The appearance of well-formed oaks, as well as of hickory, is therefore at once welcomed as an evidence of soil improvement, while that of low huckleberry bushes and small black gums indicates the reverse. An increase in the thickness and retentiveness of the soil stratum is also usually indicated by the occurrence of short-leaved pine in the long-leaf-pine areas.
The black, red, white, and Spanish oaks belong altogether to soils of medium physical constitution, only their size upon such lands depending upon the relative richness in plant-food; but without such changes producing any notable variation in their form. Clearly then, these species are intolerant of extreme physical conditions, and are practically restricted to soils of “loamy” character and easy cultivation.
CHAPTER XXV.
RECOGNITION OF THE CHARACTER OF SOILS
FROM THEIR NATIVE VEGETATION.
UNITED STATES AT LARGE.
EUROPE.
The application of the above data outside of Mississippi can mostly be verified only in a fragmentary way from such data as are casually given in the reports of State Surveys, as well as from such observations as the writer has been able to make personally elsewhere. In the latter category the most copious refer to the states of Alabama, Louisiana and Illinois.
Alabama.—The observations of Prof. Eugene A. Smith, and those of Dr. Chas. Mohr, are especially valuable and cogent as to the close correspondence of the soil and vegetative phenomena with those observed in Mississippi.[193] They are faithfully reproduced on the corresponding geological areas, including also the Flatwoods. Northwest of Mobile, on the Mississippi line, the long-leaf-pine forest is interspersed with more or less continuous areas bearing a fine oak growth, with hickories and other trees indicating a calcareous soil. This feature is most extensively developed in Alabama in what is known as the “lime-sink region,” on the borders of which the vegetative transition in passing from the non-calcareous sandy pine land, can be observed in the most striking manner and with frequent alternations. Northward of the long-leaf-pine belt, the tertiary and cretaceous areas show in Alabama the same features as in Mississippi, viz., black calcareous prairies alternating with ridge lands, among which in the cretaceous area the Pontotoc ridge is represented by a series of isolated knobs, popularly known as Chunnenugga ridge, closely resembling the former in its soils and vegetative character.
In northern Alabama, according to Dr. Smith, on the various stages of the Carboniferous formation, ranging from a sandy or conglomerate character to that of limestones of various degrees of purity, soils contrast strikingly with each other, agreeing closely with those seen in the neighboring part of Mississippi. Here, moreover, the contrast between the natural vegetative character as well as cultural value of the lands derived from the magnesian limestones (the “barrens”) contrasts strikingly with those originating in the purer limestones, on which the blue grass is at home.
Louisiana.—As to Louisiana, whose geological formations correspond closely to those of Mississippi, it may be said in general that the vegetative phenomena coincide completely with those observed in Mississippi. The “white-lime country” of northeastern Mississippi is represented in Louisiana only by patches occurring here and there on a line laid from Lake Bistineau to the coast at Petite Anse Island. But the chief characteristics of the calcareous area, among them especially that of the occurrence of red cedar and clumps of crab-apple, persistently reappear. The “Central Prairie Region” of Louisiana is quite narrow, but on it there reappear precisely the same characteristics described in connection with that area in Mississippi. In the long-leaf-pine region of Louisiana there occur, as in Mississippi, some isolated patches of a calcareous character, the largest of which is on the Bayou Anacoco in Vernon Parish, near the western border of the State. As we emerge from the sandy lands of the long-leaf pine area to that underlaid by the calcareous formation, we find, first, a change to oak and short-leaved pine, then the oak forest alone; finally, on a level black prairie of considerable extent, the post and black-jack oak in their thick-set form, clumps of crab-apple, red haw and honey locust, here and there a red cedar; exactly as has already been described in connection with the prairie lands of Mississippi. To southward of the long-leaf-pine area lies a broad belt of level, generally treeless, sandy prairie, in part dotted with groves of timber, but otherwise with nearly the same peculiar, small-seeded herbaceous vegetation observed in the corresponding portion of Mississippi. But in Louisiana there intervenes between these gray sour lands and the shell hammocks of the immediate sea-coast with their groves of live-oak, a belt of black calcareous prairie, increasing in width and clayeyness towards the West, and acquiring considerable extension in the corresponding portion of Texas. On these prairies we again find the calciphile vegetation, including the honey locust, clumps of crab-apple and red haw, etc., but not usually any oak growth, except (near the sea-coast) the live oak. In the hilly country of northern Louisiana there is reproduced substantially the vegetative character of the “short-leaf pine and oak” uplands of Mississippi ([see map on p. 490, chapter 24]), save in that, owing to the occasional outcropping of the calcareous materials of the Tertiary, small prairies with black soil are spotted about here and there. Bordering the Mississippi Bottom there are a series of oak-upland ridges with a brown loam soil corresponding to the fertile area in northwestern Mississippi, with small patches of the “Cane hills” loess soils, bearing a corresponding tree growth.[194]
In Western Tennessee the vegetative zones so distinctly shown in the adjacent portion of Mississippi are not so strikingly outlined, but so far as they do exist, the phenomena observed accord exactly with those heretofore described. The same holds true of Western Kentucky, as is well set forth and graphically described in the reports of the geological surveys of that state by Dr. David Dale Owen, and later by Dr. R. H. Loughridge.
North Central States.—North of the Ohio River the materials of the geological formations are not nearly as much varied as they are south of the same; consequently the vegetative features are also much more uniform. It must be remembered that from the Alleghenies nearly to the Mississippi, the states of Ohio, Southern Michigan, Indiana and Illinois are largely covered by drift deposits overlying the older formations, except that along the Ohio and Mississippi rivers lies the calcareous loam of the Loess or Bluff formation.
Within the states mentioned, however, not only are the older underlying formations very generally calcareous, but calcareous sand and gravel form a large proportion of the drift deposits, which in most cases overlie the rocks. Hence we find from the Alleghenies to the Mississippi a predominance of the oak forests which characterizes calcareous soils, as in the better class of uplands in Mississippi and Tennessee; interrupted only here and there by sandy belts or ridges bearing inferior growth, among which, again, the black-jack and post oaks, with short-leaved pine, are conspicuous. But in a large portion of Illinois, as well as in Western Indiana, the oak forest is interrupted by more or less continuous belts, and sometimes by a wide expanse, of black prairie, generally treeless or bearing only clumps of crab-apple and haw, and underlaid more or less directly by the carboniferous limestones, whose disintegration has materially contributed to the black prairie soils; which are noted for their high and long-continued productiveness. The lower ground is characterized, besides clumps of crab-apple and red haw, by the frequent occurrence of the honey locust, the lead plant (Amorpha fruticosa), the button-bush (Cephalanthus occidentalis), and among herbs by the polar plant (Silphium laciniatum), the prairie burdock (S. terebinthinaceum), the swamp rose-mallow (Hibiscus moscheutos), the sneezewort (Helenium autumnale), the wild indigo (Baptisia tinctoria and leucophcæa).