BlOTROPlCA 33(3): 393-408 2001 zyxwvut Hurricane Impacts on a Mangrove Forest in the Dominican Republic: Damage Patterns and Early Recovery' Ruth E. Sherman, Timothy J. Fahey Department of Natural Resources, Fernow Hall, Cornell University, Ithaca, New York 14853, U S A . and Pedro Martinez lnstituto Nacional de Recursos Hidraulicos, PROMASIR, D.N. Apartado Postal 1407, Santo Domingo, Dominican Republic ABSTRACT zyxwvuts On zyxwvutsrqpon 22 September 1998, Hurricane Georges passed over the Dominican Republic causing extensive damage to a 4700 ha mangrove forest that has been the site of a detailed study of vegetation and ecosystem dynamics since 1994. We resurveyed the vegetation in permanent plots at 7 and 18 months after the hurricane to document structural damage of the forest and evaluate early recovery patterns. The intensity of damage was patchy across the landscape. Mortality (25 cm DBH) ranged from 14 to 100 percent (by density) among the 23 different plots and averaged 47.7 percent across all plots. Reductions in total basal area ranged from 9 to 100 percent, averaging 42.4 percent. Mortality increased by 9 percent between surveys at 7 and 18 months post-hurricane. Interspecific differences in susceptibility to wind damage appeared to be a primary factor contributing to spatial patterns in mortality. Laguncubria racemosa experienced much less mortality (26%) than either Rhizophora mangle (50%) or Avicenniagerminans (64%). and plot-level mortality was strongly associated with differences in species composition. There were no clear relationships between canopy height and tree damage at this site. Over 80 percent of the of the surviving R. mangle trees exhibited less than 50 percent crown damage, whereas ca 60 percent of the L. racemosa survivors suffered almost complete (75-1OOYo) crown loss. By 18 months after the hurricane, the percentage of zyxwvut L. racemosa trees in the 75 to 100 percent damage class was reduced to 20 percent; in contrast, the health of many R. mangle individuals appeared to be declining, as the percentage of trees in the 50 to 100 percent damage class increased from 16 to 36 percent. Understory light levels, zy as measured by the gap light index, increased from an average value of 3 percent in the pre-hurricane forest to 51 percent at 7 months after the hurricane and decreased slightly to 47 percent at 18 months. Few saplings (>1 m tall and <5 crn DBH) survived the hurricane; 72 percent of the tagged individuals in transect-based plots and 66 percent of saplings in pre-hurricane canopy gaps were killed. Seedling and sapling populations of all three species appear to be recovering rapidly although their densities still are lower than in the pre-hurricane forest. It is too early to predict the trajectory of forest recovery, and continued monitoring of the spatial and temporal patterns of forest development is needed to improve our understanding of the role that large-scale disturbance events play on the dynamics of mangrove forest ecosystems. RESUMEN El 22 de septiernbre de 1998, el huracin Georges pas6 sobre la Repliblica Dominicana causando daiios extensos a 47 h2 de man& que ha sido objeto un estudio derallado de vegetaci6n y dinimica de la communidad desde 1994. Se tomar6n muestras de la vegetacion en parcelas permanentes 7 y 18 meses desputs de paso del huracin para documentar 10s daiios esrructurales del bosque y evaluar 10s modelos de recuperacibn temprana que siguieron poster- iormente. La intensidad del daiio fue irregular a travts del paisaje. La mortalidad (55 cm de dap) h e de 14 a 100 por ciento (para la densidad) en las 23 parcelas con un promedio de 47.7 por ciento. La reducci6n en Area basal total fue de 9 a 100 por ciento con un promedio de 42.4 por ciento. La mortalidad aument6 9 por ciento a 10s 7 y 18 mesa desputs del huracin. Las diferencias interspecificas en la susceptibilidad a 10s dafios causados por el viento fueron un factor contribuyente importante en 10s parrones espacios de mortalidad. Laguncubria racemosa sufri6 menor mortalidad (26%) que Rhiwphora mangle (50%) o Avicennia germinans (64%). la mortalidad en las parcelas estuvo asociada hertemente con la diferencia en composici6n de especies. No hubo ninglin patr6n definido entre la altura del dose1 y el daiio del irbol. Mbs del 80 por ciento de 10s irboles sobrevivientes de R. mangle exhibieron daoiires menores de 50 por cienro en zyxwvutsrq sus copas, mientras que ca 60 por ciento de 10s L. racernosa sobrevivientes sufri6 una perdida casi total (75-10OYo). Dieciocho meses desputs del huracin, el porcentaje de irboles de L. racemosa con daiios del 75-100 por ciento se reduj6 a 20 por ciento; en contrasre, la salud de muchos individuos de R. mangledisminuy6 conforme el porcentaje de irboles con daiios del 50-1 00 por ciento aument6 de 16 a 36 por ciento. Los niveles de penerracibn de luz en el sotobosque, medidos como el indice de iluminacion en 10s claros, aument6 de un promedio de 3 por ciento antes del huracin. a 51 por ciento 7 meses despuks del huracin, y disminuy6 ligeramente a 47 por ' Received 31 December 1999; revision accepted 8 October 2000. 393