Can a fast-growing early-successional tree (Ochroma pyramidale, Malvaceae) accelerate forest succession?

摘要

Species-specific traits of trees affect ecosystem dynamics, defining forest structure and understorey development. Ochroma pyramidale is a fast-growing tree species, with life-history traits that include low wood density, short-lived large leaves and a narrow open thin crown. We evaluated forest succession in O. pyramidale-dominated secondary forests, diverse secondary forests, both 10-15 y since abandonment, and rain forests by comparing height, density and basal area of all trees (> 5 cm dbh). Furthermore, we compared species richness of understorey trees and shrubs, and basal area and density of trees of early-and late-successional species (< 5 cm dbh) between forest types. We found that tree basal area (mean +/- SD: 32 +/- 0.9 m(2) ha(-1)) and height (12.4 +/- 1.8m) of canopy trees were higher, and density (1450 +/- 339 ha(-1)) lower in O. pyramidale forests than in diverse forests, and more similar to rain forest. Understorey shrub diversity and tree seedling density and diversity were lower in O. pyramidale forests than in diverse forests, but these forest types had a similar density of early-and late-successional trees. Canopy openness (> 15%) and leaf litter (> 10 cm) were both highest in O. pyramidale forests, which positively affected density of understorey trees and shrubs and negatively affected density of late-successional trees. In conclusion, O. pyramidale forests presented structural features similar to those of rain forest, but this constrained the establishment of understorey tree species, especially late-successional species, decreasing successional development.