Abstract: 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 natural regeneration of L. principis-rupprechtii, moderate thinning (45%) and intensive thinning (85%) were more reasonable in the follow-up forest management.

Key words: thinning intensity, natural regeneration, Larix principis-rupprechtii, structural equation model