海南岛热带山地雨林演替后期幼树的叶片特征

植物的生理生态特征决定了植物在生态系统中的分布模式和物种的丰度。本文在开展样地调查的基础上，应用Li-6400光合测定系统研究了海南岛热带山地雨林原始林3个层次的6个优势种与9个伴生种幼树的光合作用参数，并测定了相应叶片的比叶面积（SLA）和氮、磷含量。15个种的SLA为38.2~143.7 cm²·g^-1、单位面积最大光合速率（A_-area）为2.77~7.61 μmol·m^-2·s^-1、单位干重最大光合速率（A_-mass）为21.2~83.4 μmol·kg^-1·s^-1，单位面积暗呼吸速率（R_d-area）为0.02~1.15 μmol·m^-2·s^-1、单位干重暗呼吸速率（R_d-mass）为0.19~12.61 μmol·kg^-1·s^-1，光补偿点（LCP）为2.5~32.2 μmol·m^-2·s^-1，表观量子效率（Ф）为0.006 6~0.042 8 μmol·μmol^-1 photon，叶片氮（LN）含量为7.98~23.63 mg·g^-1，叶片磷（LP）含量为3.98~13.40 mg·g^-1。中上层种的幼树具有较高的比叶面积、单位干重最大光合速率和表观量子效率；上层种的暗呼吸速率最低；幼树叶片的氮、磷含量随物种成树所在层次升高而减少，次序为下层种>中层种>上层种，但差异均不显著（P>0.05）。优势种和伴生种的光响应参数与SLA存在相关关系。伴生种的LN与SLA正相关（P<0.01），LP与SLA负相关（P<0.05）；优势种的LN、LP与SLA不相关（P>0.05）。

Leaf Traits of the Saplings of Later Successional Stage Tropical Montane Rain Forest in Hainan Island

Physiological and ecological characteristics of plant greatly affect its distribution pattern and abundance in ecosystem. The objectives of this study are to find differences of leaf traits between dominant species and companion species, and differences among three different layers. By sample-plot survey, leaf traits of six dominant species and nine companion species from three different layers of later successional stage tropical montane rain forest were measured in Hainan Island, by using a Li-6400 portable photosynthesis system. Leaves were sampled to measure its specific leaf area(SLA), leaf nitrogen(LN) and leaf phosphorus(LP). SLA(specific leaf area), A_-mass(light-saturated photosynthetic rate) and Ф(photosynthetic quantum yields) of middle and upper layer species were higher than those of lower layer species, and the upper layer species had a lowest R_d(day-time dark respiration rate) among the three groups. LN and LP of saplings decreased with their mature tree height increasing, and had the order of lower layer species>middle layer species>upper layer species, but there was no significant differences among there groups(P>0.05). Photosynthetic parameters of dominant and companion species were correlated with SLA. LN of companion species was positively correlated with SLA(P<0.01), but their LP was negatively correlated with SLA(P<0.05). But for dominant species, there was no correlation between LN and SLA or LP and SLA(P>0.05).