328 THE STUDY OF PLANT COMMUNITIES ■ Chapter XII 



FlG. 174. Once-fertile farm land that has been unnecessarily destroyed by 

 surface erosion and gullying because of lack of concern (note that straight- 

 row cultivation still prevails) and lack of understanding. Perhaps this area 

 should have been put into forest long since. If it had been, it would still be 

 valuable.— U. 5. Soil Conservation Service. 



for the plowland. 223 



Maintaining stands of natural vegetation provides areas for eco- 

 logical comparison and diagnosis, insures that soil is being rebuilt 

 and retained, provides organic matter, insures a regulation of mois- 

 ture conditions that man cannot duplicate, and provides food and 

 shelter for wildlife, which may be significant in reducing crop 

 pests. 



The planning of such land use should be, in so far as possible, 

 based upon ecological principles as related to soil, topography, 

 exposure, and drainage in terms of the climate and cultivated crops 

 it will support. Special land-use problems arise on hilly land, which 

 need not necessarily be unproductive. Ecological studies of hill- 

 culture 172 are showing how some such lands may be used to grow 

 orchards, vineyards, pasture, and other crops without depletion 

 or erosion of the soil.* Where streams occur, it has been shown 



*Much of the following discussion of applied ecologv in agriculture is 

 adapted from an unpublished report by the Committee on Applied Ecology 

 of the Ecological Society of America, 1944. 



