南亚热带不同海拔常绿阔叶林树种叶性状的比较分析

Comparative Analysis of Leaf Traits of Evergreen Broad-leaved Forest Tree Species from Different Elevations in Lower-subtropical Region

摘要:

南亚热带地带性植被是季风常绿阔叶林(海拔300~600 m；简称季风林)，在中山地带则分布为山地常绿阔叶林(海拔1 000~1 500 m；简称山地林)。山地林的生态价值日益受到重视，但是对其树种的环境适应性仍缺乏足够了解。该研究基于南亚热带典型山地林(广西大明山)和季风林(广东鼎湖山)的固定样地，共测定57种代表性树种的叶形态解剖特征、机械强度和水力学性状，比较不同海拔常绿阔叶林树种叶性状以及多类性状关联性的差异。结果表明，与季风林树种相比，山地林树种叶较厚、比叶面积较小、机械强度较高，有利于提高对较高海拔山区冬季冰冻的适应能力。在2022年夏季持续高温干旱时期，季风林树种的叶水势和水力安全边界均低于山地林。但是大部分树种水力安全边界为正值且种间变异较大，表明不同海拔常绿阔叶林的水力风险较低。不同海拔常绿阔叶林的叶性状网络不同，山地林树种叶水力安全性和效率性无权衡关系，而季风林树种叶经济学性状(如比叶面积)与其他指标的关联性较弱。基于叶性状的研究揭示了南亚热带不同海拔常绿阔叶林树种适应策略的差异性和多样性。

Abstract:

The subtropical zonal vegetation is monsoon evergreen broad-leaved forest (altitude 300-600 m, monsoon forest), and the mountain evergreen broad-leaved forest (mountain forest) is distributed in the middle mountains (1 000-1 500 m). The ecological value of mountain forest has been paid more and more attention, but the environmental adaptability of its tree species is still not well understood. Based on fixed plots of typical mountain forest (Daming Mountain, Guangxi) and monsoon forest (Dinghu Mountain, Guangdong) in south subtropical region, leaf morphological and anatomical characteristics, mechanical strength and hydraulic properties of 57 representative tree species were measured, and leaf traits and correlation of various traits of evergreen broad-leaved forest species at different elevations were compared. The results showed that compared with monsoon forest species, the leaves of mountain forest species were thicker, the specific leaf area was smaller, and the mechanical strength was higher, which was conducive to improving the adaptability to winter freezing in the mountains at higher altitude. Under extreme hot-dry weather in 2022 summer, leaf water potential and hydraulic safety margin were significantly lower in the low-elevation forest than those in the high-elevation forest. However, leaf hydraulic safety margins were positive for most studied tree species and showed large inter-specific variations, indicating a low hydraulic risk in subtropical evergreen broadleaved forests. Leaf traits networks differed between the two forests. There was no tradeoff relationship between leaf hydraulic security and efficiency in mountain forest, while the correlation between leaf economic traits (such as specific leaf area) and other indexes was weak in monsoon forest. Based on leaf traits, the differences and diversity of adaptive strategies of evergreen broad-leaved forest species at different elevations in south subtropical region were revealed.