Studies On The Growth And Yield Models Of Poplar Plantations In Southern Area

The main planting area of southern type poplar is mostly mixed clones afforestation. According to the 163 sample plots which came from the pure even-aged poplar plantations in Jiangsu, Shandong, Anhui, Hunan and Hubei, the paper established a growth and yield model system with multifactorial unified description based on the diameter distribution model. Main results of the study are as follows:1. The growth difference was tested on the main planting clones I-63, I-69 and I-72 of southern type poplar. The results show the growth of diameter, height, volume demonstrated similarities in the 3 clones. The average relative error is less than ±7.0%.2. Applying sample plots, 7 index classes were divided out (baseline age is 6 years, and the interval of site index class is 2m), and single form and multiple form site index tables of poplar plantations were constructed. Meanwhile, 7 factors, eg. pH value, organic substance content, soil effective depth, soil total-nitrogen content, water table, soil bulk density and soil texture were picked out as predicting factors, and quantification site index prediction table was established so that provides a uniform quality evaluation for non-forested land and forested land.3. The relationship between basal area at breast height and stand density can be described as (-|D)_g = aN^-b in un-thinned and with same dominant height plots. After fitting, the basal area at breast height prediction model, eg. (-|D)_g=0.9681H₀ ^1.3614 N^-0.032H₀^0.5402 was selected for poplar plantations in southern area.4. The diameter distribution of poplar plantations in southern area was studied with 5 methods to estimate parameters of Logistic equation and Weibull function. The parameter recovery of Weibull function fits best, the acceptance rate reached 75.0%. The parameter prediction of Logistic equation fits worst, the acceptance rate was only 52.5%.5. Based on power function H_i=1.3+c₀D_i^c₁ and Schumacher height-diameter relationship equation H_i =1.3 + C₀e^-c₁/D_i, this paper discussed how the parameters (c₀ and c₁) vary with different stand conditions. Power function and hyperbola were used to describe the relationship between c₁, c₁ and A,H₀. Eighteen differential difference equations were chosen by different expression's combination. After fitting, the universal height-diameter curve of poplar plantations in southern area H_i=1.3+1.3094 H₀^0.9211 e^-3.7027/D_i was constructed.6. The single timber volume equation V=0.000022 D^1.8012 H^1.3184 was selected based on the fitting of 8 volume equations in common use. Further more, the estimation model of...