Restoration of a Sri-Lankan rainforest: Using Caribbean Pine Pinus caribaea as a nurse for establishing late-successional tree species

Background

In the moist tropics, studies have demonstrated poor seedling establishment of late-successional trees on lands cleared of forest. This study examines the potential for establishing late-successional tree species that dominate the canopy of rainforest by planting within and adjacent to experimental openings that were created within a Pinus caribaea plantation.

Research goals & methods

The study tests five canopy tree species (Dipterocarpus zeylanicus, Mesuaferrea, Shorea disticha, S. megistophylla and S. trapezifolia) of tropical forest in southwestern Sri Lanka. Seedlings were monitored for 2 years within treatments that removed either three rows or one row of Pinus canopy, a canopy edge treatment and a control that left the canopy intact. The greatest growth and dry mass for all species were in the canopy removal treatments. In particular, S. trapezifolia and S. disticha exhibited the greatest height growth in these treatments. Differences were shown in the number and area of leaves among species. Shorea trapezifolia and, to a lesser degree, S. disticha increased leaf area by increasing leaf production. Dipterocarpus zeylanicus and, to a lesser degree, M. ferrea increased leaf area by increasing the size of individual leaves.

Conclusions & takeaways

Guidelines based on results from this study recommend that species grow best when seedlings are planted within openings created by the removal of three rows of Pinus canopy. Where planting without canopy removal is required, S. disticha or S. megistophylla should be selected because of greater shade and drought tolerance. This experiment demonstrated that Pinus can be used as a nurse for facilitating the establishment of site-sensitive tropical forest tree species that are late-successional. In particular, results have application for similar mixed dipterocarp forest types in Southeast Asia.