Heartwood Formation And Research Of Optimal Rotation Age Of Chenshan Red-heart Chinese Fir

Chinese fir is the main fast-growing timber species in south China,which plays an important role in the practice of plantation timber production.As one of the geographical provenances of Chinese fir with excellent material,Chenshan red-heart Chinese fir has a high heartwood proportion and it is the raw material for furniture and architectural decorations.The market demand for red-heart Chinese fir is large,resulting in the shortage of red-heart Chinese fir resources.In order to cultivate the high-quality red-heart Chinese fir that meets the market demand,give full play to the resource advantage of red-heart Chinese fir plantation,it is one of the key of plantation management to determine the optimal rotation age of red-heart Chinese fir.In this study,9,15,26,34-year-old red-heart Chinese fir from Chenshan forest station and 29-year-old red-heart Chinese fir from Aoshang forest station were selected as the research object.Here,we investigated the horizontal and vertical variation of heartwood and sapwood,simulated heartwood formation process,to determine the quantitative mature age,technological mature age and economic mature age and to comprehensive analysis the optimal rotation age of red-heart Chinese fir using stem analysis method,model simulation and economic benefit analysis methods,The main results are as follows:(1)The heartwood diameter and area of Chenshan red-heart Chinese fir increased with the increase of age and xylem diameter.When the xylem diameter reached 4～8 cm,heartwood began to form.The heartwood diameter and area of Chenshan red-heart Chinese fir decreased with the increase of tree height.The sapwood width was larger at the base of the trunk and remained stable at 10%～60%relative to the height of the trunk,and then decreased sharply.(2)The mature ages of DBH,height and volume of Chenshan red-heart Chinese fir were 9 to 17 years,6 to 16 years and 20 to 28 years,respectively.Through fitting the growth process of DBH,height and volume of Chenshan red-heart Chinese fir,we found that Weibull model had the best fitting effect on DBH,tree height and volume.The results of model fitting showed that the average growth of DBH and height reached the peak value at the 10th and 11th year,respectively,while the average growth of volume reached the peak value at the 30th year,so it was determined that the quantitative maturity age of Chenshan red-heart Chinese fir was at the 30th year.(3)The wood density from the base of the trunk to the tip of the trunk decreased gradually,and increased gradually with the increase of the age.Xylem diameter,DBH,tree height,crown width and stand density all directly affected heartwood formation.Red heartwood rate decreased with the increase of the trunk height.The heartwood of red-heart Chinese fir began to form at the 7th year,and the red heartwood rate reached the peak value(60%)at about the 40th year.Therefore,it was determined that the technological maturity age of red-heart Chinese fir was 40 years.(4)The economic maturity age of red-heart Chinese fir calculated by net forest income method was 26～34 years.The economic maturity age of red-heart Chinese fir determined by present net worth method should be 34 years later.Using internal rate of return method to determine the economic mature age was 24～34 years.By selecting interest rate,wood price and forest cost,the sensitivity analysis of the economic benefit of red-heart Chinese fir showed that wood price had the greatest influence on the sensitivity of economic benefit of red-heart Chinese fir,followed by forest cost,and interest rate has the least influence on the sensitivity of economic benefit.(5)According to the basis of technological mature age,emphasizing on economic mature age,determine reasonable quantitative mature age principle to determine optimal rotation age.The quantitative mature age of red-heart Chinese fir was 30 years,the technological mature age was 40 years,the economic mature age was after 34 years.Therefore,the optimal rotation age of Chenshan red-heart Chinese fir was 40 years.This research through the study of optimal rotation age of red-heart Chinese fir,can give full play to the forest productivity and forest production potential,improve the value of the Chenshan red-heart Chinese fir,for promoting the intensive management and scientific management plantation had important practical significance,directional cultivating high-quality for decoration to provide basic data and theoretical basis.