A NATIONAL PLAN FOR AMERICAN FORESTRY 369 



The small quantity of forest along the stream courses and the small 

 scattered areas of upland forest in North Dakota are insufficient to 

 have much effect on the flow of the Red River. They are important 

 in preventing erosion. Some erosion has followed cutting on the 

 Pembina and Turtle Mountains in North Dakota, but it is of little 

 consequence except very locally. Recreational use, which would pre- 

 serve watershed values, might conceivably be the best use for this hill 

 land, because of the absence of nearby recreation areas on the Ameri- 

 can side and because the Canadian half of the Turtle Mountains is 

 managed for recreation. 



Some of the spruce forest swamp areas in Minnesota have been 

 drained for agricultural use, but increasing abandonment of cleared 

 lands indicates that these areas are probably submarginal for agricul- 

 ture. As the ditches become clogged following disuse, the forest is 

 gradually taking possession again. 



In the Red River Valley windbreaks and shelterbelts have been 

 planted about farm buildings. Their aggregate area is not large, and 

 they have little, if any, bearing on stream conditions. Further tree 

 planting, desirable from the standpoint of farm comfort, would have 

 little if any effect upon the streams. 



UPPER MISSISSIPPI RIVER BASIN 



The upper Mississippi River Basin is that portion of the area 

 north of the Ohio that drains into the main river. It includes some 

 15 percent of the entire Mississippi drainage system. It is divided 

 roughly in two by a line running in a northwest and southeast direc- 

 tion through Minnesota approximately at St. Paul and so continuing 

 through Wisconsin. In the present discussion the two divisions will 

 be referred to as the northern or heavily glaciated area and the 

 southern or silt loam uplands area. 



Both areas have been severely glaciated, first by ice sheets that 

 extended as far south as the Missouri and Ohio Rivers and later by 

 the Wisconsin stages, which reached central and southeastern Wis- 

 consin and central Minnesota. The earlier glacial soils are largely 

 till, in which clays predominate. Silt loams are common in the old 

 lake beds. The Wisconsin advance was so recent that the topography, 

 drainage, and soils of the deposit have been but little modified. Con- 

 sequently sands and gravels predominate, although clay deposits 

 have covered some of the sand. In the older glaciation, the land is 

 for the most part level or gently rolling. In the northern area are 

 pronounced moraines and drumlins, some of them sufficiently promi- 

 nent to form the divides between such Wisconsin rivers as the 

 Chippewa, Black, Wisconsin, and St. Croix. 



On the areas more recently glaciated the sandy soils support a 

 pine forest and the heavier soils support har4wood stands in which 

 beech, maple, elm, and ash are common. The swamps, some of which 

 are of considerable size, contain spruce, fir, cedar, and tamarack. 

 The heavier soils of the older glaciation having weathered and 

 leached more, support oaks, hickories, walnuts, and other typical 

 upland species. 



A small area escaped glaciation. This driftless area lies chiefly 

 in southwestern Wisconsin, and extends into Illinois, Iowa, and 

 Minnesota. Here the deep soils, derived from parent rock, are highly 



