间伐干扰对人工林林木生长、幼苗更新及植被多样性的影响

抚育间伐是森林经营的重要措施之一，合理的间伐可以优化林分结构，改善林下环境，提高森林生产力和稳定性。本研究以河北省塞罕坝机械林场华北落叶松人工林和樟子松人工林为对象，对比分析间伐和未间伐林分（自然保护区）中林木生长、物种多样性和天然更新的差异。结果表明，间伐区华北落叶松人工林胸径年均增长0.72 cm，比未间伐区提高53.2%；间伐区樟子松人工林胸径年均增长0.59 cm，比未间伐区提高25.5%。间伐区内Shannon-Wiener指数、Simpson多样性指数、Pielou均匀度指数和Margalef丰富度指数较未间伐区分别高出159.2%、185.3%、185.9%和108.4%。间伐区幼苗幼树的更新种类和数量明显高于未间伐区，其中，樟子松人工林间伐区幼苗幼树的更新种类和数量均高于华北落叶松人工林。可见，对自然保护区内未经营过的人工林进行适当抚育间伐对提高森林生产力、维持生物多样性和促进森林正向演替有重要作用。

Effects of thinning on tree growth,seedling regeneration and vegetation diversity of plantation

Tending thinning was one of the important measures of forest management.Reasonable thinning could optimize stand structure,improve understory environment and forest productivity and stability.In the study,the tree growth,biological diversity and natural regeneration between thin and non-thin forests(natural reserves)was analyzed based on the Larix principis-rupprechtii and Pinus sylvestris var.mongolica plantation in Saihanba Mechanized Forestry Farm in Hebei Province.The results showed that of the mean increment of diameter at breast height (DBH) in thin forest of Larix principis-rupprechtii planation was 0.72 cm,which increased by 53.2% than non-thin forest.The DBH of Pinus sylvestris var.mongolica plantation in intercropping area increased by 0.59 cm annually,25.5% higher than that in nonintercropping area.The Shannon-Wiener index,Simpson index、Pielou index and Margalef index in thin forest were averagely 159.2%,185.3%,185.9% and 108.4% greater than non-thin forest.The regeneration species and number of seedlings and young trees in thinning area were significantly higher than that in nonthin forest.Among them,the regeneration species,number of seedlings and young trees in Pinus sylvestris var.mongolica plantation were higher than that in Larix principis-rupprechtii plantation.It could be seen that moderately thinning of the unmanaged plantation in the nature reserve played an important role in improving forest productivity,maintaining biodiversity and promoting positive forest succession.