A comparison of light environmental characteristics for evergreen broad-leaved forest communities from different successional stages in Tiantong National Forest Park
天童国家森林公园常绿阔叶林不同演替阶段群落光环境特征比较

Evergreen broad-leaved forest (EBLF) is a typical of vegetation in the middle subtropical zone of China.In Tiantong National Forest Park,EBLF communities can be classified into six different successional stages after reconnaissance and field samplings.Dominant species,morphological characteristics,and light environment are different from other successional stages.The objective of this study was to determine effects of photosynthetic photon flux density(PPFD) on the dominant species for different successional stages in Tiantong National Forest Park by using "WinScanopy For Canopy Analysis" software.Light environmental indices of both canopy and understory of EBLF,such as PPFD,and morphological indices,such as gap fraction,leaf area index,and mean leaf angle(MLA) were interpreted by the software.Results showed the PPFD of canopy gradually decreased with successional stages,however,the PPFD decreased substantially in understory,and the PPFD difference in canopy between different stages was less than that in the understory.Standard deviations of PPFD in canopy and understory were 0.64 and 2.21,respectively.Gap fraction in canopy changed significantly,with the Pinus massoniana forest having the highest value across the successional stages.This was related to the Pinus massoniana's unique canopy characteristics in gap fraction(10.98% for Pinus massoniana forest,10.62% for Pinus massoniana Schima superba forest).The general trend was that gap fraction reduced gradually with successional stages,however,the MLA increased at early stages,decreased subsequently.LAI measured by two different methods matched well,with both standard deviations less than 1.0.Also,the LAI and leaf density increased according with successional stages.These results showed that the light environment specifically evolved due to the canopy structures and microenvironments from different successional stages in EBLF.There are many factors affecting photosynthesis of plants interactionally rather than singly.Therefore,barely studying the effects of PPFD and canopy morphology on photosynthesis is not enough,further research on interactions among those factors should be done in the future.