278 EREMOPHYTES SECT, xi 



CHAPTER LXXIII. SHRUB-STEPPE 



MOST closely related to desert is shrub-steppe. Many shrubs and 

 undershrubs do occur in desert. But where the external conditions are 

 more favourable to existence, desert-shrubs congregate to form scrub ; 

 additional species enter, and desert gives way to shrub-steppe. 



According to the terminology of Schimper and some Russian authors, 

 shrub-steppe is included within the term ' desert '. Shrub-steppe probably 

 includes several formations, which our present limited knowledge does not 

 permit us to diagnose and distinguish. Among such are those described 

 in the succeeding paragraphs. 



Vermuth-steppe . 



In northern Turan and in the south-east of Russia there stretch 

 boundless plains in which vermuth-shrubs (Artemisia maritima and 

 A. frigida) are the dominant plants ; they form a belt round the deserts 

 of Turan. Farther north and west, where the rainfall is more frequent, 

 they are fringed by a belt of grass-steppe. Grass-steppe, shrub-steppe, 

 and desert correspond to three stages of decreasing frequency of rainfall. 

 Vermuth-steppe shows preference for a loam soil. This in arid regions 

 is tolerably saline and consequently physiologically dry. In places 

 transitional between vermuth-steppe and grass-steppe one sees the saline 

 depressions occupied by vermuth-shrubs, while the slopes of the hills, 

 from which the salt has been washed out, assume the garb of grass-steppe. 

 In like manner vermuth-steppe forms a belt outside the true halophytes 

 fringing salt-lakes. Where vermuth-steppe reigns cultivation of the soil 

 is only possible by the aid of artificial irrigation ; yet the land is of utility 

 to nomadic tribes in providing fodder for sheep and camels. 



Grey, and to all appearance dead, vermuth-steppe stretches over 

 boundless tracts. The artemisias display leaves coated with white hairs. 

 Their roots, which descend to a depth of 4 metres, ensure the existence 

 of these enduring plants, even when the scorching sun's rays exterminate 

 nearly all other species present. Among the vermuth-shrubs grow such 

 shrubs and perennial herbs as Alhagi camelorum, Xanthium spinosum, 

 and Eryngium campestre. In spring-time many annual herbs and bulbous 

 plants flower, and are already in fruit at the beginning of summer. 1 



North American Shrub-steppe. 



As another example of vegetation in which scattered shrubs and under- 

 shrubs, intermingled with herbs, play the chief part, we may mention 

 the dry and barren land between the Rocky Mountains and Sierra Nevada. 

 Here, according to Asa Gray, the dominant plants are species of Artemisia, 

 woody Compositae with small capitula, and Chenopodiaceae. According 

 to Watson there is not a spot devoid of vegetation, even in the driest 

 season. Trees are wanting ; there is no carpet of grasses, but in its place 

 are a few dominant species of fruticose and suffruticose plants, which 

 apparently exterminate all other vegetation. Characteristic are the 

 uniformly coloured, mainly grey or dark-olive tinted herbs. Most 

 1 Radde, 1899; Nazarow, 1886. 



