湿地松育苗密度的研究

Study on the Seedbed Density of Growing Slash Pine Seedling

研究了不同育苗密度水平下培育１年生湿地松裸根苗的苗木质量和经济效益。在其它培育措施不变的情况下，育苗密度是决定苗木质量的主要因素。随着育苗密度的增大，苗木的总体质量下降；不同密度下的一级苗质量也有差异，以低密度时为佳。一级苗产量在１１１株／ｍ２时最高，二、三级苗产量随密度而增加，１６７株／ｍ２时三级苗百分率接近国家标准１５％的许可界限。如只允许一级苗用于造林，则６９株／ｍ２时产出投入比最高，如一、二级苗分别定价种植，产出投入比以１１１株／ｍ２最高。如只去除不合格苗（三级苗），其余均按合格苗不分级定价造林，则在试验范围内密度越高，效益越好，而质量越差，这种做法不可取。若综合对苗木质量、优质苗产量和苗木生产经济效益的分析，适宜的湿地松育苗密度应为７０～１１０株／ｍ２一级苗百分率随密度增加而降低，三级苗百分率则随之增加，分别呈负的和正的幂函数关系。二级苗百分率在试验密度范围内基本上呈增加趋势，在最高密度时则有所下降（表５）。由于总产苗量和各级苗百分率变化的共同作用，各级苗的产量则表现为一级苗产量在１１１株／ｍ２时最高，二、三级苗产量随密度而增加。在１３９株／ｍ２时，二级苗产量已超过一级苗量，１６７株／ｍ２时，三级?

The bareroot seedling quality of slash pine(1～0) grew at different nursery density levels was studied,and their economic benefits analyzed. It showes that seedbed den-sity is a decisive factor to seedling quality which decreases with the increase of density. The yield of grade l seedling are the highest at 111/m2,and the nurnber of grade 2 and 3 seedlings increase by larger density,the percentage of the grade 3 seedling reach 15%of the permissive limit of the national seedling production standard at 167/m2. If only grade 1 seedling in qual- ified ,the output/input is the highest at 69/m2; when grade 1 and 2 seedlings are used for plantation and give different prices, the output/input is highest at 111/m2. The practice of outplanting the ungraded seedlings(grade 3) which leads to higher density,at which the ben-efit of production is highest but the seedling quality is worst.A comprehensive survey of seedling quality, yield of qualified seedling and the economic benefit has been made,and the rational seedbed density would be 70～110/m2.