RESTORING CARIBBEAN DRY FORESTS - EVALUATION OF TREE PROPAGATION TECHNIQUES

Survival and height growth of tree seedlings and rooted cuttings intro duced into artificially shaded and unshaded plots in a degraded dry fo rest were measured at intervals for nine months. Ten tree species were selected to represent a range of ecological characteristics of the dr y-forest plant community on St. John, U.S. Virgin islands. Of three pr opagule types - seeds, seedlings, and rooted cuttings - introduced to field plots, seedlings survived best (52%) over the initial nine-month period. Cuttings of six species rooted successfully in a shadehouse, but only two of these species survived the nine-month field experiment . Seed germination was low, under 11% for eight of ten species tested, and foul species did not germinate. Subsequent mortality of seedling recruits was moderately high. Plumeria alba was the only species for w hich seedling height growth was not significantly greater than cutting height growth. Shading treatment (25% of full sun) significantly incr eased seedling survivorship (p = 0.03) but suppressed growth slightly for some species. Shading enhanced survival of seedlings produced from broadcast seeds, but not seed germination. Mortality occurred during dry periods, apparently from drought stress. Results suggest (2) that seedling introductions are the preferred propagule type (over seeding or rooted cuttings) for ecological restoration of degraded tropical dr y forests, and (2) that some level of shading is required to increase the survivorship of many dry-forest species or to avert complete morta lity of some species. This study suggests that early secondary dry for est may be best restored by underplanting within the existing vegetati on. Sufficient shading suitable for growth of native dry-forest trees may be attained using a nurse crop of fast-growing leguminous trees.