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20 December 1993 <br />Memo to: John Lohr, Southwestern Portland Cement <br />i <br />From: David L. Buckner, Ph.D., ESCO Associates <br />B@; Nature of Calciphily; Importance at Dowe Flats. Species Diversity Comments <br />Calclphlly <br />The affinity of some plant species for calcareous substrates is one of the oldest observations in <br />ecology (Warming 1909, Schimper 1903, Thurmann 1849), having originally been studied in <br />the Calcareous Alps of central Europe. In Colorado, the phenomenon has been documented most <br />prominently from Hoosier Ridge between Fairplay and Breckenridge. There, the Leadville <br />Limestone is the location of occurrence of several rare plant species. Some of these are <br />disjuncts, ie. plants that occur in far disjunct geographic locales, in varying degrees of <br />commoness. Others are endemics (plants that occur in a single relatively confined area and <br />nowhere else) that may have evolved since geographic separation from related plants after <br />climate change removed suitable habitat in between. <br />To varying degrees, plants tolerate scarcity of essential resources, such as nutrients. Those <br />least tolerant of the scarcity of a given nutrient are likely to be most abundant where that <br />nutrient is present in abundance. In the extreme cases of either plant intolerance of nutrient <br />scarcity, or low availability of the nutrient in the general landscapes of a region, species least <br />tolerant of scarcity may be found only on the few sites where the nutrient is available in <br />sufficient amounts. If the nutrient in question is calcium, then sites of greatest abundance are <br />likely to be those where the geologic parent material is rich in calcium, ie. limestone or gypsum <br />sites. <br />In zones of high rainfall, water percolating through the soil removes or leaches many cations, <br />including calcium, out of the root zone. Fortunately, calcium is added to soils at a small rate as <br />minerals weather and decompose through natural chemical processes. In arid and semi-arid <br />environments, calcium produced by weathering actually exceeds leaching losses and the element <br />can accumulate, resu{ting (along with the presence of other cations) in 'alkaline' soils that are <br />widespread in western North America. Consequently, under present climatic conditions, the <br />availability of calcium is widespread in natural soils and not confined to <br />sites except in a few areas where precipitation is high and soil leaching is <br />