EDAPHIC OR SOIL FACTORS: CHEMICAL 183 



Of the species which have been described as Hme-constant by 

 Contejean (1881, p. 125), the following occur also upon non-calcareous 

 soils in southern France: Melica ciliata, Carex halleriana, Hippocrepis 

 comosa, Coronilla emerus, C. minima, Prunus mahaleb, Euphorbia 

 seguieriana, and Vincetoxicum officinale. 



Flahault (1893) gives a list of species which are considered lime- 

 constant in northern France but are found in the Cevennes also upon 

 soils poor in lime. 



A similar ecological relation is shown by Fagus silvatica, Quercus 

 pubesce7is, and Bromus eredus, which thrive in the south of Europe 

 upon any kind of soil — chalk, acidic gneiss, granites — and also form 

 extensive communities upon soils poor in lime. But in central 

 Europe B. eredus is considered a lime plant, and from the close inter- 

 relation of chalk and the distribution of beech woods in England, many 

 authors have arrived at the conclusion that Fagus is directly dependent 

 upon the chemical nature of the substratum.^ 



Dired Adion of Calcium. — The direct action of Ca ions, determined 

 by the amount of soluble calcium, seems unaffected by acidity or 

 alkalinity. According to Magnin (1886), Contejean (1881), and 

 others, soils with at least 2 to 3 per cent of soluble calcium are to be 

 considered lime soils. Under particularly favorable external circum- 

 stances, with no competition from better adapted species, many calci- 

 phobous species endure this amount of lime. On the other hand, mere 

 traces of lime (0.2 to 0.3 per cent) enable calcicoles to survive. Large 

 quantities of CaCOs drive out the indifferent plants, and the calcicoles 

 or lime-constant species gain more and more monopoly over an area. 

 Magnesium carbonate, MgCOs, has a similar effect and may partially 

 take the place of CaCOs. 



As we speak of lime-constant species and calcicolous colonies, so we 

 may speak of lime-constant associations. ^ Many communities of arid 

 regions and of mountains are lime-constant in the strictest sense. 

 Among these the Festucetum glaucae of central Europe from the Jura 

 to Poland; the Caricetum firmae, the Caricetum ferrugineae, tho 

 Petasitetum nivei, and the Thlaspeetum rotundifohi on the talus of the 

 Alps; the Schoenetum nigricantis of central Europe; the Schoenu<i 



' Fine earth from the root layer of the Bromion upon chalk in central Englanrl 

 contained, according to V. Anderson (1927), at a depth of 15 to 20 cm. an average 

 of 70 to 80 per cent; at 30 to 40 cm., 90 to 95 per cent of carbonates, mostly 

 CaCOs. 



2 It is surprising that in the work of Lundegirdh (1931, p. 215) we read that 

 only very few markedly lime-avoiding species (Sarothamnus, Castanea vesca, Pinus 

 pinaster) are known. Anyone taking the trouble to look through the voluminous 

 literature on the subject will find evidence to the contrary. 



