Land use history, hurricane disturbance, and the fate of introduced species in a subtropical wet forest in Puerto Rico |
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Authors: | Jill Thompson Ariel E Lugo John Thomlinson |
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Institution: | (1) Institute for Tropical Ecosystem Studies, University of Puerto Rico, P.O. Box 21910, San Juan, 00931-1910, PR, USA;(2) International Institute of Tropical Forestry, USDA Forest Service, Jardín Botánico Sur, 1201 Calle Ceiba, Rio Piedras, 00926-1119, PR, USA;(3) California State University Dominguez Hills, 1000 E. Victoria Street, Carson, 90747, CA, USA |
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Abstract: | Tropical forests are suffering from increasing intensities and frequency of disturbances. As a result, non-native species
accidentally introduced or intentionally planted for farming, plantations, and ornamental purposes may spread and potentially
invade undisturbed native forest. It is not known if these introduced species will become invasive, as a result of recurrent
natural disturbances such as hurricanes. Using data from three censuses (spanning 15 years) of a 16-ha subtropical wet forest
plot, we investigated the impact of two hurricanes on populations of plant species that were planted in farms and plantations
that were then abandoned and from the natural spread of species introduced into Puerto Rico in the past. The populations of
four species (Citrus paradis, Mangifera indica, Musa sp., and Simarouba glauca) changed little over time. Six species (Artocarpus altilis, Calophyllum calaba, Genipa americana, Hibiscus pernambucensis, Syzygium jambos, and Swietenia macrophylla) declined between the first two censuses after Hurricane Hugo, then increased again in Census 3 after Hurricane Georges.
Spathodea campanulata gradually increased from census to census, while Coffea arabica declined. These introduced species represent only a small part of the forest basal area and few show signs of increasing
over time. The number of stems per plant, new recruits, and the growth rates of these introduced species were within the ranges
of those for native plant species. The mortality rates over both census intervals were significantly lower for introduced
species (<5% year−1) than for native ones (15% year−1). Many new recruits established after Hurricane Hugo (prior to this study) had opened the forest canopy and these high mortality
rates reflect their death as the canopy recovered. Only Swietenia macrophylla and Syzygium jambos showed an increase in stem numbers in the closed canopy area of forest that had suffered limited human disturbance in the
past. A future increase in frequency of disturbance may enable greater stem numbers of introduced species to establish, while
lower-mortality rates compared to native species, may allow them to persist during inter-hurricane intervals. An increase
in the population of introduced species, especially for those that grow into large trees, may have an impact on this tropical
forest in the future. |
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Keywords: | Alien species Exotic species Invasive species Luquillo LFDP Mature forest Non-native species |
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