HARSHBERGER: AMERICAN HEATHS AND PINE HEATHS 177 



It is typically developed on relatively poor sandy and gravelly soils, 

 whose climate is wetter than that which gives rise to steppe, the 

 climate of which is too dry for tree growth. Heath may exist side by 

 side with woods and may represent a degeneration of woodland. 

 Heath occurs in Europe in regions with an annual rainfall between 

 25 and 40 inches (60 to 100 cm.), but the Cornish heath and those of 

 the eastern Highlands of Scotland often receive a rainfall of between 

 40 and 60 inches (100 to 150 cm.) in the year. The Scottish heaths 

 develop a deeper layer of relatively pure acid humus, up to 8 or 12 

 inches (20 to 30 cm.), according to Hardy. The East Anglian heaths 

 have a rainfall of 25 inches, or less, and a minimum of dry peat forma- 

 tion, while the heaths of the southeastern counties have a layer of dry 

 peat seldom more than a fraction of an inch in thickness passing down 

 into sand darkened by humus. The surface layer of dry peat is 

 formed by lichens and mosses, which are pioneers on denuded soils. 



Drude in his comparison of the flora of Great Britain with that 

 of Central Europe^ believes that the lowland heaths, the "heath asso- 

 ciation" or "Callunetum arenosum" of Tansley, for the most part 

 correspond with those of northwestern Germany in the region of the 

 Weser and the Ems, and on the English heaths one would often feel 

 oneself transported to Germany, if it were not for the sudden oc- 

 currence of Erica cinerea between Erica tetralix and Calluna vulgaris, 

 or of Ulex minor, or Ulex gallii with masses of Schoenus nigricans, 

 Myrica gale, Narthecium and Hypericum elodes, which indicate the 

 west European conditions. 



If there is a physiognomic similarity in the heathland of England 

 and northwest Europe, then we must determine the essential character 

 of the heath vegetation and the kinds of soils on which it is found, for 

 by extension we can apply these characters as a test of heathland in 

 other parts of the world. 



Although the soils of the North German plain are the same in the 

 east as in the west, according to the researches of Graebner and others, 

 yet the vegetation of the two areas is quite distinct. In the west, in 

 Hanover, Oldenburg and Schleswig-Holstein, are great stretches of 

 heathland, whilst in the east these are entirely absent and are replaced 

 by thin pine woods (pine-heath = Kiefern-heide) and a steppe-like 

 flora. This difference is due in part to the different climate, for the 

 main heathland is west of the Elbe, where the rainfall rarely falls 

 below 24 to 28 inches per annum, whereas in the east the rainfall often 

 does not exceed 20 inches per annum. In other words, heathland is 

 developed with an oceanic climate, while pine-heath is found where 

 the climate is continental. The seasonal changes of temperature of 



3 The International Phytogeographic Excursion in the British Isles (191 1), p. 93. 



