长白山不同演替阶段温带森林林下草本植物对乔木幼苗的影响

为了解次生针阔混交林和阔叶红松林林下草本植物对幼苗生长和存活的影响,基于长白山次生针阔混交林样地(Ⅰ)和阔叶红松林样地(Ⅱ),以246个1 m×1 m幼苗样方中乔木幼苗为研究对象,通过去除草本植物的对照试验探究草本植物对乔木幼苗高度生长和存活率的影响。结果表明,(1)群落水平上,草本植物去除有助于林下乔木幼苗的高度生长。次生针阔混交林和阔叶红松林中幼苗高度生长量在除草后较对照组均有显著提高,且阔叶红松林中幼苗高度增长在对照组和处理组中均高于次生针阔混交林。(2)去除草本植物对不同年龄级水平乔木幼苗高度生长影响不同。次生针阔混交林中,去除草本显著促进四年生及以上幼苗高度生长,对一至三年生幼苗影响不显著;阔叶红松中去除草本显著促进一至三年生幼苗高度生长,对四年生及以上幼苗影响不显著。(3)除草处理后,水曲柳幼苗高度生长量在两处样地均显著增加,假色槭幼苗高度增长量只在次生针阔混交林中显著增加,而其他幼苗高度增长量只在阔叶红松林中显著增加。(4)次生针阔混交林中,幼苗存活率与草本多度和物种数呈正相关关系,与草本盖度无相关关系;阔叶红松林中幼苗存活率与草本物种数呈正相关关系,与草本多度和盖度无相关关系。结果表明,草本植物会抑制乔木幼苗高度生长;虽可能在一定程度上有助于改善微生境,但未显著提高幼苗存活率。

Effects of herbs on tree seedlings in different succession stages of temperate forests in Changbai Mountain, China

Seedling recruitment plays a key role in determining species composition and diversity. To understand the effects of herbs on tree seedlings in two forest types, a control experiment based on 246 seedling quadrats of 1 m×1 m was conducted in secondary conifer and broad-leaved mixed forests and broad-leaved Korean pine forests, including control and herb removal. The results showed that herb removal significantly increased height growth of tree seedlings at the community level in two forest types, and a higher height growth was found in broad-leaved Korean pine forests. Effects of herb removal varied at different age classes. In the secondary conifer and broad-leaved mixed forests, herb removal significantly promoted the height growth of seedlings above four years old, but not for seedlings of one to three years old. In broad-leaved Korean pine forests, conversely, herb removal significantly promoted the height growth of seedlings of one to three years old, while not for seedling of four years old and above. The height growth of Fraxinus mandshurica increased significantly in both plots. However, Acer pseudo-sieboldianum showed a significantly height growth only in secondary conifer and broad-leaved mixed forests and other species showed a significantly height growth only in broad-leaved Korean pine forests. Seedling survival was positively correlated with abundance of herb and number of herb species, but no correlation with herb cover was found in secondary conifer and broad-leaved mixed forests. In broad-leaved Korean pine forests, seedling survival just positively correlated with number of herb species. There were no correlation between seedling survival and abundance of herb and herb cover. The results indicated that the exist of herb could slow down height growth of tree seedling. To some extent, it may contribute to the microhabitat amelioration, but did not significantly improve the seedling survival.