256, APPLIED ECOLOGY 



forester understand the dangers from tree diseases, insects, fire, 

 and storms, and the effects of over-grazing and over-cutting. Since 

 animals form an important part of the environment of the forest 

 trees it is essential that the forester have an intimate knowledge 

 of the ecological relations of the animal life as well as the plant life 

 of his forest. Extremely important also, of course, is a knowledge 

 of dominance and of plant succession in relation to natural reproduc- 

 tion in the forest. 



Much of the information that is so essential to a forester can at 

 present be taught in courses in plant ecology and in technical 

 forestry. There is a very large number of pressing problems in 

 forest ecology, however, that are awaiting solution and there is 

 urgent need for an increased number of trained workers in this line 

 of research. 



151. Grazing Problems.— Millions of acres of grazing lands in 

 the w^estern part of the United States have been injured to a greater 

 or less degree by over-grazing so that the number of head of stock 

 that might otherwise be pastured on them is materially decreased. 

 Until ecological methods were applied there was no reliable means 

 of recognizing over-grazing in its early stages. The usual method of 

 estimating the condition of the range was based on observations on 

 the general abundance and luxuriance of the forage supply and the 

 condition of the stock being grazed. These general observations do 

 not enable one to recognize over-grazing until large numbers of the 

 most valuable plants have been destroyed. 



By applying the principles of plant succession to the problem of 

 over-grazing it is possible to overcome many of the difficulties. 

 Taking the ranges in central Utah as an example four major plant 

 communities are recognized. In the order of their position in the 

 successional series these are the ruderal weed community, the fox- 

 glove-sweet sage-yarrow community, the porcupine grass-yellow 

 brush community, and the wheat-grass community. The wheat- 

 grass community is the most permanent and will endure over- 

 grazing longer than any other type and it makes very efficient 

 pasture for cattle and horses but is not quite so good for sheep. 

 The porcupine grass-yellow brush community contains a larger 

 number of palatable species and will probably support more stock 

 than any other type. The other two communities are due to exces- 

 sive over-grazing and do not furnish valuable pasturage. 



Any area on this range which is ungrazed or only moderately 

 grazed develops eventually into the wheat-grass community while 



