秦岭9个树种的木质部栓塞特性与水力安全风险

doi:10.17521/cjpe.2023.0176

摘要/Abstract

摘要：

近年来, 气候变化引起秦岭森林树木死亡率升高和脆弱性加剧, 对秦岭的生物多样性和生态功能产生不利影响。该研究以秦岭森林的9个典型树种: 红桦(Betula albosinensis)、刺榛(Corylus ferox)、青榨槭(Acer davidii)、五尖槭(Acer maximowiczii)、麻栎(Quercus acutissima)、槲栎(Quercus aliena)、华山松(Pinus armandii)、云杉(Picea asperata)和华北落叶松(Larix principis-rupprechtii)为研究对象, 解析各树种木质部栓塞特性, 评估水力安全风险, 揭示秦岭森林退化的植物水力学机制, 为秦岭生态保护提供科学依据。该研究采用Cochard离心机法和Sperry离心机法测量不同水势下枝条的比导水率损失百分比(PLC), 建立木质部栓塞脆弱性曲线(VCs); 采用低压液流计法测定最大木质部比导水率(K_max); 采用压力室法原位测定正午木质部水势(P_md), 在此基础上解析各树种的水力安全边际(HSM), 评估水力失效风险。结果表明: 在9个树种中, 针叶树种华山松、云杉、华北落叶松和阔叶树种青榨槭具有“s”形栓塞脆弱性曲线, 而阔叶树种红桦、刺榛、麻栎、槲栎和五尖槭则为“r”形栓塞脆弱性曲线; 其PLC为50%时的木质部水势(P₅₀)的大小关系为: 云杉<华北落叶松<华山松<青榨槭<五尖槭<红桦<槲栎<刺榛<麻栎; HSM的大小关系为: 麻栎<刺榛<红桦<华北落叶松<槲栎<五尖槭<青榨槭<华山松<云杉, 其中, 红桦、刺榛和麻栎的HSM接近0, 具有极高的水力失效风险。总体来看, 阔叶树种比针叶树种具有更高的水分运输效率, 但是其抗栓塞能力较差, 面临着更大的水力失效风险。

关键词: 栓塞脆弱性, 脆弱性曲线, 水力安全边际, 比导水率, 水力失效风险

Abstract:

Aims Climate warming exacerbate vulnerability of forest ecosystem in the Qinling Mountains, leading to increased forest mortality, and declined ecological function. The objectives of this study were to investigate xylem embolism vulnerability and hydraulic safety margin of nine tree species in the Qinling Mountains.

Methods In this study, nine tree species of the Qinling Mountains, Betula albosinensis, Corylus ferox, Acer davidii, Acer maximowiczii, Quercus acutissima, Quercus aliena, Pinus armandii, Picea asperata and Larix principis-rupprechtii in two different forest sites, Xunyangba village in mid altitude and Pingheliang ridge in high altitude, were studied. Cochard centrifugation and Sperry centrifugation methods were used to establish vulnerability curves (VCs), which was defined as the percentage loss of hydraulic conductivity (PLC) vs. xylem water potential. The xylem maximum hydraulic conductivity (K_max) of branches was measured by low pressure flowmeter. The midday xylem water potential (P_md) was determined by the pressure chamber, which was used to obtain the hydraulic safety margin (HSM) to assess the risk of hydraulic failure for each tree species in natural conditions.

Important findings 1) Xylem embolism vulnerability of nine species was ranked as Picea asperata < Larix principis-rupprechtii < Pinus armandii < Acer davidii < Acer maximowiczii < Betula albosinensis < Quercus aliena < Corylus ferox < Quercus acutissima. The HSM was ranked as Picea asperata > Pinus armandii > Acer davidii > Acer maximowiczii > Quercus aliena > Larix principis-rupprechtii > Betula albosinensis > Corylus ferox > Quercus acutissima. 2) The six broadleaf species in the Qinling Mountains had less negative 50% PLC water potential (P₅₀) and narrower HSM in average than the three conifer species, and therefore were under greater risk of hydraulic failure. 3) The HSM of B. albosinensis, C. ferox and Q. acutissima were close to 0, which indicated an extremely high risk of xylem embolism. In conclusion, broadleaf species in Qinling Mountains had higher water transport efficiency than conifer species, in the cost of higher risk of xylem embolism and hydraulic failure.

