大兴安岭南段次生林区倒木对森林更新的影响

Impact of Fallen Trees in The Southern Section of Daxing'anling on Forest Regeneration

[目的]内蒙古大兴安岭南段赛罕乌拉森林生态系统是内蒙古罕山次生林的典型地段。研究该地区的倒木分布情况以及倒木对森林更新的影响。[方法]采用样地调查法对样地内的倒木及其森林更新的情况进行调查。[结果]研究发现,倒木样地更新密度为(4050±824)株·hm^(−2),枯立木样地更新密度为(2950±265)株·hm^(−2),对照样地更新密度为(2625±237)株·hm^(−2);赛罕乌拉倒木平均储量有(58.51±16.56)m^(3)·hm^(−2),其中分解等级Ⅱ、Ⅲ、Ⅳ、Ⅴ级的倒木分布密度分别为(50±21)、(806±198)、(189±76)、(22±5)株·hm^(−2)。研究区倒木主要以“干基折断”的形式存在,占倒木总数的68.78%。[结论]大量倒木积累在林内,对种子、幼苗、幼树等更新产生障碍、拦截、遮阴作用,同时倒木在倾倒瞬间和倾倒后较长时间会对林下的更新幼苗等植物产生严重的压死、砸伤等负面影响,压死砸伤率为5.3%~7.8%。但是适量高分解等级的倒木可促进幼苗、幼树生长,合理利用倒木与森林更新之间的关系,可有效促进森林健康发展。

[Objective]To study the distribution of fallen wood and the impact of fallen wood on forest regeneration of Saihanwula forest ecosystem,a typical area of Hanshan Mountains secondary forests locating at the southern parts of Daxing'anling Mountains,Inner Mongolia.[Method]The sample plot survey method was used to investigate the fallen wood and forest regeneration.[Result]The regeneration density of the fallen wood plot was 4050±824 plants·hm^(−2),the regeneration density of the standing wood plot was 2950±265 plants·hm^(−2),the regeneration density of the control plot was 2625±237 plants·hm^(−2);the average reserve of the fallen wood in Saihanwula was 58.51±16.56 m^(3)·hm^(−2).Among them,the distribution densities of the fallen wood for decomposition grades Ⅱ,Ⅲ,Ⅳ,and Ⅴ were 50±21,806±198,189±76,and 22±5 plants·hm^(−2).The fallen logs in the study area mainly existed in the form of"trunk base fracture",accounting for 68.78%of the total number of fallen logs.[Conclusion]A large amount of fallen wood accumulates in the forest,which has the effect of obstructing,intercepting and shading the renewal of seeds,seedlings,saplings,etc.At the same time,the fallen wood will severely crush the renewed seedlings and other plants under the forest at the moment of dumping and for a long time after dumping.Negative effects such as crushing injuries,the rate of crushing injuries is 5.3%~7.8%.However,the proper amount of fallen trees with high decomposition levels can promote the growth of seedlings and young trees,and the rational use of the relationship between fallen trees and forest regeneration can effectively promote the healthy development of forests.