. The Canadian field-naturalist. Natural history. 1995 Catling and Brownell: Alvars of the Great Lakes Region 149 has been recently discussed elsewhere (Catling 1995). Useful general descriptions of alvar plant associa- tions are available for various sites (, Catling et al. 1975; Reschke 1990; McKay-Kuja and Kavanagh 1992*; Belcher et al. 1992; Norris 1994*; and see under "Regional Perspectives"). Extensive and detailed quantitative studies are lacking. Problems in developing a predictive model of alvar vegetation within the Great Lakes Region include regional vari- ation, frequ
. The Canadian field-naturalist. Natural history. 1995 Catling and Brownell: Alvars of the Great Lakes Region 149 has been recently discussed elsewhere (Catling 1995). Useful general descriptions of alvar plant associa- tions are available for various sites (, Catling et al. 1975; Reschke 1990; McKay-Kuja and Kavanagh 1992*; Belcher et al. 1992; Norris 1994*; and see under "Regional Perspectives"). Extensive and detailed quantitative studies are lacking. Problems in developing a predictive model of alvar vegetation within the Great Lakes Region include regional vari- ation, frequent intergradation of plant associations, and capability of any one of several frequent plant associates to act as a dominant. Plateau Alvar Vegetation of alvars on limestone or marble table- land located inland from shorelines frequently has a particular pattern of parallel openings and parallel bands of forest (Figure 4, top). The forested areas often correspond to ridges with cracks or low escarp- ment edges. The long narrow bands of forest follow- ing the ridges ("curtain forests", Figure 4, bottom), may also be a result of long bands of sand and gravel deposited on otherwise exposed limestone pavement. Soil depth and the extent of periodic wetness are both important factors in relation to the kinds of plant associations on alvars. Four major associations can be recognized, but some sites are without one or. high pavement alvar grassland ,q^ paiement woodland alvar savanna Figure 4. Diagramatic cross-section of a plateau alvar complex with alvar grasslands, high pavement (pave- ment ridge), low pavement, and alvar savanna with sur- rounding woodland and curtain Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Ottawa Field-Naturalists' Club. Ottawa, Ottawa Field-Naturalists' Club
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