关键词: 叶片, 化学性状, 结构性状, 光合性状, 权衡, 光响应曲线, CO₂响应曲线

Abstract:

Objective: This stusy aims to examine the trade-offs between leaf traits, including chemical-, structural- and photosynthetic traits, and the relationship between leaf chemical- and structural traits and photosynthetic traits. Method: In the community, the dominant main woody species include Larix principis-rupprechtii, three broad-leaved trees, Fraxinus chinensis, Phellodendron amurense and Acer pictumsubsp.mono, and two shrubs, Lespedeza bicolorand Spiraea salicifolia. The 13 leaf traits were measured for the woody species in the L. principis-rupprechtii community in Bahushan, Beijing using portable analyzer during July-August in 2021. Photosynthetic traits included maximum net photosynthetic rate (P_nmax), saturation irradiance (I_sat), dark respiration rate (R_d), saturation intercellular CO₂ concentration (Ci_sat), maximum rate of carboxylation (V_cmax), maximum potential rate of electron transport (J_max), water use efficiency (WUE), and photosynthetic nitrogen-use efficiency (PNUE). The structural traits were leaf thickness (LT), specific leaf area (SLA), and leaf tissue density (LTD). The chemical traits were carbon-nitrogen ratio (C∶N), and nitrogen-phosphorus ratio (N∶P). One-way analysis of variance, Spearman correlation analysis, principal component analysis and linear regression were used to analyze the correlation of leaf traits and the effects of leaf chemical and structural traits on photosynthetic traits in the L. principis-rupprechtii community. Result: 1) The PNUE and SLA showed the largest inter-species variation with variation coefficient of 60.88% and 56.83%, respectively, indicating that the species in the commnuity competed for light resource. 2) Shrubs had higher SLA in order to increase light acquisition ability on vertical structure in the community. Meanwhile, N∶P in tree leaves was 14.58, while that in shrub leaves was 21.10. Compared with trees, shrubs had lower C∶N, but higher N∶P, indicating that the shrub allocated more nitrogen into leaf to obtain light and maintain growth. 3) C∶N, N∶P and SLA were 18.19, 16.04 and 193.77 cm²·g^?1 in broad-leaved trees, respectively, and were 39.6, 10.2 and 82.2 cm²·g^?1 in needle-leaved trees, respectively. Compared with broad-leaved trees, the needle-leaved trees had higher C∶N, but lower N∶P and SLA, indicating that the needle-leaved trees tended to construct the more defensive organization and had higher resistance to stress and lower light interception capability. 4) L. principis-rupprechtii was located at “slow investment-return”, shrubs were at “fast investment-return” in leaf economic spectrum. L. principis-rupprechtii had higher WUE but lower PNUE, suggesting that the trade-off between WUE and PNUE occurred, with WUE increasing at the expense of PNUE. 5) Compared with other broad-leaved trees and shrubs, the P_nmax of A. pictum subsp. mono and S. salicifolia were not obviously higher, but the R_d were significantly lower than other species. 6) The I_sat, R_d WUE and PNUE were significantly correlated with C∶N, LT and SLA (P<0.05). Conclusion: These results suggest that there is obvious leaf economics spectrum existed across the woody species in the community, and the interspecific competition is mainly for light resource. Although A. pictum subsp. mono and S. salicifolia are not the dominant species in the community, their net carbon sequestration capacity in per unit area is stronger than other species. The C∶N, LT and SLA can be used as the indicators predicting the photosynthetic capacity. Species with higher C∶N, LT and lower SLA have higher tolerance to strong light and higher water use efficiency, but have stronger utilization of weak light and less carbon consumption. Meanwhile, photosynthetic nitrogen utilization efficiency is lower. The results can provide theoretical support for subsequent forest management.

Key words: leaf, chemical trait, structural trait, photosynthetic trait, trade-off, light response curve, CO₂ response curve