长白山杨桦次生林采伐林隙幼苗更新动态

Regeneration Dynamics of Logging Gaps in Populus davidiana-Betula platyphylla Secondary Forests in Changbai Mountain

采用样线调查法,从林隙大小和林隙年龄2个方面研究长白山杨桦次生林经营采伐形成的林隙及其更新特征。结果表明：〈50m^2的林隙占7%,50-100m^2的占21%,100-150m^2的占36%,150-200m^2的占29%,〉200m^2的占7%;林隙一般由7-10株山杨、白桦或山槐被伐后形成;林隙内更新幼苗的种类组成较简单,但分布极不均匀;林隙内更新幼苗的种数、个体密度、叶面积指数、平均高生长和径生长均优于非林隙林分;色木槭、花楸、山槐等适合于在林隙内更新,而水曲柳、山荆等更适合于在郁闭林下更新;随着采伐林隙形成时间的延长,林隙内的凋落物和土壤养分含量不断提高,更新幼苗的种数、个体密度显著增加,生长状况也明显提高,相比于非林隙更新,林隙更新的优势更加突出;由于林隙内的光照、土壤养分和凋落物存在较大的空间异质性,不同位置的更新状况差异也较大,3龄林隙的西缘最好,中心及北部最差,9龄林隙内规律不明显;〈50m^2林隙内的更新状况与非林隙林分相近,〉200m^2林隙内的更新最差,100-150m^2林隙内更新状况最优,不但幼苗个体密度大,而且叶面积指数、平均高生长和径生长也最好,这主要是由不同大小林隙内和非林隙林分光合有效辐射的强度差异较大造成的。100-150m^2是长白山杨桦次生林林隙更新的最适面积。

Regeneration dynamic in logging gap of different sizes and ages was studied in Populus davidiana-Betula platyphylla secondary forests in Changbai Mountain by using line transects method. The results showed： The gaps occupied 7 % （canopy gaps area 〈 50 m^2 ） ,21% （50 - 100 m^2 ） ,36% （ 100 - 150 m^2 ） ,29% （ 150 - 200 m^2 ） ,7% （ 〉 200 m^2 ） in the proportion of logging gap sizes respectively; Gaps were usually formed after 7 - 10 trees logged that were mainly composed of P. davidiana, B. platyphylla and Maackia amurensis. The composition of seedlings species was simple and the distribution of seedlings was not evenness in gaps. The species number, individual density, LAI, mean height and mean basilar diameter of seedlings were better in gaps than in non-gaps. Some species, such as Aeer mono, Sorbus pohuashanensis, M. amurensis adapted well to gaps, but other species, such as Fraxinus mandshurica and Malus baccata adapted well to non-gaps. With the increasing of gap ages, owe to the litter and nutrition content increasing in soil, the species number and individual density of seedlings increased distinctly, and seedlings growth was improved, the adyantage for regeneration in gaps was more obvious than in non-gaps. The seedling trait was obvious difference at different position, within gaps result from the obvious space heterogeneity of PAR, soil nutrition content and litter. The regeneration was best at west edge of gap and most inferior at center and mid-north of gap. The seedlings of regeneration in 〈 50 m^2 gaps were as equivalent as those in non-gaps, the least in 〉 200 m^2 gaps and excellent in 100 - 150 m^2 gaps where the individual density, LAI, height growth and basilar diameter growth were first-class, which was due to the huge difference of PAR in gaps of different sizes. Therefore, the gap of 100 -150 m^2 benefited the regeneration of seedlings best.