DEMOGRAPHY AND HARVEST POTENTIAL OF LATIN AMERICAN TIMBER SPECIES: DATA FROM A LARGE, PERMANENT PLOT IN PANAMA

Abstract

Basic demographic data on valuable timber species in the tropics are seldom known but crucial for sustainable management. With data from a permanent, 50-ha census plot, we examined mortality and growth patterns and simulated timber harvest for a dozen prominent wood-producing species of Latin America. Standing wood volume was high for three of the species - 44 m³ ha^-1 in Hura crepitans, 25 m³ ha^-1 in Anacardium excelsum, and 22 m³ ha^-1 in Prioria copaifera - but the first two lacked advance regeneration in the plot. Annual mortality rates of individual species varied from below 1% y^-1 to as high as 2-3% y^-1. Regressions of instantaneous relative growth rate on stem diameter (dbh) provided lifetime age-size relations, starting at 10 mm dbh, for seven species. Species fell roughly into three groups: one species took 60 years to reach 300 mm dbh at mean growth, four species took 100-150 years (depending on census interval), and two took > 200 years. Projected survivorship from 10 to 300 mm dbh was > 50% in moderate-growth species with low mortality but < 10% in slow-growing species with high mortality. A simulation model was developed in seven species to predict timber yield for 120 years after an initial harvest. Recruitment was not simulated, so the model only addressed the production of residual stems left from the first harvest. In four species, future harvests were so low relative to the initial harvest that sustainable management would not likely be feasible, but in three, the productivity of future harvests was reasonably high. Judging by total wood production after 120 years, each had a different optimum harvest schedule: for Cordia alliodora, a 30-year rotation coupled with a 300-mm dbh minimum harvest sixe led to the largest total wood output; for Calophyllum longifolium, it was a 60-year rotation and 300-mm limit; and for Prioria, a 60-year rotation and 600-mm limit. Variation between species in demography and schedules of sustainable wood production illustrates the need for management schemes that are tailored to individual species.