林窗对大兴安岭南段杨桦次生林林下更新特征的影响

Effects of Forest Gaps on the Regeneration Pattern of the Undergrowth of Secondary Poplar-Birch Forests in Southern Greater Xing′an Mountains

研究杨桦次生林不同林窗大小对林下物种更新特征的影响,为人为近自然模拟林窗干扰更新提供理论依据和参考。以内蒙古大兴安岭南段杨桦次生林为研究对象,按海拔梯度将6hm 2大样地分为坡上、坡中及坡下,每个坡位划分为4个林窗面积等级,每个等级内选择3个不同面积林窗,作为3个重复,每个坡位选择林窗36个,在每个林窗内设置更新苗调查样方5个。同时设置相同面积的对照样方(CK)36个。共调查林窗更新苗样方180个,林内对照更新苗样方180个。结果表明,林窗具有使原先锋物种(蒙古栎)更新密度下降的趋势;林窗内蒙古栎均为主要更新物种,从坡下到坡上,蒙古栎更新苗密度分别占总更新密度的61.19%,50%,39.86%;林窗中更新苗都以低矮植株(<60cm)为主,更新苗在不同坡位、不同林窗面积中均表现为随高度级的增加,更新苗数量降低。不同坡位不同高度级内更新苗数量基本呈现出大林窗多于小林窗;坡位及林窗面积均对蒙古栎更新苗基径影响显著([WTBX]P<0.05);林窗能够显著促进蒙古栎更新苗粗生长,在林窗面积为80~100m 2达到最大;林窗内坡上及坡下蒙古栎更新苗基径均大于林内,坡中没有如此表现。总的来看,林窗能够显著促进林下物种更新与生长,并且具有使原有先锋物种(蒙古栎)更新密度下降的趋势。

The effects of different forest gap sizes on the regeneration pattern of the undergrowth of secondary Poplar-birch were studied,which provided theoretical basis and reference for the artificial near-natural simulation of forest gap disturbance renewal.Taking the secondary Poplar-birch forest in the Southern Greater Xing'an Mountains,Inner Mongolia as the research object,the 6hm2 large plots were divided into the upper part,the middle and the lower part of slopes according to the altitude gradient.Each slope was divided into 4 forest gap area grades,and each grade was selected 3 forest gaps of different sizes,as three repetitions,36 forest gaps are selected for each slope position,and 5regeneration seedling survey samples are set in each forest gap.At the same time,36 control samples(CK)of the same area were set.A total of 180 regeneration seedlings samples and 180 CK samples were set up and surveyed in the forest gaps.The results showed that the forest gap had the tendency to decrease the regeneration density of the original pioneer species(Mongolian scorpion);the sorghum in the forest gap was the main renewed species.From the lower part,to the middle part and the upper part of slopes,the regeneration seedling density of Quercus mongolica accounted for 61.9%,50%and 39.86%of the total renewal density respectively.The regenerated seedlings in the forest gaps are mainly low-lying plants(<60 cm),and the number of regenerated seedlings show a decrease with an increase of height level in different slope positions and different forest gap areas.The number of regenerated seedlings in different heights of different slopes showed that there were more large forest gaps than small ones.The slope position and forest gap area all had significant effects on the algae diameter of Quercus mongolica(p<0.05),forest gaps could significantly promote the regeneration of Quercus mongolica.The growth of seedlings was the largest in the forest gap area of 80-100 m 2.The diameter of the seedlings in the forest gapin the lower part and the upper part of slopes were higher than those in the forest,and there was no such performance in the middle part of slopes.In general,forest gaps can significantly promote the regeneration and growth of undergrowth species,and have a tendency to reduce the density of regeneration of the original pioneer speciesMongolian mongolica.