Distribution and Ecology of Geophytes in Chile. Conservation Threats to Geophytes in Mediterranean-Type Regions
In this chapter, we study the distribution of geophytes in Chile and review the literature on their biology and ecology. This may help in understanding the causes accounting for their distribution patterns, and the results may serve to determine the conse
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13.1 Introduction In this chapter, we study the distribution of geophytes in Chile and review the literature on their biology and ecology. This may help in understanding the causes accounting for their distribution patterns, and the results may serve to determine the conservation status of geophytes in central Chile. To our knowledge, this is the first time that an assessment of the conservation status, based on objective data, has been attempted for geophytes. Finally, we analyze conservation problems for geophytes in other mediterraneantype regions. The design of conservation measures for geophytes is urgent in these regions, where anthropogenic intervention has occurred for many years. We refer briefly to the conservation status of geophytes in Chile, California, the Iberian Peninsula and South Africa. Rather than discussing particular problems in each country, we analyze what is known, what can be done, and what has been done toward the conservation of geophytes in mediterranean regions. On the other hand, many of these plants have attractive flowers (Hoffmann 1989), and knowledge of their biology and requirements is useful for cultivation, in turn helping to preserve some threatened species. Geophyte is a generic term used for plants that survive both by seed and by diverse storage organs where the perennating buds or shoot apices are buried in the ground during the unfavorable season. The underground organs are commonly bulbs, corms, rhizomes or root tubers. Some bulbs are replaced annually, while others are perennial (Raunkiaer 1934; Rees 1989; De Hertogh and Le Nard 1993). Geophytes include both dicotyledonous and monocotyledonous species, but only the petaloid monocotyledons will be considered here. Monocotyledonous geophytes seem to have evolved in the tropics, from ancestors with a sympodial growth habit (Rees 1989). This growth form appears ideally suited for the development of resting organs that allow plants to cope with unfavorable periods when they spread to seasonal, unpredictable climates. Ecological Studies, Vol. 136 Rund el et al. (eds.) Land scape Degrad ation and Biodiversity in Medit erran ean- Type Ecosystems © Spr inger -Verlag Berlin Heidelberg 1998
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A.I. Hoffmann et al.
Geophytes are important components of mediterranean-type and semi desert climate vegetations (Raunkiaer 1934; Dafni et al. 1981a,b; Rees 1989; Dafni 1993), but are generally rare in extreme desert climates (Shmida 1981). In Chile, with a native vascular flora of around 5100 taxa (Marticorena and Quezada 1985; Marticorena 1990), there are about 250 geophyte monocotyledonous species, which represent ca. 5% of the flora. The geographic and climatic features of the country, with precipitation increasing and temperature decreasing toward higher latitudes, provides a good opportunity to study the distribution of geophytes in a north-south climatic gradient of about 4000km, and to test the hypothesis that geophytes are especially frequent in the mediterranean regions (Raunkiaer 1934). The natural distribution patterns of g
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