Using Caribbean pine to establish a mixed plantation: testing effects of pine canopy removal on plantings of rain forest tree species.

摘要

The potential was tested for establishing shade-tolerant tree species within different canopy removal treatments of an 18-yr-old Pinus caribaea (Caribbean pine) plantation (used as a nurse species), as a means of providing a solution to the problemsof dispersal, weed competition, and pathogen/insect problems experienced by rain forest tree species during their initial establishment on sites previously cleared of forest. The plantation was originally established on abandoned swidden adjacent to theSinharaja Man and the Biosphere rain forest reserve in SW Sri Lanka. The 5 species selected for the study were Caryota urens, Dipterocarpus zeylanicus, Pericopsis mooniana, Shorea stipularis and Swietenia macrophylla. Seedlings were monitored over 2 yrfor survival, root collar diameter and height growth along transects in 7 environmental treatments within the Pinus plantation. The treatments comprised: (i) under plantings beneath a closed canopy of Pinus that were unaffected by any row removal; (ii) the centres of clear felled strips of Pinus 6 m wide; and (iii-vii) and 5 treatments across clear felled strips 12 m wide within closed canopy Pinus. The 5 treatments within the 12 m wide clear felled strip included inside edges beneath the Pinus canopy on the eastern (iii) and western (iv) sides of the strip; outside edges on the eastern (v) and western (vi) sides of the strip; and the centre (vii) of the strip opening. At the end of 2 yr, a sample of the seedlings growing within each environmental treatment were taken and measured for dry mass and leaf area. All the species grew poorly and had higher mortality in the Pinus understorey than in the other treatments. The dipterocarp species (D. zeylanicus, Shorea stipularis) were slower growing and moresensitive to to treatments than the non-dipterocarp species. Swietenia macrophylla grew tallest in all the treatments. Overall, the best environments for seedling establishment and growth for all the species were in the centres of the canopy strips (6-12m).