辽东山区次生林乔木优势树种幼苗更新动态

以辽东山区次生林4 hm²动态监测样地为平台,2014—2016年连续3年对样地进行乔木优势树种幼苗调查和半球面影像拍摄,分析森林更新过程中林下乔木幼苗和冠层结构的动态,研究幼苗的天然更新规律及其对冠层结构变化(以叶面积指数LAI的变化来表示)的响应.结果表明: 调查期间冠层LAI先减少后增加,且存在显著的年际差异.12种乔木优势树种幼苗对冠层结构变化存在明显的响应,且不同树种幼苗的响应明显不同;中性树种幼苗的相对多度或频度一般会随着冠层LAI的减小而增大;阳性树种幼苗的相对多度或频度一般会随着冠层LAI的增大而减小.2014—2016年乔木优势树种幼苗的多响应置换过程分析表明,优势树种幼苗的数量组成和分布存在显著差异,且年际间的差异逐渐减少.调查期间优势树种幼苗指示种发生明显变化,也反映出其对冠层结构变化的响应.

Seedlings regenerative dynamics of dominant trees in a secondary forest in montane region of eastern Liaoning Province,China

To reveal the seedlings dynamics of dominant trees and their response to canopy changes (as indicated by changes in leaf area index), we analyzed the seedlings dynamics of dominant trees and canopy structure during forest regeneration based on three-year (2014 to 2016) censuses and hemispherical photography in a 4 hm² forest dynamics monitoring plot. The results showed that canopy LAI first decreased and then increased during the survey period, with significant interannual difference. The seedlings of 12 dominant tree species showed notable response to the change of canopy structure, with the response varying among different tree species. The relative abundance or frequency of seedlings for neutral tree species generally increased with the decreases of canopy LAI. The relative abundance or frequency of seedlings of light-demanding tree species generally decreased with the increases of canopy LAI. In multi-response permutation procedures by analyzing the numeric composition and distribution of dominant tree seedlings, there was significant difference among the three censuses. Such interannual difference gradually decreased from 2014 to 2016. Significant change occurred in the indicator species of dominant tree seedlings, reflecting their responses to the changes of canopy structure.