| Abstract from DBPedia | 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 support an unbroken herbaceous layer consisting primarily of grasses. According to Britannica, there exists four savanna forms; savanna woodland where trees and shrubs form a light canopy, tree savanna with scattered trees and shrubs, shrub savanna with distributed shrubs, and grass savanna where trees and shrubs are mostly nonexistent. Savannas maintain an open canopy despite a high tree density. It is often believed that savannas feature widely spaced, scattered trees. However, in many savannas, tree densities are higher and trees are more regularly spaced than in forests. The South American savanna types cerrado sensu stricto and cerrado dense typically have densities of trees similar to or higher than that found in South American tropical forests, with savanna ranging from 800 to 3300 trees per hectare (trees/ha) and adjacent forests with 800–2000 trees/ha. Similarly Guinean savanna has 129 trees/ha, compared to 103 for riparian forest, while Eastern Australian sclerophyll forests have average tree densities of approximately 100 per hectare, comparable to savannas in the same region. Savannas are also characterised by seasonal water availability, with the majority of rainfall confined to one season; they are associated with several types of biomes, and are frequently in a transitional zone between forest and desert or grassland, though they're mostly a transition between desert to forest. Savanna covers approximately 20% of the Earth's land area. Unlike the prairies in North America and steppes in Eurasia, which would feature cold winters, savannahs are mostly located in areas having warm to hot climates, such as those in Africa, Australia, Thailand, South America and India.サバナ（Savanna、サヴァナまたはサバンナとも＊主に学校ではサバナと書いている）とは乾季と雨季のある熱帯に分布する、疎林と低木を交えた熱帯長草草原地帯である。年間降水量が 600mm以下で夏に雨季があり、その他の季節に長い乾季をもつ地域に分布する。イネ科の草本を主体とする草原に樹木が疎に生える。草本は雨季に葉をつけて繁茂するが、乾季に地上部は枯れる。アフリカではバオバブ樹などが見られる。大型の草食動物が群れをなして多く生活をしている。 熱帯草原を一般的にサバナと呼んでいるが、これはスーダン先住民が使用した呼称に由来し、地域によりリャノ（オリノコ川流域）、カンポ（ブラジル高原）、グランチャコ（パラグアイ）などの名称もある。 (Source: http://dbpedia.org/resource/Savanna) |
