Abstract
Natural regeneration of native seedlings is important to the future composition and structure of forests. In this study, we investigated relationships between microenvironmental variables and native tree seedlings (including their composition and structure) in a logged China fir (Cunninghamia lanceolata) plantation, in order to propose management and restoration strategies. Our study site was located in the Huisun Experimental Forest Station, central Taiwan. After logging practices, the canopy and subcanopy layers were respectively dominated by residual China fir and naturally regenerated native trees. We set up 30 seedling subquadrats (each 1×2 m) in this plantation. The communities in these subquadrats could be clustered into 3 groups based on the species composition and abundance of 121 tree seedlings recorded in censuses. The first group was dominated by the moderately shade-tolerant shrub species, Lasianthus fordii, and was located at the habitat with high overstory (canopy and subcanopy) cover. The second group was dominated by the shadeintolerant tree species, Mallotus paniculatus, and the habitat of the group was characterized by low overstory cover and high understory fern cover. The third group was dominated by the moderately shade-tolerant tree species, Machilus zuihoensis, and its habitat was characterized by low understory fern cover. In terms of community structure, seedling density and diversity indices were significantly negatively correlated with subcanopy cover. Residual coarse woody debris of China fir had no significant effects on species composition, stem density, or species diversity. Regeneration of native trees was mainly influenced by the canopy, subcanopy, and understory cover, while the seedling community structure (stem density and species diversity) was mainly influenced by the subcanopy cover. We proposed that it is necessary to maintain the heterogeneity of overstory cover when managing logged plantations through passive strategies, since habitat heterogeneity facilitates the coexistence of seedlings with different regeneration needs and in turn maintains species diversity.