Treefall Pits and Mounds, Buried Seeds, and the Importance of Soil Disturbance to Pioneer Trees on Barro Colorado Island, Panama

Abstract

In mature forest on Barro Colorado Island (BCI), Republic of Panama, 0.09% of the ground surface is covered by pits and mounds created by uprooted trees as compared to 14—60% of the ground surface in temperate forests. Newly formed treefall pits on BCI rapidly filled with soil at an average rate of 8 cm/yr. Although pits and mounds rapidly disappeared on BCI, pioneer (gap phase or forest nomad) trees were more concentrated on mineral soil associated with freshly uprooted trees than elsewhere in treefall gaps. There was a large population (742 seeds/m2) of viable buried seeds, primarily of common pioneer tree species, in the top 10 cm of soil in closed forest; these seeds may give rise to many of the pioneers colonizing the disturbed soil. Large treefall gaps are more frequently colonized by pioneer trees than are small treefall gaps, partially because large gaps are more often caused by uprooted, thus soil—disturbing, trees.