江西九连山常绿阔叶林主要树种叶建成消耗的比较

Comparison of leaf construction cost in dominant tree species of the evergreen broad-leaved forest in Jiulian Mountain, Jiangxi Province

叶建成消耗（或叶构建消耗）是指构建单位质量（面积）叶片所需要的葡萄糖当量，是植物碳收获过程中必要的成本投资．反映植物在叶片水平上的能量和碳分配策略。基于热值、灰份含量、叶氮含量和比叶面积的测定，估算了江西九连山常绿阔叶林16个主要树种的叶建成消耗，分析比较了不同树种、不同叶寿命、比叶面积和冠层不同部位对叶建成消耗的影响。结果表明，热值组分的变化对单位质量叶建成消耗的影响最大；树种间单位质量叶建成消耗的差异不大（变化率仅3％～6％），但其单位面积叶建成消耗则存在显著差异（变化率达27％～28％）；热值和单位质量叶建成消耗与比叶面积密切相关，而比叶面积随取样高度呈显著的降低趋势，最终导致热值及单位质量和单位面积的叶建成消耗均随取样高度呈显著的增加趋势。研究结果指出：（1）较高的叶建成消耗是由于植物叶片内含有较高能量投资的化学组分；（2）叶建成消耗和比叶面积随取样高度的变化综合反映了植物对光照和水分资源垂直梯度变化的可塑性适应。

Leaf construction cost is the amount of glucose required to produce per unit leaf mass or leaf area, which reflects the fundamental energy invested for carbon gain of leaves and is related to processes driven by light interception, or limited by diffusion to the plant surface. In this study, we presented observed data of specific leaf area, the heat of combustion, organic nitrogen content and ash content in leaves collected from different canopy positions across 16 dominant tree species in a subtropical evergreen broadleaved forest in Jiulian Mountain of Jiangxi Province. Calorimetric method was used to estimate mass- and areabased construction costs （ CCm and CCa） of leaves in different annual cohorts according to tree species and sampled canopy heights. The heat of combustion was the main determinant of leaf CCm · Across tree species, the CCm varied little with coefficient of variation （CV） of 3 % - 6 % , while the CCa varied greatly with CV of 27 % - 28 % . The heat of combustion and the CCm were negatively correlated with specific leaf area. Because specific leaf area generally declined with the increasing of sampled canopy heights, both CCm and CCa generally increased with sampled canopy height across the 16 tree species. Our results suggest that： 1） higher leaf CCm results from the higher content of chemical components that cost high energy; 2） the height-related variations in leaf construction costs and special leaf area may be considered as integrated indicators of plant plasticity in response to changes in light and water resources along a canopy profile.