Abstract:
The effects of historical land use on tropical forest must be examined to understand present forest characteristics and to plan conservation strategies. We compared the effects of past land use, topography, soil type, and other environmental variables on tree species composition in a subtropical wet forest in the Luquillo Mountains, Puerto Rico. The study involved stems greater than or equal to10 cm diameter measured at 130 cm above the ground, within the 16-ha Luquillo Forest Dynamics Plot (LFDP), and represents the forest at the time Hurricane Hugo struck in 1989. Topography in the plot is rugged, and soils are variable. Historical documents and local residents described past land uses such as clear-felling and selective logging followed by farming, fruit and coffee production, and timber stand improvement in the forest area that now includes the LFDP. These uses ceased 40-60 yr before the study, but their impacts could be differentiated by percent canopy cover seen in aerial photographs from 1936. Using these photographs, we defined four historic cover classes within the LFDP. These ranged from cover class 1, the least tree-covered area in 1936, to cover class 4, with the least intensive historic land use (selective logging and timber stand improvement). In 1989, cover class I had the lowest stem density and proportion of large steins, whereas cover class 4 had the highest basal area, species richness, and number of rare and endemic species. Ordination of tree species composition (89 species, 13 167 stems) produced arrays that primarily corresponded to the four cover classes (i.e., historic land uses). The ordination arrays corresponded secondarily to soil characteristics and topography. Natural disturbances (hurricanes, landslides, and local treefalls) affected tree composition, but these effects did not correlate with the major patterns of species distributions on the plot. Thus, it appears that forest development and natural disturbance have not masked the effects of historical land use in this tropical forest, and that past land use was the major influence on the patterns of tree composition in the plot in 1989. The least disturbed stand harbors more rare and endemic species, and such stands should be protected.

Author Keywords:
biodiversity, conservation, disturbance, land use history, Luquillo Experimental Forest, Puerto Rico, soil, species diversity, topography, tree community, tropical forest

KeyWords Plus:
RICO LUQUILLO MOUNTAINS, PUERTO-RICO, RAIN-FOREST, NATURAL DISTURBANCE, SPECIES RICHNESS, TABONUCO FOREST, MOIST FOREST, IVORY-COAST, DYNAMICS, VEGETATION

Addresses:
Thompson J, Univ Puerto Rico, Inst Trop Ecosyst Studies, POB 23341, San Juan, PR 00931 USA
Univ Puerto Rico, Inst Trop Ecosyst Studies, San Juan, PR 00931 USA
Univ New Mexico, Dept Biol, LTER Network Off, Albuquerque, NM 87131 USA
Florida Gulf Coast Univ, Coll Arts & Sci, Ft Myers, FL 33965 USA
US Forest Serv, USDA, Ctr Forest Mycol Res, Forest Prod Lab, Luquillo, PR 00773 USA
Missouri Bot Garden, St Louis, MO 63166 USA
Univ Puerto Rico, Dept Biol, San Juan, PR 00931 USA
Harvard Forest, Petersham, MA 01366 USA

Publisher:
ECOLOGICAL SOC AMER, 1707 H ST NW, STE 400, WASHINGTON, DC 20006-3915 USA

IDS Number:
614PM

ISSN:
1051-0761