Dynamics of a Late-Stage Secondary Forest on Barro Colorado Island

Long-term late-stage changes in the composition and structure of a late-stage secondary forest were quantified by repeated censuses of a 1.5-ha plot starting in 1968. When first established, the plot lacked canopy gaps and was dominated by Gustavia superba. During the following 46 years, canopy gaps have been numerous, small in area, and clustered in a portion of the plot. The dominance by G. superba has declined, but the number of tree species has remained relatively constant (maximum, 129). Stem density declined largely because recruitment was low relative to nearby old-growth forest. BrayCurtis dissimilarity in tree species composition with nearby old-growth forest decli from 0.70 in 1968 to 0.57 in 2014, with most of the decline occurring before 2000. Tree basal area has fluctuated, which might be a characteristic of late-stage secondary forest as large pioneers die off. Much work remains to be done on tree growth rates, the dynamics of recruitment and mortality, and the gradual transition to the species composition of old-growth forest.