568 INTRODUCTION TO PLANT GEOGRAPHY [CHAP. 



valuable to indicate local plant productivity. Exclusion or enclosure 

 of animals may usefully be practised to indicate the extent to which 

 browsers, etc., are modifying the local vegetation. Transplant experi- 

 ments of plants or whole clumps of vegetation may also be valuable 

 in indicating climatic, edaphic, or biotic impress. Vegetation maps 

 of various types and on various scales, based on the closest possible 

 observation of the composition and boundaries of the communities 



Fig. 181. — Part of a maze of jfullies which crosses more than an entire county 

 in the southern United States and has ' permanently ' destroyed more than a 

 hundred thousand acres of excellent land. The original gully had begun about 

 70 years previously with a drip from a barn roof. (Courtesy of U.S. Soil Con- 

 servation Service.) 



involved, and often supplemented by quadrats, transects, or other 

 special methods of study of test areas, are also often prerequisite 

 to successful application of modern agricultural and forestral 

 techniques over wide stretches of country. Much the same is true 

 of soil maps, indicating the type and extent of the main soils of 

 different areas. In these and other ways, the study and under- 

 standing of vegetation and its habitats are of fundamental importance 

 to prudent land utilization and, consequently, to humanity. 



