The Forest Habitat of the University of Kansas Natural History Reservation Part 3

As this oak seems to be in process of being replaced by other trees, is slow-growing, and slow in dispersal, it seems probable that the areas now occupied by its stands supported stands of it under original conditions. Whether it can regain dominance under present conditions of protection from cutting, fire and grazing remains to be seen.

The chestnut oak produces a mast crop which is utilized by many kinds of animals. Fox squirrels, gray squirrels, and white-footed mice feed upon the acorns and store them. Blue jays, red-headed woodp.e.c.k.e.rs (_Melanerpes erythrocephalus_), and red-bellied woodp.e.c.k.e.rs also eat them. The red-eyed vireo, summer tanager and tufted t.i.tmouse are among the birds that most frequently forage for insect food in chestnut oaks. Relatively few kinds of birds seem to use this tree as a nest site.

#Quercus prinoides.#--The chinquapin oak on this area is a small shrubby tree, usually not more than 15 feet high and more typically only six to eight feet. It occurs chiefly in dry rocky situations along hilltop edges and upper slopes, usually where the slope exposure is at least partly to the south. In such situations it may grow in nearly pure stands. Often it is a.s.sociated with dogwood. The trunks are usually two to four inches in diameter, gnarled and twisted. The crowns are dense and spreading.

This oak is the dominant plant in certain small areas of its preferred habitat. In other areas of hilltop edge and upper slope it is being eliminated by stands of hickory, chestnut oak, black oak and elm, which shade it out. The species is tolerant of moderate to heavy browsing, but seemingly can be eliminated by more intensive utilization; even the higher foliage is often within reach of livestock. In "Horse Woods" one of the hillside areas that was open to livestock until 1949, this oak was almost absent, but it was abundant in adjoining parts of the woods that were fenced in the thirties to exclude livestock.

The thickets formed by this shrubby oak are frequented by cottontails, which feed upon the bark and foliage. The small acorns are used as food by rodents, especially the white-footed mouse. On several occasions, in winter, groups of long-eared owls (_Asio otus_) have been found roosting in thickets of chinquapin oak. Crows also utilize these thickets for roosting occasionally. The white-eyed vireo (_Vireo griseus_), gnatcatcher (_Polioptila caerulea_), and tufted t.i.tmouse, frequent the oak thickets.

#Quercus rubra.#--The red oak is one of the important climax species of the area. At present it is largely confined to a ravine in the northeastern part of the section. The woodland here is less disturbed than on most other parts of the Reservation, and red oak is the dominant species. There are large trees, rather evenly distributed, growing on east-facing and west-facing slopes. Just east of the Reservation, in the "Wall Creek" area, the small valley on either side of the creek and the adjacent lower slopes are dominated by giant red oaks larger than any now growing on the Reservation. Farther up the slope in the area of limestone outcrops, dominance s.h.i.+fts to chestnut oak. That red oaks of similar size, and even larger, formerly occurred on the Reservation, at least in the area still dominated by the species, is shown by the presence of a stump 49 inches in diameter, now in an advanced state of decay.

[Ill.u.s.tration: Fig. 6. Map of Reservation showing present distribution of black oak (smaller dots) and red oak (larger dots). Neither species is spreading and both are thought to be largely confined to the area that was wooded before 1860.]

The large acorns of the red oak are a favorite food of the gray squirrel, which is most numerous on the parts of the Reservation where these trees are present. The red-headed woodp.e.c.k.e.r on the area tends to concentrate its activities where there are red oaks. The fox squirrel, white-footed mouse, and blue jay are important consumers of the acorns of red oak. A pair of barred owls resided in the deep woods formed by these oaks and the a.s.sociated trees.

#Quercus velutina.#--Black oak is one of the dominant species of the original forest climax, and is still one of the more important trees of the woodland. Like chestnut oak it shows little tendency to spread beyond its present limits. Wherever there are small trees there are old mature trees or remains of them nearby. For this reason the present distribution of black oak on the area is thought to fall entirely within the area occupied by the original forest. At present it occurs throughout most of the woodland except in the warmer and drier situations, such as on south slopes. In some hilltop situations it is common, with occasional large mature trees. In some parts of the bottomland and lower slopes it is abundant also, but there are scarcely any on the upper dry rocky slopes that are the preferred habitat of chestnut oak.

Growth in the black oak is somewhat more rapid than in the chestnut oak, as the black oak usually grows on better soil. For 15 the average growth amounted to 3.21 annual rings per inch of trunk diameter.

In 1954 a study of annual rings in a large, long dead, black oak at the bottom of a north slope near the Reservation headquarters showed that the tree was 96 years old, and hence was growing before the area was settled. Within the period of this study black oak underwent reduction in numbers more severe than that noted in any other species of tree on the Reservation. The effect of drought may have been the primary factor, although undoubtedly disease was involved also. In 1953, the second successive drought year, mortality was noticeable.

