THE RECOGNITION OF CHARACTER OF SOILS FROM THEIR NATIVE VEGETATION;
MISSISSIPPI.
_Climatic and Soil-Conditions._—Next to climatic conditions, chief
among which are temperature and moisture, the physical and chemical
nature of the soil and subsoil is the most potent factor in determining
the natural vegetation of any region. The limitations we observe in the
adaptation of cultivated lands to certain crops, even with artificial
help, must be much more strongly pronounced when no such aid is given,
and the struggle for the survival of the fittest is continued, subject
only to seasonal variations, for thousands of years. It is obvious
that within the limits of the regional flora, _the natural vegetation
of any tract represents the best adaptation of plants to soils, in the
results of long periods of the struggle for existence between competing
species_; the survivors being those best adapted to the entire
environment.
[183] The special object of this chapter as a whole has seemed to the
writer to require a repetition of much that is already said in the
preceding chapters.
In countries uninhabited by man the chief conditions outside of the
direct influence of climate and soil that may materially affect the
results of the competition are connected with the animal creation;
and within the latter, insects are probably the most influential,
beneficially in the part they play in the fertilization of flowers,
injuriously in their role as parasites. Since in the absence of man,
the effects of fire would ordinarily be conditioned upon the occurrence
of thunderstorms, its effects would then properly come under the head
of climatic influences. But while these and some other disturbing
factors must not be forgotten in considering the relations of soils to
the natural vegetation borne by them, the common consensus of mankind
has long recognized the intimate connection existing between the two,
and has everywhere made it the basis of at least a general estimate of
the agricultural value of the land concerned.
NATURAL VEGETATION THE BASIS OF AGRICULTURAL LAND VALUES IN THE UNITED
STATES.[184]
In countries long settled, as in Europe, where the nature of the
original forest is unknown or a matter of tradition only, the
adaptations of the several kinds of land to culture plants and forest
trees has been gradually ascertained by cultural experience, and
their designations, values and uses determined accordingly. In the
United States, the character of the original forest growth is mostly
in evidence, or is definitely known by tradition, even in the older
states. West of the Alleghenies, there is as yet little difficulty in
this regard, partly because even where the original forest growth has
disappeared its character remains on record, the assessed land values
being very commonly based upon the tree growth of the wild land. In
the Southern States especially, the classification of uplands into
“pine lands” and “oak lands” is universal, and is associated with
certain limits of valuation, both by assessors and purchasers. Within
each of these two classes, however, there are well-defined gradations
of cultural value according to the kind (species) _e. g._, of pine or
oak that occupies the ground, either alone, or in intermixture with
other trees whose presence or absence is considered significant. In
the case of “bottoms” or alluvial lands, corresponding distinctions
and classifications obtain; we hear of hickory, beech, gum, and cherry
bottoms, hackberry hammocks, etc. each name being associated with
certain cultural values or peculiarities of soil, well understood by
the farming population.
[184] See above, pp. 313 to 315, chapter 18.
INVESTIGATION OF CAUSES GOVERNING THE DISTRIBUTION OF NATIVE VEGETATION.
It seems singular that such well and widely understood designations
and important distinctions should not long ago have been made the
subject of careful investigation and precise definition by agricultural
investigators. For apart from their practical importance as guides to
the purchaser of land, or settler, this correlation of land-values and
natural vegetation is of the utmost interest in offering an opportunity
for researches on the factors which determine the choice of these
several trees and the corresponding shrubby and herbaceous growths.
Moreover, the cultural results and adaptations corresponding to certain
natural growths being known from experience, a thorough knowledge
of the soils so characterized should enable us to project into new
lands, where experience is lacking, the benefits of experience already
had; even in cases where, from some cause, the natural vegetation is
different, or absent. Only very fragmentary and casual observations
in this line are on record thus far, almost the only generally
recognized chemical characterization of plant habit being that of
calciphile (lime-loving), and calcifuge (lime-repelled) ones, but with
few attempts at more than local application. Yet, to ascertain by
the physical and chemical examination of soils what are determining
factors of certain natural vegetative preferences, which are invariably
followed by certain agricultural results, should not be an unsolvable
problem, and its practical importance should justify its most active
investigation.
_Investigations in Mississippi._—In his explorations connected with
the Geological and Agricultural Survey of the State of Mississippi, as
well as, later on, in similar researches carried on in other states,
the writer was forcibly struck with the close correspondence of the
limits of geological formations with those of vegetative zones; so much
so that he was led to rely very largely on the latter as indicative of
the probable occurrence of outcrops that otherwise, in a level country,
would have passed unperceived.
These observations upon the correlations between virgin soils and their
native vegetation having originally been made by the writer, in great
detail, in the state of Mississippi, from 1855 to 1872, and that state
being from natural causes a peculiarly cogent illustration of such
correlation: it seems advisable to describe first, somewhat in detail,
the facts observed there, and subsequently to compare them with what
has been observed elsewhere by him or others.
No claim is made to an even approximately exhaustive presentation of
the whole subject, even within the United States; nor is it intended
to give complete lists of vegetation.[185] The object is to give such
facts as have been fairly well established by observation, hoping
that more thorough investigations in the same line will thereby be
stimulated.
[185] Such lists, so far as the State of Mississippi is concerned,
may be found in the writer’s Report on the Agriculture and Geology of
Mississippi, 1860. See also Plant Life of Alabama, by Charles Mohr.
VEGETATIVE BELTS IN NORTHERN MISSISSIPPI.
The diagram below is a sketch-map of the most northern part of
Mississippi, showing the narrow parallel belts of successive geological
formations or terranes running north and south, which bear the varying
zones of vegetation characteristic of each one, as indicated in the
legend beneath.
[Illustration: FIG. 77.—Sketch map of Soil Belts in Northern
Mississippi, east and west.]
