50 



in the north. A comparison as to the number of trees per acre shows that 

 the northern forests have about twice as many as the southern, and that 

 they are often even-aged, whereas in the southern region they are rarely 

 so. In the even-aged stands the oldest have been growing about 90 years, 

 the majority, between 60 and 90 years ; the diameters are mostly under 

 18 inclies ; 65 per cent of the trees have a D. B. H. of 10 inches or better ; 

 and the average acre has about 80 trees. The number of trees per acre 

 and the representation of species in the stands by per cents for both the 

 northern and the southern part of the state is shown in tabulation on 

 page 54. 



The belt of heavily wooded bluffs extending from Alexander county 

 north, terminates at about the northern boundary of Monroe county. 

 In this distance of more than one hundred miles, there is scarcely a break 

 in the forests as viewed from the Mississippi bottoms. North of Mon- 

 roe county, even this westernmost slope is freely cleared, and the forests 

 are disconnected strips along the slopes, rather than a continuous belt. 

 Only in the rougher sections of Jersey and Calhoun, and to a lesser de- 

 gree in Jo Daviess counties, are there comparatively continuous upland 

 forests. 



In Jersey and Calhoun counties, the uplands bordering the Missis- 

 sippi and Illinois rivers are heavily wooded. (See Map V, C.) 

 Calhoun is a narrow unglaciated headland between the Illinois and the 

 Mississippi rivers and is but five miles wide in its narrower parts. The 

 divide, often 300 feet above the rivers, is buried under a shallow loessal 

 deposit and the slopes break more abruptly on the eastern than on the 

 western side. Air drainage and soil conditions combine to make this 

 upland especially adapted to apple production, and the less precipitous 

 uplands along the crest are cleared, together with much of the western 

 slope, but the abrupt eastern slopes are wooded. Black oak is the domi- 

 nant tree, and much white oak, hard maple, elm, hackberry, black walnut, 

 and basswood occur. The stands approach the even-aged type, and are 

 of seedling rather than sprout origin. The same rugged topography and 

 forest conditions exist in the western six miles of the uplands of Jersey 

 county, although the stands here have been more heavily culled for sawlog 

 and tie material. The area forested in these rough uplands, where forests 

 are comparatively continuous, totals approximately 50,000 acres. 



The topography of Jo Daviess county, with the exception of a small 

 strip along the eastern border which has been modified by glaciation, is 

 that of an old eroded upland through which the southwestward flowing 

 streams have cut deep valleys. In the north, the slopes lead back to the 

 broad uplands and culminate in occasional conical mounds. The highest 

 of these, Charles Mound, with an altitude of 1,241 feet above sea-level, 

 is the highest point in the state. In the central and the southern sections 

 the slopes rise rather moderately from the narrow stream-valleys until 

 the upper slopes are reached. Here the slope is steep or precipitous up 

 to the narrow flat-topped ridge. In the north-central part streams have 

 cut through the rock, forming canyons or gorges. The most notable, 



