关键词: 温带, 针阔叶混交林, 常绿树种, 呼吸作用, 温度

Abstract: [Obiective] This study aimd to investigate the interspecies variation in leaf respiratory characteristics and its underpinning factors, and quantify the impacts of such variation on the estimation of leaf carbon flux.[Method] Five evergreen species of Chamaecyparis thyoides, Pinus rigida, P. resinosa, P. strobes and Tsuga canadensis, which are common to temperate coniferous-broadleaf forest of Northern America, were chosen in this study. Leaf light photosynthetic response curves, and CO₂ response curves and respiration temperature response curve as well as leaf morphological and biochemical traits were measured. Using linear regression, we analyzed the relationship among leaf respiratory characteristics, leaf structural, biochemical and physiological attributes. A coupled stomata-photosynthesis model was adopted to simulate the dynamic of leaf level carbon flux during the experimental period.[Result] Our results showed:(1) Interspecific difference was found in leaf area-based nitrogen content(N_area), but not in mass-based nitrogen content(N_mass). Likewise, there was obvious difference in the area-based respiration rate(R_narea) was highly regulated by leaf morphological traits; 2) Leaf respiration rate could be well explained by its nitrogen content. Moreover, a positive relationship was also found among R, maximum net carbon assimilation rate(A) and specific leaf area(SLA); 3) Light inhibited leaf dark respiration in all species investigated, with the ratio of mitochondrial respiration under daylight to dark respiration rate(R_L/R_n) spanning from 0.39 to 0.90. The R_L/R_n ratio was positively correlated with maximum oxygenation rate(v_o1500)and carboxylation rate(v_c1500)of Rubisco. In addition, strong correlation was also found between leaf R_n and R_L; 4) Q₁₀ of dark respiration ranged from 1.44~2.24. Activation energy of respiration(E₀) varied among species, but the variation was marginal; 5) With using fixed Q₁₀ and assuming R_L=R_n affected the estimation of leaf carbon flux was affected in all 5 species, but the extent and magnitude of influence were species-specific. The sum of carbon flux for the 5 species was only slightly affected.[Conclusion] In summary, those results clearly demonstrated that leaf respiratory characteristics were species-specific. Factors underlying the inter-specific variation include leaf nitrogen content and leaf morphological traits. The light inhibition of dark respiration was regulated by Rubisco carboxylation and oxygenation, reflecting that leaf photosynthesis and respiration were inter-related. Simulating leaf level carbon flux without considering the effects of Q₁₀ and light inhibition of dark respiration would lead to incorrect outcomes in terms of leaf carbon gain. Apparently, such error will be undoubtedly magnified when scale up to canopy, ecosystem or global level.

Key words: temperate zone, deciduous-evergreen mixed forest, evergreen species, respiration, temperature