The Optimal Management Mode Of Large And Medium Diameter Timber In Larch Plantation

Based on the data of provincial forest resource inventory and 95 sample trees in 22 sample plots for Larch plantation in Mengjiagang forest farm, stand growth and yield model, the diameter distribution model, taper equation, were established; stand merchant volume ratio and rotation were analysed; the effect of stand density was studied, the best stand density model was obtained to using dynamic programming; thinning techniques were studied to determine the initial, also as the interval period of thinning and the thinning quantity. This paper applies theory of dynamic programming on different cultivate objectives of forest to determine specific thinning ways. Based on the studies, the optimal management model was obtained large and middle diameter timber. The main contents include:1,Based on the data of fixed sample plot and key ecological forest monitoring plots in heilongjiang province,the growth model of average tree height, average diameter, stand density, stand basal area, stand volume and so on were systematically built.2,The site information were expressed by dummy variables in the study, the prodictor model of stand factors were fitted by traditional model including dummy variables, to resolve the compatibility problem of components and entire, the model of stand basal area and volume were established with nonlinear measure error simultaneous equations, to solve the traditional regression model parameter estimation question. It improved the precision of the models.3,The growth and yield model of larch plantation in Heilongjiang were tested by using independent inspection data, the results showed, the model had high precision and powerful applicability. The system of stand growth model offered good stability, high accuracy.4,Using the model of stand growth and yield, The quantitative maturity age was obtained in the stands of different planting density and site index.The quantitative maturity ages of larix gmelinii were 20-35 years. The quantitative maturity age was a negative correlation site index and stand density, it was early in high site index and density stand, and had certain duration.The quantitative maturity age of small diameter timber was prior, middle diameter timber was more than 30 years, large diameter timber was over 50 years. According to the buck standard, stand out-of wood species was got by diameter distribution and taper function, The technology maturity age of middle diameter was 33-40 years, large diameter timber was 50-55 years, Using NPV method for calculating economic mature, the economic mature age of middle diameter was 33-41 years, large diameter timber was 49-55 years, the sensitivity analysis found that the biggest influence on net present value is lumber sales price, the second is the interest rate changes, the lowest cost, as the site class reduced, sensitive to changes in factors influence the effect of annual net present value was increased, In 16 site index under the conditions of the exponential sensitive factor, the biggest influence on change, so the biggest risk of face. The rotation period was determined by comprehensive analysis method, According to the three mature age, showed the following conclusions:the middle diameter timber was suited on 16 site index, rotation was 39-41 years,18 site index developed the middle diameter timber, rotation was 36-38 years, large diameter timber rotation was 53-55 years,20 site index cultivated large diameter timber, rotational was 49-52 years.5,Density effect model of larch plantation was established, the elasticity of production and marginal effects were analysed, the relationship of volume and density can be very well explained. Based on the model, the optimal density control model of larch plantation were derived with dynamic programming method, as age and site index increased, number of stems were decreases. The optimal stand density were received in different site conditions6,the initial stage, the interval and intensity are analyzed in the study, trees growth began to decline was regard as then the initial period of thinning, the interval was not only effected site conditions and planting density, was but also relation with last thinning intensity, this paper studies found that starting period of thinning in larch was over 18-24 years, the interval was 4-6 years, intensity was 20%-30%.The thinning types of cultivation target timber were determined by dynamic programming method (the initial stage, the interval and intensity), the research found that the thinning shorten the rotation, and improved yield of final cutting.7,based on comprehensive comparison of different management pattern, the site conditions, the optimal operation model were developed in different site. the middle diameter timber was suited on 16 site index, the stands of 3300N/hm2 and 4400N/hm2 were thinning 3 times, and had maximum economic benefits, the internal rate of return was more than 15%; large diameter timber was suited on 18 site index, the density of the plants (4400N/hm2) were thinning five times and 3300 N/hm2 were 4 times can obtain the biggest economic benefit.20 site index cultivated large diameter timber, after thinning 4-5 times, the stand will gain the maximum economic benefits.The results have an important significance that resolved lumber shortage and accelerate to cultivate wood timber industry, and were theoretical basis for improving larch plantation management...