REVIEWS 



The Relation of Plant Succession to Crop Production. By Adolph 

 E. Waller, Ph. D. Ohio State University Bulletin, XXV, 9, 1921. 

 Contribution in Botany No. 117. 



Foresters who are interested in the evolution of present-day vege- 

 tation find difficulty in passing without careful scrutiny any serious 

 effort in the line of ecology. The paper under review, which is highly 

 readable and instructive, attracts at once by its rather ambitious title, 

 which suggests the idea that if there is a close relation between plant 

 successions and crop production, the delineation of potential forest 

 land through a study of successions should be a fairly simple matter. 

 The reviewer believes that this is to some extent the case, but the 

 paper by Waller seems to show that the value of land for crops is 

 almost wholly dependent on edaphic factors, which influence the cost 

 of production, while in the formation of climaxes climatic factors are 

 fully as important. The paper is divided into three main parts : 



Part I, Plant Successions, is a general discussion of the more im- 

 portant principles of ecology, directed, as the author states in his 

 introduction "toward farmers, albeit they may be a special group of 

 farmers. Most of the members of this group will be interested in the 

 scientific aspects of plant life." We shall return to this section. 



Part II, Factors Influencing Crop Distribution in the United States, 

 is devoted to a discussion of the general relations between climatic, 

 edaphic and economic factors on the one hand, and the dominance of 

 certain crops on the other. The northeastern evergreen forest region 

 is dominated in agriculture by timothy, spring wheat, rye, buckwheat 

 and potatoes, all crops which do best in a rather cool climate : Corn, 

 winter wheat, oats, red clover and beans overlap on the regions of the 

 central deciduous forests and the prairies. These crops predominate 

 in a region where the ratio of rainfall to evaporation varies from GO 

 per cent to over 100 per cent. The author, therefore concludes that 

 the growing of these crops, and particularly profits, is dependent rather 

 on edaphic or topographic than on climatic conditions. It is pointed 

 out that oats and corn do not ecologically belong together, but are 

 grown most abundantly in practically the same region because the one 

 supplements the other. Oats for horse feed are necessary for profits 



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