EDAPHIC OR SOIL FACTORS: CHEMICAL 



189 



species. Among these are the ferns Asplenium adulterinum and A. 

 cuneifolium. These are widely distributed in Europe, very local in 

 their occurrence, and their distribution coincides exactly with the 

 occurrence of serpentine. 



Novak (1928) has studied the serpentine problem and added to the 

 list of plants peculiar to serpentine and magnesium substrata. He 

 cites among others certain paleoendemic species of the Balkan Pen- 

 insula, such as Halacsya sendtneri, 

 Potentilla visiani, and Fumana 

 honapartei together with various 

 subspecies and varieties. He con- 

 siders that the serpentine vegeta- 

 tion is controlled by the Mg:Ca 

 ratio, which must be greater than 

 unity; that is, there must be in 

 the soil an excess of Mg ions. 

 Most of the facultative serpentine 

 plants have an extraordinarily 

 developed root system, whereas 

 the surface parts of the plants 

 are rather meagerly developed, 

 and frequently their flowers and 

 fruits are quite sparse. Little 

 is known about the plant com- 

 munities of immature serpentine 



^•1 T„ ^ ^-^^r.^- +^ ^^^^^^„^ Fig. 101. — Soil profile above serpentine 



soils. In contrast to COmmun- ^^^j^ ^^^^ ^j^^ Ochsenkopf near Parpan. 



itieS peculiar to the saline soils 2,400 m., showing 2 to 3 cm. black humus 



of nrid rpHons the semen- ^''^'^^ 4 to 5 cm. grayish brown organic 



01 arm regions, xne serpen j^^^ pjj ^^ ^^^^. ^g ^^ 20 cm. yellowish 



tine vegetation presents a purely brown weathered soil, pH 5.8 (fi); and 



local, edaphically controlled TZTbL^T::;;,!!:^ ''''■ ""'" 

 phenomenon. 



Soil development upon serpentine substrata proceeds slowly. On 

 steep slopes the dark-green immature serpentine soil, with few plant 

 inhabitants, is everywhere exposed to view. Only on slightly inclined 

 or flat places can the soil and the vegetation reach a true climax. In 

 the alpine zone, the soil-forming process upon serpentine results in a 

 rather finely dispersed, clay-like upper layer of decalcified rendzina 

 soil (Fig. 101), which, in contrast to the raw serpentine soil, bears an 

 acidophilous vegetation (Fig. 102). 



3. Iron. — The presence of iron oxide in the soil is indicated by a 

 reddish or brownish-yellow coloration. It is iron sesquioxide, Fe203, 

 which gives the characteristic red or red-brown color to the so-ca/led 



