342 The Ohio Journal of Science [Vol. XIX, No. 6, 



HUMUS FORMATION THE REAL PROBLEM. 



To the field worker the instability of the ground produced 

 by the operation of these factors appears so important as to 

 overshadow all else in the problem of revegetation. But 

 experience with areas of high wind and loose soils outside the 

 Katmai district clearly indicates that the shifting sands would 

 be quickly caught and stabilized by the advancing vegetation 

 if it were not for the lack of sufficient "plant food" in the ash. 

 If such plants as start were able to grow thriftily, it would be 

 only a relatively short time until the whole valley was again 

 covered with luxuriant vegetation. 



The real problem of revegetation is, therefore, the nitrogen 

 supply. When the ash was thrown out from the Volcano in a 

 fused condition, it was of course completely free of organic 

 nitrogen. Dr. Shipley's work, reported in the fifth paper 

 of this series, page 213, shows that the ash soil still remains 

 extraordinarily poor in nitrogen compounds. 



The task before us is, therefore, to follow the process by which 

 a supply of combined nitrogen is built up in these soils as vegeta- 

 tion gradually returns, supplementing field observations on 

 the plants with chemical and bacteriological examinations of 

 the substratum. If this process of humification can be followed 

 successfully, the knowledge so obtained will throw much light 

 on many problems concerning the relations of plants to the 

 soil, of great importance from both a theoretical and a practical 

 point of view. 



