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Pachypodium habitats consist of isolated, specialized, micro–environmental niches, generally xeric, rocky, frost-free areas within parts of western Madagascar and southern Africa. ''Pachypodium'' species are often indifferent to the regional ecological, biotic zone of vegetation, a fact which explains some of ''Pachypodium'' morphology and architecture. The large scale vegetation zones are in some cases irrelevant to the micro-environments of ''Pachypodium'', in the sense that the xeric niches may be embedded in larger mesic biomes. Most ''Pachypodium'' are rupicolous species occur on rocky outcrops, steep hills, and on inselbergs or kopjes, land or rocky masses which have resisted erosion and stand isolated in level or gently sloping terrain, sometimes above a forest canopy. Rocky outcrops, steep hills, and inselbergs create microclimate conditions that may be different from the general climate of a region. The habitats of ''Pachypodium'' are thought of as arid ecological, even when they occur in prehumid zonobiomes, because the taxon's topographic position and microclimate conditions differ significantly from the context of the greater ecological conditions within the landscape. The prehumid zonobiomes are humid zones of regional biotic community characterized chiefly by the dominant forms of plant life and prevailing climate, such as forests or mountains. On these ecological islands the flora significantly differs from the greater surrounding zones of vegetation, where a smaller immediate area under the influence of a micro-environmental condition is defined. In larger areas of vegetation, the isolation of these plants in these "arid islands" become very conspicuous during prolonged periods without rain. ==Environmental conditions== The plants on outcrops, steep hills, and inselbergs are subjected to fluctuating moisture, high winds, and extremes in temperatures. This exposure occurs because, in the case or outcrops and inselbergs, all plants typically are growing in fissures that often have shallow soil and are exposed within the landscape. Pachypodium typically grows in frost-free areas with the exception of P. bispinosum and P. succulentum. The latter two species can sustain winter temperatures reaching into -10°C). The regions where ''Pachypodium'' biotypes exist are (a) situated between sea-level and 2000 meters and (b) are defined by the effects of temperatures. Without exception, all ''Pachypodium'' share in a preference for sunny, xeric habitats. Their exclusion from humid forests is almost entirely the case except where "inselbergs" surge above the humid, forest canopy: an example of ''Pachypodium'' response to micro-environments than larger vegetative types. Only plants with special adaptations to extreme drought can survive exposed rocky habitats. Plants with special morphological adaptations produce offspring that can bear the intensity of these arid, xeric, exposed micro-environments. ''Pachypodium'' employs two mechanisms to adapt to these conditions: *Spinescent: The presence of spines that collect moisture in fogs and dews and point downward so that moisture falls to the ground at the base of the plants. *Pachycaule Trunks: The use of an abnormally thickened trunk or stem of various shapes to store water in times of drought. In some instances, the pachycaule trunks are geophytic and exist underground as is the case for ''Pachypodium bispinosum'' and ''Pachypodium succulentum.'' 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「Pachypodium habitats」の詳細全文を読む スポンサード リンク
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