554 INTRODUCTION TO PLANT GEOGRAPHY [CHAP. 



value ' as it is called. Nevertheless many dominants, and some 

 other special instances such as the European Beech or Ash or even 

 beds of Stinging Nettles, may be useful as individual indicators. 

 Far more reliable, however, are groups of species or, preferably, 

 whole communities. These make up vegetation, which, as we have 

 seen, often provides the most characteristic (though variable) surface 

 feature not only of landforms but also of entire landscapes. 



Apart from the truism that, in the absence of drastic disturbance, 

 the luxuriance and form of the vegetation developed on an area 

 will give to everyone some indication of its productivity, consider- 

 able local knowledge is commonly required to interpret vegetation 

 and use it as a basis for agricultural or forestral planning. Given 

 this local knowledge and some practical experience in its employ- 

 ment, an observant farmer or forester can usually tell more about 

 the uses to which a particular tract of land can be put, from observa- 

 tion of its standing vegetation, than can be determined from much 

 tedious measurement. Nor is this surprising, for it is often not so 

 much this or that particular factor of the environment which is 

 likely to affect the natural vegetation, as the result of interaction of 

 all the factors obtaining locally. Of this composite result the 

 vegetation is, in a sense, a measuring apparatus, and an extraordinarily 

 delicate one. For the type, composition, and degree of luxuriance 

 of the plant communities are apt to be immediately eloquent on 

 the subject of local conditions, and it is inconceivable that any 

 battery of instruments, however complicated and delicate, could ever 

 really emulate natural vegetation in this respect. 



Often the vegetation will not only give an indication of minor 

 and unsuspected habitat differences but also emphasize gross ones 

 such as landforms in a landscape. An example of the former is 

 the common persistence of beds of Stinging Nettles {Urtica dioica) 

 about the sites of old habitations or areas of loosened soil and, of 

 the latter, the existence of dark clumps of trees in depressions in 

 many grasslands. Yet in other instances vegetation may obscure 

 the local conformation of the earth's surface, including some striking 

 if minor landforms, by its very luxuriance. 



To such further questions as * Where, so far as surface and 

 vegetation features indicate, ought I to build my house and dig my 

 garden ', there is again no simple answer : it will depend on the 

 region and various other circumstances. But a close study of the 

 vegetation of likely situations, coupled, perhaps, with observation 

 of the plant growth around already established dwellings in similar 



