热带亚热带喀斯特森林木本植物的水力脆弱性分割

doi:10.17521/cjpe.2022.0262

摘要/Abstract

摘要：

脆弱性分割是树木抗旱生理机制之一, 但是关于喀斯特干旱生境植物的脆弱性分割情况及其生理意义尚不明确。该研究以热带、亚热带喀斯特森林共57种典型木本植物为研究材料, 测定叶、茎脆弱性曲线以及最低水势, 计算叶和茎的脆弱性分割(P50_leaf-stem; 数值越大代表脆弱性分割越强)以及水力安全边界, 比较不同类群P50_leaf-stem的差异并分析其与水力安全边界的相关关系。结果表明: (1)该研究木本植物的P50_leaf-stem范围为-1.28-4.63 MPa, 平均值为1.32 MPa, 其中49种植物的P50_leaf-stem为正值(正向脆弱性分割); (2)灌木的P50_leaf-stem显著大于乔木, 喀斯特山脊植物的P50_leaf-stem显著大于山谷植物, 但是常绿和落叶植物之间的P50_leaf-stem差异不显著; (3)在旱季时期, P50_leaf-stem越大的植物, 其叶水力安全边界越小, 茎水力安全边界越大, 说明叶片发生栓塞有助于降低茎干木质部的水力风险。该研究证实脆弱性分割是大部分热带亚热带喀斯特木本植物应对干旱胁迫的重要水力机制。

关键词: 栓塞, 干旱适应, 水力安全边界, 最低水势, 植物类群

Abstract:

Aims Vulnerability segmentation is one of physiological mechanisms underlying drought resistance for tree species. The aim of this study is to clarify the patterns of vulnerability segmentation and its physiological significance for woody species from drought-prone tropical and subtropical karst forests.

Methods A total of 57 typical woody species were selected from tropical and subtropical karst forests. We measured their leaf and stem vulnerability curves and minimum water potential to calculate vulnerability segmentation (P50_leaf-stemis the difference in cavitation resistance between leaf and stem, with larger values indicating stronger vulnerability segmentation) and hydraulic safety margin. We compared the differences in P50_leaf-stem between different plant taxa and explored the relationships between P50_leaf-stem and hydraulic safety margin.

Important findings (1) The P50_leaf-stem across the woody species ranged from -1.28 MPa to 4.63 MPa, with an average value of 1.32 MPa. Out of the 57 species, 49 species showed a positive P50_leaf-stem. (2) Shrub species showed higher P50_leaf-stem than tree species, and species from karst ridge showed higher P50_leaf-stem than those from karst valley. However, there was no significant difference in P50_leaf-stem between evergreen and deciduous species. (3) During the drought period, species with higher P50_leaf-stem tended to have smaller leaf hydraulic safety margin but larger stem hydraulic safety margin, indicating that occurrence of cavitation in leaves can reduce hydraulic risks of stems. This study confirms that vulnerability segmentation is an important hydraulic strategy for most tropical and subtropical karst woody species to deal with drought stress.

Key words: cavitation, drought adaptation, hydraulic safety margin, minimum water potential, plant taxa

余俊瑞, 万春燕, 朱师丹. 热带亚热带喀斯特森林木本植物的水力脆弱性分割. 植物生态学报, 2023, 47(11): 1576-1584. DOI: 10.17521/cjpe.2022.0262

YU Jun-Rui, WAN Chun-Yan, ZHU Shi-Dan. Hydraulic vulnerability segmentation in woody plant species from tropical and subtropical karst forests. Chinese Journal of Plant Ecology, 2023, 47(11): 1576-1584. DOI: 10.17521/cjpe.2022.0262

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链接本文: https://www.plant-ecology.com/CN/10.17521/cjpe.2022.0262

https://www.plant-ecology.com/CN/Y2023/V47/I11/1576

图/表 3

图1 典型喀斯特峰丛地形和植物分布概念图。正向(A)和负向(B)脆弱性分割植物的叶(蓝色)和茎(红色)脆弱性曲线。蓝色和红色垂直虚线分别表示叶和茎导水率损失50%时的水势值(P50leaf和P50stem), 表征其抗栓塞能力。通过叶和茎抗栓塞能力的差值计算脆弱性分割的程度(P50leaf-stem)。

Fig. 1 Conceptual model of karst mountains landform and distribution of woody plant species. Vulnerability curves of leaves (blue) and stems (red) for trees with positive (A) and negative (B) vulnerability segmentation. The blue and red vertical dashed lines indicate water potential at 50% loss of hydraulic efficiency in leaves (P50leaf) and stems (P50stem), respectively, which qualifies their cavitation resistance. The vulnerability segmentation (P50leaf-stem) is calculated as the difference in cavitation resistance between leaves and stems. Ψ, water potential; PLC, percentage loss of conductivity.

图2 热带亚热带喀斯特森林57种木本植物的脆弱性分割(P50leaf-stem) (A)以及不同类群P50leaf-stem的差异性(B-D)。*, p < 0.05; ns, p > 0.05。

Fig. 2 Vulnerability segmentation (P50leaf-stem) (A) of the 57 woody plant species from tropical and subtropical karst forests, and difference of P50leaf-stem between different plant taxa (B-D). *, p < 0.05; ns, p > 0.05.

图3 热带亚热带喀斯特森林木本植物(n = 41)脆弱性分割(P50leaf-stem)与叶水力安全边界(HSMleaf) (A)、茎水力安全边界(HSMstem) (B)以及最低水势(Ψmin) (C)之间的相关关系。***, p < 0.001。○, 山谷乔木; △, 山谷灌木; ●, 山脊乔木; ▲, 山脊灌木。

Fig. 3 Correlations of vulnerability segmentation (P50leaf-stem) with leaf hydraulic safety margin (HSMleaf) (A), stem hydraulic safety margin (HSMstem) (B), and minimum water potential (Ψmin) (C) across woody plant species from tropical and subtropical karst forests (n = 41). ***, p < 0.001. ○, valley tree species; △, valley shrub species; ●, ridge tree species; ▲, ridge shrub species.

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