不同密度中幼龄湿地松人工林生长过程的经济效益分析

Economic Benefit Analysis of the Growth Processes of Young and Half matured Slash Pine Plantations with Different Densities

用１６ａ连续测定资料，分析了不同密度中幼龄湿地松人工林生长过程的经济效益状况．结果表明：密度对林木分化和产品结构的影响明显，密度越小，Ⅰ，Ⅱ级木株数所占百分比大，其大径材的出材量也高，反之林木分化明显，Ⅳ，Ⅴ级木所占比例增加，小径材出材量高；各密度林分在５ａ前投入大于产出，成本效益比小于１，净现值和收益率为负数，随着林分年龄增大，成本效益比、净现值和收益率逐年增加，其中成本效益比与净现值在１３～１４ａ达到最大值，收益率第９～１０年为最大，此后逐年下降；不同密度林分的总出材量、成本效益比、净现值和内部收益率以密度为３２００株／ｈｍ２的林分最高，其经济效益最佳．

Based on the data collected for 16 years,the economic benefit of the growth of 4 young and half matured slash pine plantations with different densities have been studied.The results indicate that density had a significant influence on the tree division and timber product structure.The less density,the higher the ratio of class Ⅰ and class Ⅱ trees,and the large log volume increased.Conversely,the more density,the higher the ralio of class Ⅳ and class Ⅴ trees,and the division of tree was more considerable and the small log volume increased.The input exceeded the output in the first 5 years after afforestation,but cost and benefit ratio ( B/C ),net present value ( NPV) and internal rate of return (IRR ) increased gradually with the growth of plantations. B/C and NPV culminated at 13～14 years while IRR reached the highest at 9～10 years,then they reduced gradually.Among different density plantations,the economic indicators such as B/C , NPV and IRR amounted to the highest at the density of 3 000 stems·hm -2 .