SOIL REGIONS OF NORTHERN MISSISSIPPI, SHOWING CHANGES
FROM EAST TO WEST, AND LIME PERCENTAGES IN SOILS.
|Lime, p.c.| Soil Character.| Vegetation.
| | |
1. | .40— .60|Clay loams, clay. |Oaks, sweet gum, tulip tree,
| | | walnut, red cedar, ash,
| | | hickories.
| | |
2. | .05— .14|Sandy loams, sands.|Short-leaf pine, post, scarlet
| | | and black-jack oaks, black gum,
| | | chestnut.
| | |
3. |1.00—1.40|“White lime” |Red cedar, crab-apple, Chickasaw
| |prairie; clays and | plum, sturdy post and black-jack
| |clay loams. | oaks, honey locust.
| | |
4. | .30— .50 |Mellow red loams of|Oaks, hickories, walnut, tulip
| |“Pontotoc ridge.” | tree, ash, cherry, umbrella
| | | tree.
| | |
5. | .08— .18 |Heavy gray clay |Scrubby post and black-jack oak,
| |soils, some gray | short-leaf pine.
| |sands. “Flatwoods.”|
| | |
6. | .15— .25|Sandy ridges and |Post, black-jack, scarlet and
| |uplands, broken. | upland willow oaks, small; some
| | | chestnut.
| | |
7. | .25— .35 |Mellow clay loams |Fine black, red, post, Spanish
| |of “Table lands.” | and black-jack oaks, hickories,
| | | sweet gum.
| | |
8. |2.00—5.00|Calcareous sandy |Oaks as above, tulip tree, ash,
| |silt, “Bluff loess”| honey locust, linden, sassafras,
| |“Cane Hills.” | umbrella tree, cane.
---+----------+-------------------+---------------------------------
9. | .40—1.10 |Mississippi Bottom.|Basket, white and black oaks,
| | | ash, tulip tree'
9a.| 1.12— |Yazoo backland |honey locust, pecan, shell-bark
| |buckshot clay. | hickory, walnut, hackberry,
| | | cane.
9b.| .40 |Sandy alluvium, |Sweet gum, maple, willow oak,
| |“Frontland.” | elm, hackberry.
---+----------+-------------------+---------------------------------
10.| .26— .40 |Light sandy loam of|Dogwood, sweet gum, holly, ash,
| | “Dogwood ridge.” | sassafras, prickly pear.
| | |
---+----------+-------------------+---------------------------------
_Limestone Belt._—beginning on the east we have, first,
a narrow belt of limestones of the carboniferous formation,
on which there is a fine growth of various oaks, with walnut,
hickory, sweet gum, tulip tree and red cedar, and a very
productive soil.
“_Pine Hills._”—Next adjoining on the west comes a
belt of sandy, non-calcareous beds of the lower Cretaceous
formation, about 18 miles wide. It has a hilly surface,
and outside of the narrow valleys, the prevalent timber is
short-leaved pine and scrubby black-jack oak, with some post
oak and small black gum, and a few large chestnut trees.
_“Prairie” Belt._—Westward of this belt we descend
into a level “prairie” region, six to twelve miles wide;
the “white lime country,” having heavy black clay soils,
underlaid by the cretaceous “rotten limestones;” which are
profusely productive. The sparse tree growth consists of
stout, vigorous and dense-topped post and black-jack oaks,
with clumps of crab-apple, Chickasaw plum thickets, and an
occasional red cedar.
_Pontotoc Ridge._—West of the prairie belt we ascend
into a ridgy hill country, twelve to fourteen miles wide;
the “Pontotoc ridge,” formed of the soft limestones and
marls of the upper cretaceous formation, and covered with
a deep red soil, which bears a rich growth of oaks, with
hickory interspersed, and black walnut, umbrella and
tulip tree even on the ridges. This is one of the finest
agricultural regions of the State.
_Flatwoods._—From the Pontotoc ridge and its fine
lands and timber we descend to westward into the “Flatwoods”
belt, three to eight miles wide; a level country underlaid
by heavy gray non-calcareous clays of the tertiary
formation, from which most of its soil is directly formed.
It bears a pretty dense growth of the same species of oaks
that characterize the prairies farther east, but the form,
habit and size of the trees is so different that many of
the inhabitants believe them to be different species. The
black-jack oak looks like small, dense-topped apple trees;
the post oak, on the contrary, has an open top of the form
of a short-handled, spreading broom. The soil is poor and
unthrifty, as are the few disappointed settlers, who bought
the land on the strength of its oak-tree growth. (See page
500).
_Brown Loam Region. Table Lands._—Adjoining the
Flatwoods on the west is a broad upland region, with a
brownish-yellow soil and subsoil, extending nearly to the
edge of the Mississippi bottom. In its eastern portion
it is rather broken and hilly, with sandy ridge soils, a
mixed growth of oaks and short-leaved pine, and occasional
chestnuts; a fair farming country only. To westward the
ridges become lower and broader, assuming a plateau
character. The pine disappears, and black, Spanish, red and
white oak, with much hickory, largely replaces the black
jack and post oak; thus characterizing the fertile brown-loam
“table-lands” that extend through western Tennessee and
Mississippi into Louisiana, and have long been noted for
their high production of fine upland cotton.
_Cane Hills._—On the western border of the table-land
region, and here forming a strip only a few miles wide along
the edge of the Mississippi bottom, but from 70 to 450 feet
above it, lies the remnant of what farther south constitutes
a wide and important agricultural belt; the Bluff or Loess
formation, locally known as “the Cane Hills.” The soil is
largely composed of grains of sand and silt cemented by
lime carbonate; it is therefore calcareous, and as on the
Pontotoc ridge, described above, we find here the black
walnut, the tulip tree, ash and others, elsewhere restricted
to the alluvial “bottoms,” on the ridges themselves, from
sixty to a hundred feet above the stream beds.
