A Look at Amazon Basin Seasonal Dynamics with the Biophysical ...

STEM RECRUITMENT AND MORTALITY IN AN EASTERN AMAZONIANSECONDARY FORESTJ. M. Tucker 1 , R. de F.R. Pantoja 2 , D. J. Zarin 3 , I. Miranda 41 Projeto MANFLORA, School of Forest Resources & Conservation, University of Florida, P.O. Box 110760,Gainesville, FL, USA 32611, E-mail: jmtucker@ufl.edu; 2 Faculdade de Ciências Agrárias do Pará, E-mail:robertapantoja@zipmail.com.br; 3 UF, E-mail: zarin@ufl.edu; 4 FCAP, E-mail: izildinhamiranda@uol.com.brWe examined stem recruitment and mortality (DBH > 1 cm) in twelve 100-m 2 plotsestablished in a 12-year-old secondary forest in Castanhal, Pará, Brazil. From November1999 to June 2001, mean stem density declined from 213 to 189 stems plot -1 (P < 0.001,one-way repeated measures ANOVA); 352 stems present in the first inventory died,corresponding to 14 percent mortality, while 64 stems were added, corresponding to 3percent recruitment. The rate of mortality reported here is significantly higher than theannual mortality rates usually reported for old-growth tropical rainforest (1-2 percent).Lacistema pubescens (Lacistemataceae), Myrcia sylvatica (Myrtaceae) and Vismiaguianensis (Clusiaceae) accounted for 61, 18 and 6 percent of all dead stems, anddisplayed net mortality of 19, 10, and 16 percent, respectively. These three speciesrepresent 70 percent of all stems in the stand (tree species richness = 64) and commonlycolonize abandoned agricultural land in the region. Most recruits were less-commonspecies already present in the sample plots. In a nearby 4-year-old stand, the densities ofL. pubescens and M. sylvatica stems (DBH > 1 cm) were lower, while the density of V.guianensis was higher than in the 12-year-old stand. Relative abundance values for L.pubescens and V. guianensis in regeneration surveys (DBH < 1 cm) were 1.0 and 0.5percent, respectively, suggesting that the decline of these shade-tolerant species is likelyto continue. Relative abundance of M. sylvatica in the regeneration surveys was greaterthan 50 percent, suggesting that this shade-tolerant species will likely persist in the subcanopy.Keywords: secondary forest, succession, mortality, recruitment, forest dynamics.