The Demography of Miconia prasina (Melastomataceae) During Secondary Succession in Puerto Rico1

Abstract

ABSTRACT Miconia prasina (Melastomataceae) is an important colonizing species during early stages of secondary succession in Puerto Rico but its abundance declines with increasing stand age. We studied its demography for 2 yr (1995–1997) in three populations across a pasture to forest chronosequence (1‐, 12‐, and 25‐yr old) and in one population in a hurricane‐disturbed older forest (>60‐yr old). Vegetative growth was positive in the two young sites, but negative in the two older sites. The highest percentage of plants that flowered occurred in the two younger sites but highest seed production occurred in the 25‐yr‐old site. Although seed germination occurred in the two older sites, no seedlings established. Vegetative reproduction (root sprouts) was found in all sites, with most sprouts occurring in young sites. The 2 yr of census data were used to construct stage‐based transition matrices. In the two young sites, the average population growth rate was positive (λ > 1), while average population growth was negative in the two older sites (λ < 1). Elasticity, a measure of the effects of proportional changes in life‐history transitions to the long‐term population growth rate, varied across both stages and sites. Elasticity shifted from large plants in young sites to small plants in older sites. Across all sites, elasticities related to survival were more important than those of growth or vegetative reproduction. The demographic analysis supported the previous observations of changes in the density of M. prasina based on the chronosequence and also suggests that establishment via seeds must occur prior to abandonment in active pastures.