Key words: embolism vulnerability, vulnerability curve, hydraulic safety margin, xylem-specific hydraulic conductivity, hydraulic failure risk

陈思佚, 唐燕, 何腾, 江永康, 杜光源. 秦岭9个树种的木质部栓塞特性与水力安全风险. 植物生态学报, 2024, 48(9): 1213-1222. DOI: 10.17521/cjpe.2023.0176

CHEN Si-Yi, TANG Yan, HE Teng, JIANG Yong-Kang, DU Guang-Yuan. Xylem embolism characteristics and hydraulic safety risks of nine tree species in Qinling Mountains. Chinese Journal of Plant Ecology, 2024, 48(9): 1213-1222. DOI: 10.17521/cjpe.2023.0176

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链接本文: https://www.plant-ecology.com/CN/10.17521/cjpe.2023.0176

https://www.plant-ecology.com/CN/Y2024/V48/I9/1213

图/表 6

图1 秦岭9个树种栓塞脆弱性曲线(平均值±标准差)。Ad, 青榨槭; Am, 五尖槭; Ba, 红桦; Cf, 刺榛; Lp, 华北落叶松; Par, 华山松; Pas, 云杉; Qac, 麻栎; Qal, 槲栎。

Fig. 1 Vulnerability curves of nine tree species in Qinling Mountains (mean ± SD). Ad, Acer davidii; Am, Acer maximowiczii; Ba, Betula albosinensis; Cf, Corylus ferox; Lp, Larix principis-rupprechtii; Par, Pinus armandii; Pas, Picea asperata; Qac, Quercus acutissima; Qal, Quercus aliena.

表1 秦岭9个树种的木质部水势特征值(平均值±标准差)

Table 1 Xylem water potential eigenvalues of nine species of trees in Qinling Mountains (mean ± SD)

树种 Tree species	P₁₂ (MPa)	P₅₀ (MPa)	P₈₈ (MPa)
麻栎 Quercus acutissima	-0.268 ± 0.098^B	-0.788 ± 0.089^E	-1.399 ± 0.227^G
刺榛 Corylus ferox	-0.259 ± 0.035^B	-1.089 ± 0.054^D	-1.893 ± 0.273^EF
槲栎 Quercus aliena	-0.769 ± 0.157^A	-1.389 ± 0.021^D	-2.236 ± 0.345^E
红桦 Betula albosinensis	-0.264 ± 0.082^B	-1.554 ± 0.421^D	-1.842 ± 0.083^EF
五尖槭 Acer maximowiczii	-0.267 ± 0.100^B	-1.925 ± 0.213^C	-2.765 ± 0.237^D
青榨槭 Acer davidii	-0.365 ± 0.088^B	-3.050 ± 0.191^B	-3.914 ± 0.144^C
华山松 Pinus armandii	-0.231 ± 0.078^B	-3.283 ± 0.124^B	-3.889 ± 0.331^C
云杉 Picea asperata	-0.282 ± 0.207^B	-4.178 ± 0.281^A	-5.290 ± 0.311^A
华北落叶松 Larix principis-rupprechtii	-0.276 ± 0.097^B	-3.419 ± 0.178^B	-4.568 ± 0.390^B

图2 秦岭针叶树种木质部导水率损失的百分数达到50%时的木质部水势(P50)和阔叶树种木质部导水率损失的百分数达到88%时的木质部水势(P88)的差异(平均值±标准差)。不同大写字母表示针叶树种和阔叶树种的栓塞阈值之间的差异显著(p < 0.05)。

Fig. 2 Differences between water potentials at which 50% of hydraulic conductivity is lost (P50) of conifers and water potentials at which 88% of hydraulic conductivity is lost (P88) of broadleafs in Qinling Mountains (mean ± SD). Different uppercase letters indicate significant differences in embolism thresholds of conifers and broadleafs (p < 0.05).

