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cipal types, are generally rolling and many times resemble sand dunes in form and appearance. It is highly probable that a large portion of this section of the country was formerly old sand dunes on which plants have obtained a foothold and checked the action of the wind and the resulting movements of the sand. Considerable of this type was originally covered with timber, but the trees were chiefly scrub oaks with a few other less valuable trees of medium size scattered here and there.

The second group of counties, Clinton, Howard and Grant, is centrally located and must be taken as typical of central Indiana. The climatic conditions are about the same as the average mean temperature and precipitation for the State. The surface features of this area consist of undulating plains, with broad level areas between the natural drainage basins, which become more or less rolling and sometimes quite hilly as they near the water courses.

The underlying rocks are in some places exposed along the streams that have cut through the glacial drift. In general, however, they have such a limited exposure as to have little influence upon the character and productiveness of the soils. The greater part of the area is covered with a comparatively deep deposit of glacial drift, broken and eroded in many places by natural waterways. Hills of washed gravel are also frequently found which were deposited by streams beneath the melting glacier, the finer sediments being carried on to form the surface soils of areas farther south.

The soils of this locality are largely made up of clay loam, with small intervening areas of muck and sandy loam. Four prevailing types are recognized. The clay loam is the type most frequently found and ranges in depth from 6 to 12 inches. It grades into a clay or heavy clay loam of a stiff heavy character, which is generally underlain by gravel or gravelly clay. At varying depths in the subsoil are found beds of gravel and sand, which when near the surface have resulted in a gravelly loam, underlain by gravelly clay or gravel. These gravelly clays are frequently met with throughout the extent of central Indiana. They are, however, in narrow streaks, particularly along river courses, and are in general the result of surface washing and erosion.

Under the above conditions the original growth of timber was magnificent. It consisted of a mixture of oaks, ash, hickories, elm, beech and sugar maple. This original stand, once dense and heavy, has gradually disappeared, and now instead of extensive forests we find a few scattered woodlots.

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The other important soil types of these counties are black clay loam, Madison loam, consisting of brown or yellow loam or fine sandy loam from 8 to 14 inches deep, and muck, a term given to the class of soils in which organic matter in various degrees of decomposition is the dominant characteristics.

The third group of counties, Orange, Martin and Washington, are of the southern location and are indeed typical of this rough, broken region. Being one of the most heavily timbered sections of the State, the settlers from the earliest down to the present time, have depended largely, and in many cases wholly, upon forest products as their main source of income. That this statement holds true to a certain extent, even to the present time, is due, almost entirely, to the physiographic features of this section of the State.

Two controlling factors have been active in the physiographic development of this locality—the limestone, sandstone and arenacious shale, and the black slaty shale. The upper strata of the first group, which cap the hills in the southern part of these counties, have resisted the agencies of erosion better than the softer underlying shale, and the results are a broken and hilly topography. The shales belonging to the second group, which underlie the soils in many localities, have given rise to a more rolling and undulating character. The numerous hills have been cut by streams which have formed v-shaped valleys. Excellent examples of such valleys are common in the western part of the section along the course of the east fork of White River, which has cut its way many feet through the sandstone deposits. Broad valleys and level uplands are often encountered, where the summits of the surrounding hills are comparatively level, and the hillsides slope gradually towards the small streams. More often, however, the hillsides are steep and the soil covering very thin. At these points erosion and weathering are most effective and the removal of the timber and underbrush soon cause them to assume a desolate appearance. Many such washed and denuded areas are present throughout our southern counties and are generally the direct result of a poor understanding of natural laws and existing conditions. For an example of such conditions, see Fig. 21. This photograph represents the general washed and weathered condition of much of the hilly land surrounding Paoli, Orange County. Also, see Fig. 22, where the steep hillside is securely held against erosive agencies by a dense and luxuriant growth of red cedar.

The geological formations which underlie this area are most frequently exposed on the steeper slopes and are indeed seldom at any

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Fig. 22. Young growth of Red Cedar on hillside, showing nature's method of soil binding against the agencies of erosion.

great depth below the surface. See Fig. 20. Many of these underlying rocks are of a type that weather rapidly upon exposure, and have undoubtedly entered largely into the composition of the various classes of soils. See Fig. 20 for outcropping of rock strata, where all gradations from the solid rocks to the heavy clay soil is plainly evident. Being derived in this way, from the underlying rocks, the soils of this region consequently present a more limited variety of conditions, favorable to the development of plant life. Although it is believed by many that a considerable portion of the surface material covering many of these southern counties is of glacial origin, it is very probable that it was mainly local in its derivation. This probability is confirmed by the scarcity of glacial bowlders or fragments of igneous rocks in the soil.

Four types of soils are found in this locality, all coming under the general head of silt soils. Of these, three are thought to be derived directly from the weathering of the underlying geological formations. The fourth, which occurs only in the low, flat "river bottom land,” is derived from materials brought down and deposited by streams.

This general discussion of soil formation and distribution has been thought necessary to the better understanding of the following statements, which relate to the conditions most favorable to the growth of the oaks, ashes and hickories.

OAKS.

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The oaks are widely distributed over the central and eastern parts of the United States. The natural range, generally speaking, extends from Nova Scotia to the region west of Lake Superior and south to eastern Kansas and northern Georgia. This wide range of distribution suggests the varying conditions under which many species of the oaks may be found. They are associated forms and are found growing with elm, basswood, chestnut, hickories and other of the common hardwoods. Their soil requirements are variable and in the nine localities investigated they were found growing equally well upon several distinct types of soils. Only when we reach the low undrained glacial basins of northern Indiana do we see a falling off in the development of the oaks. this region we have the magnificent forms of central and southern Indiana replaced by the stunted Spanish and swamp white oaks. These forms are too near their northern limit to develop naturally, and the other valuable species extending this far north are so influenced by physiographic conditions that they rarely exceed more than a low branching form unfit for commercial purposes.

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