Study On The Effect Of Broad-leaved Trees On The Growth Of Moso Bamboo In Bamboo-broad Mixed Forests Based On Terrestrial Laser Scanning

Bamboo is an important economic forest species in southern China,not only for its economic,ecological and social benefits,but also for the important role it plays in water and soil conservation.As a management model of bamboo forest that has been promoted in recent years,bamboo-broad mixed forest can not only significantly improve the economic benefits of bamboo,but also contribute to the sustainable management of bamboo forest.In this study,two types of mixed plots were set up in the bamboo-broad mixed forest in Tianbaoyan Nature Reserve,Yong'an City,Fujian Province:(1)20 circular plots of bamboo-broad mixed forest,in which broad-leaved trees mainly include Castanopsis carlesii,Choerospondia axillariss,Castanopsis fargesii and Alniphyllum fortunei.and 3 plots of pure bamboo forest were set up;(2)15 square plots of bamboo and broad mixed forests with different mixing proportions,and 5different mixing ratio gradients are set,which are 0-10%,10%-20%,20%-30%,30%-40 and over 40%,and 3 control plots were set at the same time.The parameters of each plot were extracted by Terrestrial Laser Scanning(TLS),and the treatment and analysis were carried out to obtain the Diameter at breast height(DBH),tree height,crown diameter,crown volume and crown surface area of broad-leaved trees,as well as the number,DBH and AGB of bamboo in the plots.Relationship between the growth of different broad-leaved tree species on the growth of bamboo,the relationship between the canopy characteristics of different broad-leaved trees and the growth of bamboo,the competition between different broad-leaved tree species and bamboo,and the relationship between broad-leaved trees and bamboo growth in different mixing proportion forests were obtained.The main results are as follows:(1)Effects of different broad-leaved tree species on the growth of bambooThe number of bamboo in the unit area of C.fargesii and C.axillariss decreased with the increase of distance,while the number of bamboo in unit area of the C.carlesii and A.fortunei plots increased first with the increase of distance,and the maximum appeared at 2 m and 3 m respectively.The maximum DBH of bamboo in the plots of C.fargesii,C.carlesii and A.fortunei were found to be 4 m away from the broad-leaved trees,while the maximum DBH ofbamboo in the plots of C axillariss appeared at 2 m away from the broad-leaved tree.And the DBH at 4 m was close to 2 m in the plots of C axillariss.The AGB of bamboo in the plots of C.axillariss is much higher than that of the other three species.Among them,the average number of bamboo in the plot of A.fortunei is the least,but the DBH is the largest,making its AGB higher than that in the plots of C.fargesii and C.carlesii.In addition,compared with pure bamboo forest,these two types of broad-leaved trees promoted the increase of bamboo AGB,and the AGB of bamboo in the deciduous broad-leaved tree species was larger than that of evergreen broad-leaved trees.(2)Relationship between crown characteristics of different broad-leaved trees and growth of bambooWhen the same specie of broad-leaved tree was mixed with bamboo,the difference of crown diameter,crown volume and crown surface area of broad-leaved tree had significant effects on the number,DBH and AGB of bamboo.In addition,the diameter,volume and surface area of the broad-leaved tree crown are not consistent with the number,DBH and AGB of bamboo.In general,the effect of crown volume and surface area on the growth of bamboo was consistent,while the effect of broad-leaved crown diameter on the growth of bamboo showed a difference between these two factors.(3)Competition between different broad-leaved tree species and bambooThe CI(competition index)corresponding to the maximum number of bamboo in the C.fargesii,C.carlesii,A.fortunei and C.axillariss plots were 1.01,0.80,1.13 and 0.71,the maximum average DBH of the bamboo were 0.91,0.57,1.13 and 0.44 and the maximum AGB of bamboo in the unit area were 0.91,0.55,1.13 and 0.71,respectively.Among them,the maximum number,DBH,and AGB of bamboo in the plot of the A.fortunei correspond to the same broad-leaved tree CI,while the other three broad-leaved species have certain differences.For the plots of the same broad-leaved tree species,the effect of the CI on the number of bamboo,DBH and AGB of the bamboo in the unit area is different,and the difference is obvious when the CI changes.(4)Relationship between broad-leaved tree and bamboo growth in mixed forests with different mixed proportionsAmong the mixed forests with different mixed proportions,the effects of broad-leaved trees on the growth of bamboo were significant,and the effects of different mixed proportions on the number,DBH and AGB per unit area of bamboo were inconsistent.When the mixed proportion is 10%-20%,the broad-leaved tree has the best promoting effect on the bamboo number and AGB.When the mixed proportion is 20%-30%,the broad-leaved tree has the best promoting effect on the growth of DBH.Therefore,the proportion of these two kinds of mixed forest can be selected according to the management purpose.TLS technology can extract the parameter information of bamboo-broad mixed forest accurately and non-destructively,especially the crown characteristics information of broad-leaved trees.In addition,the crown characteristics of different broad-leaved trees have significant effects on the number,DBH and AGB of bamboo.This paper specifically analyzes the relationship between the crown characteristics of four target species and the growth of bamboo,which can provide certain data for the management of bamboo and broad-leaved mixed forest.basis.