Popular Science Monthly/Volume 51/July 1897/North and South
|NORTH AND SOUTH.|
PROFESSOR OF BIOLOGY IN SWARTHMORE COLLEGE, PENNSYLVANIA.
A WRITER has somewhere remarked upon the different atmosphere that surrounds two well-known railway stations in the city of Baltimore. The Union Station, in the upper and newer section of the city, has about it all the life and bustle of a Northern railroad center, while at the Camden Station, for so many years the terminus of a Southern trunk line, there is an air of easy-going uncertainty that breathes of the South. If this difference in the influence of the Northern and the Southern life is felt within the narrow limits of a metropolis, it is still more apparent in the region that lies between the "City of Monuments" and its more northern neighbor. As a matter of fact, the frontier of the South extends some distance north of the region with which we are accustomed to associate it, and the real line of demarcation is a natural boundary fixed by certain well-marked geographical features and indicated by the distribution of certain animals and plants. When Mason and Dixon ran their celebrated "line," they did more than settle the dispute of a boundary between colonial Commonwealths. Their arbitrary survey embodied, in an approximate way, a more or less natural division between the people of two great physical areas, each one of which is broadly defined as a distinct geographical and political unit—the North and the South. Each of these domains is characterized by certain marked peculiarities, both in natural productions and in the life of the people, which have their origin in climatic and topographical features. Through nearly two and a half centuries the physical environment has slowly worked its subtle influence into the blood and tissues of the inhabitants in each contrasted area, producing a certain cast of thought, speech, and action which are highly characteristic and which present unmistakable marks of difference.
The Northern and the Southern seaboard States of the Atlantic slope are decidedly different in their physical aspects as a result of topography. The numerous mountain ranges embraced in the Appalachian highland have a long, southwesterly trend from New England to Alabama. In the former section, north and east of the lower Hudson Valley, the eastern slopes of the mountainous highland reach to the sea, forming the bold and rocky coast line of New England. South of the Hudson the mountain ranges become more nearly parallel; and the long chains of the Blue Ridge and the Alleghanies, trending more and more toward the southwest, stand some distance inland, leaving a gently sloping lowland between them and the ocean—the Atlantic coast plain.
The coast plain is first found as a narrow strip in New Jersey. A line drawn from about the locality of Long Branch diagonally across the State to the Delaware River, at a point some distance below Philadelphia, serves roughly to indicate its inland boundary, marking it off from the upland terraces that form the foot of the highland slope. The line of demarcation then runs more and more inland, cutting off a small section of southeastern Pennsylvania, and, proceeding across the upper streams and estuaries of Chesapeake Bay, passes along the edge of the mountainous regions of Maryland and Virginia and the upland slopes of the Piedmont lands in North Carolina.
The traveler who journeys southward through William Penn's "low counties" finds himself on this line of demarcation between "the North" and "the South." Philadelphia, the last of the "Northern cities," lies behind him, and when Baltimore is reached the traveler begins to feel that he has passed into a different atmosphere. A certain unmistakable difference in voice and speech and a softer manner are, more than anything else, the first Southern characteristics to strike the stranger. The colored folk become more plentiful, and pickaninnies at the doors of whitewashed cabins form a not unfamiliar foreground touch in the landscape south of the city of Penn. From a car window one sees little of the change that comes over the face of Nature in passing from one region to another. But to him who fares by the way, with a keen instinct for things afield, comes the knowledge of just where the subtle change takes place. For it is by the range of country that a bird inhabits or where some particular tree or wild flower grows that Nature maps out the boundary lines of regions.
Naturalists have long recognized the fact that certain kinds of animals and plants were characteristic of certain regions of country, and that the boundaries of these regions coincided with lines of temperature or isotherms. Every species of animal and plant is definitely related to a certain fixed quantity of heat which is required for the full development of its reproductive activities. It is a habit fixed by purely physiological conditions. Various species of animals and plants, for some occult causes dating back to a remote period in their history, require a greater amount of heat throughout the period of reproductive activity than do other species, even though they be closely related. The species of animal or plant that requires the greater sum total of heat will find the northward limits of its range farther south than the species that requires a less amount. The breeding range of many birds, the dispersal of various species of mammals and reptiles, and the growth and development of many different kinds of forest trees and wild flowers are thus definitely outlined.