_Mississippi Bottom._—At the western foot of this
bluff there lies the great Mississippi Bottom, with its
rich soils and varied forest growth. This also, however,
subdivides into at least three distinct soil and vegetative
zones, viz., the sandy “Frontlands,” which lie on the
immediate banks of the great river and its main branches,
and the heavy clayey “Back-land” areas, whose soils are
partly the product of modern swamp deposits from backwaters,
partly result from the disintegration of strongly calcareous
clays constituting the lower part of the Bluff or Loess
formation. A third natural subdivision is the “Dogwood
ridge,” a narrow belt of slightly elevated land, mostly
above ordinary overflows, which extends diagonally from the
Mississippi river to the Yazoo bottom, and seems to be the
continuation of “Crowleys ridge” in Arkansas. Each of these
soil belts has its own characteristic forest growth, as
indicated in the table below the map.
We have here along an east-and-west line of about 200 miles, eleven
markedly distinct zones of vegetation, readily recognized as such by
every farmer, and each underlaid by a distinct geological terrane. It
does seem as though a close study of these and of the soils overlying
them should lead to some definite results showing the physico-chemical
causes of these differences.
_Lime apparently a governing Factor._—The connection of some of these
changes in vegetation with the calcareous nature of the corresponding
formation has already been referred to. As regards four of the eleven
divisions, this is obvious even to the casual observer, and is well
known to the population, who speak of the “lime country” or belts
being, as a matter of common knowledge, the best land; in full accord
with what, in Kentucky and elsewhere, has passed into a popular
maxim.[186]
[186] “A lime country is a rich country.”
Taking as a guide the trees and plants which characterize the obviously
calcareous lands, our next step should be to verify, if possible, the
fact that wherever these occur naturally, lime is abundant in the
soil in comparison with those lands in which such vegetation does
not occur naturally, or perhaps even fails to flourish when planted
without special fertilization. This the writer has sought to do,
first in connection with the survey work of the state of Mississippi,
and subsequently in the wider field that has since come under his
observation.
SOIL BELTS IN SOUTHERN MISSISSIPPI.
In Mississippi, the general conclusions derived from the observations
made on the northern cross section, are corroborated many times over
in other portions of the state. Aside from the cretaceous prairie
region, there runs across the middle of the state a belt of varying
width, of calcareous tertiary beds, which also give rise to more
or less extensive tracts of “black prairie” lands, interspersed
with non-calcareous, mostly sandy ridges, the lower slopes of
which, influenced by the calcareous beds, bear an oak and hickory
growth, while the higher portions have only pine, and usually remain
uncultivated. Southward of this “central prairie” belt lies the
long-leaf-pine forest area of the state, underlaid throughout by
sandy, non-calcareous formations, with poor sandy soils, save here and
there in patches, which can be at once recognized by the replacement
of the long-leaved pine by a vigorous oak growth; as is also the case
where the pine area abuts against the calcareous “Cane Hills” on the
west. The bottom soils of this region are largely “sour,” and bear
the gallberry (_Prinos glaber_), bay galls (_Persea Carolina_), ti-ti
(_Cliftonia monophylla_), candleberry (_Myrica cerifera_), various
whortle-berries, the pitcher plants (_Sarracenia_), yellow star grass
(_Aletris_), sundews, _Xyris_, _Eriocaulon_, and other plants of
similar habits.
_Vegetative and Soil Features of the Mississippi Coast Belt._—South of
the long-leaf pine area lie the coast flats, with sour, sandy soils
underlaid by stiff clays. On these “pine meadows” of the Mississippi
coast occur some of the most striking cases of modifications of
vegetation due to physical and chemical causes.
As is well known, the long-leaved pine habitually belongs to the
dry sandy uplands of the Gulf States; the deciduous cypress, on the
other hand, is most characteristic of the swamps, where its roots
are permanently submerged in water. But on the pine meadows of the
Mississippi coast we see these two incongruous trees growing side by
side, though sadly worsted by their mutual concessions; their heights
usually ranging from 12 to 15, rarely as much as 18 feet.[187] Yet
both preserve their characteristic forms, the cypress being an exact
miniature reproduction of the usual level-topped swamp form, except
as to the “knee” feature; while the pine differs only in stature from
its giant brethren of the pine hills, from which it can be traced
down through all grades of transition. The soil on which this growth
occurs is a sour, sandy one, one and a half to three feet in depth,
underlaid by a solid, impervious gray clay, above which is usually
found several inches of coffee-colored bottom water, which drains
slowly into the sluggish water-courses, themselves carrying brownish,
sour, but very clear waters. Analysis shows the soil to be sour and
extremely poor, especially in its lime and phosphates (see chapter
19, p. 352); its herbaceous vegetation consists exclusively of very
small-seeded, “calcifuge” plants (sedges, orchids, Juncus, Hæmodoraceæ,
Xyris, Polygala, etc.). This land is wholly unproductive and affords
but indifferent pasturage, except the first season after burning-over;
probably because of the effect of the minute amount of ashes so added.
As the coast is approached, the clay subsoil has an increasing depth of
sandy soil-mass above it, and on these “sand hammocks” the long-leaved
pine gradually assumes more and more of its usual stature; the cypress
disappears, and the Cuban pine (here called pitch pine) gradually comes
in; while the sedgy vegetation diminishes and finally disappears. On
this land crops may be grown as in the long-leaf-pine uplands.
[187] R. M. Harper, who has graphically described the vegetative
features of the coastal plain of Georgia (Contr. from the Dep. of
Bot. Colum. Univ. Nos. 192, 215, 216, 1902-05; also Bull. Torr. Bot.
Club 29-32), claims the deciduous cypress of the wet pine-barrens and
ponds therein, the vegetation of which greatly resembles that of the
pine meadows of the Mississippi sea-coast, to be a distinct species,
_Taxodium imbricarium_, the leaves of which are imbricated, instead of
two-ranked and with spreading leaflets. He supports this distinction
mainly by the differences in habit from the Louisiana swamp cypress,
and the fact that the imbricated form occurs wholly on non-calcareous
land, while the other is at home in the calcareous alluvial areas.
