大兴安岭新林林业局3种林分类型天然更新幼苗幼树的空间分布格局

基于大兴安岭新林林业局落叶松林、白桦林和混交林3种主要林分类型16块样地的调查数据,依照幼苗幼树的株高划分为3个等级: Ⅰ级, 株高≤60 cm; Ⅱ级, 60 cm＜株高≤200 cm; Ⅲ级, 株高＞200 cm且胸径＜5 cm.在4种取样尺度下,采用负二项指数等7种聚集度指数,判定幼苗幼树的分布格局及格局强度,分析格局变化和格局规模.结果表明: 除落叶松林的落叶松幼苗幼树Ⅱ级最多,且随等级升高幼苗幼树密度先升高后降低外,白桦林和混交林的落叶松以及3种林分的白桦幼苗幼树Ⅲ级最多,而Ⅰ级最少,随等级升高,幼苗幼树密度均升高.落叶松幼苗幼树在3种林分4种取样尺度下均呈聚集分布.白桦幼苗幼树在白桦林中除在10 m×20 m尺度为随机分布外,均呈聚集分布.除落叶松幼苗幼树在混交林中5 m×10 m尺度时聚集强度最大外,落叶松在其他林分以及白桦在3种林分均在5 m×5 m尺度下聚集强度最大.在落叶松林,落叶松和白桦幼苗幼树的聚集强度随等级增大而减小,其中白桦由聚集分布变为随机或均匀分布;在白桦林和混交林中,落叶松和白桦幼苗幼树的聚集强度随等级升高不断增大,由均匀分布变为聚集分布.在3种林分类型中,不同更新等级落叶松和白桦幼苗幼树种群的格局规模均为25 m².落叶松和白桦幼苗幼树种群格局强度在不同林分类型、不同更新等级中差异明显.

Spatial distribution pattern of seedlings and saplings of three forest types by natural regene-ration in Daxin’an Mountains Xinlin Forestry Bureau,China.

Based on the survey data of 16 sampling plots in three main forest types (including Larix gmelinii forest, Betula platyphylla forest, and mixed coniferous and broad-leaved forest) in Daxing’an Mountains, the seedlings and saplings were divided into 3 grades according to plant height, i.e., Grade I, height ≤ 60 cm; Grade II, 60 cm < height ≤ 200 cm; Grade III, height ≥ 200 cm and diameter at breast height <5 cm. With four different sampling scales, distribution pattern and pattern intensity of seedlings and saplings were determined, and the pattern change and size were analyzed using seven clumping indices. The results showed that the seedlings and saplings of L. gmelinii were dominated by grade II, and the density increased first and then decreased with the increase of grade. However, L. gmelinii in the other two forest types (i.e., B. platyphylla forest and mixed fore-st) and B. platyphylla seedlings and saplings in all three forest types were dominated by grade III, with the smallest number in grade I, and the seedling density increased with the increase of grade level. L. gmelinii seedlings and saplings in the three forest types all had a clumping pattern on four different sampling scales. B. platyphylla seedlings and saplings in B. platyphylla forest also had a clumping pattern on four scales except the random distribution on 10 m × 20 m scale. L. gmelinii seedlings and saplings in mixed forest had the largest clumped intensity on 5 m × 10 m sampling scale, while L. gmelinii in the other two forest types and B. platyphylla seedlings and saplings in the three forest types had the largest clumped intensity with the sampling scale of 5 m×5 m. The clumped intensities of L. gmelinii and B. platyphylla seedlings and saplings in L. gmelinii forest decreased with the increase of grade level, in which the distribution of B. platyphylla changed from clumping to random or uniform pattern. The clumped intensities of L. gmelinii and B. platyphylla seedlings and saplings in B. platyphylla forest and mixed forest increased with the increasing grade, changed from uniform to clumping pattern. The L. gmelinii and B. platyphylla seedlings and saplings with different regeneration grades in all three forest types had the same population pattern size of 25 m². The population pattern intensities of L. gmelinii and B. platyphylla seedlings and saplings were significantly different in different forest types and regeneration grades.