336 THE STUDY OF PLANT COMMUNITIES ■ Chapter XII 



that properly managed wood lots can yield as great a return as 

 any average farm acreage, but the wood lot pasture persists. A 

 study of maple groves in Ohio 225 showed that in three years the 

 elimination of grazing resulted in an increased yield of maple 

 syrup, worth more than twice what the rental for pasture would 

 have been. At the same time, the condition of the stand was no- 

 ticeably improved. As more such information is accumulated 83 it 

 is to be hoped that its application will follow. 



Regional pasture studies must be continued so that both species 

 and their culture can be recommended with confidence for cli- 

 mate, soils, and land management policies as they occur. To obtain 

 such results, it would appear that ecological methods should be the 

 most promising. 



Insect Problems.— The relationship between land-management 

 practices and insect populations is inadequately known. 116 

 Whether insect pests will increase or decrease with strip-cropping 

 or particular crop rotations cannot be said with certainty. Prob- 

 ably more complex are the relationships of insect populations to 

 the birds and mammals that will appear in response to such con- 

 servation practices as cover crops, hedges, and field border plant- 

 ings. Whenever the acreage of a cultivated species is increased 

 extensively in an area or a new species is introduced for special 

 purposes such as erosion control, insects may appear with it or 

 abruptly increase in numbers to pest proportions. Such relation- 

 ships and innumerable others need more study. The possibilities 

 for applied insect ecology in agriculture and forestry are almost 

 unlimited. 



Rodent Problems.— Especially for range lands, ecological knowl- 

 edge of rodents is still inadequate. In spite of this, rodent control 

 has been attempted in these areas for years. More should be known 

 of the effects upon rodent populations of kinds and degree of 

 grazing as well as what effects the various rodent-control measures 

 have on the condition of the range. With the latter, it should be 

 possible to say what percentage of a rodent population can be 

 destroyed by a control measure, how long before the surviving 

 population will return to normal, and to what extent species move 

 in from untreated areas. Complicating the above problems is the 

 usually cyclical fluctuation of most rodent populations and the 



