Effect of disturbance intensity on regeneration mechanisms in a tropical dry forest

Abstract

We examined the effect of disturbances of varying intensity on the dominant modes of regeneration among woody plants in tropical dry forest in lowland Bolivia. Seed survival and density, mortality, height, crown area, and basal diameters of seedlings and sprouts were compared among four treatments of varying disturbance intensity (high-intensity burn, low-intensity burn, plant removal, and harvesting gap) over a period of 18 months following treatments. High- and low-intensity burns reduced densities of viable seed by an average of 94 and 50%, respectively. Tree seedlings were more abundant than tree sprouts in all treatments. There were few differences in seedling density among treatments. Sprouts were most common in the plant removal and low-intensity burn treatments than in harvesting gap and high-intensity burn treatments. Seedling mortality was higher than sprout mortality during the first year following treatments. Sprouts were taller, had more stems per individual, larger crown areas, and larger basal diameters than seedlings. Origin of sprout differed among treatments. Eighteen months following treatments, 85% of individuals >2.5 m tall were sprouts. Most seedlings >2.5 m tall after 18 months had established in high-intensity burn treatments. Sprouting individuals dominated regeneration after all treatments, however, in high-intensity burn treatments, sprouts were relatively less dominant due to smaller sprouts and larger seedlings after high-intensity burns.