The imbricated form has been observed and commented on before, as a
mere ecological variation, and in the writer’s opinion this is all
that can be claimed, in view of the much greater differences in the
form of other trees, notably oaks, illustrated below, caused also by
lime. There would, _à fortiori_, be reason for claiming at least three
different species of post oak and black-jack (and two of willow oak),
which differ not only in tree form but also in the form and number
of leaf lobes, and yet can be traced into one another by innumerable
transition forms. If new species are to be established on such grounds,
it is hard to see where the variations manifestly due to environment
are to come in.
But on the immediate coast, evidently under the influence of the
aboriginal “shell mounds,” the yellow sandy soil becomes blackish from
the (humus-forming) effect of the lime thus supplied; and concurrently
the coast live-oak (_Q. virens_), grape vines, the Hercules club
(_Aralia spinosa_), “l’herbe a trois quarts” (_Verbesina sp._), and
numerous leguminous plants (which are wholly absent from the pine
meadows) take possession of the land, which is very productive and has
been specially utilized in the growing of Sea Island cotton. Here the
clay stratum is 15 to 20 feet below the surface, and roots penetrate
to great depths in the pervious soil, whose great thickness makes up
for its low percentage of plant-food (see table below). This land is
distinctly limited by the extent of the shell heaps, past or present,
and shows a respectable percentage of lime.
[Illustration: FIG. 78.—Schematic profile of the Mississippi Coast
Belt, through Jackson County.]
The annexed schematic profile (fig. 78) illustrates these changes
of soil and vegetation, which furnish a striking example of the
effective modification of vegetative features by physical and chemical
soil-conditions.
It would be difficult to find a more striking exemplification of the
effect of lime carbonate, not only upon the vegetation but also upon
the physical and chemical characters of the hopelessly unproductive
soil of the sand hammocks and pine meadows; no longer brown and sour,
but jet black and neutral, modifying favorably every physical quality.
Humus likewise nowhere shows its benefits more strikingly.
_Table of Lime-Percentages._—The table below shows the average lime
percentages observed in most of the several vegetative areas mentioned
above. To meet the objection sometimes made that the vegetative changes
noted may be due to the larger amounts of phosphoric acid and potash
frequently found in calcareous lands, the percentages of the latter are
also given. Considering the origin of limestones, such a connection
is not unexpected, but it is far from constant. On the contrary, the
frequent co-occurrence of much lime and high production with small
percentages of phosphoric acid and potash leads to the conclusion,
already discussed (see chapter 19, p. 365), that in presence of
abundance of calcic carbonate, smaller percentages of phosphoric acid
may be considered adequate than when lime is deficient, on account of
greater availability. Almost the same may be said of potash; and it
is quite possible that the presence of large amounts of lime tends
to prevent the leaching-out of this base, in consequence of greater
facility for the formation of zeolites. Illustrations of this kind have
already been given (chapters 3, 22).
_Definition of “Calcareous Soils.”_—It will be noted that the very
obvious and important changes of vegetation are brought about by
comparatively slight differences in lime-content. In fact, only two
of the soils enumerated above would, according to the estimates
usually given in books on soil composition, be considered as properly
calcareous. But the decisive feature in this matter must evidently
be the _native vegetation_, which expresses the nature of the land
much more clearly and authoritatively than any arbitrary definition
or nomenclature can possibly claim to do. _A soil must be considered
as being calcareous whenever it naturally supports the vegetation
characteristic of calcareous soils._
TABLE SHOWING NATIVE FOREST GROWTH, POPULAR ESTIMATE OF DURABILITY
AND INITIAL PRODUCTION, AND PERCENTAGES OF LIME, PHOSPHORIC ACID
AND POTASH, IN MISSISSIPPI LANDS.
===+==========+============================+=======================
No.| Name. | Natural Vegetation. | Production Per Acre.
| | |
---+----------+----------------------------+-----------------------
| Black |Mainly sturdy black-jack and|400 lbs. cotton lint,
172| Prairie | post oak, red cedar, crab | decreasing to 200 lbs.
| Soil. | apple and honey locust. | in 30 years.
| | |
---+----------+----------------------------+-----------------------
| Pale |Scarlet, post and Spanish |200 lbs. cotton first
164| Yellow | oak, small. | year, tailing off
| Ridge | | to 75 to 100 lbs.
| Loam. | | by 5th year.
---+----------+----------------------------+-----------------------
| Pontotoc |Oak, hickory, walnut, sweet |350-400 lbs. cotton
226| Ridge |and black gum, honey locust.| lint, 300 lbs. after
| Soil. | | 20 years.
---+----------+----------------------------+-----------------------
| Heavy |Post and black-jack oak, |20 bushels of corn
230| Flatwood | and some short-leaved pine.| first year--then
| Soil. | | nubbins only.
---+----------+----------------------------+-----------------------
|Black-Jack|Black-jack oak, pine, |Unproductive.
345| Ridge | huckleberry. |
| Soil. | |
---+----------+----------------------------+-----------------------
| Oak and |Red and post oak, pig-nut |200 lbs. cotton lint
| Pine | hickory, short-leaved pine.| at first; 100 lbs.
142| Upland | | 6-8 years.
| Loam. | |
---+----------+----------------------------+-----------------------
| Brown |Black, post, Spanish and |400 lbs. cotton--250
219|Table-land| black-jack oak, hickory, | lbs. after 20 years.
| soil. | sweet and black gum. |
---+----------+----------------------------+-----------------------
| Bluff or |Cane, black and white oak, |400 lbs. cotton,
237| Loess | tulip tree, linden, | decreasing to 250 lbs.
| Soil. | sassafras. | after 30 years.
---+----------+----------------------------+-----------------------
|“Buckshot”|Hickory, ash, sweet gum, |800 lbs. cotton lint,
390| Soil. | pecan, cow oak, honey | reduced to 500 lbs.
| | locust, cane, crab-apple, | in 30 years
| | plum. | cultivation.
---+----------+----------------------------+-----------------------
| Pine |Long-leaved pine, with |20-30 bushels corn for
206| Hill | scarlet and post oak, | one year--then
| Soil. | scattered small and | nubbins. Usually
| | occasional pig-nut | good sweet potatoes
| | hickory. | for 2-3 years.
