紫耳箭竹克隆形态可塑性对典型冠层结构及光环境的响应

在重庆金佛山国家自然保护内,选择了3种典型群落类型(落叶阔叶林、常绿落叶阔叶混交林和常绿阔叶林),使用Hemiview数字植物冠层分析系统量化群落冠层结构和光环境特征,并对林下紫耳箭竹(Fargesia decurvata)的形态可塑性特征进行调查,分析冠层结构和光环境特征改变下紫耳箭竹形态可塑性的差异,并探讨它们之间的相互关系。结果表明:(1)随着落叶阔叶林"常绿落叶阔叶混交林"常绿阔叶林演替的进行,群落的冠层开度降低,叶面积指数增加,平均叶倾角变小,趋于水平化,冠层对光的截获能力提高,林下光照的强度降低(P0.05)。(2)随着光照强度的降低,紫耳箭竹分株矮小化,叶片变窄,生物量积累降低,但通过增大比茎长、叶面积率和比叶面积提高对光的利用效率,并增大分枝角度和比隔长有效适应弱光环境。(3)在光照条件差的常绿阔叶林下,紫耳箭竹降低对地下茎的投资,将较多的生物量用于秆的增高增长和叶片的生长;而在光照条件好的落叶阔叶林环境下,紫耳箭竹降低对枝、叶生物量的分配,则加大对地下茎的投资,可认为是克隆植物对水分资源所表现的一种觅食行为。研究表明,紫耳箭竹种群随着冠层结构的改变发生了明显的可塑性变化,这些可塑性变化是种群对冠层结构和光环境差异的适应性反应的结果,有利于增强种群对异质生境中光资源的获取和利用;群落内部可以通过调控冠层结构的改变协调和控制小径竹种群的发展。

Response of clonal morphological plasticity of Fargesia decurvata to different forest canopy structures and light conditions

Clonal morphological plasticity, closely related to the maintenance and regeneration of populations, is the ability for a plant to adapt to a changing environment. In a field experiment, the Hemiview digital canopy analysis system was used to measure the canopy structures (canopy openness, CO; leaf area index, LAI; mean leaf angle, MLA) and light conditions (direct solar radiation under canopy, Dir; diffuse solar radiation under canopy, Dif; Total solar radiation under canopy, Tot) in three typical forest types (deciduous broad-leaved forest, evergreen and deciduous broad-leaved mixed forest, evergreen broad-leaved forest) in Jinfo Mountains National Nature Reserve, Chongqing. The clonal morphological plasticity of understory dwarf bamboo, Fargesia decurvata, was also measured. Moreover, the relationship between canopy structure and morphological plasticity of F. decurvata was discussed. The results showed that:(1) With the development of forest succession, the CO and MLA decreased, but LAI increased, resulting in the increase in light interception capability of forest canopy and the decrease in the light intensity under forest canopy (P < 0.05). (2) Forest canopy condition had a significant effect on the morphological plasticity of F. decurvata ramets. With the decrease in light intensity, the culm height, basal diameter, leaf area, and biomass of F. decurvata ramets decreased. However, decreased light intensity can increase the specific culm length, leaf area ratio, and specific leaf area to improve the utilization efficiency of light and increase the branch angle of spacer and specific spacer length to adapt to low light environments. (3) Under the low light environment in an evergreen broad-leaved forest, F. decurvata reduced its investment in rhizome but allocated more biomass for culm and leaf growth. However, in the deciduous broad-leaved forest, F. decurvata reduced the allocation of branches and leaves and increased the investment in rhizome growth (spacer length and diameter), which can be considered as a foraging behavior to searching much more water resources. These results suggested that the morphological plasticity of F. decurvata underwent significant change in different forest canopies, which is the result of adaptive response to different forest canopy structures and light conditions and enhances the ability to acquire and utilize light resources in heterogeneous light environments. Moreover, the communities may be able to coordinate and control the development of dwarf bamboo by controlling the change of canopy structures and light conditions.