554 A NATIONAL PLAN FOR AMERICAN FORESTRY 



effect of this overgrazing on the farm woodlands is the retardation, 

 deformation, and usually the complete elimination of timber repro- 

 duction between the heights of 6 inches and 12 feet. This, combined 

 with the death and occasional cutting of mature timber, is rapidly 

 converting the woodlands of the better agricultural sections into open 

 pastures. 



Overgrazing of farm woodlands in the Central and Northeastern 

 States is ordinarily detrimental to watershed values of the forest. 

 For instance, studies by the Central States Forest Experiment 

 Station in the farm woodlands revealed the marked effect of grazing 

 upon the depth of litter and humus. On 87 plots in the oak-hickory 

 type, ungrazed plots had an average depth of litter of 1.8 inches; 

 lightly grazed, 1 inch; moderately grazed, 0.7 inch; and heavily 

 grazeol, 0.4 inch. 



The average depth of humus on the plots under the grazed condi- 

 tions in the order named above was 0.5, 0.3, 0.2, and 0.1 inch. The 

 top 9 inches of soil was found to be 15 percent heavier and more 

 compact in grazed then in ungrazed woodlands. As shown in the 

 " Watershed and Related Forest Influences" section of this report, 

 litter, humus, and soil porosity are important for conserving precipi- 

 tation and preventing undue run-off and erosion. 



If timber production appears to be the best source of income, 

 grazing should be adjusted to protect forest reproduction and assure 

 future timber crops. To continue to use entire woodlands on many 

 farms so heavily that timber reproduction is seriously damaged would 

 hardly appear best from either the standpoint of timber production 

 or most effective farm-land use. At least 1 million acres now classed 

 as commercial forest, mainly in the Corn Belt, should be considered 

 as primarily valuable as shade and shelter for livestock, and so with- 

 drawn from the area of commercial forest. This acreage would be 

 made up of a great many small units, doubtless of a few acres at 

 most, on individual farms where a part of the present grazed wood- 

 land would be fenced off for livestock. From a forestry standpoint 

 it would be best if grazing were eliminated from the balance of the 

 woodland. Where grazing is continued in farm woodlands held for 

 timber production, it should be limited to the actual feed available, 

 so that undue damage will not be done to the timber reproduction 

 and forest litter. The fundamental consideration in the use of for- 

 est pastures in these regions is primarily one of economic values. 

 The whole situation demands further study of coordination of grazing 

 with timber growing and other forest-land uses and an adequate 

 program of extension and education to apply the practices developed. 



