Can thinning of overstory trees and planting of native tree saplings increase the establishment of native trees in exotic acacia plantations in south china?
Assessing the effect of thinning of overstorey trees and planting of native trees will be helpful to better understand the vegetation restoration. A stand conversion experiment was conducted in a 12-year-old Acacia auriculiformis plantation in 1996. Treatments were thinning and underplanting, underplanting, thinning, and control. Results showed that thinning enhanced the establishment and growth of underplanted and regenerated native seedlings. The thinning and underplanting treatment reduced soil organic matter, soil total nitrogen, soil bulk density and soil water content but increased soil phosphorus and potassium contents. The establishment and growth of underplanted native species depended on their responses to light and soil resources. Thinning increased recolonisation by native species. Since some of the underplanted native trees grow rapidly, the regenerating canopy cover can become dense after thinning, and the density of the new canopy inhibits regeneration of other native tree species. Therefore, moderate thinning should be periodically performed as part of the long-term management of plantation and different thinning intensities can be used to increase spatial variability in the overstorey. The shade tolerance of native species was the most important characteristic in determining the response of the native trees to the treatments.