Tree growth and death in a tropical gallery forest in Brazil: understanding the relationships among size, growth, and survivorship for understory and canopy dominant species

摘要

We studied the relationships between size, growth, and survival for two functional groups, the persistent canopy and understory dominant tree species in a tropical gallery forest in Southeastern Brazil. In 28 plots of 10 × 30 m we tagged, identified, and measured the diameter of all trees with diameter at ground level ≥5 cm in 1993/1994, 1998, and 2004. We choose the three dominant canopy species (Protium spruceanum, Copaifera langsdorffii, and Pera glabrata) and two dominant understory species (Ixora brevifolia and Trichilia emarginata) for the comparisons. We assessed the relationship between previous growth rates and mortality, variation in growth and mortality rates among size classes, and temporal correlations in growth rates. Trees (whole community) with null or negative growth had a higher mortality, although this effect was not significant for individual species. Growth patterns were consistent along consecutive periods of evaluation for canopy species, but not for understory species. Canopy species had higher and more variable growth rates than understory species, which we attribute to greater access to light at the canopy level and also to a wider range of light conditions experienced during growth. Canopy species and one understory species, T. emarginata, showed accelerated growth as they became larger. Mortality rates were higher for the smallest trees for the community overall and for P. spruceanum.