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Structural response of Caribbean dry forests to hurricane winds: a case study from Guánica Forest, Puerto Rico

Authors

  • Skip J. Van Bloem,

    Corresponding author
    1. Department of Plant Biology, Michigan State University, East Lansing, MI, USA
      *Skip J. Van Bloem, Department of Agronomy and Soils, University of Puerto Rico at Mayagüez, PO Box 9030, Mayagüez PR 00681.
      E-mail: svanbloem@uprm.edu
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  • Ariel E. Lugo,

    1. International Institute of Tropical Forestry, United States Department of Agriculture Forest Service, Ceiba 1201, Jardín Botanico Sur, Río Piedras, Puerto Rico, USA
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  • Peter G. Murphy

    1. Department of Plant Biology, Michigan State University, East Lansing, MI, USA
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*Skip J. Van Bloem, Department of Agronomy and Soils, University of Puerto Rico at Mayagüez, PO Box 9030, Mayagüez PR 00681.
E-mail: svanbloem@uprm.edu

Abstract

Aim  Tropical dry forests in the Caribbean have an uniquely short, shrubby structure with a high proportion of multiple-stemmed trees compared to dry forests elsewhere in the Neotropics. Previous studies have shown that this structure can arise without the loss of main stems from cutting, grazing, or other human intervention. The Caribbean has a high frequency of hurricanes, so wind may also influence forest stature. Furthermore, these forests also tend to grow on soils with low amounts of available phosphorus, which may also influence structure. The objective of this study was to assess the role of high winds in structuring dry forest, and to determine whether soil nutrient pools influence forest response following hurricane disturbance.

Location  Guánica Forest, Puerto Rico.

Methods  Over 2000 stems in five plots were sampled for hurricane effects within 1 week after Hurricane Georges impacted field sites in 1998. Sprout initiation, growth, and mortality were analysed for 1407 stems for 2 years after the hurricane. Soil nutrient pools were measured at the base of 456 stems to assess association between nutrients and sprout dynamics.

Results  Direct effects of the hurricane were minimal, with stem mortality at < 2% and structural damage to stems at 13%, although damage was biased toward stems of larger diameter. Sprouting response was high – over 10 times as many trees had sprouts after the hurricane as before. The number of sprouts on a stem also increased significantly. Sprouting was common on stems that only suffered defoliation or had no visible effects from the hurricane. Sprout survival after 2 years was also high (> 86%). Soil nutrient pools had little effect on forest response as a whole, but phosphorus supply did influence sprout dynamics on four of the more common tree species.

Main conclusions  Hurricanes are able to influence Caribbean tropical dry forest structure by reducing average stem diameter and basal area and generating significant sprouting responses. New sprouts, with ongoing survival, will maintain the high frequency of multi-stemmed trees found in this region. Sprouting is not limited to damaged stems, indicating that trees are responding to other aspects of high winds, such as short-term gravitational displacement or sway. Soil nutrients play a secondary role in sprouting dynamics of a subset of species. The short, shrubby forest structure common to the Caribbean can arise naturally as a response to hurricane winds.

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