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.
Seasonally-flooded
grassland (Pampa Aguada)
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.
