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The Sierra de Lema is a mountainous upland area of Bolívar state, Venezuela.〔 Lying north of the Gran Sabana, it marks the divide between the drainage basins of the Caroní and Cuyuni Rivers.〔 It is partly within the bounds of Canaima National Park〔 Torres, I.N. & D.D. Martín (November 2007). Mejorando Nuestra Herencia.〕 and encompasses a number of prominent tepuis, including the entire Los Testigos chain and Ptari Massif.〔〔 The elevational range of the Sierra de Lema is around above sea level.〔Huber, O. (1995). Geographical and physical features. In: P.E. Berry, B.K. Holst & K. Yatskievych (eds.) ''Flora of the Venezuelan Guayana. Volume 1. Introduction.'' Missouri Botanical Garden Press, St. Louis. pp. 1–61.〕〔Durán Rangel, C., A. Reif & L. Hernández (April 2011). (Understanding small-scale disturbances in Guayana's montane forests: gap characterization in the Sierra de Lema, Venezuela. ) ''Interciencia'' 36(4): 272–280.〕 The names Sierra Rinocote and Sierra Usupamo (or Usupama Mountains) have historically been applied to its eastern and western portions, respectively.〔 The chain of mountains that comprises the Sierra de Lema is around wide.〔 Brewer-Carías, C. (2012). (La Sierra de Lema: una bisagra de vida ). ''Río Verde'' 7: 73–86.〕 Because the toponymy of the region remains largely unresolved, the stated ''length'' of the Sierra de Lema can vary widely, depending on the definition used.〔〔 When considering only the uplands that mark the northern boundary of the Gran Sabana, the Sierra de Lema spans around . But the extent of the range exceeds if the entire chain separating the Caroní and Cuyuni drainage basins is included. By the latter definition, the Sierra de Lema stretches from Cerro Venamo in the east to Serranía Supamo and Cerro Santa Rosa in the west (very close to the confluence of the Paragua and Caroní Rivers).〔 The old-growth forest of the Sierra de Lema remains virtually intact, covering a contiguous area of some .〔 It is characterised by nutrient poor soils with a low pH and high aluminium content.〔Durán Rangel, C. (July 2011). (Forest gaps structure and tree regeneration in a montane Guayanan forest, Sierra de Lema, Venezuela. ) Doctor of Science thesis, Albert-Ludwigs Universität, Freiburg im Breisgau.〕 The El Mirador ("The Lookout") area at the base of the Sierra de Lema exhibits unusually high levels of the radioisotope Caesium-137, in both its soils and vegetation.〔LaBrecque, J.J. & P.R. Cordoves (June 2005). Cesium-137 spatial activity in surface soils near and surrounding the Gurí Reservoir (Venezuela). ''Journal of Radioanalytical and Nuclear Chemistry'' 265(1): 91–94. 〕〔LaBrecque, J.J., J.A. Alfonso & P.R. Cordoves (August 2008). Anomalously high activities of 137Cs in soils and vegetation on and near a diabase outcrop in La Sierra de Lema, Venezuela. ''Journal of Radioanalytical and Nuclear Chemistry'' 277(2): 405–411. 〕 This is likely related to the ground composition and cloud forest conditions of the site.〔 The undulating, forested landscape of La Escalera ("The Staircase") also forms part of the Sierra de Lema.〔〔Hernández, L., N. Dezzeo, E. Sanoja, L. Salazar & H. Castellanos (March 2012). (Changes in structure and composition of evergreen forests on an altitudinal gradient in the Venezuelan Guayana Shield ). ''Revista de Biología Tropical'' 60(1): 11–33.〕 The Sierra de Lema consists of an igneous-metamorphic basement overlain by Precambrian sedimentary rocks of the Roraima Group, with Mesozoic diabase intrusions.〔〔 __NOTOC__ ==See also== * Distribution of ''Heliamphora'' 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Sierra de Lema」の詳細全文を読む スポンサード リンク
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