A gallery forest is one formed as a corridor along rivers or

wetlands A wetland is a distinct semi-aquatic ecosystem whose groundcovers are flooded or saturated in water, either permanently, for years or decades, or only seasonally. Flooding results in oxygen-poor ( anoxic) processes taking place, especially ...

, projecting into landscapes that are otherwise only sparsely treed such as

savanna A savanna or savannah is a mixed woodland-grassland (i.e. grassy woodland) biome and ecosystem characterised by the trees being sufficiently widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach th ...

grassland A grassland is an area where the vegetation is dominance (ecology), dominated by grasses (Poaceae). However, sedge (Cyperaceae) and rush (Juncaceae) can also be found along with variable proportions of legumes such as clover, and other Herbaceo ...

s, or

desert A desert is a landscape where little precipitation occurs and, consequently, living conditions create unique biomes and ecosystems. The lack of vegetation exposes the unprotected surface of the ground to denudation. About one-third of the la ...

s. The gallery forest maintains a more temperate

microclimate A microclimate (or micro-climate) is a local set of atmosphere of Earth, atmospheric conditions that differ from those in the surrounding areas, often slightly but sometimes substantially. The term may refer to areas as small as a few square m ...

above the river. Defined as long and narrow forest vegetation associated with rivers, gallery forests are structurally and floristically heterogeneous. The habitats of these forests differ from the surrounding landscapes because they are, for example, more nutrient-rich or moister and/or there is less chance of fires. The forests are sometimes only a few meters wide, because they depend on the water they lie along.

Ecology characteristics

The

riparian A riparian zone or riparian area is the interface between land and a river or stream. In some regions, the terms riparian woodland, riparian forest, riparian buffer zone, riparian corridor, and riparian strip are used to characterize a ripar ...

zones in which they grow offer greater protection from fire which would kill tree

seedling A seedling is a young sporophyte developing out of a plant embryo from a seed. Seedling development starts with germination of the seed. A typical young seedling consists of three main parts: the radicle (embryonic root), the hypocotyl (embry ...

s. In addition, the alluvial soils of the gallery habitat are often of higher fertility and have better drainage than the soils of the surrounding landscape with a more reliable water supply at depth. As a result, the boundary between gallery forest and the surrounding woodland or grassland is usually abrupt, with the

ecotone An ecotone is a transitional area between two plant communities, where these meet and integrate. Examples include areas between grassland and forest, estuaries and lagoon, freshwater and sea water etc. An ecotone may be narrow or wide, and it ma ...

being only a few metres wide. Gallery forests have shrunk in extent worldwide as a result of human activities, including domestic livestock's preventing tree seedling establishment and the construction of

dam A dam is a barrier that stops or restricts the flow of surface water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation, human consumption, industrial use, aqua ...

s and

weir A weir or low-head dam is a barrier across the width of a river that alters the flow characteristics of water and usually results in a change in the height of the water level. Weirs are also used to control the flow of water for outlets of l ...

s causing flooding or interfering with natural stream flow. In addition to these disturbances, gallery forests are also threatened by many of the same processes that threaten savannas. Riparian zones offer protection from fire and stress from

water shortage Water scarcity (closely related to water stress or water crisis) is the lack of fresh water resources to meet the standard water demand. There are two types of water scarcity. One is ''physical.'' The other is ''economic water scarcity''. Physic ...

s. The name "gallery" comes from an older sense of that word meaning a narrow passageway; compare with " mine gallery". They are clearly identified in the landscape by sticking to the course of the river, forming a corridor completely different from the rest of the vegetation, in color and height.

Areas

Gallery forests are able to exist where the surrounding landscape does not support forests for a number of reasons. Gallery forests are often found along so-called "foreign rivers" in arid areas where no other forest grows due to the lack of water (river-accompanying gallery forest). The gallery forest is an

azonal In geography, azonal is an adjective that refers to processes or things that are not restricted to any climate zone. It can be used to describe soils, landforms, geomorphic processes or vegetation. Volcanism and mountain-related processes are exam ...

form of vegetation here, it only thrives there because of the special local conditions. Gallery forest can also form due to more favorable soil conditions on the

river bank In geography, a bank is the land alongside a body of water. Different structures are referred to as ''banks'' in different fields of geography. In limnology (the study of inland waters), a stream bank or river bank is the terrain alongsid ...