---+----------+----------------------------+-----------------------
| Pine |Dwarf long-leaved pine, |Unproductive. Bears
215| Meadow | cypress, sedges, orchids, | small-seeded “sour”
| Soil. | Hæmodoracæ, etc. | vegetation.
---+----------+----------------------------+-----------------------
| Shell |Live and water oak, cedar, |300 lbs. sea-island
88| Hammock | magnolia, holly, dogwood, |cotton for 15 years.
| Soil. | sweet gum, hickory, |
| | sassafras, grape, Hercules |
| | club, etc. |
---+----------+----------------------------+-----------------------
===+==========+===============+=======+=====+=====+======+=======
No.| Name. | Physical | K₂O. | CaO.| MgO.| P₂O₅.| Humus.
| | Character. | | | | |
---+----------+---------------+-------+-----+-----+------+-------
| Black |Heavy adhesive | | | | |
172| Prairie | dark-colored | .333 |1.367| .363| .104 | 1.25
| Soil. | clay. | | | | |
| | | | | | |
---+----------+---------------+-------+-----+-----+------+-------
| Pale | Pale yellow | | | | |★
164| Yellow | sandy loam. | .093 | .069| .126| .033 | .50
| Ridge | | | | | |
| Loam. | | | | | |
---+----------+---------------+-------+-----+-----+------+-------
| Pontotoc | “Mulatto” | | | | |
226| Ridge | medium loam. | .374 | .281| .234| .082 | 1.00
| Soil. | | | | | |
---+----------+---------------+-------+-----+-----+------+-------
| Heavy | Heavy gray | .753 | .178| .831| .052 | .305
230| Flatwood | clay. | | | | |
| Soil. | | | | | |
---+----------+---------------+-------+-----+-----+------+-------
|Black-Jack| Very sandy | | | | |★
345| Ridge | loam. | .073 | .142| .100|Trace.| .20
| Soil. | | | | | |
---+----------+---------------+-------+-----+-----+------+-------
| Oak and | Medium | | | | |
| Pine | loam. | | | | |★
142| Upland | | .236 | .092| .196| .091 | .50
| Loam. | | | | | |
---+----------+---------------+-------+-----+-----+------+-------
| Brown | | | | | |
219|Table-land| Clay loam. | .630 | .270| .450| .210 | .79
| soil. | | | | | |
---+----------+---------------+-------+-----+-----+------+-------
| Bluff or | Sandy loam. | .511 |5.921|3.278| .143 | .72
237| Loess | | | | | |
| Soil. | | | | | |
---+----------+---------------+-------+-----+-----+------+-------
|“Buckshot”| Heavy | | | | |★
390| Soil. | calcareous | 1.104 |1.349|1.665| .304 | 1.0
| | clay soil. | | | | |
---+----------+---------------+-------+-----+-----+------+-------
| Pine | Light sandy | | | | |
206| Hill | loam; mere | .259 | .129| .180| .030 | .35
| Soil. | sand at | | | | |
| | 3 feet. | | | | |
---+----------+---------------+-------+-----+-----+------+-------
| Pine | Very sandy | | | | |
215| Meadow | loam, gray | .061 | .023| .069| .021 |
| Soil. | clay subsoil. | | | | |
---+----------+---------------+-------+-----+-----+------+-------
| Shell | Very sandy | | | | |
88| Hammock | loam, deep. | .080 | .115| .065| .107 | .75
| Soil. | | | | | |
---+----------+---------------+-------+-----+-----+------+-------
Starred values (★) are approximate.
DIFFERENCES IN THE FORM AND DEVELOPMENT OF TREES.[188]
It will be noted that in the above table, as well as in the discussion
preceding it, identical species of trees are ascribed to vegetative
areas of widely different productive capacity. Perhaps the most
striking example is that the cretaceous prairies and the adjoining
flatwoods belt, standing respectively highest and lowest in the scale
of productiveness, are yet bearing specifically identical tree-growth,
to-wit, the post oak (_Quercus minor_) and the black-jack oak (_Q.
marylandica_). While to the field botanist[189] there can be no
question as to the absolute specific identity of the two trees as
growing on the respective areas, yet the mode of development of both
is so different in the two cases, that, as before remarked they are
popularly supposed to be different “kinds.”
[188] It is a matter of regret to the writer that owing to the long
distance intervening and the difficulty of securing competent and
sympathetic observers for such work, it has not been possible for him
to secure photographs of the tree-forms here discussed. At the time his
own observations were made, photography was practically unavailable as
yet, and the figures given are therefore based upon sketches made at
the time, and partly upon recollection. They represent types rather
than definite individuals, which were however described when fresh in
mind, in the Report on the Agriculture and Geology of Mississippi,
1860, pages 254 et seq.
[189] It has been already, and doubtless will be again and
increasingly, attempted to make distinct “species” of these widely
different forms of trees. But this is simply begging the question.
Mere external diagnostic marks will not avail here; it would have to
be shown that the seed of these different forms do not produce the
other forms under changed conditions. Until this has been done, the
number-less transition forms which he that runs may observe in the
field, throw upon the species-makers the onus of proof of differences
of specific value—if it be possible to define such value.
