ADAPTABlIiITY OF THE STATE TO TREE GROWTH. 

 TOPOGRAPHY. 



The surface of Iowa is in general an undulating plain, bounded on 

 the east by the Mssissippi River and on the west by the Missouri 

 and Big Sioux rivers. The numerous tributaries of these large rivers 

 make up the drainage system of the State. As a rule it is only along 

 the valleys of these streams that the surface is broken to any extent. 

 The difference in elevation between the highest and lowest points is 

 so slight (less than 1,100 feet) that the drainage over large areas of 

 the State is imperfect, and this affects the value of the land for agri- 

 culture or forestry. There is only one main watershed, and that is 

 not well defined. It extends in an irregular line from Dickinson 

 County on the north to Wayne County on the south. 



On account of the slightness of the differences in elevation and 

 other physical characteristics, there is no wide divergence in the 

 types of tree growth in the State, and hence the problems of tree 

 planting and woodlot management are simplified. There are two 

 forest types — one in the low, level, moist areas along streams, made 

 up largely of alluvial soils, and the other on higher, well-drained 

 slopes and uplands back from water courses, or in scattered areas 

 over the undulating prairies. These types merge into each other and 

 it is seldom possible to define their boundaries. In the bottom type 

 are such moisture-loving trees as cottonwood, willow, honey locust, 

 black ash, elm, and coffeetree, and in the upland type are the oaks, 

 hickory, ironwood, butternut, white ash, and hackberry. Through- 

 out the State the soil is adapted to the growth of forest trees. 



SOIL. 



Iowa soils may be divided into four classes — geest, which occurs 

 maioly in the northeastern portion of the State and constitutes less 

 than 1 per cent of the total area; alluvium, which is usually found in 

 stream valleys and forms less than 6 per cent of the total area; loess, 

 a wind-formed soil, which covers 66 per cent of the State; and till or 

 drift, which is the product of glacier movement, and covers the 

 remainder of the State. It was observed that upon the geest and 

 drift soils reproduction is more abundant and growth more vigorous 

 and that the trees attain a greater age than on either loess or 

 alluvium. 



Whenever it is possible, trees, especially the slower growing ones, 

 should be planted on the sandier and coarser soils of the farm, and 

 these soils should be used for growing seedhngs in preference to the 

 finer loess or heavier alluvial soils, especially as the finer soils are of 

 greater value for agricultural purposes. 



[Cir. 154] 



