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Coastal Freshwater Wetland Plant Community Response to Seasonal Drought and Flooding in Northwestern Costa Rica
Citation:
OSLAND, M. J., E. GONZALEZ, AND C. J. RICHARDSON. Coastal Freshwater Wetland Plant Community Response to Seasonal Drought and Flooding in Northwestern Costa Rica. WETLANDS. The Society of Wetland Scientists, McLean, VA, 31(4):641-652, (2011).
Impact/Purpose:
Along Central America’s Pacific coast, wetland ecosystem properties and processes are visibly dictated by distinct and extreme seasonal flooding and drought cycles. Most freshwater wetlands are flooded during the wet season and have no standing water for part of the dry season. The objective of this study was to better quantify the impact of these seasonal cycles on the plant community in a large and ecologically-important coastal freshwater wetland in northwestern Costa Rica [Palo Verde Marsh (PVM), Palo Verde National Park; a RAMSAR Wetland of International Importance].
Description:
In tropical wet-dry climates, seasonal hydrologic cycles drive wetland plant community change and produce distinct seasonal plant assemblages. In this study, we examined the plant community response to seasonal flooding and drought in a large coastal freshwater wetland in northwestern Costa Rica [Palo Verde Marsh, Palo Verde National Park]. We quantified compositional change following disturbance emphasizing seasonal differences in plant life-form abundance across life history stages. Whereas the dry season standing vegetation was dominated by species with an emergent life form, floating-rooted, free-floating, and submerged species were more dominant during the wet season than dry season. Interestingly, species richness was highest during periods of flooding. Seed bank and in situ seedling recruitment measurements indicated that many of the dominant species in Palo Verde Marsh are resilient with life history traits that enable them to take advantage of the pronounced and fluctuating environmental filters associated with seasonal flooding and drought. Our results highlight the importance of precipitation intensity at the onset of the wet season for plant regeneration and community change. Central America has been identified as one of the most prominent tropical climate change “hot-spots” because models consistently predict drier conditions during June and July (which is the start of the wet season and end of the dry season). Our results indicate that a prolonged dry season will likely have a tremendous impact upon drought-stressed wetland ecosystems in the region and would likely result in landscape-level wetland plant community change with drought-tolerant emergent species becoming more abundant.