_Forms of the Post Oak._—The post oak of the prairie lands is a tree
50 to 70 feet high, with a stout, excurrent, rather conical trunk,
often somewhat curved to one side above, and densely clothed from
within 12 or 15 feet of the ground with comparatively short, sturdy
branches set squarely to the trunk, much crooked (geniculate), often
reflexed downward; altogether forming a dense head, beneath whose
thick foliage, a bird or squirrel is quite secure from the hunter’s
aim.—In the flatwoods, on the contrary, the post oak has a thin, rather
short trunk, divided up at 15 or 20 feet height into long, rod-like
branches, spreading broom-fashion, and scantily clothed with short
twigs bearing tufts of leaves; thus forming an open head, in which no
creature can hide effectually. On the brown-loam table-lands, again,
the post oak has a straight, rather slender, excurrent trunk with long
and more or less crooked limbs projecting at a large angle, sometimes
even drooping, and freely divided up into lateral, leafy branches; the
trees attain from 40 to 55 feet in height. Again, on the high sandy
ridges which are interspersed in the eastern portion of the brown loam
area, we find, generally associated with a similarly depauperated form
of the black-jack oak, and with the Upland Willow oak (_Q. cinerea_), a
form of the post oak intermediate between that of the Flatwoods and the
Table lands; twelve to fifteen feet high, with thin trunk, “sprangling”
long, crooked branches, clothed with sparse tufts of leaves. These four
strikingly distinct types are shown schematically, in their extreme
development, in the subjoined figures.
It is hardly necessary to say that between these extreme forms there
are many degrees of transition, corresponding to the transitions
between the several soil-classes respectively represented by them; or
they may be developed into depauperated types. Thus, for example, the
forms of the post and black-jack oak found on the sandy ridges of the
yellow loam region, hardly need experience in the observer to interpret
them as characterizing a wretchedly poor soil.
_Forms of the Black-jack Oak._—Not less striking are the
characteristics of the forms of the _black-jack oak_ as developed upon
these several kinds of land. The black-jack of the prairies is a low
tree with a dense rounded head, often somewhat flattened above, and a
low, thick-set trunk divided up into square-set branches, so densely
clad with foliage that no light penetrates into the interior, and birds
can safely hide and nest within it. The height rarely exceeds 35 feet,
the head being 20 to 30 feet across.
The Flatwoods form, on the contrary, rarely exceeds 15 feet in height,
with a very rough bark and a small, rather dense, rounded top, giving
the whole the appearance of a small apple tree. Practically the same
form is seen on poor, clay ridges of “hog-wallow” land.
[Illustration: Loam Upland.]
[Illustration: Sandy Ridges.]
[Illustration: Flatwoods.]
[Illustration: Black Prairie.
FIG. 79.—Extreme Forms of Post Oak (_Quercus minor Marsh., obtusiloba_
Mich.).]
On the brown-loam lands the black-jack, like the post oak, has a
rather slender, often somewhat crooked, but excurrent trunk 35 to 50
feet high, with more or less crooked limbs of moderate length, well
provided with leafy branches, but forming altogether a rather open
crown. A depauperated form of this type occurs on the sandy ridges of
the yellow-loam region and is 12 to 15 feet high, with slender, crooked
branches, clothed with scanty foliage; as shown in Figure No. 80,
alongside of the other typical forms.
[Illustration: Loam Upland.]
[Illustration: Flatwoods.]
[Illustration: Sandy Ridges.]
[Illustration: Black Prairie.
FIG. 80.—Extreme Forms of Black-Jack Oak (_Q. marylandica Mursh, nigra
Wangh_).]
In all these variations of the tree forms, there is also a concomitant
variation in the forms and other characters of the leaves. Thus in
the compact forms of the black-jack oak, the trilobate leaf is almost
completely obliterated, the leaf being simply rounded-cuneate, somewhat
auriculate at base. In the sparse-branched upland forms the leaves are
deeply three-lobed, and the ferruginous tomentum of the lower surface
is much less pronounced. The lobation of the post oak also varies
considerably both in the numbers of lobes and in their obtuseness.
Similar differences prevail in the case of the black and Spanish oaks;
thus in the latter, the long terminal, falcate lobe is always most
pronounced on “rich” soils, while on poor ones the trilobate leaf
predominates.
Of course all these forms may be found bearing acorns, so that they
undoubtedly represent adult trees.
_Characteristic Forms of other Oaks._—Similar general features are
repeated in the case of the other species of oaks, and also more
or less in other kinds of trees; though mostly less pronouncedly
than with the two species above described. Among the more striking
are the two forms of the willow oak (_Q. phellos_), which on low,
undrained ground assumes the low, rounded, “apple-tree” form, while on
well-drained uplands of good fertility it is a beautiful, slender tree
producing almost the effect of the acacia type; it is then a sign of
first-class land. The scarlet oak rather reverses these types; on good,
“brown-loam” upland it is of rounded form, not very tall, with sturdy,
rough-barked trunk; while on poor hillside lands its tall, smooth,
white trunk stands out as a conspicuous admonition to the land-seeker
to beware of a poor purchase. The black and Spanish oaks also indicate,
by tall thin trunks, a deterioration of the land as compared with the
lower and more sturdy growth on areas relatively richer in lime.
_Sturdy Growth on Calcareous Lands._—One feature invariably repeated,
not only in Mississippi but throughout the United States, is that _in
many strongly calcareous soils the growth of all trees, as well as of
shrubs and of many herbaceous plants, is of a more sturdy and thick-set
habit_ than that of the same species grown on thin, sandy, or generally
on non-calcareous land. This effect is quite as apparent in the arid
region of the Pacific Coast as in the Atlantic States, on the prairies
of the Middle West, and of the Gulf Coast. The experienced farmer
recognizes this habit of the tree-growth as a sign of good land, and
the reverse, viz., trees of lank, tall and thin growth, as evidence to
the contrary, from the Atlantic to the Pacific.
_Cotton Plant._—The cotton plant affords very striking evidences of
this influence of lime. On the bottom lands of a creek in Rankin
county, Mississippi, the writer found a “patch” of cotton with
luxuriant stalks reaching above the head of a man on horseback, but
almost devoid of “squares” or blooms. The soil was very dark and
rich-looking, but was derived from a non-calcareous tertiary terrane
surrounding the heads of the stream. A few rods below, the latter
crosses the line of a calcareous terrane, from which copious marly
debris have been washed down on the bottom soil. Here the cotton was
just half as high as above, and thickly covered with squares, blooms,
and bolls.
