A NATIONAL PLAN FOR AMERICAN FORESTRY 325 



WOODLAND PASTURES 



In pastured farm woodlands of the Middle West, studies by the 

 Central States Forest Experiment Station show that overgrazing 

 results in the destruction of the sprouts of hardwood timber species, 

 and that trampling of the livestock tends to destroy the litter and 

 compact the soil, making it less receptive of precipitation and subject 

 to erosion. Under extreme use, such as occurs in the Corn Belt where 

 many farm woodlands are used as much for shade as for the feed they 

 produce, practically the entire understory of vegetation and the litter 

 covering the soil has been destroyed. When such a situation has 

 developed the topsoil is invariably lost. Bates and Zeasman 27 have 

 shown, on comparable soils, that, from a plot in pastured oak wood- 

 land with a slope of 38 percent, 13 percent of the rain ran off, while 

 from a dense unpastured oak forest with a slope of 42 percent only 

 0.2 percent ran off, and only 2 percent from open unpastured oak 

 woods with a slope of 49 percent ran off. 



Auten (op. cit.) has shown in his studies of soil conditions in grazed 

 and ungrazed woods in Ohio that the top 9 inches of soil in the grazed 

 areas averaged 15 percent heavier than similar topsoil from ungrazed 

 woods. This increase in density is a reflection of the greatly reduced 

 capacity of the grazed soils to absorb water. 



The work of Stewart 28 reveals the same tendency in New York 

 State for long-continued grazing use to reduce permeability and water 

 storage of soils. 



SMELTERS 



Fumes from smelters and other industrial plants may completely 

 destroy or injure forest and other vegetation. Destruction by smelter 

 fumes is found near Ducktown, Tenn., Kennett, Calif., Anaconda and 

 Butte, Mont., and in the vicinity of a number of other smelters located 

 within forested areas. Large areas around them demonstrate to a 

 superlative degree the debt mankind owes to vegetation for its influ- 

 ence on surface run-off and erosion and the price we must pay when 

 we destroy it. At Ducktown, an area of from 10 to 12 square miles 

 around the smelters has become denuded of natural vegetation with 

 the exception of occasional clumps of sage grass and wild smilax. 

 Bordering this barren region is one varying from 1 to 5 miles in width, 

 covered with sage grass, vines, and a few stunted shrubs and small 

 trees, the latter often with dead tops. Beyond this border of almost 

 treeless vegetation the country is not heavily wooded for some dis- 

 tance, the growth being unthrifty and trees with dead or dying tops 

 being numerous. 



Glenn (op. cit.) states that the annual rainfall hi the region is 50 

 to 60 niches, and often torrential, so that during the downpours soil 

 surfaces almost literally melt away. The wasted soil accumulates 

 along the stream courses. He states further: 



On Potato Creek this waste has been accumulating for a number of years at the 

 rate of a foot or more each year, and has been built into a flood plain from 100 

 to 300 yards wide, in which telephone poles have been buried almost to their 

 cross arms and highway bridges, roadbeds, and trestles have either been buried 

 by the debris or have been carried away by floods. ^. . . The normal flow of 

 Potato Creek is said to be only about half as large as it used to be, and there can 



27 Bates, C. G., and Zeasman, O. R. Soil Erosion, Wise. Agric. Expt. Sta. Res. Bui. 99. 1930. 



28 Stewart, Q. R. "A study of soil changes associated with the transition from fertile hardwood forest 

 land to pasture types of decreasing fertility." Ecological Monographs, January 1933. 