Topographical conditions exert an important influence in the distribution of surface temperature. High mountain ranges, running southward, carry the cooler or more temperate conditions of the regions to the north along their crests far into the warm zone which they penetrate. Likewise, lowland plains, extending northward, carry the conditions of greater warmth into the cooler area of higher latitudes. It is not surprising, therefore, in passing from lowland to upland districts to find more or less of a change in the character of the vegetation and in the animal life. Certain species, quite abundant in the lowland region, disappear on the higher ground, where other kinds, not met with in the lowlands, make their appearance.
Through the researches of biologists it has been found that the continent of North America may be divided north and south into several great temperature belts or heat zones, each one of which is characterized by peculiarities in its inhabitants. The boundaries of these heat zones are marked by isotherms which include a certain definite range of temperature that characterizes the contained area of country and which is definitely related to the reproductive functions of the animals and plants inhabiting it. It is an interesting fact to note that the isotherm representing the boundary between two of these heat zones coincides with the line that marks off the inland border of the Atlantic coast plain from the interior uplands of the highland region. If we turn our attention to the distribution of life in North America, we shall find some facts that do not quite agree with our already conceived ideas as to the divisions of the continent. An irregular line drawn from the coast of northern New England northwestward across the Great Lakes to the head waters of the Saskatchewan serves roughly to mark off a vast northern area known as the boreal zone. Its chief characteristic is the predominance of coniferous forests which stretch away northward to the Barren Grounds of arctic America. The inland border of the Atlantic coast plain, after bending around the end of the Appalachian highland region in northeastern Alabama, runs northward along the western base of the mountains to Lake Ontario. Then, turning sharply westward, it pursues an irregular course across the lower lake region and upper Mississippi Valley to the base of the Rocky Mountains. This extremely irregular line marks off a vast territory to the south known as the austral zone. It is evident that the southern boundary of the boreal and the northern boundary of the austral zones do not coincide, but leave more or less of an intermediate territory where the peculiar types of the northern and the southern life mingle. This overlapping area is known as the transition zone.
Dr. Merriam has shown that these three great life zones—boreal, transition, and austral—are also temperature zones, each one of which is characterized by a definite sum total of heat throughout the reproductive period. Thus the mean daily summer temperature of the boreal zone never aggregates above ten thousand degrees Fahrenheit, while the daily temperatures of the transition zone always aggregate above this. The austral zone is marked by two temperature belts—the upper austral, aggregating above eleven thousand five hundred, and the lower austral, aggregating above eighteen thousand degrees Fahrenheit. It is a significant fact that this subdivision of the austral zone into two temperature belts conforms exactly with its subdivision into two characteristic life regions. The boundary separating these is indicated by a line that, starting at the mouth of Chesapeake Bay, runs southwestward to the borders of Georgia and Alabama, and, then turning northward, reaches the mouth of the Ohio. This line of demarcation coincides with what geologists know as the "fall line," where the various rivers, in their course from the highland region to the sea, break into a series of rapids as they flow from the higher and older formations of the Piedmont lands to the lower and more recent Tertiary deposits of the alluvial plains.
Each of these great zones is characterized by the presence of certain animals and plants that do not range beyond its limits. A traveler journeying northward from the tropical shores of the Gulf States, with their flocks of pelicans and flamingoes and their characteristic palms and mangrove swamps, marks the change from one region to another in the different species of plants and animals which he encounters. The change in vegetation alone is striking. The persimmons, tulip trees, magnolias, sweet gums, sassafras, papaws, and other forms that characterize the landscape of the Southern States give place to the oaks, hickories, and chestnuts, and, farther north, to the maple and beechwoods and the birches and aspens of the highland and mountain regions in the Middle States and New England. Beyond these deciduous woods of the transition zone the traveler enters the vast domain of coniferous forests that mark the boreal region of North America. Days of journeying through the wilderness of evergreens bring the wayfarer at length out into the "tree-line zone," scattered clumps of spruces and firs that straggle along the southern edge of the inhospitable Barren Grounds of arctic America—a treeless, blizzard-swept waste of mosses and saxifrages, the home of the wolf, the musk ox, and the Barren Ground caribou, stretching away to the shores of the Arctic Ocean.
