Diameter increment patterns among 106 tree species in a logged and silviculturally treated Costa Rican rain forest

Studies of growth rates of trees in managed neotropical forests have rarely employed complete botanical identification of all species, while published information for Central American lowland rain forests largely concerns for ests free of recent disturbance. We studied diameter increments of trees in a managed Costa Rican rain forest. The Pentaclethra macroloba-dominated fo rest was located on low hills with Ultisols in Holdridge's Tropical Wet For est life zone. The 540 m x 540 m (29.2 ha) experimental area was lightly lo gged during 1989-1990. The 180 m x 180 m (3.24 ha) experimental plots compr ised a 100 m x 100 m (1.0 ha) central permanent sample plot (PSP) with a 40 -m wide buffer strip. Post-harvest silvicultural treatments were liberation /refinement (in 1991) and shelterwood (in 1992), applied under a complete r andomized block design with three replicates, using logged but untreated pl ots as controls. All live trees greater than or equal to 10 cm DBH in the P SPs, were identified to species; data reported are for 1993-1996. Cluster a nalysis was used to group species on the basis of the median and quartiles of their diameter increment distributions, separating data by silvicultural treatments; five diameter increment groups were established and subdivided on the basis of the adult height of each species (four categories), giving 17 species groups in the final classification. Adult height and silvicultu ral treatment made a significant contribution to growth rate variation. Med ian annual increments of the slowest-growing species groups, which featured many under- and middle story species, were ca. 1 mm; those for the fastest growing species, which were mainly canopy and emergents, were ca. 16 mm. A ll species in the groups of very fast growth were pioneers, whether short o r long-lived, though many other pioneer species did not show fast growth. T he proportions of species found in groups of moderate, fast or very fast gr owth were greater in the silviculturally treated plots than in the controls , and one complete diameter increment group, of fast growth, was only repre sented in the treated plots. Crown form, crown illumination and presence of lianas in the crown, showed significant correlations with diameter increme nts, though the importance of these latter two variables varied with silvic ultural treatment. The very fast growth groups differed from the others in having higher proportions of trees with well-formed, well-illuminated crown s and an irregular diameter distribution with relatively few individuals in the smallest DBH class. Comparison with data from other neotropical forest sites shows that long-lived pioneers such as Vochysia ferruginea and Jacar anda copaia grow fast or very fast at all sites, while non-commercial canop y and emergent species of Chrysobalanaceae and Sapotaceae appear to be unif ormly slow-growing. Growth data for the majority of species are, however, p ublished for the first time. (C) 1999 Elsevier Science B.V. All rights rese rved.