间伐强度对华北落叶松天然更新的影响

Effect of thinning intensity on natural regeneration of Larix principis⁃rupprechtii

以山西庞泉沟自然保护区华北落叶松纯林为对象,设置5个间伐强度(5%、25%、45%、65%、85%),利用相关性分析,构建间伐强度-林下生境-天然更新的结构方程模型,分析间伐强度对华北落叶松天然更新的影响机制。结果表明:中度间伐(45%)和强度间伐(85%)林地的更新指数明显大于其他间伐强度并且差异显著。构建的结构方程模型适配度良好,间伐强度对各因子的影响依次为:土壤碱解氮(-0.564)>更新指数(0.548)>土壤容重(-0.462)>母树平均高度(-0.348)>草本植物盖度(-0.343)>土壤有机质(0.173)>枯落物未分解层厚度(-0.146)>土壤全氮(0.110),间伐强度对更新指数有正向影响,这种影响主要通过调整母树高度、加速枯落物分解、改善土壤理化性质,间接促进华北落叶松天然更新。抚育间伐能够有效改善更新苗的生存环境,在后续森林经营中从华北落叶松天然更新的角度考虑,间伐强度选取中度间伐(45%)和强度间伐(85%)更为合理。

We analyzed the impacts of thinning intensity on the natural regeneration of Larix principis⁃rupprechtii in Shanxi Pangquangou Nature Reserve,with an experiment of five thinning intensities(5%,25%,45%,65%and 85%).We constructed a structural equation model of thinning intensity⁃understory habitat⁃natural regeneration by using correlation analysis.The results showed that the regeneration index of moderate thinning(45%)and intensive thinning(85%)stand land was significantly higher than that of other thinning intensities.The constructed structural equation model had good adaptability.The effects of thinning intensity on each factor were as follows:soil alkali⁃hydrolyzable(-0.564)>regeneration index(0.548)>soil bulk density(-0.462)>average height of seed tree(-0.348)>herb coverage(-0.343)>soil organic matter(0.173)>undecomposed litter layer thickness(-0.146)>total soil nitrogen(0.110).Thinning intensity had a positive impact on the regeneration index,which was mainly through adjusting height of the seed tree,accelerating litter decomposition,improving soil physical and chemical properties,and thus indirectly promoting the natural regeneration of L.principis⁃rupprechtii.Tending thinning could effectively improve the survival environment of regeneration seedlings.From the perspective of natu⁃ral regeneration of L.principis⁃rupprechtii,moderate thinning(45%)and intensive thinning(85%)were more rea⁃sonable in the follow⁃up forest management.