间伐强度对华北落叶松人工林植被物种多样性的影响

在北京市延庆县营盘村附近低山，对造林密度为5151株/hm2的23a生华北落叶松人工林，设置4个间伐强度处理。5a后，通过比较林下植被组成、外貌及多样性的变化，研究不同间伐强度对华北落叶松人工林群落稳定的影响。结果表明，间伐改变了群落的生活型谱，随间伐强度增大，地面芽植物和地下芽植物所占比重上升，而高位芽植物却呈相反的趋势。间伐强度不同，华北落叶松林下植被的建群种各异。间伐可提高林下植被的丰富度和多样性，这种效应以弱度间伐最为明显。间伐对草本层物种丰富度、多样性影响较灌木层大，而对林下植被分布均匀性影响甚微。因此，及时对郁闭林分进行合适强度的间伐，促进林下植被发育，是实现华北落叶松人工林可持续发展的有效途径。23a初植密度5151株/hm2的华北落叶松选择58.75%左右的间伐强度林下植被发育最优

Effect of Thinning Intensities on the Species Diversity of the Undergrowth Vegetations of Larix principis Plantation

The effect of thinning intensities with four different treatments of 75.25%(Ⅰ), 71.85%(Ⅱ), 67.48%(Ⅲ) and 58.75%(Ⅳ) on the undergrowth were carried out in the 23-year-old stands Larix principis with initial density of 5151 trees/hm2 , in lower hilly lands of Yingpan, Yanqing Country of Bejing Municipality. In 2005, 5 years after thinning, the composition, abundance and diversity of the undergrowth in the four plots were investigated and compared. The results showed that both the numbers of species and the composition of the dicotyls were enhanced by thinning density. Meanwhile, the life-form spectrums were influenced and the percentage of chamaephytes and geocryptophyte went as follows: Ⅰ<Ⅱ<Ⅲ<Ⅳ, opposite to the trend of the phanerophytes. Also, the composition of the dominant species of the undergrowth varied greatly, which of the herb layer responded more than shrub layer. The abundance of undergrowth was improved more greatly than evenness by thinning intensities. Additional, the shrub layers were more influenced than the herb layers in the all plots. Based on the results, it was concluded that reasonable thinning intensity was benefit to the development of the undergrowth and so can be an effective way for the sustainable use of plantations. Generally, when the stand with initial density of 5151trees/hm2 grows up to 23 years old, the reasonable thinning intensity should be about 58.75%.