Evaluation On Tending Effect Of Typical Stands In Chongyi County,Jiangxi Province

Relying on the national forestry and grassland Bureau’s "national forest quality precision improvement" project,we set up 40 sample plots at 8 observation points in Chongyi County,Jiangxi Province,to monitor and evaluate the forest quality.In order to explore the influence of thinning on the growth of trees,to observe the changes of the structure of tree diameter and order,and to explore the response differences of different ages of Chinese fir(Cunninghamia lanceolata(Lamb.)Hook)to thinning,we carried out tending thinning on some artificial forest land mainly composed of Chinese fir,Lechang Michelia(Michelia chapensis Dandy).The changes of the tree layer biodiversity and the diameter step structure were monitored in two forest sites.The main conclusions are as follows1.Thinning has a significant promoting effect on the annual radial growth of Cunninghamia lanceolata and Michelia Lechang.The radial growth of the tending sample plot is 1.3-2.2 times of that of the control plot;the annual sectional area of the tending sample plot is also significantly increased,and the tending sample plot is 1.4-3.0 times of that of the control plot;for the change of individual volume,the tending sample plot is 1.5-2.6 times of that of the control plot.The volume growth rate of tending sample plot was also significantly higher than that of the control plot,but the volume of tending sample plot did not show the same change,the volume of tending sample plot did not change much,while the volume of the control sample plot increased to a certain extent.In this study,the effect of thinning on tree height was not consistent2.Thinning has a significant effect on DBH structure of the same age Chinese fir plantation.After thinning,the proportion of trees at the peak and above of the thinning sample plot is significantly higher than that of the control plot.The number of trees at the peak and above of the thinning sample plot is about 55%higher than that before thinning,which is significantly higher than that of the control plot After thinning,there was a large diameter stage which was not found in the control plot.The results showed that thinning significantly increased the proportion of large-scale trees in the stand and made the diameter structure of the same age stand tend to normal distribution3.The order of annual average radial growth after thinning is 22 years>15 years>34 years;the order of high growth after thinning is 15 years>34 years>15 years,and the difference of high growth is large.In terms of the average annual growth of sectional area,the order was 22 years old>34 years old>15 years old.The younger stands have a higher average annual volume growth rate,and the 15 year old stands have an obvious advantage.For the average annual volume growth,the result is just the opposite,but the older stands have a higher growth rate,34 years old>22 years old>15 years old.4.In the short term,tending has little impact on the biodiversity of arbor layer.From 2016 to 2018,the tending and control of various plots have little change on Simpson index and Shannon Weiner index.The natural broad-leaved forest and Castanopsis Castanopsis natural broad-leaved mixed forest are more stable in inverted "J" type distribution through human intervention,which makes the diameter structure of the forest reasonable,so as to make the forest more healthy and reasonable growth.