Global Ecology and Biogeography (1999) 8, 29–38 RESEARCH LETTER Hurricane Gilbert and structural changes in a tropical forest in south-eastern Mexico O. SA ´ NCHEZ SA ´ NCHEZ and G. A. ISLEBE El Colegio de la Frontera Sur, Herbario Unidad Chetumal, AP 424, CP 77000 Chetumal, Quintana Roo, Mexico. E-mail: odilon@nicte-ha.ecosur-qroo.mx ABSTRACT Resumen. Este trabajo se refiere al cambio estructural y dan ˜os generales que sufrio ´ la This paper describes structural change and damage vegetacio ´ n natural del Jardı ´n Bota ´nico Dr Alfredo to the natural tree vegetation in the Dr Alfredo Barrera Marı ´n, despue ´s del paso del huraca ´n Barrera Marı ´n Botanical Garden, following Gilberto en septiembre de 1988. El estudio toma Hurricane Gilbert in September, 1988. Post- como punto de comparacio ´ n un trabajo previo hurricane data were compared with pre-hurricane realizado por Sa ´nchez (1987), quien efectuo ´ sus data from the same plots, focusing mainly on mediciones en tres parcelas que fueron establecidas composition and structure. Near complete y estudiadas tres an ˜ os antes del huraca ´n. La mayor defoliation of trees and plants of the understorey parte del dan ˜ o incluyo ´ la defoliacio ´n cercana al occurred and average foliage loss was estimated to 100% de a ´rboles y plantas del sotobosque cayendo be 4.5 t/ha. The density of trees decreased by 33%, en promedio 4.5 t/ha de hojas. La densidad de and the basal area decreased by 12%. Small diameter a ´ rboles disminuyo ´ 33%, significando un decremento trees accounted for the great majority of losses and de 12% en el a ´rea basal. Los a ´rboles de diame ´tro trees in the largest diameter classes survived best. pequen ˜ o fueron derribados en su gran mayorı ´a, The average height of trees in the lower canopy mientras que los a ´rboles de las clases diame ´tricas decreased by 6% and for those in the upper canopy by 9%. The frequency of understorey plants ma ´s grandes sobrevivieron. El promedio de altura decreased by 51% and their cover decreased by 70%. para los a ´rboles entre 3–8 m disminuyo ´ 6% y para Floristic richness decreased only slightly after the los a ´rboles entre 8.1–16 m disminuyo ´ 9%. La hurricane. densidad de plantas del sotobosque disminuyo ´ 51% y su cobertura tuvo un decremento de 70%. La Key words Tropical forests, structural changes, riqueza especı ´fica disminuyo ´ ligeramente para tree mortality, Yucatan Peninsula, Mexico, Hurricane Gilbert. despue ´s del huraca ´n. INTRODUCTION factors that affect vegetation are the intensity of the winds, often with velocities up to 300 km/h, and heavy Tropical storms are among the strongest forces of rainfall, which can cause severe inundation. On 14 September 1988, a wide region in the Mexican states nature due to the strength of the wind, heavy rainfall, and flooding, which often accompany such events of Quintana Roo and Yucatan was severely affected by Hurricane Gilbert. The strongest winds reached up (Ja ´uregui, Vidal & Cruz, 1980). Hurricane damage includes economic, social, and ecological aspects. to 350 km/h. The study area was under the influence of the hurricane for about 12 h. Meteorologists from Vegetation is especially vulnerable and hurricanes can cause dramatic changes depending on the composition the U. S. National Hurricane Center in Miami (Florida) rated Hurricane Gilbert in the highest storm intensity and structure of the vegetation. Vegetation can even disappear, as in the case of the coastal dune vegetation category of the five-point Saffin Simpson scale (Ja ´uregui, 1989). at Puerto Morelos, which was destroyed by Hurricane Gilbert (personal observations). The most important Relevant studies concerning the effects of tropical 29  1999 Blackwell Science Ltd. http://www.blackwell-science.com/geb