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Ecological Overview
Drivers of Biodiversity
Although there has been widespread speculation for many years on the causal factors responsible for the high levels of vascular plant biodiversity in MTEs, few clear generalizations have emerged. What is known is that there are conditions promoting the coexistence of seemingly ecologically equivalent shrubs, geophytes, and graminoids (Restionaceae) in frequently burned shrublands on nutrient-poor soils of fynbos and kwongan communities. Slow growth rates and diverse strategies of postfire regeneration and reestablishment appear to promote this coexistence. MTEs on less-infertile soils and with longer intervals between fires (chaparral, matorral, maquis) have lower diversity as short-lived species are excluded by rapidly growing shrub dominants. Open woodlands in the Mediterranean Basin and California, however, may have very high local diversity of annuals and short-lived perennials, where grazing maintains open habitat for species establishment. Regional topographic and climatic heterogeneity per se, which might be thought to be logical correlates of comparative diversity among the five MTEs, is a poor predictor of diversity. Instead, natural selection has operated to allow for a fine-scale discrimination of habitats and niches under the selective pressures of stable climates, predictably frequent fires, and periodic drought that promote community turnover and diversification. Thus, fynbos in the southwestern Cape Region…
Natural Disturbance Regimes
Although the five mediterranean-climate regions share many aspects of natural climatic and environmental disturbance regimes, there are significant differences as well. While all five regions experience characteristic summer drought, for example, the magnitude of this drought is particularly severe in California and Chile, where 6–8 months or more may pass without measurable rainfall. Extreme drought such as this is rare in South Africa and southwestern Australia where summer months frequently have light showers. The dense canopies of evergreen sclerophyllous shrubs make fire an important component of natural disturbance regimes. Natural fires, however, are significant ecological events in consuming aboveground vegetation in only four of the five MTEs. Central Chile, where natural fires are a rare event, is the exception among MTEs. This mediterranean-climate region is protected from summer storms and lightning moving westward across Argentina by the high Andean Cordillera. The native flora of Chile shows little evidence that fire has been an important ecological disturbance regime in the evolution of life history characteristics. Natural fire frequencies are quite different among the other four mediterranean-climate regions. In South Africa, for example, fynbos vegetation in the Cape Region commonly burns at intervals of 10–15 years, while in California natural frequencies are…
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MEDECOS
About MEDECOS
The origins of MEDECOS and ISOMED date back to March 1971 when an international meeting of Mediterranean-region ecologists was convened in Valdivia, Chile. This meeting was organized by Francisco di Castri and served as the initiation of a new program of study of convergent ecosystems within the International Biological Program (IBP). This conference led to a synthesis of the comparative geography and ecology of the world’s five Mediterranean-climate regions (di Castri and Mooney 1973). This edited volume and the comparative studies of Chile and California that followed in the IBP program brought a broader ecological and evolutionary perspective to comparative ecosystem studies. There was a consensus at the Valdivia conference of the need to initiate a cycle of international conferences that would rotate among the five Mediterranean-climate regions. With this impetus the second MEDECOS conference, although not yet called by this name, was held in the summer of 1977 at Stanford, California, organized by Hal Mooney. An international group of more than 100 scientists attended this meeting, which focused on the environmental consequences of fire and fuel management practices on the functioning of mediterranean-climate ecosystems (Mooney and Conrad 1977). The third international conference, termed MEDCOM, took place in Stellenbosch,…
Previous Conferences
MEDECOS XIV 2017
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