Population dynamics of five tree species in a monodominant Peltogyne forest and two other forest types on Maracá Island, Roraima, Brazil

Abstract

A forest type dominated by Peltogyne gracilipes (Caesalpiniaceae) occurs on Maracá Island, Roraima, Brazil, on a range of soil types. This paper assesses whether Peltogyne is a persistent dominant and whether this dominance is related to a higher survival rate of Peltogyne in seedling and subsequent stages. Three forest types were chosen according to the occurrence of Peltogyne trees: (1) Peltogyne-rich forest (PRF); (2) Peltogyne-poor forest (PPF); (3) forest without Peltogyne (FWP). Three 0.25 ha plots were set up in each of three forest types and comparisons were made between Peltogyne and four other non-pioneer tree species which occurred commonly (as trees ≥ 10 cm diameter at breast height, dbh) in at least one of the three forest types: Ecclinusa guianensis, Lecythis corrugata, Licania kunthiana and Pradosia surinamensis. All trees (≥ 10 cm dbh) in the plots were tagged and measured in October 1991. Seedlings and saplings of the selected species were also sampled in October 1991 in five subplots of 2 m × 1 m (seedlings) or 4 m × 4 m (saplings). Further censuses were made in April 1992, July 1992 (seedlings only), March 1993 and March 1994 (seedlings only). Seedlings of the study species had significant year-to-year variation in mortality and height growth, but there was no clear pattern among species. Peltogyne had a relatively faster growth in PRF. Peltogyne was by far the most abundant species in PRF in all size-classes. In FWP and PPF, Ecclinusa, Lecythis and Licania occurred with the largest number of individuals in the smallest size-classes, indicating good regeneration. However, in PRF, Licania and Lecythis populations are apparently declining and are relicts in an expanding Peltogyne forest. Thus, Peltogyne apparently has a stable, actively regenerating population with the ability to persist in the understorey. The persistent canopy dominance of Peltogyne in PRF seems to be related to low postgermination mortality rates of its seedlings and saplings.