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タイトル: FACTORS CONTROLLING GEOGRAPHICAL DISTRIBUTION IN SAVANNA VEGETATION IN NAMIBIA
著者: OKITSU, Susumu
キーワード: Annual precipitation
Colophospermum mopane
Deciduous tree
Evergreen nanophyll
Evergreen notophyll
Savanna.
発行日: 31-Mar-2005
出版者: The Center for African Area Studies, Kyoto University
誌名: African Study Monographs. Supplementary Issue.
巻: 30
開始ページ: 135
終了ページ: 151
抄録: Here, I describe the geographical distribution of the savanna types in Namibia and identify the factors controlling the occurrence of each savanna type in relation to the amount of annual precipitation and the various physiographical regions, including the mopane (Colophospermum mopane) area. The different types of savanna can be distinguished on the basis of the leaf habits of the dominant vegetation: deciduous, evergreen nanophyll, and evergreen notophyll. In general, vegetation performance (i.e., vegetation cover and maximum height) was positively correlated with the amount of annual precipitation. However, the occurrence of a particular savanna type coincided well with physiographical region regardless of the amount of annual precipitation received. Deciduous savanna occurred primarily in the Central Highland and had the smallest total vegetation cover among the three types. The dry soil of this region determined inevitably the deciduous leaf habit of the vegetation during the dry season and thus the smallest total vegetation cover. Evergreen nanophyll savanna was found mainly in the Mega Kalahari, where I observed a clear relationship between the amount of annual precipitation and total vegetation cover. The soil moisture in this region favored an evergreen leaf habit, even in the dry season, resulting in the effective use of soil water throughout the year. This probably accounted for the large increase in total vegetation cover with increasing annual precipitation. Evergreen notophyll savanna exclusively appeared in the mopane area, regardless of the physiographical region, and had the largest total vegetation cover, apparently as a result of the ecological characteristics of mopane. Therefore, it appears that the geographical distribution of the various savanna types in Namibia is principally controlled by two different factors that are independent of the amount of annual precipitation: the water-holding capacity of the soil and the ecological characteristics of mopane.
DOI: 10.14989/68455
URI: http://hdl.handle.net/2433/68455
出現コレクション:30 (Studies on the Environmental Change and Human Activities in Semi-Arid Area of Africa)

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