Another similar example was noted on the Chickasawhay river, in Wayne
county, Miss. Where that stream flows through the non-calcareous,
lignitiferous area of the tertiary formation, its bottom lands bear
cotton crops of medium productiveness only, the stalks being of the
usual height of about three feet, and only fairly bolled. But a short
distance below the point where the soft marls of the marine tertiary
are cut into by the stream, the cotton plants on the bottom lands
are from 18 to 20 inches high only, closely branched, and literally
thronged with cotton bolls, so that the fields appear a solid mass
of white. The only objection urged against this land is that to pick
such cotton “breaks the backs” of the pickers. The tree growth of the
bottom, of course shows a corresponding change.
_Lime Favors Fruiting._—In connection with the obvious changes of
form and stature caused by the presence of an abundant supply of lime
carbonate in soils, there is another that has been long noted in
cultivation, but is no less striking in the native vegetation. The
abundant fruiting of oaks on such lands as compared with the same
species on non-calcareous soils is a matter of common note in the
Mississippi Valley states; and the same is true of other trees, and
of herbaceous plants as well. The fruit on the lime soils is often
smaller, unless much humus is present; but the statement made in
Europe that cultivated fruits, and especially grapes, are sweeter on
calcareous lands, is abundantly verified in the native fruits of the
Mississippi Valley states as well; where the various wild berries,
haws, plums, etc., are well known to the younger part of the population
to be much sweeter and higher-flavored in certain (calcareous)
localities than in others, besides being usually more abundant.
This is entirely in accord with the well-known fact that the
application of lime checks the excessive wood and leaf growth resulting
from excess of nitrogen as well as moisture; while on the other hand,
the injurious effects of overdressing with lime or marl are known to
be repressed by the use of stable manure, or by green-manuring. The
repression of excessive wood growth by lime would seem to offer a
simple explanation of the compact habit of growth on calcareous lands;
and the extraordinary sweetness of fruits grown in the arid region as
compared with the same in the humid, is fully in accord with the high
lime-content of the arid lands.
_Stunted Growth._—In practice it will be found in most cases that a
stunted native growth is due not so much to lack of plant-food in the
soil, as to unfavorable physical conditions. Among these, _shallowness,
and extreme heaviness_ of the soil are the most common causes. The
“scab lands,” underlaid by impervious rock at a depth too slight for
culture plants, as in many plateaus of the Pacific Northwest, and in
rocky or mountainous regions generally, are cases in point. Strata of
impervious clay often produce the same result; but in this case, should
such clay be intrinsically capable of supporting plant growth, the
land can often be made available for orchard purposes by blasting with
dynamite (see chapter 10, p. 181).
The post oak (and black-jack) flats of the Mississippi Valley states
are familiar examples of land whose dwarfed tree growth causes it
to be avoided by settlers; similarly, a dwarfed growth of red elm
(_Ulmus rubra_), hackberry and ash indicates in the flood plain of
the Red river of Louisiana a heavy “waxy” red clay, or “gumbo” land,
scarcely available for agricultural purposes.[190] The gray or white
“cray-fishy” bottom and bench lands of the Southwestern States, so
poor in lime, phosphates and humus as to be worthless under existing
conditions, are characterized by an easily recognized scrubby growth of
Water and Willow Oaks (_Q. nigra_, or _aquatica_, and _phellos_), with
low, rounded tops; while the same trees, when well developed, indicate
highly productive lands.
[190] Rep. of Geological Reconnaissance of Louisiana; New Orleans,
1873, p. 27.
_Physical_ vs. _Chemical Causes of Vegetative Features_.—The extent
to which the modifications of form alluded to above are referable to
chemical and physical causes respectively, can be approached by the
discussion of the presence or absence of certain trees from soils
of extreme physical character, but otherwise normally constituted.
As has been shown above, the black-jack and post oaks belong, as
species, equally to the heaviest and lightest soils within the state of
Mississippi; to the black and yellow “prairie” soils, as well as to the
sandy ridges of the yellow-loam region; showing for these two species
as such, an independence of physical conditions and an extraordinary
adaptability, found in few other trees. They are frequently found
either alone or associated with only a few other species of local
adaptation, such as, in the prairie lands, the crab-apple, wild plum,
and the juniper or red cedar. On the soils of intermediate or loam
character, on the contrary, they are always associated with other oaks
as well as with hickory, and in that association attain what may be
considered their normal type or form.
From the fact that the dense, rounded top is formed by the black-jack
oak both on the rich prairie lands and on the poor soils of the
Flatwoods, it would seem that that form is the outcome of a physical
cause, viz., the extreme “heavy-clay” character of both kinds of land;
and we may note that exactly the reverse effect is observed in the
form growing on the poor sandy ridges, as shown in fig’s 79 and 80.
Yet it will also be noted that in the case of the post oak, the poor,
heavy-clay soil of the Flatwoods produces an open, broom-shaped top,
while the form assumed on the sandy ridges is substantially the same
for both species. Care must therefore be exercised in drawing general
conclusions as to the effects produced by either physical or chemical
causes, _alone_, upon tree forms.
_Lowland Tree Growth._—The variations occurring in the valleys or
alluvial bottoms are less obvious to superficial observation, yet
equally important and cogent to the close observer. In the properly
alluvial lands, one dominant condition, that of _adequate moisture_
supply, is almost always fulfilled, irrespective of soil quality. In
addition to this, as stated in chapter 2 (see page 24), practically all
the alluvial lands of the humid region may be considered as being of
a more or less _calcareous_ character, as compared with the adjacent
uplands. These two important conditions dominate in a great measure the
minor ones of variation in soil-texture. Yet where, as is largely the
case in the southern part of the State of Mississippi, the amount of
calcic carbonate is insufficient to overcome the sourness of the soil,
the vegetative contrasts become extremely striking and characteristic,
as explained above.