Zoölogists recognize several well-defined regions within these life zones, each of which is characterized by some forms of reptiles, birds, and mammals that do not range or breed beyond its limits. These geographical life areas have received the name of faunas. In the eastern United States four such regions are recognized and are known as the Canadian, Alleghanian, Carolinian, and Louisianian faunas. The Canadian fauna belongs to the boreal region. It is characterized by certain species of mammals that do not range south of it, as the moose, caribou, and wolverine, and by certain birds that breed within its borders. Among these latter are the well-known snowbird, several species of wood warblers, the winter wren, and the hermit thrush. This fauna extends southward to Georgia along the hemlock-crowned crests of the Appalachians, where the altitude produces conditions similar to those prevailing in the coniferous forests of the boreal zone to the north. Through the deep, cool shades of these hemlock woods floats the song of the hermit thrush—a vesper strain that falls on the sense like the tinkling of some far-off, sweet-toned bell, rising and swelling in an amplitude of liquid melody that fills the twilit aisles and dies away in still solitudes. The pleasing song of the snowbird breaks upon the forest stillness, quite different from its sharp, clicking notes so familiar in our winter walks about home. Along the brawling mountain brooks and trout streams of the Alleghanies the water thrush, with oddly jerking motions, bobs up and down on the rocks, and the winter wren flits about the windfalls or steals away from its nest, that is hidden under the gnarled roots of some old stump that overhangs the bank. To an ornithologist these and other features indicate a decided Canadian tinge in the summer bird fauna of the higher ranges from the Catskills to Georgia.
The so-called Alleghanian fauna of the eastern transition zone includes all the more familiar species of birds, reptiles, and mammals inhabiting the New England and Middle States and the lower ranges of the Appalachian highland to the south. Its chief characteristic is a mingling of the life of the other two zones—the boreal and the austral. Such decidedly northern forms as the bay lynx or catamount, the red squirrel, porcupine, woodchuck, chipmunk, jumping mouse, and certain other mammals find their ranges restricted along the southern boundary of this fauna. A number of familiar birds, as the brown thrasher, scarlet tanager, bluebird, house wren, chewink, indigo bird, meadow lark, the orioles, the common dove, and the bob-white or quail do not breed beyond its northern boundary. The brook trout does not range south of this fauna, and the rattlesnake, the copperhead, the puff adder, the green snake, the milk snake, and the water snake are not found beyond its northern border.
The Carolinian fauna is a distinctly southern type and characterizes the upper austral zone, which includes that portion of the coastal plain region that reaches from the foot of the Appalachian highland to the "fall line" of the various Atlantic streams. The northern limit of this fauna thus coincides with the inland border of the coastal plain which we have already referred to and which may be looked upon as the true dividing line between the North and South. The presence of such birds as the cardinal, the yellow-breasted chat, the Carolina wren, the tufted titmouse, the Acadian flycatcher, and the blue-winged, Kentucky, and worm-eating warblers during the breeding season is a sure sign of the Carolinian fauna. These species never go beyond its northern limits. Moreover, such species as the brown thrasher, the wood thrush, the house wren, the chewink, the dove, and the field sparrow, which find their northern limit in the transition zone, are far more abundant in the Carolinian region, and might almost be regarded as representatives of its fauna.
It becomes a matter of profound interest, not only to the ornithologist and the student of geographical distribution, but to every one who has in his heart a love of woods and fields, to locate this natural boundary by such fine shadings as the nesting place of a bird or the habitat of a forest tree. Let us take that portion of the line that cuts off a small corner of southeastern Pennsylvania. To the ordinary observer this special tract of country presents no marked difference from the landscape a hundred miles or more to the north or south of it. Its detail of features is quite similar and seasonal changes follow much the same course that they do in northern Virginia and southern New England. To the northwest, beyond the low, irregular ridge of the "upland terrace" that marks the gneiss and schist rocks of an ancient shore line, the country breaks into the rolling hills and dales of the interior uplands. To the southeast lies the flat lowland of the Delaware plain, and beyond this the pine barrens and marshes of the Atlantic coast plain of New Jersey. One who has an eye for the woods, however, will note a certain change in the trees from southern New England and the highlands of the Middle States. Groves of tall tulip trees, with their broad, smooth leaves of shining green and large, creamy blossoms streaked with orange that open toward the end of May, form a characteristic feature of the woodland scenery. The sassafras and the persimmon are scattered more or less abundantly through the woods and old pastures and along the borders of the streams. The sweet gum or bilsted, with its gray-colored branches winged with corky ridges, its spiny autumn fruit, and its five-starred leaves, fragrant when crushed and turning crimson in the fall, is a characteristic tree of this borderland. Curiously enough, too, it is confined to the lowlands, growing quite abundantly in the moist woods along the Delaware just south of Philadelphia, but unknown in the northern suburbs save as a transplanted tree.
