CHAP, xcv THE PEOPLING OF NEW SOIL 355 



moors provide another opportunity for watching the struggles among 

 different kinds of vegetation ; in some places they are succeeded im- 

 mediately by the appearance of Senecio sylvaticus and Epilobium 

 angusti folium. The names applied to the latter in Denmark and America 

 respectively, ' Ildmarke ' and ' fireweed *, denote that in both countries 

 it is among the first plants to settle on burnt sites. 



Other Sources of New Soil. 



New soil is produced by such a removal of sods as lays the ground bare. 

 In North Europe after heath-shrubs have been removed, together with 

 the upper layers of soil, for use in place of straw or for absorbing manure, 

 the bare ground first clothes itself with mosses, including Polytrichum, 

 and small annual herbs, including Radiola, Centunculus, and Cicendia, 

 between which ling-seedlings, and often young birches, pines, and other 

 trees raise themselves. 1 



A peculiar cause of the genesis of new soil is the natural death of old 

 vegetation. This occurs in the case of ling-heath in Jutland and 

 North Germany, 2 because Calluna lives for only between ten and twenty 

 years, and often dies of old age. When Calluna-plants die simultaneously 

 over a large area, because they have attained the same age, the soil is 

 laid bare and the heath is regenerated by means of seedlings. 



In like manner on ah 1 other sites where old vegetation covering the 

 ground is decimated, there arises a community which differs from the 

 original one, but is, as a rule, eventually suppressed by the latter. When 

 wind makes a breach in an old, long-established, fixed dune, another type 

 of vegetation arises ; in fact, by this means, way is made for the re-entrance 

 of sea- marram. 3 Where water here and there collects to form puddles in 

 littoral meadow, the submerged mat-herbage is destroyed, and there 

 appears a different type of vegetation, which consists essentially of annual 

 halophytes, such as Salicornia and Suaeda maritima. 4 Where an avalanche 

 passing through a forest has left behind it a treeless track, this is mostly 

 clothed with plants differing from those elsewhere in the forest. 



Where cultivated land is left to itself, not only in the cases already 

 discussed, but also in general, there appears new soil that is rapidly 

 colonized by a horde of plants, which are essentially weeds. For example, 

 in Jutland, fields that are neglected because their poor soil has yielded 

 only a scanty crop of corn gradually become converted into heath. 

 Again, in Blekinge (in Sweden), according to Hult's admirable investiga- 

 tions, 5 the new soil first becomes covered with weeds and plants whose 

 seeds are easily transported by wind. After some years the weeds have 

 vanished and the field has become a grassy plain with a tolerably rich 

 flora that includes forty to sixty species of Spermophyta. Subsequently 

 trees and shrubs are found, and forest arises. On poorer soil ling seizes 

 the field, but where better soil lies at a slight depth below and no hard 

 pan occurs, the ling may be vanquished by forest. 



Everywhere one sees the same struggle going on : only one more 

 example of this is given here. In Corsica, when cultivated soil formerly 

 covered with maqui is left to itself, the first plants to appear are herbs, 



1 Grabner, 1895. ' Grabner, loc. cit. Warming, 1907. 



4 Warming, 1906. Hult, 1885. 



Aa2 



