Study On Growth Model And Sustainable Management Of Chinese Fir Plantation In Hunan Province

In order to explore the interaction mechanism between soil properties and growth characteristics of Chinese fir plantation,in order to comprehensively evaluate the sustainable management of Chinese fir plantation in Hunan Province,this paper applies five different ages of Chinese fir plantations at 6,8,10,12 and 20 years.A total of 43 standard plots were set up.The site factors and growth characteristics of Chinese fir plantations in the plot were investigated,and the physical and chemical properties of the soil were determined.The effects of different forest ages and site factors on the growth characteristics of Chinese fir plantations were studied to construct a regression equation.And density effect model,screening main site factors,analyzing soil properties of Chinese fir plantations with different forest ages.(1)The results of production elasticity analysis of the density effect of Cunninghamia lanceolata plantation in Hunan Province show that Ep(H)=1.581 is in the increasing phase of effect,so high-position index,that is,afforestation in a good site quality should be selected to increase the volume per plant;When the average advantage of the stand increased by 1%,the volume per plant increased by 1.581%.And Ep(N)=-0.761,the effect is in the negative effect stage,so the forest density of Chinese fir plantation should be reduced;when the forest density is reduced by 1%,the stand volume of the stand is increased by 0.761%,indicating that Hunan will be the same as Chinese fir.If the density of the forest is too large,the density should be appropriately reduced.When the plantation of Chinese fir plantation in this area increases Z%by many different factors,the yield increase is less than Z%.(2)Calculate the marginal yield of afforestation density and dominant wood height.The results show that under the existing conditions,when the other conditions are determined to be constant,the height of the dominant wood per hectare increases by 1 m,and the volume per plant increases by 0.024 m3;For each additional tree,the yield per plant of Chinese fir plantation was reduced by 0.00005 m3.(3)Regression analysis results of the relationship between growth characteristic factors and different forest ages of Chinese fir plantations with different forest ages showed that the estimation model of breast diameter of different forest ages under logarithmic function had the best effect,and the reciprocal function for tree height and accumulation of different forest ages The estimation model works best,and the polynomial function works best for the estimation model of single-soil volume of different forest ages.The regression analysis of the height of the tree height of the same forest age showed that the power function had the best fitting effect on the height of the DBH of the 6-year-old Chinese fir plantation,and the fit of the high DBH regression equation for the 8th,12th and 20th annual Chinese fir plantations.The best is the S function.In the 10-year-old Chinese fir plantation,the cubic function has the highest fitting height to the tree height.(4)The comprehensive evaluation index of sustainable management of Chinese fir plantation in Hunan Pro'vince is 0.60,which is a medium sustainable level.Among them,the site factor comprehensive index is:0.67,which is a moderately sustainable level;the soil property factor comprehensive index is:0.51,which is a general sustainable level;the growth characteristic factor comprehensive index is:0.58,which is a general sustainable level.(5)Growth characteristics of Chinese fir plantations with different forest ages:DBH,tree height,volume per plant and accumulation increased with the increase of forest age,and the stability of growth characteristics gradually increased with the increase of forest age..The average DBH of the 6th,8th,10th,12th and 20th annual Ch:inese fir plantations were 6.40cm,11.87cm,13.08cm,513.65cm and 22.26cm respectively;the volume per plant was 0.0113m3,0.0728m3,0.0949 m3,0.1064 m3,0.3605 m3;the average storage volume is 28.88 m3/hm2,183.82 m3/hm2,240.18 m3/hm2,254.81 m3/hm2,and 321.78 m3/hm2,respectively.