ly] LANDSCAPES AND VEGETATION 551 



Striking, such features are minor in being uncommon and in occupy- 

 ing very limited areas. 



Additional agents of erosion include gravity, giving for example 

 screes and talus-heaps below cliffs, and animals (including Man), 

 which are constantly producing new surfaces, either directly or 

 indirectly, as has repeatedly been indicated in earlier chapters. 



Interpretation and Uses 



Landscapes are typically made up of the smaller to medium-size 

 landforms. However, in viewing a landscape in most parts of the 

 world, it is chiefly the clothing vegetation which is seen. This, 

 like all other vegetation, as we have already observed, varies greatly 

 with local conditions. Therefore it affords a ready and evident 

 means of distinguishing the landforms and other local features which 

 make up a landscape, in turn being of assistance in their interpretation 

 and consequently proving of value to the ecologist when he has to 

 decide on the uses to which particular areas may be put. For it 

 has been rightly said that the study of vegetation, especially when 

 it is of established communities and they are mature, affords more 

 reliable indications of the action and interaction of local factors than 

 direct measurements, and is often the best basis for agricultural and 

 allied planning. 



To the common question of what is the explanation of particular 

 plants growing in particular places, there can scarcely be a satis- 

 factory general answer. To be sure, the presence of, say, a certain 

 tree in a spot is an expression of something more or less definite, 

 and indeed, much of this book has been devoted to consideration of 

 the kind of items that would have to be satisfied before such presence 

 could come about, and of what, in consequence, it implies. But 

 these items vary enormously and complicatedly from instance to 

 instance and even from spot to spot. Thus before we could have 

 any chance of contemplating our tree where it grows, a viable dis- 

 seminule would have had to be produced and liberated at a suitable 

 place and brought by some means to the relevant point at some time 

 in the past. Moreover, this disseminule would have to be fortunate 

 enough in its circumstances to find sufficient water for germination 

 and for the successful establishment of the resulting plant — which 

 implies also suitable conditions of climate, soil, and so forth for the 

 growth of the plant in that particular spot. Any deficiency or serious 

 deviation at a critical stage might easily have proved fatal. And 



