USING SOILS TO UNDERSTAND ECOSYSTEM CHANGE IN WETLANDS IN PALO VERDE NATIONAL PARK, COSTA RICA

Ecosystems function as interactive matrices and the cause of an obvious problem may be deeply embedded within components of the system. Understanding the dynamics of each component is an important part of examining the whole picture. Dry tropical forests are presently one of the most endangered ecosystems on earth, threatened by encroaching development and agriculture. Within these forests, wetlands serve as havens for wildlife and are vital components in nutrient cycling. Palo Verde National Park (PVNP), located in the Guanacaste region of northwestern Costa Rica, along the lower Tempisque River, is an outstanding example of a large wetland system within a dry tropical forest. Guanacaste is a geologically dynamic area, near the collision zone of the Cocos and Caribbean Plates, and is subject to episodic tectonic/volcanic disturbances. Within the past five years, many open water areas of the PVNP in Costa Rica have been invaded by cattails, disrupting local wetland ecology and migratory waterfowl patterns. Because soils play an important role in nutrient cycling, a general lack of knowledge of the soils in PVNP may be hindering identification of the cause of this cattail invasion. Severe flooding during Hurricane Mitch (1998) likely changed local hydrology and soil properties through heavy sediment deposition. Soil and water chemistry (e.g., nutrient fluxes) were altered in ways that may have promoted cattail invasions. Properties of soil samples collected in PVNP wetlands indicate ecosystem changes that influence cattail growth, with implications that invasions are a natural response to environmental changes.

This study examines changes in sediment deposition, soil chemistry and available nutrients following flooding of a wetland in PVNP caused by Hurricane Mitch. Results and conclusions from this effort provide an expanded database of the soil resource in PVNP, vital in developing management plans for the sustainable use of the national park. Pressure to satisfy both local agricultural needs and the lucrative foreign eco-tourism market emphasizes the need for a comprehensive long-term management plan. Sustainable management of the natural and agricultural ecosystems is accomplished by a thorough understanding of the area’s soil resource and it’s dynamics.