A Study On Key Techniques For Directive Cultivation Of Masson Pine Plantations In Guangxi Province

For solving the problem of directive cultivation technical system of masson pine plantations in Guangxi Province, effects of afforestation techniques, fertilization, density control on the yields and wood characteristics of Masson pine plantations were studied. Based on the data investigated for many years, this paper, summarized the results as follows:(1) Afforestation methods had a significant effect on survival rate and growth of young masson pine plantations, and the method with"burning forest land plus artificial weed control"could achieve best survival and growth perfomance.(2) Fertilizing significantly improved the growth of middle-aged and near-mature plantation of masson pine in southern region, while application of P fertilizer could increase timber quality and economic benefits.(3) Planting densities had significant effects on plantation growth and economic benefits. With the increase of planting density, diameter at breast height (DBH), single tree volume and crown diameter decreased, whereas a positive relationship between stand volume and planting density was observed. However, this planting density effect would disappear as the stand age increasing. With stand age increasing, correlation of net present value (NPV) and stand density transformed from positive to negative and internal rate of return (IRR) of all planting density treatments dropped and approached the same. The time of NPV peak was postponed with the increase of stand density, but application of thinning techniques could improve the wood quality and economic benefits of masson pine plantations. Density control mathematic model system developed based on the theory of nature thinning provided a scientific guide for directive cultivation of masson pine plantations in future.(4) The results from this study indicated that fertilization had significant effects on foliar nutrient content of N,P,K,Ca and Mg, and nutrition diagnosis is necessary during fertilization of masson pine plantations. However, fertilization had not significant effects on return of total amounts of nutrients through litterfall.(5) As planting density increased, the width of growth ring decreased, while wood basic density increased. The tracheid morphological form of masson pine plantation was not significantly affected by the planting density. Fertilization could improve the wood quality, but it did not affect the wood fiber length significantly.(6) According to cultivation objectives and main cultivation measures, 2～3 kinds of optimum cultivation patterns were developed for each site index by using the dynamic economic evaluation, which increased 1.6～5.0% IRR compared to those in old cultivation patterns.