Research - Habitat Diversity

Probably the most interesting feature of El Refugio is the diversity of habitats accessible from the station. The main camp provides access to all the major habitat types represented on the property: forest, riparian zones, and seasonally-flooded grassland. The forests at El Refugio include terra firme forest, riparian forest, and a small patch of dry forest on a rocky outcrop of the Brazilian shield. Riparian habitats include the Rio Paragua and several marshes in the grasslands that maintain seasonal connections with the Paragua, but often dry down completely in the dry season. The grasslands include open areas of relatively short-statured grass, small isolated marshes, and forest islands.

The seasonally-flooded grassland at El Refugio (known locally as pampa or pampa aguada) is covered by about 30 cm of water from approximately December to June, though the temporal and spatial distribution of rainfall varies greatly. Some parts of the pampa do not flood at all or only do so to a depth of 10 cm for a short part of the year, whereas other areas flood up to two meters and retain water most of the year. The temporal distribution of rainfall varies from year to year and is best described as unpredictable. The more shallowly-flooded portions of the pampa are dominated by graminoids in the families Poaceae and Cypercaceae. Portions of the pampa that flood more deeply for a longer portion of the year (curiches) are dominated by emergent aquatic plants including Thalia geniculata, Rhynchospora sp. and Eleocharis sp. Forest islands in the pampa range in size from a few square meters to approximately 10 ha; common genera on forest islands include Cecropia, Astrocaryum, Attalea, Curatella, Tabebuia, and Bauhinia. Fires play an important role in the ecology of the pampa, which is quick to recover after a burn (below right). The spatial extent of burns varies, resulting in a mosaic of burn histories in the pampa, as seen above left.

Forest

Most of the forest at El Refugio is upland, semi-deciduous forest. However, there is seasonally-flooded forest along parts of the Rio Paragua, and a patch of dry forest with characteristic Cereus cacti on an outcrop of the Brazilian shield (above center). The amount of deciduousness in the forest varies from year to year. The composition of the forest is a mixture of Amazonian and dry forest elements. Common species in the forest around El Refugio include Ficus spp., Chorisia speciosa, Ceiba samauma, Caesalpinia floribunda, Tabebuia spp., Sheelea princeps, Attalea phalerata, and Euterpe precatoria.

Aquatic Habitats

The Rio Paragua separates a large patch of continuous forest from the pampa aguada and forest islands at El Refugio. The Río Paraguá is a small river ranging from about 10m to 30m in width and rises and falls approximatley three m over the course of a year. For much of its length the Paragua is covered by thick mats of vegetation (colchas) dominated by graminoids; Eichornia azurea colonies also cover much of the river. Approximately 3 km of open river are accessible from El Refugio, including a large bay off the main channel of the Paragua.