间伐强度对油松人工林植被发育的影响

在北京市延庆县营盘村附近低山，对造林密度为3 130株/hm2的18年生油松人工林，设置40.1%、51.3%、65.7% 3个间伐强度及对照共4个处理. 3年后，通过比 较林下植被组成、外貌、多样性及生物量的变化，研究不同间伐强度对油松人工林群落稳定 性的影响. 结果表明:①间伐可提高物种在科、属分布上的均匀性；②间伐改变了林下植物 的生活型谱；③与对照相比，弱度间伐、中度间伐地面芽植物所占比重上升，强度间伐下降 ，而高位芽植物却呈相反的趋势；④间伐强度不同，油松林下植被的优势种各异；⑤间伐可提高林下植被的丰富度和多样性，这种效应以中度间伐最为明显；⑥林下植物生物量与间伐 强度呈正比.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，是实现油松 人工林可持续发展的有效途径.18年生初植密度3 130株/hm2的油松幼林选择51.3%左右的间伐强度林下植被发育最优. 

Effects of thinning intensity on the development of undergrowth in Pinus tabulaeformis plantations

The effects of thinning intensity with four different treatments of 0(CK), 40.1%(Ⅰ), 513%(Ⅱ) and 65.7%(Ⅲ) on the undergrowth were carried out in the 18 years old Pinus tabulaeformis stands with initial density of 3.130 trees/hm2 in the lower hilly lands of Yingpan, Yanqing County of Beijing. In 2005, ie three years after thinning, the composition, abundance, diversity, and biomass of the undergrowth in the four plots were investigated and compared. The results showed that both the number and evenness of species predominated by genus and family were enhanced by thinning density. Meanwhile, the life_form spectra were influenced and the percentage of chamaephytes was as the following: Ⅲ