长柄双花木叶性状异速生长关系随发育阶段和海拔梯度的变化

Changes of allometric relationships among leaf traits of Disanthus cercidifolius var. longipes in different ontogenetic stages and altitude gradients

关键词:  长柄双花木, 发育阶段, 异速生长, 资源利用策略, 江西省

Key words:  Disanthus cercidifolius var. longipes, developmental stage, allometry, resource utilization strategy, Jiangxi Province

摘要:

长柄双花木(Disanthus cercidifolius var. longipes)是一种仅分布于我国东南地区的珍稀濒危植物。为研究该物种叶性状异速生长关系和叶片资源利用策略及其随发育阶段和海拔梯度的变化规律,该文以分布于江西省不同海拔梯度的长柄双花木群落为研究对象,调查分析了群落中不同发育阶段长柄双花木植株的叶片面积、叶片体积以及叶片含水量与叶片干重之间的异速关系。结果表明:不同发育阶段植株之间叶性状异速生长关系有着显著差异。成树叶片面积的增长速度低于或等于叶片干重的增长速度,幼树、幼苗叶片面积的增长速度低于叶片干重的增长速度; 成树叶片体积与叶片干重呈等速增长,幼树、幼苗叶片体积的增长速度高于叶干重的增长速度; 成树叶片含水量的增长速度低于叶干重的增长速度,幼树、幼苗两性状间保持等速增长。海拔梯度对长柄双花木叶性状异速生长关系也有影响,植株叶体积和叶含水量与叶干重的异速生长指数在不同海拔间有显著性差异。在低海拔区域,叶体积与叶干重呈等速增长,叶含水量的增长速度低于叶片干重的增长速度。在高海拔区域,叶体积的生长速度低于叶干重的生长速度,叶含水量和叶片干重呈等速增长。这说明长柄双花木叶片资源投资策略随着发育阶段和海拔梯度的不同发生变化。成树主要将叶生物量投资于光捕获面积和同化结构,幼树和幼苗则主要投资于维管组织的建设。由于海拔升高会引起风力增大、光强增强和土壤理化性质改变,长柄双花木在中低海拔倾向于增大叶体积以抢占资源,在高海拔倾向于加强机械组织和维管组织的建设来抵抗外界因子干扰。

Abstract:

Disanthus cercidifolius var. longipes is a rare and endangered plant distributed only in the southeast area of China. In order to research the allometric relationship of leaf trait, characteristic of leaf resource utilization, and their changes with ontogenetic development and altitude gradient, we investigated and analyzed allometric relationships among the lamina mass, lamina area, lamina volume and lamina water content of D. cercidifolius var. longipes plants at different developmental stages in D. cercidifolius var. longipes communities distributed along altitude gradient in Jiangxi Province. The results showed that there were significant different allometric relationships among plants at different deve-lopmental stages. The increasing rate of lamina area was lower than or equal with that of lamina mass in adult trees, meanwhile the growth rate of lamina area was lower than that of lamina mass in saplings and seedlings; The lamina vo-lume and lamina mass of adult trees grew at the same rate, but the lamina volume of saplings and seedlings grew faster than the lamina mass of them; The growth rate of lamina water content was slower than that of lamina mass in adult trees, meanwhile the growth rate of both characters grew at the same rate in saplings and seedlings. Altitude gradient also influenced the allometric relationship among leaf traits. The allometric relationships between the lamina volume, lamina water content and lamina mass differed significantly among altitude gradients. At the low elevation, the lamina volume and lamina mass grew at the same rate, meanwhile lamina water content grew slower than lamina mass. At the high elevation, the lamina volume grew slower than lamina mass, and the lamina water content and lamina mass grew at the same rate. These results suggested that the investment strategy of leaf resources of D. cercidifolius var. longipes changed with the change of ontogenetic development and altitude gradient. The adult trees of D. cercidifolius var. longipes invested more lamina biomass in the development of light-harvesting area and assimilation structure, meanwhile the saplings and seedlings mainly invested lamina biomass in the development of vascular tissue. As the increase of altitude would increase wind and light intensity, and change physicochemical properties, D. cercidifolius var. longipes plants tends to increase the lamina volume to capture more resources at the middle and lower altitudes, and tends to strengthen the construction of machinery and vascular tissue to resist external interference at the higher altitude.