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Variation of Tasmanian vegetation from East to West
Tasmania can be broadly divided into two distinct regions, eastern and western, that exhibit major differences in climate, geology and vegetation. This divide, termed Tyler’s Line since 1989 (in recognition of Peter Tyler, a Tasmanian limnologist), runs from just south of the northwestern corner, and continues south, cutting roughly down the center of the island. The vegetation changes occur principally due to variations in soil types, which are a result of the geological composition, and the vast difference in climate across the state. Generally, the west has a higher mean rainfall but poor acidic soil while the east has a lower mean rainfall but slightly more fertile soil. This results in a larger proportion of rainforest, moorland and wet sclerophyll vegetation dominating in the west and predominantly dry sclerophyll in the east.〔
==Geology and Soil==
Tasmania, despite its size, has a very complex and diverse geology. As a geologic simplification, the western half of the state is characterised as being a more ancient fold province and the east, a younger intruded fault province. Western Tasmania contains a vast variety of ancient, deeply folded metamorphosed and non-metamorphosed rocks, namely the Mesoproterozoic quartzite, schist and phyllite. Other more recent geologic signatures are scattered across the west, such as Ordovician limestone, Neoproterozoic dolomite basalt, Devonian granite (in the northwest) and Cambrian sediments. The extensive folding of these rocks (particularly the quartzite) formed jagged mountain ranges and deep river valleys. Exposed to lengthy periods of erosion, the Mesoproterozoic rocks were worn down to shallow, acidic and infertile soil due to their high silica content.〔 The central (central highlands) and southeastern areas are composed of much younger sedimentary rocks that have been intruded by magma, which forms sills and dykes of dolorite.〔 This area has also been impacted by volcanic activity (in the Tertiary period) that has deposited basaltic rock across the landscape. Contrasting with the generally quartzitic soil of the west, basalt is higher in nutrients and, depending on extent of weathering, fertility.〔 The weathering of eastern dolorite intrusions produces clay based soils that (with enough water), like basalt, will allow higher levels of plant production than in the west.〔〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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