Precipitation continued below normal until August 1954. By then the oaks had been decimated. On a sample strip of hilltop where 29 were recorded, 21 had recently succ.u.mbed, and their leaves were dry and withered; two were dying, though still having some green foliage, and only six were surviving, all evidently in critical condition. The mortality included trees of all sizes, even the largest and oldest. No further mortality was noted in 1955 when precipitation was only slightly below normal. On the Reservation there are many old logs, and snags still standing, of mature black oaks long dead. Earlier drought periods such as those of 1936-37 and 1925-26 possibly were also times of unusually heavy mortality. In any case it seems clear that this oak was originally more prominent in the woodlands than it is at present, and has been steadily losing ground. Even where the mature trees remain in greatest numbers the saplings are relatively scarce as compared with those of elm, ash, hackberry, and hickory. The westernmost limits of the range are nearly 100 miles west of the Reservation.

Black oak provides a mast crop which is utilized by various small mammals, notably squirrels and white-footed mice. Gray squirrels have often been noticed in or about these trees. Hairy woodp.e.c.k.e.rs (_Dendrocopos villosus_), black and white warblers (_Mniotilta varia_), and brown creepers (_Certhia familiaris_) have often been noticed foraging on the trunks. Blue jays, myrtle warblers (_Dendroica coronata_), tufted t.i.tmice, and summer tanagers frequently forage through the crowns. Often black oak trunks are hollow and the cavities are utilized by various birds and mammals including the screech owl (_Otus asio_), barred owl, racc.o.o.n, opossum, fox squirrel, gray squirrel, woodrat, and white-footed mouse.

#Quercus marilandica.#--Black Jack oak is localized in four small compact groves on the Reservation. These sites, though well separated, are similar. All are on steep lower slopes, where there is dry rocky clay soil and the exposure is mainly south. Probably all four groves date back to the time when the area was still in an undisturbed state.

Originally they were perhaps largely separated from the remainder of the woodland. Black Jack oak is more tolerant of heat and drought than most of the other hardwoods are. The species is intolerant of fire, but perhaps was partly protected under original conditions by the spa.r.s.eness of herbaceous vegetation on the poor soil where the groves were situated.

These oaks are relatively slow-growing. One stump of 9-inch diameter, typical of the larger Black Jack trees, had approximately 60 annual rings. Under present conditions there is little or no reproduction and these trees are dying out as a result of compet.i.tion by other hardwoods. Under protection from fire and browsing, elms, other oaks, locust and dogwood have closed in about the groves and seem to be shading them out.

There are several mature oaks of anomalous appearance, in different places within a few hundred feet at most of the groves of Black Jack.

Most of these appear to be hybrids between the present species and _Q.

velutina_, as they are somewhat intermediate in size, bark texture, and leaves.

This oak produces a mast crop used by various birds and mammals, and groves are frequented by blue jays, fox squirrels, white-footed mice and woodrats. In the mid-forties when the woodrat population was high, there were many of the rats' stick houses in the groves, built either at the bases of the trunks or among the dense branchlets in tops of fallen trees. By 1952 the population of woodrats was much reduced and had disappeared entirely from these groves. The houses were collapsed and decaying.

Horned owls (_Bubo virginia.n.u.s_) and barred owls often make their day roosts among the dense interlacing twigs of these trees, and red-tailed hawks have been known to roost for the night in the same kinds of situations.

#Ulmus americana.#--On most parts of the area American elm is the dominant tree. It occurs throughout the woodland, and most of the larger trees are of this species. In each of the fields that were formerly cultivated, and in the pasture areas, there are many saplings. More than one hundred elms of DBH two feet or more have been recorded. Presumably these mostly date back 90 years or more and were already growing on the area when it was relatively undisturbed. On the area the distribution of these large elms corresponds in a general way with the present distribution of the oak-hickory type. The coinciding distribution of the climax species and of the largest trees is believed to reflect the distribution pattern of the original forest, except that clearing was thorough in the bottomlands so that hardly any trees of the climax species, or large trees of any kind remain.

Several elms of three feet or more DBH were recorded, and the largest one measured was 46 inches. The largest elms are in alluvial soil near small creeks in the two valleys. Also many large elms grow along the upper slopes, especially along the outcrops of the two main strata of the Oread Limestone. Such sites along the outcrops on open slopes are the first to be invaded. The rock strata are relatively impervious to water, which is held at a depth where it is readily available to the trees. Along rocky upper slopes between the two outcrops, where chestnut oak is abundant, elms are relatively scarce and seem unable to compete successfully. It is noteworthy that elm is not mentioned in several of the descriptions (Taft, 1950; Parks, 1854; Robinson, 1899) of the original forest, even in listings of the species present. It must have been much less prominent until favored by disturbed conditions.