These woodland features give a decided southern tinge to the region, and are especially significant when we come to know that the tulip tree belongs with the magnolias, a typical southern group, and that the persimmon is one of the ebony trees, a family characteristic of the tropics. But it is the presence of a Carolinian element in the fauna, especially the bird fauna, that marks this region as the beginning of the southern realm. At all seasons of the year the clear whistle of the Virginia redbird—the crested cardinal with mask of black—may be heard in the woods of the lower Delaware Valley and along the tributary streams. I have seen its flash of red against the whiteness of midwinter snowdrifts. In the bramble thickets that fringe the streams and on the wooded slopes above, the Carolina wren finds a home the year round, and its clear, ringing song breaks loudly on the frosty stillness of late winter mornings. I know of no more characteristic sounds in these woods in the early springtime than this wren's song and that of the tufted titmouse. It is a noteworthy fact that these three Carolinian birds are resident throughout the year along the northern limit of the fauna. When the spicebush has blossomed, and "all the wood stands in a mist of green," the first bird waves of the spring tide of migration appear. We wake some morning to hear the chipping sparrow striking pebbles together, and catch the plaintive song of the field sparrow in the pastures and the budding copses along the edge of spring woods. Only yesterday these sounds of the spring were but a memory. The thrasher pours out a medley of sweet notes from the high tree top, and later, in the warm days of early May, the reedy, mellow lute of the wood thrush comes from the bosky glade. During the migration the voices of birds sound unceasingly through the woods from dawn to twilight. When the blackberry is white with blossoms and the arrowwood is in bloom, most of the migrants have passed on to their northern breeding grounds, and those that stay with us have built their nests. Among these latter are several Carolinian birds. In the depths of smilax and brier-tangled thickets the skulking chat—the wildest bird of the woodland—utters its weird, delusive cries. The low-pitched, insectlike notes of the blue-winged warbler and the song of the worm-eating warbler that sounds like a chipping sparrow in the underwoods, where a chipping sparrow is never found, remind the ornithologist that he is on the edge of the Carolinian zone, for these and the handsome Kentucky warbler find their breeding limit on the northern confines of this fauna.
One of the most characteristic birds of this region, and yet one of the most unfamiliar, is the curious barn owl, which makes its home in certain low tracts of woodland south of Philadelphia. Those of us who were brought up on the transatlantic story books of a generation ago know this bird as the strange-faced "staring owl" of our childish fancies. The barn owl of this country is only a geographical race of this long familiar owl of the English towers and belfries.
The turkey buzzard, though frequently observed as far north as southern New England, is never found abundantly beyond the Carolinian fauna. It nests among the rocks, often in communities of considerable size, in southern Pennsylvania, and winters in southern New Jersey. Almost any day from April to November numbers of turkey buzzards may be seen in the neighborhood of Philadelphia, soaring on motionless wing, often at a great height, or gathering in large flocks over the woods to feast on the carcass of some animal. Farther south, especially toward the coast, the turkey buzzard becomes less abundant where the black vulture or carrion crow, a closely related species that scarcely ever occurs north of Charleston, takes its place.
A notable mammal of the southern realm is at home in the woodland tracts of this region. The opossum is quite as abundant along the northern edge of the Carolinian fauna in southeastern Pennsylvania and New Jersey as it is farther south, but is rarely found north of this locality on the Atlantic seaboard. Its nocturnal habits preclude it from ordinary observation, and only in the autumn and early winter, when tempted into some rabbit snare or caught in its predatory midnight rambles and its fat body swings before the market door, are we aware that this curious marsupial dwells in our midst. From the Delaware southward a fat "’possum" is the delight of the darkey, and most toothsome is it indeed if caught in a persimmon tree after feeding on the frost-ripened fruit. A less common mammal is the little gray fox, which formerly was much more abundant on the northern range of the Carolinian fauna than it is at the present day. The gray fox must be the "Brer Fox" of Uncle Remus, for the more familiar and larger red fox of the Northern States does not range far beyond the limits of the transition zone. The red fox is now the most abundant species in southeastern Pennsylvania, and this may be due to a difference in habits. The gray fox makes his lair under the roots of a tree or a shelving rock, while the red fox tunnels out a burrowlike den underground. With the clearing of the country this last is undoubtedly the most favorable method of holding territorial rights.
