Research On Characteristics Of Forest Canopy Structure And Light Environment At Funiu Mountain Nature Reserve

Forest canopy is the most direct and active interracial layer between forest with the outside environment, It has an important influence on energy exchange of ecosystem,biodiversity,climate change and so on.canopy structure belongs to one of the important aspects of forest canopy research. It plays a significant role in interactions between plant communities and environment.Through studying canopy structure,we can obtain a deep understanding about patterns,processes and operating mechanism of forest ecosystem.Canopy structure also can change understory light distribution through light transmission,reflection and absorption.To understory vegetation,their growth and regeneration depend on light heterogeneityThe Funiu Mountain Nature Reserve is the combination of Subtropics and Warm-temperate zone,It has the north and south climate characteristic,and also protect completive.It is the good place to study the forest canopy structure along the environmental gradients.This research develops in Funiu Mountain Nature Reserve,the object of this study is the deciduous broad-leaved forest ecosystem which contains evergreen species on the south slope and the typical deciduous Broad-leaved forest ecosystem on the north slope.We use the Winscanopy analyzer to study the forest canopy structure and light environment.The main conclusions this Paper comes to are as follows:On the north slope of Funiu mountain,from 900m to 1900m,GF decreases with the elevation and then increases.LAI has the opposite changes.This is because human disturbances are serious at lower elevation,leading to sparse forest density.In such forest stand,most of the trees are very young.At mid-elevation,forest community is less affected by human disturbance,and it has the perfect hydrothermal condition for supporting Quercus aliena growth.Limited by habitat conditions, elfin wood is widely distributed in high altitude.MLA concentrates in 20～30°.MLA of high elevation communities is small compared to low-mid elevation.PPFD over canopy shows a trend of rise with the increase in elevation.However,direct PPFD and total PPFD under canopy display a "high-tow-high" tendency.,On the south slope of Funiu mountain,there are not obvious different among communities as a result of good vegetation protection.Study results show that GF value are big in Quercus acutidentata over mature forest(1550m),Quercus variabilis forest(1050m) and elfin wood(1850m).The maximum value of LAI appeares in Quercus acutidentata mature forest (1450m).Like the north slope,the value of MLA concentrates in 20～30°,however,is larger than north slope on the whole.In communities of lower altitude,the values of PPFD under canopy are more or less similar each other.But there are obvious differences among communities in the midaltitude. Direct site factor fluctuates according to the altitude,however,the change of diffuse site factor is not so obvious.The same as Quercus glandulifera forest,LAI of Quercus acutidentata mature forest has maximum value in September.However,in May,forest canopy is not so closed because leaves have not become mature enough at this season.So,LAI value is smaller than September.Both MLA and GF reach maximum in November after leaves falling.daily variation of total PPFD over canopy presents unimodal curve both Quercus glandulifera forest and Quercus acutidentata mature forest,reaching peak at about 12 o'clock.Daily variation curve of PPFD under canopy appears fluctuation,and Quercus acutidentata mature forest is more drastically.So,we can know that the canopy of Quercus acutidentata mature forest has a greater impact on the solar radiation than Quercus glandulifera forest.As for seasonal variation,the PPFD under canopy of Quercus glandulifera forest are higher than mature forest at different times.By comparing site factor,it shows that light transmittance of Quercus glandulifera forest is higher than mature forest.The differences of canopy structure between the two stands lead to heterogeneity of understory light environment. Through this study,we have gotten some ideas about canopy structure and light environment of Funiu Mountain Nature Reserve.The results will provide theoretical and data basis for species diversity and dominant species regeneration researches.At the same time,it has important practical significance for restoration and reasonable management of forest ecosystem...