林下植被演替过程中毛竹枝叶形态质量和抽枝展叶效率变化特征

Characteristics of Phyllostachys edulis(Carrière)J.Houz shoot morphology,branching,and leaf expansion efficiency during understory vegetation succession

本研究分别选取林下植被演替前毛竹(Phyllostachys edulis(Carrière)J.Houz)纯林经营、竹材6~8年采伐一次形成的林下植被演替9、21年以及纯林(对照)等3类毛竹林,调查分析了1度、2度竹的主侧枝枝叶形态质量、抽枝展叶效率及生物量异速生长关系等。结果显示:(1)随林下植被演替的进行,1度竹主枝叶片主要形态质量性状呈降低趋势,2度竹则呈“V”型变化;(2)1度、2度竹主侧枝的枝长、纤细率显著提高,枝基径、枝干物质含量、枝干重等性状呈倒“V”型或升高趋势,枝形态变化较枝质量变化明显;(3)1度竹抽枝展叶效率指标呈“V”型变化,而2度竹主侧枝抽枝展叶效率显著降低,胡波尔值明显提高;(4)一定演替年限内,立竹主侧枝枝叶生物量生长关系从等速生长向异速生长变化,尔后恢复为等速生长。可见,林下植被演替对毛竹林立竹枝叶形态质量、抽枝展叶效率和枝叶生物量异速生长关系均产生重要影响,叶片趋于变小,枝条趋于细长,且具有明显的演替年限效应和立竹年龄效应,主要对主枝叶片产生影响,1度竹较2度竹敏感;演替过程中立竹将更多的资源投资于枝的生长,以增强空间资源的竞争能力。

This research examined three types of moso bamboo stands:pure moso bamboo forest prior to understory vegetation succession,understory vegetation succession formed by harvesting bamboo timber once every 6–8 years over periods of 9 and 21 years,and pure forest(control).We investigated the morphological quality of the main and lateral branches and leaves,efficiency of pumping and spreading,and biomass anisotropic growth relationship of 1st-and 2nd-degree bamboo.Results showed that:(1)With the succession of understory vegetation,the primary morphological and quality traits of the main branch leaves of 1st-degree bamboo showed a downward trend,while 2nd-degree bamboo showed a significant“V”-shaped change;(2)Length and slenderness of the main and lateral branches of 1st-and 2nd-degree bamboo increased signifi-cantly,while branch diameter,branch dry matter content,and branch dry weight showed an inverted“V”-shaped or increasing trend,with the changes in branch morphology being more pronounced than those in branch quality;(3)The leaf spreading efficiency index of 1st-degree bamboo showed a“V”-shaped change,whereas that of the main and lateral branches of 2nd-degree bamboo decreased significantly,with the Huber value increasing significantly;(4)Within a certain succession period,the biomass growth relationship of the main and lateral branches of the standing bamboo transitioned from isochronous to anisotropic growth,then reverted to isochronous growth.Thus,understory vegetation succession exhibited an important effect on the morphological quality of bamboo branches and leaves,efficiency of branching and spreading,and relation-ship between anisotropic growth and branch and leaf biomass in moso bamboo forests.Notably,leaves ten-ded to be smaller and branches slenderer.Furthermore,successional age and age of standing bamboo had obvious effects,mainly on the leaves of the main branches,with 1st-degree bamboo being more sensitive than 2nd-degree bamboo.Hence,during the succession process,bamboo invests more resources in branch growth to enhance competition for spatial resources.