The southern portion of New Jersey presents a unique area in the Middle Atlantic States. In all its essential features—topographical, geological, and also in certain biological aspects—it is related to the region farther south, being the northward extension of the Atlantic coast plain. The most characteristic feature is the "pine-barren" region that reaches from the foot of the higher country to the maritime marshes and beaches that immediately fringe the coast. The tourist journeying to the seaside resorts south of Long Branch has the monotonous sandy waste of the pine barrens for a landscape. Here and there the white, loamy soil gives place to loose beds of yellow gravel. Sluggish streams of water, stained dark brown from the leachings of the cedar stumps, meander through swampy jungles. The landscape varies somewhat with the character of the trees in different places. In some sections the tall pitch pine forms vast stretches of forest, while in others a low and scanty woodland growth of the "Jersey" or scrub pine and several species of scrub oak prevails. The cedar swamps that lie scattered in the course of the numerous streams form a remarkable feature of this interesting region. Dense jungles of white cedar growing out of the dark water and surrounded by an impenetrable undergrowth of tangled vines and brier thickets form a harbor for many wild animals and birds. The tropical effect of these cedar swamps is heightened by broad-leaved magnolias and the long festoons of graybeard moss that fringe the branches. In these dark recesses, and through the pine barrens generally, the botanist finds many plants which belong to a more southern flora. Indeed, all the way along the coast from New Jersey to Maine, in favorable situations, representatives of distinctively southern forms may be found which in these higher latitudes do not occur inland. The mockingbird, which is highly characteristic of the Louisianian fauna, has been met with as a straggler during the breeding season in the New Jersey pine barrens; and in the cedar swamps near Cape May the hooded warbler, a typical Carolinian species, breeds regularly. In times long past the rare and curious Carolina parroquet, now known only from the Gulf region, was an occasional visitor as far north as the lower Delaware and its tributaries.
River valleys are topographical features of great importance in determining the distribution of living beings. The conditions of greater humidity and higher average temperature that prevail in the bottom lands along a river's course, as compared with the higher ground of the upland districts which forms its watershed, is strikingly illustrated in the case of Carolinian birds. Certain species are found regularly during the breeding season in the valleys of the Susquehanna, Delaware, Hudson, and even the Connecticut Rivers, extending inland for a greater or less distance, but are unknown in the surrounding higher country. Thus, Carolina wrens, cardinals, turkey buzzards, and other no less characteristic Carolinian birds are abundant in the bottom lands along the Susquehanna in Lancaster County, Pennsylvania, but are scarcely ever found on the uplands above the wooded slopes of the river, though the conditions of food and shelter seem equally favorable.
Much of the outside world enters a man's soul and becomes the ground of his joy through life. We all owe something to the region in which we dwell, unconsciously perhaps, but still something that is assimilated by the tissues of the inner life, and that goes to the making of what we really are. Those of us who dwell on the borderland of Dixie owe some fragmentary moments of inspiration, even of happiness, to the genial influence of its proximity. We think of ourselves as belonging with the North, but has not the South spun a few threads into the web of our lives? The cardinal whistles the same sweet tune as he does in "Old Virginia" the opossum and the persimmon savor of the South; even the turkey buzzard suggests the warmer clime. And then spring is always two weeks earlier just down the Delaware, and this is something; even if it is too far off to start the "spring feeling," it hints of fresh early strawberries and the first run of the shad.
- Especially those of Dr. C. Hart Merriam. See National Geographic Magazine, vol. vi, p. 229. The Geographic Distribution of Life in North America. From Smithsonian Report for 1891, p. 365.
- Witmer Stone. The Birds of Eastern Pennsylvania and New Jersey, p. 10.