yo4 ZONES AND REGIONS [Pt. Ill, Sect. IV 



2. PLANT-LIFE IN MOUNTAIN REGIONS. 



i. MOUNTAIN-WOODLAND. MOUNTAIN-GRASSLAND. 

 MO UNTAINDESER T. 



The change of climate in passing from lowland to mountain in the first 

 place is favourable to woodland, because in the mountain the rains descend 

 in copious downpours, by which the subsoil is kept constantly moist. Con- 

 sequently, the slopes of the basal and montane regions are commonly elad 

 tvith woodland, which in rainy countries usually surpasses in luxuriance that 

 of the neighbouring lowland. 



In the lower belt of the alpine region atmospheric precipitations are less 

 abundant than in the montane and basal regions and do not take the form 

 of copious prolonged downpours, but, owing to the slight capacity of the 

 rarefied air for water- vapour, they assume that of light, short, frequent, 

 drizzling rain, which, however, more frequently saturates the surface. Hence 

 the climate of the lower part of the alpine region possesses rather the 

 character of a grassland climate. Moreover, in the frequent, strong winds, 

 which favour transpiration more than in the lowlands, owing to the rarefied 

 and frequently very dry air, the climate possesses an element decidedly 

 hostile to trees. The climatic formations of the lower belt of the alpine 

 region are accordingly grassland ; woodland appears only as low xerophilous 

 local formation on very porous stony soil that is unfavourable to grassland. 



In the upper belt of the alpine regions, on the one hand, the atmospheric 

 precipitations become constantly less, while, on the other hand, the desic- 

 cating action of the rarefied air becomes constantly more potent. Therefore 

 the grassland climate passes over into a desert climate in the upper belt 

 of the alpine region. Except in wet places the vegetation is extremely 

 scanty, and finally is limited to a few lichens. 



The sequence — woodland, grassland, desert — corresponds to three stages of 

 altitude, and it occurs only on the highest tropical or subtropical mountains, 

 for instance on Kilimanjaro, apparently also in Tibet. Usually perpetual 

 snow extends down close to the grassland. 



The formations of the basal and montane regions exhibit no essential 

 oecological deviations from lowland formations, and the same terms may 

 therefore be applied to them. In alpine regions, on the other hand, plant 

 formations bear the characteristic impress of the mountain climate and must 

 receive an appropriate designation, which in this case will be achieved by 

 the addition of the term alpine. Hence we contrast alpine grassland, alpine 

 shrubland, and alpine desert with those of the lowlands, and retain for alpine 

 forest merely the title elfin-wood 1 . 



1 'Elfin-wood' and 'elfin-tree' are the terms introduced here as the equivalents of 

 ' Krummholz.' 



