Description of the Panamá and Iguanita mangrove stands of Bahía Culebra, North Pacific coast of Costa Rica
Jimena Samper-Villarreal, Jorge Cortés, Catalina Benavides-Varela
ABSTRACT
Mangrove forests are abundant and important coastal marine ecosystems that are being impacted by human activity in Costa Rica. There are two mangrove stands (Panamá and Iguanita) in Bahía Culebra, Guanacaste, North Pacific coast of Costa Rica. Their forest structure was determined with the Point-Centered Quarter Method (PCQM) during the dry season (December 2007-March 2008). Eleven transects were established at Panamá mangrove, with a total of 52 points and 208 quadrats. Two transects were established at Iguanita with a total of 16 points and 62 quadrats given access difficulty. Mapping of both stands was done with two georeferenced MASTER CARTA 2005 images. Images were digitized to 1:5000 scale using the following categories: mangrove forest, low density mangrove, no mangrove, transition to dry forest, sand and water. In the area studied at Panamá was 13.7ha, and 40.8ha for Iguanita. Panamá is mostly composed of dense mangrove forest (51% of total study area) and dry forest species (35% of total study area). A small area (2%) had dry soil and scarce mangrove trees and the remaining 12% corresponds to water, sand and other areas without vegetation. At Iguanita, 84% was dense mangrove, 5% scarce mangrove trees and the remaining 10% corresponds to water, sand and other areas without vegetation. Five mangrove species were encountered at Panamá (Avicennia germinans, Avicennia bicolor, Conocarpus erectus, Laguncularia racemosa, and Rhizophora mangle), and three at Iguanita (A. germinans, L. racemosa, and R. mangle). Species zonation was similar at both stands; with Rhizophora near water channels and inundated areas, Avicennia frequent in drier areas, and Laguncularia (both stands) and Conocarpus (only Panamá) more frequent near fresh water input. Densities at both stands (Iguanita= 67.2 and Panamá= 8.4 stems/0.1 ha) were lower than reported for the north Pacific of Costa Rica. Complexity index was higher at Iguanita (CI= 86.5) with R. mangle dominance, than Panamá (CI= 1.1) with A. germinans dominance. While both stands are in Bahía Culebra, structurally they are very different and seem to be under two different hydrodynamic contexts. Sea level rise related to global climate change might impact both mangrove stands as they would not be able to migrate further inland (given land elevation at the back of Iguanita, and a paved road at Panamá). Given the socio-economic and ecological importance of mangrove habitats, further study and continued conservation efforts of Costa Rican mangroves are needed.
RESUMEN
Los manglares son abundantes e importantes ecosistemas marino-costeros en Costa Rica pero están siendo afectados por la actividad humana. Se analizó la estructura y cobertura de ambos manglares presentes en Bahía Culebra (Panamá e Iguanita), Guanacaste, Pacífico norte de Costa Rica. Se utilizó el PCQM para estructura durante la época seca entre diciembre 2007 y marzo 2008. Se utilizaron dos imágenes MASTER CARTA 2005 georreferenciadas para mapeo. El área aproximada de bosque de manglar en Panamá fue de 13.7ha; y de 40.8ha en Iguanita. Panamá contiene 51% de manglar denso en el área de estudio, 35% bosque seco, 2% sin vegetación y 12% de arena o agua. En Iguanita el 84% del área corresponde a manglar denso, 5% manglar de baja densidad y 10% sin cobertura vegetal o era arena o agua. Se hallaron cinco especies de manglar en Panamá (Avicennia germinans, Avicennia bicolor, Conocarpus erectus, Laguncularia racemosa y Rhizophora mangle); y tres en Iguanita (A. germinans, L. racemosa y R. mangle). En general, la presencia de las especies de manglar siguió un patrón similar en ambos manglares. La densidad total fue menor que en manglares cercanos; y Panamá (8.4tallos/0.1ha) mucho menor que Iguanita (67.2tallos/0.1 ha). El Índice de Complejidad (IC) fue mucho mayor en Iguanita (IC= 86.5), con dominancia de R. mangle, que en Panamá (IC= 1.1), con dominancia marcada de A. germinans. Estructuralmente ambos manglares son muy distintos entre sí y parecen encontrarse en contextos hidrodinámicos diferentes.