Study On The Effect Of Lianas On The Secondary Forest Community At Low Altitude In Wuzhishan City

Because of its strong adaptability to the environment,liana can grow rapidly,twine climbing trees and cover their crowns,which results in the abnormal photosynthesis of trees,affects the growth of trees and even leads to tree death.In this study,the secondary forest at low altitude in Changhao Township of Wuzhishan City was taken as the research object.The biological characteristics of main lianas,Merremia boisiana and Pueraria lobata were observed,the biomass structure of supporting wood climbing by rattan plants was measured,and the influence of cutting on the secondary forest community characteristics was investigated,in order to explore the influence of rattan on the secondary forest community,which is the secondary forest community at low altitude in Wuzhishan City and provide scientific basis for recovery and renewal.The main results are as follows:(1)Through the preliminary investigation in the early stage,it is found that the two kinds of lianas:Merremia boisiana and Pueraria lobata are the most important in this area.In the observation of the growth characteristics of Merremia boisiana,it was found that the petiole length of Merremia boisiana was 1.76 times as long as that of the same stem diameter under full light condition when the light condition was insufficient;the leaves could grow from new leaves to mature leaves in about one month;the survival rate of weak branches was very low,and it was easy to appear the phenomenon of tip withering until the whole branch died.30 observation objects grew naturally three months later The survival rate was only 3.33%,the disappearance rate of 60 day old was the highest,and the life expectation was the highest at 0 day;the disappearance rate of strong branches was the highest at 30 day old,and the life expectation was the highest at 0 day.After 3 months,20 of the 30 strong branches still kept good growth,and the survival rate was 66.67%.The average intemode length of the main branch is not related to the average internode length of the branch;the stem diameter is not related to the internode length;the green stem of the samples of Merremia boisiana collected in July accounts for 38.26%of the total biomass,which shows a significant increase compared with 22.66%in May,indicating that May to October is the rapid growth period of the growth of the Merremia boisiana;there is no significant difference in the proportion of leaves to the total biomass in different seasons.In the observation of the growth characteristics of Pueraria lobata,it was found that the new leaves of Pueraria lobata would also grow rapidly after primary growth,and grow to maturity and finalization in about one month.The leaves of Pueraria lobata had strong shade tolerance.The stem of Pueraria lobata also has strong branches and weak branches,and it is also easy to wither at the tip.At the age of 60 days,the disappearance rate of weak branches is the highest,the life expectancy is the highest at 0 days,and only 6 plants survive after 30 weak branches grow naturally for 3 months;strong branches grow new lateral branches,and survive through the growth of lateral branches after the tip withers.The disappearance rate is the highest at the age of 30 days,and the life expectation is the highest at 0 day.After the natural growth of 30 observation objects for 3 months,22 plants survive.The internode length of Pueraria lobata will not change with seasons.The average stem of Pueraria lobata collected in July accounts for 22.79%of the total biomass,while the green stem of Pueraria lobata collected in October accounts for 44.87%of the total biomass,indicating that the period from July to October is the period of rapid growth of Pueraria lobata length.(2)The common Dimocarpus longan,Heteropanax fragrans and Litsea monopetala in the secondary forest area of Wuzhishan city are easy to be climbed by lianas;Pueraria lobata,Merremia boisiana,Tetracera asiatica and Broussonetia kaempferi are common climbing lianas in this area.The biomass distribution of trunk,branch and leaf of Dimocarpus longan,Heteropanax fragrans and Litsea monopetala were almost not affected when they were not climbing or a small amount of lianas were climbing.However,the biomass of trunk of the three plants did not change significficantly when they were climbing by excessive lianas.and the proportion of branches and leaves to the total biomass decreased significantly.Different kinds of supporting trees have different climbing conditions,and their abilities to resist the interference of lianas are also different.Lianas climbing on Dimocarpus longan often have more than Heteropanax fragrans and Litsea monopetala,and Dimocarpus longan has stronger resistance to the interference of lianas than Heteropanax fragrans.The proportion of leaves and stems of lianas attached to each plant is basically the same,among which the proportion of stems is 81.4%-86.2%,and the proportion of leaves is between 13.8%and 18.6%.(3)Three kinds of secondary forest communities were set up to investigate the species.The results showed that the proportion of Merremia boisiana,Pueraria lobata and Combretum olivaeforme in climbing lianas and crawl lianas was large.With the increase of recovery time after eliminate lianas,the sum of important values of Merremia boisiana,Pueraria lobata and Combretum olivaeforme decreased gradually,and the species of creeper and climber also increased;After eliminate lianas,the lianas has the largest important values changed from Merremia boisiana to Pueraria lobata.The sum of the important values of the positive tree species in the three secondary forest communities was 0.719 for not eliminate lianas areas,0.556 for the areas of eliminate lianas 2 years,and 0.536 for the areas of eliminate lianas 4 years,which indicated that the three secondary forest communities were in the primary stage of the succession mainly composed of the heliophilous species.The number of dead trees in the secondary forest community with eliminate lianas after 4 years is less than that of the secondary forest community without cutting;the tree diameter breast height of dead trees in the secondary forest community with 3 kinds of cutting treatment is not eliminate lianas>after eliminate lianas 2 year>after eliminate lianas 4 year.It indicated that a large number of small-scale trees died after eliminate lianas.The average tree diameter breast height and abundance of arbor layer were the largest in the areas after eliminate lianas 4 year,and the average crown diameter of secondary forest community without eliminate lianas was the smallest.The coverage and crown diameter of shrub layer are as follows:not eliminate lianas>after eliminate lianas 4 year>after eliminate lianas 2 year;the height of shrub is as follows:after eliminate lianas 2 year>after eliminate lianas 4 year,and the abundance is as follows:after eliminate lianas 4 year>after eliminate lianas 2 year.The abundance of herbaceous layer was after eliminate lianas 4 year>after eliminate lianas 2 year>not eliminate lianas.The abundance of crwal lianas was not eliminate lianas>after eliminate lianas 4 year>after eliminate lianas 2 year.The abundance of climbing lianas was the same as that of crawl lianas,showing a trend of decreasing first and then increasing,indicating that crawl lianas and climbing lianas also gradually recovered and spread after eliminate lianas.The Margalef species richness index,Simpson index,Shannon Wiener index and Pielou index of the arbor layer in the area after climinate lianas 4 year forest community were all higher than those of the area without eliminate lianas secondary forest community.The richness index and species diversity index of herbaceous layer increased significantly from the area without eliminate lianas to the area after eliminate lianas 4 year.The Margalef species richness index,Simpson index and Shannon Wiener index of creeping liana all showed that the species richness index of crawl lines for the mrea after eliminate lianas 4 year was higher than the area without eliminate lianas.The Margalef species richness index and Shannon Wiener index of climbing lianas increased with the increase of recovery time,while Simpson index showed that the area after eliminate lianas 4 year was higher than the without climinate lianas.The results of correlation analysis showed that the growth of climbing lianas inhibited the shannon-Wienner index and Pielou index of arbors and shrubs.In addition,the influence of the abundance and length of crawl lianas on the uniformity of shrub layer was also inhibitory.There was a positive correlation between the climbing height of climbing lianas and the species richness of herbaceous strata.The abundance of creeping liana had a strong negative correlation with the species richness of herbaceous layer.