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

Our study tested the potential for establishing shade-tolerant tree species within different canopy removal treatments of an 18-year-old Pinus caribaea (Caribbean pine) plantation. We investigated whether planting within a Pinus plantation can be a solution to the dispersal, weed competition, and pathogen/insect problems rain forest tree species have during their initial establishment on sites previously cleared of forest, The plantation was originally established on abandoned swidden adjacent to the Sinharaja Man and the Biosphere rain forest reserve in southwestern Sri Lanka. The five species selected for the study were Caryota urens. Dipterocarpus zeylanicus, Pericopsis mooniana, Shorea stipularis, and Swietenia macrophylla. Seedlings were monitored over two years for survival, root collar diameter and height growth along transects that were in seven different environmental treatments within the Pinus plantation. Environmental treatments comprised: (i) under plantings beneath a closed canopy of Pious that were unaffected by any row removal; (ii) the centres of clearcut strips of Pious that were 6 m width; (iii-vii) and five treatments across clearcut strips within closed canopy Pinus that were 12 m wide. The five treatments within the 12 m wide clearcut 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 two years, a sample of the seedlings growing within each environmental treatment were taken and measured for dry masses and leaf areas. Results demonstrate that all species grew poorly and had higher mortality in the Pinus understorey than the other environmental treatments. The dipterocarp species (D. zeylanicus, S. stipularis) were slower growing and more site-sensitive to changes in environmental treatment than the non-dipterocarp species, S. macrophylla grew tallest in all environmental treatments as compared to the other species. Overall, the best environments for seedling establishment and growth for all species were in the centres of the canopy strips (6-12 m), This study contributes to investigations testing the feasibility of using Pinus as a nurse for establishing more shade-tolerant species; and as a technique for forest restoration in south and southeast Asia. (C) 1998 Elsevier Science B.V.