Forest succession over fifty years in the Cabo Blanco Absolute Reserve, Costa Rica
Authors:Nathalie Del Rosario, Travis Hall
Mentor:Diana Lieberman, Research Faculty Tropical Ecology of Costa Rica, California State University Monterey Bay
Forest in Cabo Blanco Absolute Reserve on the Pacific coast of Costa Rica has been protected from disturbance for 50 years. Prior to that time, most of the area was under cultivation. Farming in the area bordering the reserve was abandoned 28 years ago. Forest has subsequently regrown naturally, in both areas. Stand structure, species richness, species composition and population structure of tree species were characterized in 0.02 ha forest inventory plots representing 28 yr old and 50 yr old successional forest and small areas of primary forest in and near the Reserve. A total of 30 plots were laid out, in which all stems ≥ 5 cm were measured and identified. The highest canopy levels were recorded from primary forest (24-36 m), followed by 50 year old (10-33 m) and 28 year old (11-25 m) successional plots. Size class distributions showed a greater proportion of large trees (≥50 cm) in the 50 yr old forest. A total of 43 species of woody plants were in the samples. Total species richness was higher in the younger successional plots (21 species) than in the older plots (15 species). Ordination analysis showed significant variation in species composition with respect to successional age of the plots. Species composition of 50 year old forest plots was indistinguishable from the primary forest. Stand structure appears to have recovered since abandonment of agriculture, with little difference seen between 28 yr old, 50 yr old, and primary forest. Species composition has changed more slowly; 50 yr old forest resembles that of primary forest in composition, but differs from that of 28 yr old forest. The rapid recovery of forest on this site may be due to a high percentage of sprouting tree species, as well as high seed dispersal into fields from nearby patches of undisturbed forest.