment on the Growth Sensitivity to Drought Stress for Various Tree Species Growing at Diverse Habitats——A Case Study in Saxony,Germany

【目的】研究城市森林中的多个树种在多样化生境条件下对持续干旱的生长反应和敏感性,为快速筛选抗旱性强且能健康生长的适应性树种提供参考依据。【方法】通过测量不同生境(郁闭林、开敞林和行道树)中不同树龄(幼龄、低龄和成年)的17种树木在2005—2020年的各年年均枝长变化,计算其相对增长率(干旱年的年均枝长增长量与非干旱期相应值的比)(RAI)来评价树木枝条生长对干旱胁迫的敏感性。【结果】1)年均枝长随树龄增大而减小,郁闭林中幼龄树木和开敞林中低龄树木的年均枝长高于成年行道树。2)各树种的年均枝长与标准化降水指数呈显著性相关(r^(2)=0.687,P<0.01),郁闭林中的欧洲水青冈和夏栎,以及开敞林中的欧梣和夏栎的枝长生长对干旱不敏感,但各生境中有14种树木对干旱极为敏感。3)各树种的叶片膨压损失点水势的平均值与极小值呈显著相关(r^(2)=0.549,P<0.01),但与生长敏感性不相关。4)木质部结构与RAI(r=0.553,P<0.01)和生长敏感性(r=0.545,P<0.01)呈显著性相关,散孔材和半环孔材树种比环孔材树种对干旱更敏感。【结论】各树木的年均枝长受多种因子影响,年均枝长可推荐作为一种简便、快速、有效的评价树木生长活力的新方法,能反映不同树种对生境条件的敏感性和适应性,为城市林业和园林绿化相关部门筛选应对气候变化的抗逆性树种提供科学依据。

【Objective】This study aims to find the response and sensitivity of multiple tree species in urban forests to drought under diverse habitat conditions and provides a reference basis for rapid screening of adaptive tree species with high drought tolerance and healthy growth.【Method】The measurement of annual shoot lengths(ASL)of 24 tree species with different age(early-young,young,and mature)in diverse habitats(closed forest,open forest,and avenue tree)between 2005 and 2020 was conducted,and the calculation of the relative ASL increase(RAI,the ratio of the ASL increase between before and after drought to the non-drought period)was used to indicate trees’growth sensitivity in response to drought stress.【Result】1)Trees’ASL was decreasing consistently with age,and the early-young trees growing in the shaded forests and young trees in the open stands showed relatively higher ASL values than the mature trees planted along the avenues.2)The correlation between the ASLs and the standardized precipitation indices of the present-year and the previous-year was significantly strong(r^(2)=0.687,P<0.01),Fraxinus excelsior and Quercus robur in the shaded forest,as well as F.excelsior and Q.robur in the open forests,were found to be nonsensitive to drought,but the other 14 tree species were drought-sensitive.3)The mean value and minimum of the leaf water potential at the turgor loss point significantly correlated with each other(r^(2)=0.549,P<0.01),but did not correlate to growth sensitivity.4)Xylem structure significantly correlated with RAI(r=0.553,P<0.01)and growth sensitivity(r=0.545,P<0.01),and the ASL performance of the ring-porous species was better than semi-ring-porous species and diffuse-porous species.【Conclusion】Although the responses of tree annual shoot growth to drought were affected by multiply interior and external factors,ASL measurement was recommended to be an easy,fast and effective method to assess tree growth vitality and adaptability in response to their habitats,this method was also helpful to select urban tree species with high tolerance under climate change impacts.