图3 秦岭9个树种在自然状态下的木质部比导水率(Ks) (平均值±标准差)。Ad, 青榨槭; Am, 五尖槭; Ba, 红桦; Cf, 刺榛; Lp, 华北落叶松; Par, 华山松; Pas, 云杉; Qac, 麻栎; Qal, 槲栎。Ks预测值基于测量的Pmd (表2)和栓塞脆弱性曲线(图1)。不同大写字母表示树种间在自然状态下的木质部比导水率之间的差异显著(p < 0.05)。

Fig. 3 Natural xylem specific hydraulic conductivity of nine species of trees in Qinling Mountains (Ks) (mean ± SD). Ad, Acer davidii; Am, Acer maximowiczii; Ba, Betula albosinensis; Cf, Corylus ferox; Lp, Larix principis-rupprechtii; Par, Pinus armandii; Pas, Picea asperata; Qac, Quercus acutissima; Qal, Quercus aliena. The predicted Ks was calculated from measured Pmd (Table 2) and the vulnerability curves (Fig. 1). Different uppercase letters indicate significant differences in natural xylem specific hydraulic conductivity of nine species (p < 0.05).

表2 秦岭9个树种的水势特征和比导水率(平均值±标准差)

Table 2 Xylem water potential characteristics and xylem-specific hydraulic conductivity of nine tree species in Qinling Mountains (mean ± SD)

树种 Tree species	P_md(MPa)	HSM (MPa)	K_max(kg·MPa^-1·s^-1·m^-1)	K_s(kg·MPa^-1·s^-1·m^-1)
麻栎 Quercus acutissima	-0.688 ± 0.122^E	-0.110 ± 0.054^E	4.637 ± 0.842^A	2.660 ± 0.483^B
刺榛 Corylus ferox	-1.111 ± 0.103^D	-0.013 ± 0.096^E	1.240 ± 0.371^D	0.610 ± 0.183^D
红桦 Betula albosinensis	-1.367 ± 0.111^C	0.001 ± 0.421^E	1.810 ± 0.572^C	1.092 ± 0.345^C
华北落叶松 Larix principis-rupprechtii	-2.478 ± 0.227^A	0.887 ± 0.178^D	0.197 ± 0.077^F	0.131 ± 0.051^E
槲栎 Quercus aliena	-0.470 ± 0.050^F	0.934 ± 0.021^CD	3.293 ± 0.648^B	3.142 ± 0.618^A
五尖槭 Acer maximowiczii	-0.792 ± 0.183^E	1.216 ± 0.213^CD	0.694 ± 0.358^DEF	0.462 ± 0.238^DE
青榨槭 Acer davidii	-1.737 ± 0.087^B	1.315 ± 0.191^C	1.054 ± 0.529^DE	0.721 ± 0.362^D
华山松 Pinus armandii	-1.277 ± 0.078^CD	1.850 ± 0.124^B	0.541 ± 0.081^EF	0.391 ± 0.059^DE
云杉 Picea asperata	-1.438 ± 0.301^C	2.969 ± 0.426^A	0.261 ± 0.132^F	0.194 ± 0.098^E

图4 秦岭9个树种的水力安全边际(HSM) (平均值±标准差)。Ad, 青榨槭; Am, 五尖槭; Ba, 红桦; Cf, 刺榛; Lp, 华北落叶松; Par, 华山松; Pas, 云杉; Qac, 麻栎; Qal, 槲栎。

Fig. 4 Hydraulic safety margin of nine species of trees in Qinling Mountains (HSM) (mean ± SD). Ad, Acer davidii; Am, Acer maximowiczii; Ba, Betula albosinensis; Cf, Corylus ferox; Lp, Larix principis-rupprechtii; Par, Pinus armandii; Pas, Picea asperata; Qac, Quercus acutissima; Qal, Quercus aliena.

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