摘要：
To explore the effect of density on growth of young Mytilaria laosensis stands with na tural seed re-generation on clearcut land, a single factor randomized block design experiment with natural spacing (ck treatment, three replications) and spaced seedling (TA, TB and TC treatments, three replications) stands was es-tablished, and variance analysis of the stands were analysed with Least Significant Difference methods in Data Processing System (14.5), to test diameter at breast height (DBH), tree height, and single volume. Results showed that: (1) between ck and spaced seedling stands, during 3.5 years after spacing, stand density signifi-cantly decreased (P0.05). Spaced treatments (finished in 1.5 years old of seedling, remain density in hectare: TA 1650, TB 2800, and TC 2500)significantly improved (P<0.01) the average growth of the stands and reduced differentiation of diameter grades in the stands. (2) The higher stand density(ck), the earlier intersection time of the average growth curve and the annual growth curve for av-erage DBH or tree height of the stand was appeared. Also, the peak value of annual growth for average DBH of ck stands occurred in the second year, and the peak value of spaced stands was during the second and 4th year. Before the 5th year, it was fast growth period for the stands with natural seed regeneration, so spacing was very important with radial growth of the stands. (3) The time of intersection for curves of average growth and annual growth of tree height in the ck stands was between the second and third year, but with the spaced stands did not intersect before the 5th year. Growth for tree height of dominant trees in all stands before the 5th year was fast (the annul increment of top height in each treatment was more than 1.49 m in each year). (4) Different types of stands had different diameter distributions; the ck stand had an inverted J distribution, but the spaced stands had an approximately normal distribution. (5) In the spaced stands, after 3.5 years, the av-erage growth for DBH, tree height, and volume of less dense forest stands (TA treatment stands) was better than those with higher density treatments (TC or TB stands). Thus, understanding of the mature period for seeds, the seed falling-stage, and natural regeneration characteristics of Mytilaria laosensis could enhance the scientific cutting time, cutting methods, clean ways for removing residues, shrubs, and herbaceous plants, and methods for spacing seedlings to enable effective natural regeneration on cutover land thereby promoting forest growth.%为探索米老排Mytilaria laosensis皆伐迹地种子天然更新幼林生长及密度效应,基于单因素随机区组试验设计,研究了米老排皆伐迹地不同密度种子天然更新幼林生长状况.结果表明:①在间苗作业后1.0～3.5 a,未间苗抚育林分(ck)与间苗抚育林分在平均胸径、 平均树高和平均单株材积生长量(总生长量与连年生长量)上差异显著;但各林分优势木胸径、 树高和单株材积的总生长量差异不显著.间苗处理提高林分平均生长水平和减小林分径阶分化程度的作用明显.②间苗抚育林分平均生长量曲线与连年生长量曲线的相交时间与密度呈负相关;未间苗抚育林分平均胸径连年生长量的峰值出现在第2年,间苗抚育林分出现在第2～4年.前5a为种子更新林径向生长的旺盛期,间苗抚育保留合理密度对林分的径向生长极为重要.③未间苗抚育林分平均树高的连年生长量与平均生长量在第2～3年相交,而间苗处理平均树高的连年生长量与平均生长量在第5年仍未相交;林分优势木前5a的高生长处于旺盛期.④未间苗抚育和间苗抚育的林分径阶分布类型不同,前者呈倒J型分布,后者近似正态分布,间苗处理改变林分径阶分布的类型、 峰值和分化程度作用明显.⑤在间苗抚育后第3.5年,密度较低林分的平均生长量优于密度较高处理林分.⑥充分利用米老排种子成熟期、 落种期和天然更新特性,通过科学的采伐期、 采伐方式、 迹地剩余物清理方式和迹地更新林的间苗抚育措施,可有效实现采伐迹地天然更新和促进其更新林的生长.
