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

wetlands A wetland is a distinct ecosystem that is flooded or saturated by water, either permanently (for years or decades) or seasonally (for weeks or months). Flooding results in oxygen-free (anoxic) processes prevailing, especially in the soils. The ...

, 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) ecosystem characterised by the trees being sufficiently widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to ...

grassland A grassland is an area where the vegetation is dominated by grasses (Poaceae). However, sedge (Cyperaceae) and rush (Juncaceae) can also be found along with variable proportions of legumes, like clover, and other herbs. Grasslands occur natur ...

s, or

desert A desert is a barren area of landscape where little precipitation occurs and, consequently, living conditions are hostile for plant and animal life. The lack of vegetation exposes the unprotected surface of the ground to denudation. About on ...

s. The gallery forest maintains a more temperate

microclimate A microclimate (or micro-climate) is a local set of atmospheric conditions that differ from those in the surrounding areas, often with a slight difference but sometimes with a substantial one. The term may refer to areas as small as a few squ ...

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. Riparian is also the proper nomenclature for one of the terrestrial biomes of the Earth. Plant habitats and communities along the river margins and banks ar ...

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 transition area between two biological communities, where two communities meet and integrate. It may be narrow or wide, and it may be local (the zone between a field and forest) or regional (the transition between forest and gras ...

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 ...

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 river 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: physical or economic water scarcity. Physical water scarcity is wher ...

s. In addition,

alluvial soil Alluvium (from Latin ''alluvius'', from ''alluere'' 'to wash against') is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. Alluv ...

s offer greater fertility and better drainage, as well as greater water supply. As a result, the boundary between gallery forest and surrounding open areas is sharp and abrupt, with the

only a few meters wide. The name "gallery" comes from the fact that its vegetation covers the river forming a kind of tunnel, like in a mine gallery. They are clearly identified in the landscape by sticking to the course of the river, forming a corridor or corridor completely different from the rest of the vegetation, in color and height.

Areas

Awash River Valley, Asaita, Afar, Ethiopia

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 exampl ...

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. 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, sav ...

Venezuela Venezuela (; ), officially the Bolivarian Republic of Venezuela ( es, link=no, República Bolivariana de Venezuela), is a country on the northern coast of South America, consisting of a continental landmass and many islands and islets in th ...

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

laterite Laterite is both a soil and a rock 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 ...

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 The Tagus ( ; es, Tajo ; pt, Tejo ; see below) is the longest river in the Iberian Peninsula. The river rises in the Montes Universales near Teruel, in mid-eastern Spain, flows , generally west with two main south-westward sections, to e ...

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 Tagus, a bit upstream the discharge of the Jarama. , the municipality h ...

, which have been classified as

World Heritage Site A World Heritage Site is a landmark or area with legal protection by an international convention administered by the United Nations Educational, Scientific and Cultural Organization (UNESCO). World Heritage Sites are designated by UNESCO for h ...

s. Gallery forests also exist along the valleys of Omaruru,

Swakop The Swakop River ( naq, Tsoaxaub) is a major river in western central Namibia. Its river source is in the Khomas Highland. From there it flows westwards through the town of Okahandja, the historic mission station at Gross Barmen, and the set ...

and

Kuiseb The Kuiseb River is an ephemeral river in western-central Namibia. Its source is in the Khomas Highland west of Windhoek. From there it flows westwards through the Namib-Naukluft National Park and the Namib desert to Walvis Bay. Several settlement ...

in the Central

Namibia Namibia (, ), officially the Republic of Namibia, is a country in Southern Africa. Its western border is the Atlantic Ocean. It shares land borders with Zambia and Angola to the north, Botswana to the east and South Africa to the south and ea ...

. 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 A riparian forest or riparian woodland is a forested or wooded area of land adjacent to a body of water such as a river, stream, pond, lake, marshland, estuary, canal, sink or reservoir. Etymology The term riparian comes from the Latin word '' ...

) 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 and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

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, ISBN 3-522-72040-7 Early

hominin The Hominini form a taxonomic tribe of the subfamily Homininae ("hominines"). Hominini includes the extant genera ''Homo'' (humans) and '' Pan'' (chimpanzees and bonobos) and in standard usage excludes the genus ''Gorilla'' (gorillas). The t ...

species such as

Ardipithecus ramidus ''Ardipithecus ramidus'' is a species of australopithecine from the Afar region of Early Pliocene Ethiopia 4.4 million years ago (mya). ''A. ramidus'', unlike modern hominids, has adaptations for both walking on two legs ( bipedality) and life i ...

Australopithecus anamensis ''Australopithecus anamensis'' is a hominin species that lived approximately between 4.2 and 3.8 million years ago and is the oldest known ''Australopithecus'' species, living during the Plio-Pleistocene era. Nearly one hundred fossil specimens ...

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 confide ...

have inhabited gallery forests.

References

{{DEFAULTSORT:Gallery Forest Riparian zone Forests Habitats Habitat

Ecology characteristics

Areas

See also

References