基于光照强度变化的毛竹扩张对杉木影响的探讨

Light intensity changes on Cunninghamia lanceolata in mixed stands with different concentrations of Phyllostachys pubescens

为分析毛竹Phyllostachys pubescens蔓延对杉木Cunninghamia lanceolata的影响,采用手持照度计测定了毛竹纯林边缘3种林分类型内的光照强度,并测定了毛竹、杉木及其幼苗的光补偿点。结果表明:①3种林分内光照强度由高到低依次为毛竹林、针阔-毛竹混交林、针阔混交林,分别较空旷处下降了49.31%,55.91%和85.70%,说明毛竹的扩散,使毛竹纯林内光照强度大于毛竹-针阔叶混交林和针阔叶混交林;3种林分内光照强度(I)关系式为:I针阔=0.027 3I针阔-毛竹+0.032 0I毛竹+2.297 0。②在光补偿点方面,毛竹最高,杉木、杉木幼苗次之,分别为19.60,9.77和9.78μmol.m-2.s-1。在毛竹林扩散过程中,光照强度并没有降至杉木及其幼苗的光补偿点之下,其光合作用依然大于呼吸作用,可以持续补充有机物。然而,由于杉木幼苗的喜荫特性,光照强度的增强可能会使杉木更新受到影响。为全面地研究毛竹扩张导致杉木死亡的原因积累了经验。

To help accumulate knowledge on the causes of death of Cunninghamia lanceolata due to expansion of nearby Phyllostachys pubescens bamboo stands,light intensity of three forest stands： a P.pubescens forest;a needle,broadleaf mixed forest with C.lanceolata;and a needle,broadleaf with C.lanceolata,and bamboo mixed forest;at the edge of P.pubescens bamboo stands was obtained using a quantum meter in 8：00-17：00,from July to September,to detect the light intensity（I）,and using Li-6400 Portable Photosynthesis System to detect the light compensation point（LCP）,from 9：00 to 10：00.Results showed that light intensity（I）,increased with greater concentrations of P.pubescens within the forest stands：P.pubescens（bamboo）forest needle,broadleaf with C.lanceolata,and bamboo mixed forest needle,broadleaf with C.lanceolata mixed forest.Compared with an open field light intensity decreased 49.31% for the P.pubescens forest;55.91% for the needle,broadleaf with C.lanceolata,and bamboo mixed forest;and 85.70% for the needle,broadleaf with C.lanceolata mixed forest.A light intensity relationship was shown with the equation：Ineedle,broadleaf=0.027 3 Ineedle,broadleaf,bamboo＋0.032 0 Ibamboo＋2.297 0.Also,the highest LCP was found with P.pubescens（19.60 μmol·m-2·s-1）,then adult C.lanceolata（9.77 μmol·m-2·s-1）,and then C.lanceolata saplings（9.78 μmol·m-2·s-1）;thus,light intensity of adult C.lanceolata and its seedlings was higher than the LCP,and the forests with C.lanceolata could continue to make organic matter.But because of the shadow characteristics of C.lanceolata seedlings,the increased light intensity could influence the C.lanceolata seedlings due to less shade.