Relative time scales of ecological processes in the Luquillo Experimental Forest, Puerto Rico.
Haines, Bruce*,1, Scatena, Fred2, Covich, Alan1, Crowl, Todd3, Hall, Charles4, Zou , Xiaoming 5, 1 The University of Georgia, Athens, GA, USA2 University of Pennsylvania, Philadelphia, PA, USA3 Utah State University, Logan, UT, USA4 SUNY College of Environmental Sciences and Forestry, Syracuse, NY, USA5 Institute for Tropical Ecosystem Studies, San Juan, PR, USA
ABSTRACT- Turn over times (the quantity of material stored in a reservoir / the annual average flux of that material through that reservoir) and recovery times (times required following a disturbance for a structure or a rate to return to pre-disturbance state) were calculated for lower elevation forested watersheds in the Luquillo Experimental Forest, in Northeastern Puerto Rico. Turn over times for 160 periods and 55 recovery times were calculated for both abiotic and biotic reservoirs. Water and nutrient fluxes through the system were faster than the fluxes of biological materials through reservoirs by internal nutrient cycling. Turns over times of biological reservoirs by nutrient cycling were faster than turn over times resulting from natural disturbances. Landforms and physiographic features were the most stable with turn over times ranging from 1000s to millions of years. Turnover times for soils ranged from 10,000 to 100,000 years, while times for biota ranged from 1 to 100 years. Relative disturbance effectiveness (flux following disturbance / long term daily average flux) was calculated for 38 fluxes. Landslides had the highest relative disturbance effectiveness. In conclusion, the Luquillo landscape is a dynamic complex of subsystems in which recovery time increases as the turn over time increases. System component responses to and recovery from disturbances occur at different rates thus steady state conditions are rarely achieved between all abiotic and biotic components. Comparisons of turn over times, recovery times and relative effectiveness following disturbances in different LTER sites are likely to be instructive.
Key words: disturbance, turn over times, recovery times, tropical forest
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