Meadows & Marshes

The herbaceous world, marshes and grasslands in the Amazonia

Marshes are usually considered wetlands with aquatic herbaceous vegetation, either rooted or not, though some trees and shrubs are usually present as well, though not dominant. Marshes are variously known as swamp or marisma in Spanish and pântano or charco in Portuguese, though these terms are not commonly used specifically for marshes in the Amazon. Marsh communities are difficult to distinguish from wetland forests because they often fringe or grow interlaced on floodplains or along riverbanks and floodplain lakes. Nevertheless, their presence can be detected with satellite imagery and major areas of their development can be quantified during high and low water periods. For management purposes, marshes will probably have to be managed together with flooded forests because of their proximity.

 

Conservando la Cuenca Amazónica Aguas Amazonicas

Floating meadows, including giant arums in the background, on the lower Amazon River floodplain. Department – Country: Pará, Brazil Main Basin – Sub Basin: Amazon River Main Stem – Eastern Amazon River Main Stem Photographer: Michael Goulding

In the Amazon, marshes are most common on the whitewater floodplains where nutrients are sufficient to support large expanses of floating meadows, which include both rooted and free-floating herbaceous plants. However, they are also common in savanna areas inundated by local rainwater, and, although they receive relatively few from it, they have sufficient nutrients from non-alluvial soils.

Some blackwater and clearwater rivers also support marshes, though these are less developed and less productive than those of the whitewater rivers. During the floods, some marsh grasses on whitewater floodplains can grow 20–30 cm a day as the water levels rise. After reaching 4–6 meters, the grasses break loose from the soil and float. During the dry season, freshwater marshes shrink considerably though many herbaceous species survive the dry phase by rooting in the soil. The floating meadows found in whitewater floodplain marshes are among the most productive aquatic habitats in the Amazon Basin. They are also biologically important for many vertebrate and invertebrate animal species. For example, they are nurseries for many migratory fish species.

Where floodplains have been deforested, light conditions stimulate the expansion of herbaceous plant communities. This is especially evident on the Amazon River floodplain downriver from its confluence with the Negro River, and it has probably also occurred in what are now savannas, such as in eastern Bolivia where major wetland modification took place even in pre-Columbian period.

Outside the floodplains, extensive marshes exist on savannas that become inundated during the rainy season. Although dominated by herbaceous vegetation, they almost always have scattered shrubs and often trees, especially along streams borders. The most notable are those of the Llanos de Moxos of Eastern Bolivia, the Bananal Island between the Tocantins and Araguaia rivers and the Roraima savannas of the Branco Basin.

 

 

WETLANDS TYPES