Testing the self-thinning rule in Chinese fir (Cunninghamia lanceolata) plantations
Twenty-eight years of observation data on Chinese fir (Cunninghamia lanceolata) in even-aged pure stands were used to scrutinize Reineke’s (1933) empirically derived stand density rule (N∝d?,N = tree number per unit area,d= mean stem diameter),Yoda’s (1963) self-thinning law based on Euclidian geometry (v∝N?,v = mean tree volume),and West,Brown and Enquist’s (1997,1999) (WBE) power rule based on fractal geometry (v∝d?).Ordinary least square regression (OLS),reduced major axis regression (RMA),and stochastic frontier function (SFF) algorithms were used to estimate the self-thinning exponents for seven mortality rate intervals (2-68%,5-68%,10-68%,15-68%,20-68%,25-68% and 30-68%).The estimated exponents were then tested against the theoretical self-thinning exponents.Estimates of Reineke’s exponent ? were significantly different from -1.605Reineke’s rule and -2 WBE’s rule; estimates of Yoda”s exponents ? varied around -3/2Yoda’s law but were significantly different from -4/3WBE’s rule; estimates of WBE’s exponent ? tended to follow neither 3Yoda’s law nor 8/3 WBE’s rule.Self-thinning exponents fluctuated with mortality rate intervals and were not constant irrespective of the method of fitting self-thinning exponents.The empirical self-thinning laws can only serve within a certain stand-density interval.None of the three self-thinning models could explain the instantaneous relationship between tree size and stand density.Lack of objectivity in selecting data points and in the method of fitting coefficients for estimating the self-thinning boundary line leads to different self-thinning trajectories using the same empirical data.Homogeneity of the model’s assumptions and ignorance of the instantaneous relationship between size and numbers is an obstacle.We should attempt to explain the deficiencies of the law’s assumptions and focus on differences in tree size at different self-thinning growth stages.
Cunninghamia lanceolata (Lamb.) Hook self-thinning law stand density rule mortality rate intervals
Hong-gang Sun Li-hua Fu Jian-guo Zhang Ai-guo Duan
Institute of Subtropical Forestry Research of Chinese Academy of Forestry Zhejiang Fuyang 311400 Saihanba Machinery Forestry Center Hebei Weichang 068466 Institute of Forestry Research of Chinese Academy of Forestry,Beijing 100091
国内会议
南京
英文
1-15
2012-09-01（万方平台首次上网日期，不代表论文的发表时间）