关键词: 格木, 生长过程, 林分分化, 密度管理, 大径材培育

Abstract:

Erythrophleum fordii is one of the main native precious timber species in southern China.Understanding the tree growth characteristics and stand differentiation process of plantations,and accordingly determining appropriate thinning timings are crucial for optimizing large-size timber cultivation techniques for the E.fordii.From 10 sample-plot investigation in E.fordii middle-aged plantations,the trees were divided into three social classes involving dominant,average,and suppressed trees.With the competitive responses and growth dynamics of trees across different social classes,the differentiation processes within the stand and proposed corresponding management strategies were analyzed.The results showed that:1) Significant growth differentiation is among individuals within the stands.Trees at competitive disadvantage typically exhibit higher stem form factors,height-to-diameter ratios,and crown-to-diameter ratios,but lower crown length-to-height ratios.The competitive responses were primarily manifested by increased tree height,while Diameter at breast height(DBH) and crown dimensions showed relative declines in E.fordii plantations.2) DBH increased slowly in the first 5 years,entered a rapid growth phase from Year 6 to 25,and significant class differentiation emerging at Year 7,while height differentiation occurred earlier with two distinct divergences at Year 3 and 7,respectively,and its rapid growth phase initiated at Year 3 and persisted until approximately Year 15.The intersection points of current annual increment(CAI) and mean annual increment(MAI) occurred at Year 22 to 24 for DBH and Year 10-12 for height.Individual tree volume entered rapid growth phase after Year 15,its CAI and MAI not intersecting by Year 35,indicating unattained quantitative maturity.During Year 25 to 35,tree volume of dominant trees consistently accounted for approximately 50% of stand volume per unit area,reflecting intense competition unfavorable for target tree development.3) Through comprehensive analysis of the tree species characteristics and stand differentiation process,especially the early branching of E.fordii could result in low branch height and numerous knots after forest formation,which adversely affects the later timber yield and wood quality,therefore,the large-size timber cultivation of E.fordii could take phased management strategy,emphasizing stem form and quality improvement during the young and middle stages of plantations,followed by yield optimization in the later stage,and initial target tree selection could be at Year 7,but not need thinning;the first thinning would be around Year 15;and the second and the third thinning would be around Year 25 and 35,respectively.

Key words: Erythrophleum fordii:growth process, plantation differentiation, density management, large-size timber cultivation