_Contrast Between “First” and “Second” Bottoms._—A very striking phase
of transition between the alluvial bottoms and the uplands proper in
the Cotton States are the second bottoms or hammocks of the streams,
whose soil and tree-growth in most cases differ markedly from those
of the first bottom; and these being usually closely adjacent, often
afford a very striking contrast to the latter. From some antecedent
geological cause not fully understood, these hammocks, usually elevated
from 4 to 10 feet above the present flood plain, have almost throughout
soils of a fine sandy, pulverulent or silty nature, frequently in
strong contrast to heavy clay soils in the first bottom.
They seem, moreover, to have been at some time subject to prolonged
maceration under water, resulting in the reduction of the ferric oxid,
and its accumulation in the lower portion of the deposit in the form of
bog-ore spots or “black gravel.” Since such a process always results
in the abstraction of phosphoric acid from the general mass of the
soil, to be accumulated in the bog ore in an inert condition,[191]
these hammock soils, usually whitish or gray in color, are almost
throughout poor in phosphates as well as in lime; the latter having
been definitively leached out. The resulting vegetation, as may be
imagined, is widely different from that of the bottom proper, as well
as, frequently, from that of the adjacent uplands; and though level and
fair to see, these hammocks are usually unthrifty and last but a short
time under exhaustive cultivation. Accordingly, their forest growth
is prevalently that of the poorer class of uplands, viz., small-sized
post and black-jack oaks, and in the low ground depauperated water oak,
or less commonly willow oak, of the low, stunted type indicative of a
soil of inferior productiveness. The luxuriant growth of the present
alluvial bottom is often seen within a few feet of the unthrifty
vegetation of these hammocks. It is usually only in the limestone
regions, and in the lower course of the larger streams, that the
hammocks or second bottoms are found to be of good fertility.
[191] See Chapter 2, p. 24.
_The Tree Growth of the First Bottoms. The Cypress._—Among the
trees occupying the low ground of the first bottom in the southern
Mississippi states, the deciduous cypress (_Taxodium distichum_)
deserves special mention as an example of extreme variation in form.
In sloughs and swampy tracts, as is well known, the cypress grows with
roots submerged throughout the season, excepting only the excrescences
known as “knees,” which project above the water, probably performing
some function in connection with the aeration of the root, which is
essential to the root functions in all plants. The trunk rising from
the water is supported by numerous projecting buttresses for from
8 to 15 feet above the water; higher up it becomes cylindrical for
a height of from 40 to 70 feet, then divides up into a few widely
spreading, thick, almost conical branches, whose twigs and foliage form
an almost level surface to the head. This level-topped forest growth
characterizes at once the submerged areas of the river and coast swamps.
But the cypress is by no means confined to the swamps and sloughs;
it is also found occupying the better class of hammock lands, 12 or
15 feet above water level. In this case, however, the tree assumes a
shape and growth so wholly different from that described above as to
lead to a popular assertion of a difference of species. As a matter
of fact, however, the cones of these upland cypresses, when dropping
into the water below them, reproduce exactly the common swamp form.
The extraordinary difference in the aspect of the tree under these
different conditions is best seen in the subjoined diagram, showing
the upland cypress to assume the form of the tall willow oak, with
which it is sometimes locally associated.
[Illustration: Swamp.]
[Illustration: Upland.
FIG. 81.—Forms of Deciduous Cypress on overflowed and on bench-land.]
The trees from which the annexed sketch is taken grew within thirty
feet of each other, on Yellow creek, a small tributary of the Tennessee
river, in Tishomingo county, Miss. The soil stratum is underlaid by a
shaly limestone, and bears lime vegetation.
The fact that the deciduous cypress grows without difficulty on the
moister class of lowlands in California, 12 or 15 feet above bottom
water, is of interest in this connection. It then assumes the upland
form shown in the figure above, although not growing quite as tall. The
calcareous nature of these soils is probably an important factor in
this apparently incongruous adaptation of a subtropical swamp tree to
arid conditions. In its swamp form the cypress usually grows in rather
shallow, heavy clay soil, into the dense subsoil of which the roots
penetrate but little.
_Other Lowland Trees._—The lowland hickories, like their brethren on
the highlands, seem on the whole to prefer the lighter or loamy bottom
soils to those of a heavier character. This is especially true of the
Pecan. The latter, as well as the shell-bark hickory, is especially
indicative of the highest class of bottom soils. The black walnut,
while apparently also best suited in loamy soils, is also more or
less found on heavy bottom lands, provided they are sufficiently
calcareous; and the same is measurably true of the tulip or white-wood
tree. The most frequent occupants of heavy bottom lands, however, are
the black gum and sweet gum, so that “gum swamps” are usually found
to be of that character.[192] But in the prairie region, where the
bottom soils are very calcareous and heavy, as well as in corresponding
soils of the “buckshot” lands of the great Mississippi Bottom, the
chestnut-white (cow- or basket-) oak sometimes occupies such ground
almost exclusively. Among the accompanying trees are especially the
honey locust, the crab-apple, mulberry and sweet gum, as well as ash.
[192] Hence perhaps the vernacular name “gumbo” for heavy, adhesive
clay soils in the north central states; which may also, however, be
derived from a comparison with the “gummy” pods of the cultivated okra
or gumbo plant.
_General Forecasts of Soil Quality in Forest Lands._—While the oaks and
pines mentioned as forming the bulk of the timber constitute in the
cotton states the _primà facié_ evidence, as it were, of the general
character of the land, there are numerous other trees and plants which
serve the discriminating land-seeker as a guide for the quality of
the soils in different localities. While everywhere, well-developed
black, red, Spanish and white oaks are considered as signs of a high
quality of land, the tall, thin scarlet, the upland willow, and the
barrens scrub oak are considered as indications detracting materially
from the producing value wherever they prevail. The various hickories
are throughout considered as indicating good land when mixed with
the oaks, or by themselves; while the presence of walnut, linden and
tulip tree will usually raise the estimate of uplands to the highest
class. On the other hand, the occurrence of small black-gum trees and
short-leaved pine, with low huckleberry, among the oaks of whatever
kind, accompanied as they usually are by the disappearance of the
black, white and Spanish oaks, will materially depress the land-values.
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.