Basnet K.

Effect of Topography on the Pattern of Trees in Tabonuco (Dacryodes excelsa) Dominated Rain Forest of Puerto Rico

Effect of Topography on the Pattern of Trees in Tabonuco (Dacryodes excelsa) Dominated Rain Forest of Puerto Rico
Khadga Basnet
Vol. 24, No. 1 (Mar., 1992), pp. 31-42

The structure, composition, and spatial patterns of tree species in two adjacent watersheds of the Luquillo Experimental Forest, Puerto Rico were investigated. Both watersheds had the same vegetational characteristics. Dacryodes excelsa! Sloanea berteriana, and Guarea guidonia were the most important trees in the overstory. A profile diagram, chisquare criterion, and multivariate techniques showed the same result: trees were related significantly to topographic variables. Large trees, especially the dominant species, tabonuco, were associated significantly with ridges and slopes. Size-class distributions of individual species varied as a function of broad ecological factors such as topography and disturbance regime. Past anthropogenic disturbance was still apparent in the pattern of distribution of large trees along the elevational gradients of the watersheds. Dacryodes excelsa is the dominant species, even though Sloanea berteriana has higher representation in smaller size-classes.

Hurricane Hugo: damage to a tropical rain forest in Puerto Rico

Hurricane Hugo: Damage to a Tropical Rain Forest in Puerto Rico
Khadga Basnet, Gene E. Likens, F. N. Scatena and Ariel E. Lugo
Journal of Tropical Ecology
Vol. 8, No. 1 (Feb., 1992), pp. 47-55

Hurricane Hugo of September 1989 caused severe damage to the rain forest in the north-rust corner of Puerto Rico. We assessed the severity of damage distributed in space, species, and size-classes of trees in the Bisley Watersheds of the Luquillo Experimental Forest. We analyzed pie- and post-hurricane data for vegetation from transects established in 1987 and 1988. The severity of damage was significantly greater in valleys than on ridges and slopes. All the species except Dacryodes excelsa, Sloanea berteriana, and Guarea guidonia showed 100% severe damage. Large trees (> 70 cm DBH) were highly susceptible to hurricane damage, but there was no clear pattern in the small size-classes. D. excelsa (tabonuco) was the most resistant to damage by the hurricane. Tabonuco which has extensive root-grafts and root anchorage to bedrock and subsurficial rocks, apparently can survive frequent hurricanes and continue as a dominant species in this montane tropical rain forest. The high frequency of hurricanes, which can override other ecological and topographic factors, may largely determine the overall spatial pattern of species in this rain forest.
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