. Examples of this are the plains of the

Llanos The Llanos ( Spanish ''Los Llanos'', "The Plains"; ) is a vast tropical grassland plain situated to the east of the Andes in Colombia and Venezuela, in northwestern South America. It is an ecoregion of the tropical and subtropical grasslands, ...

Venezuela Venezuela, officially the Bolivarian Republic of Venezuela, is a country on the northern coast of South America, consisting of a continental landmass and many Federal Dependencies of Venezuela, islands and islets in the Caribbean Sea. It com ...

, where grasses predominate despite high rainfall and only the embankments are wooded. On the plains, a hard

laterite Laterite is a soil type rich in iron and aluminium and is commonly considered to have formed in hot and wet tropical areas. Nearly all laterites are of rusty-red coloration, because of high iron oxide content. They develop by intensive and prolo ...

crust in the soil, the arecife, which is hardly penetrable for roots, prevents the growth of trees. The exceptional nature of some of these forests makes them the object of special protection, such as those on the banks of the Tagus River in

Aranjuez Aranjuez () is a city and municipality of Spain, part of the Community of Madrid. Located in the southern end of the region, the main urban nucleus lies on the left bank of the Tagus, a bit upstream of the discharge of the Jarama. , the munici ...

, which have been classified as

World Heritage Site World Heritage Sites are landmarks and areas with legal protection under an treaty, international treaty administered by UNESCO for having cultural, historical, or scientific significance. The sites are judged to contain "cultural and natural ...

s. Gallery forests also exist along the valleys of Omaruru, Swakop and Kuiseb in the Central

Namibia Namibia, officially the Republic of Namibia, is a country on the west coast of Southern Africa. Its borders include the Atlantic Ocean to the west, Angola and Zambia to the north, Botswana to the east and South Africa to the south; in the no ...

. Here the riverbeds are filled with a thick layer of sand, through which groundwater flows even when there is no rain. Gallery forest in cultivated land can be found on waterbodies in pasture and farmland (e.g. alluvial forest) as well as on terrain levels (hillside forests in Europe), i.e. plots of land that are not suitable for farming. It is often the small forest as a private economic wood reserve, or unusable or inaccessible fallow land as a natural forest residue. Gallery forests have persisted in

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

prairie Prairies are ecosystems considered part of the temperate grasslands, savannas, and shrublands biome by ecologists, based on similar temperate climates, moderate rainfall, and a composition of grasses, herbs, and shrubs, rather than trees, as the ...

-dominated areas along rivers and streams. In dry to temperate zones, the presence of water is not the only factor that determines species. Grassland fires, even where they are rare, have had a high selective pressure value against woody vegetation.C.-P. Hutter, K. Blessing, U. Kozina: Wälder, Hecken und Gehölze. Weitbrecht Verlag, Stuttgart 1995, . Early

hominin The Hominini (hominins) form a taxonomic tribe of the subfamily Homininae (hominines). They comprise two extant genera: ''Homo'' (humans) and '' Pan'' (chimpanzees and bonobos), and in standard usage exclude the genus '' Gorilla'' ( gorillas) ...

species such as Ardipithecus ramidus,

Australopithecus anamensis ''Australopithecus anamensis'' is a hominin species that lived roughly between 4.3 and 3.8 million years ago, and is the oldest known ''Australopithecus'' species, Nearly 100 fossil specimens of ''A. anamensis'' are known from Kenya and Ethiopia ...

and

Homo rudolfensis ''Homo rudolfensis'' is an extinct species of archaic human from the Early Pleistocene of East Africa about 2 million years ago (mya). Because ''H. rudolfensis'' coexisted with several other hominins, it is debated what specimens can be confiden ...

have inhabited gallery forests.

References

{{DEFAULTSORT:Gallery Forest Riparian zone Forests Habitats Habitat

Ecology characteristics

Areas

See also

References