Mapping vegetation and open water in Palo Verde National Park, and impact of Fangueo technique : a descriptive study

Details

Supervisors

Javaux, Mathieu ; Alonso, Alice

Faculty

Faculté des bioingénieurs

Degree label

Master [120] : bioingénieur en sciences et technologies de l'environnement, à finalité spécialisée

Abstract

The Palo Verde National Park (PVNP), in Costa Rica, is an ecologically important wetland in Central America. After 1980, the wetland landscape changed from diverse vegetation and large open water areas to a monotypic stand of cattail, Typha domingensis. Programs to reduce Typha invasion were initiated and the Fangueo technique was adopted to reduce Typha spread. Studying Typha spatial distribution in the area, quantifying and mapping open water, and evaluating the long-term impact of the Fangueo technique on open water and vegetation cover is desirable to improve our knowledge of the eco-hydrology of PVNP. Thresholded enhanced vegetation index (EVI) was used to create an indicative map of Typha distribution in PVNP. This method could be effective to map Typha in areas with similar hydrological situations. Open water areas were quantified and mapped by thresholding the near-infrared spectral band (NIR). The year-round dynamic indicated that there could be two peaks of open water area, one during the wet season and the other during the early dry season induced by aquatic vegetation retreat. Comparison of areas with versus without Fangueo was used to evaluate the impacts of the Fangueo technique. It was found that the initial increase in open water induced by Fangueo was not sustained over time. The method employed to monitor vegetation using EVI time series was found unsuccessful at assessing whether Fangueo leads to a long-term decrease of Typha cover in intervention areas.