[Ill.u.s.tration: Fig. 7. Map of Reservation showing present distribution of the largest American elms, those more than two feet in trunk diameter. American elm is increasing and spreading on the area, and smaller trees are abundant even in former cultivated fields and pastures. Growth rate varies according to site, but these larger trees are, in many instances, 90 years or more in age and most of them are thought to be in the area wooded in the eighteen sixties and before.]

In July and August, 1954, a large proportion of the elms on the area died. The die-off included trees of all sizes, and evidently the c.u.mulative effect of drought in 1952 and 1953, continuing into the spring and summer of 1954, was the primary cause, although diseases such as phloem necrosis, and insect infestations, may have intensified its effect. In August of 1954 the bare dead elms stood out conspicuously in the ma.s.s of green foliage surrounding them. Most of them had survived the two dry summers of 1952 and 1953 with little evident loss in vitality. However, the continued lack of moisture as the 1954 growing season progressed, and the extremely hot weather of June and July caused heavy mortality. In the course of a few days the foliage of the upper branches would wither, die and turn brown. In some instances numerous sucker shoots grew from the trunk of the tree as the top was dying. Mortality was especially heavy on south-facing slopes. Certain ecologists believe that over the years, as trees deplete subsoil moisture and periodic droughts make their effects felt, other species also will die off and eventually prairie will replace them where the present forests are growing in dry and exposed situations.

Infestations of the introduced bark beetle, _Scolytus multistriatus_, were common and probably contributed to death of many elms. In the winter of 1953-54 before much mortality had occurred, the bark beetle infestations had become conspicuous. Especially on south slopes elms of about six inches DBH were heavily infested. Woodp.e.c.k.e.rs, including the downy, hairy, and red-bellied, habitually resorted to the elm trunks to forage. As a result of their activities chips of bark acc.u.mulated sometimes to a depth of several inches around the bases of the trunks, and the exposed inner layers of brown bark caused the infested trees to contrast with the predominantly gray color of those that were still healthy and retained the outer layer of bark.

In April and early May seeds of the American elm const.i.tute a major food source for birds, including the black-capped chickadee, tufted t.i.tmouse, junco (_Junco hyemalis_), red-eyed towhee (_Pipilo erythrophthalmus_), Harris sparrow (_Zonotrichia querula_), cardinal, goldfinch, tree sparrow (_Spizella arborea_) and field sparrow (_S.

pusilla_). Birds recorded as nesting in the American elm include the mourning dove (_Zenaidura macroura_), Cooper hawk, red-tailed hawk, broad-winged hawk (_Buteo platypterus_), turkey vulture (_Cathartes aura_), screech owl, horned owl, barred owl, red-bellied woodp.e.c.k.e.r, downy woodp.e.c.k.e.r, tufted t.i.tmouse, black-capped chickadee, gnatcatcher, red-eyed vireo, summer tanager, indigo bunting (_Pa.s.serina cyanea_), field sparrow and cardinal.

Opossums, racc.o.o.ns, fox squirrels and white-footed mice often live in cavities in elms.

Insectivorous birds that find their food on foliage and prefer elm or use it to a large extent are: yellow-billed cuckoo, tufted t.i.tmouse, black-capped chickadee, blue-gray gnatcatcher, red-eyed vireo, white-eyed vireo and warblers, including the myrtle, Audubon (_Dendroica auduboni_), yellow (_D. petechia_), black-throated green (_D. virens_), black-poll (_D. striata_), Tennessee (_Vermivora peregrina_), orange-crowned (_V. celata_), Nashville (_V.

ruficapilla_) and American redstart (_Setophaga ruticilla_).

#Ulmus rubra.#--The red elm (or slippery elm) is widely distributed over the area, but only a few trees with a trunk diameter of twelve inches or more are present. Throughout the woodlands of the Reservation the saplings of this species const.i.tute a prominent part of the understory. However, few survive beyond the sapling stage. The red elm is never abundant in Kansas woodlands. It is intolerant of drought conditions, and is one of the first trees to die. This fact probably explains the scarcity of mature trees of this species on the Reservation.

#Celtis occidentalis.#--Hackberry is widely distributed on the area, but is not dominant anywhere. Its favorite site is along hilltop limestone outcrops, especially where there is south exposure. There are few on hilltops away from the outcrops. Hackberries are scattered in small numbers over the wooded slopes. There are a few of unusually large size, along edges of the bottomlands. Hackberries are slow-growing. Counts of annual rings for four indicated an average of 7.1 rings per inch of trunk diameter. Young hackberries of all sizes are numerous throughout the woodland. Therefore it seems likely that this species is in process of spreading and probably has already extended beyond the situations which it originally occupied.

The fruits of hackberry provide a fall and winter food supply for various animals. Opossums are especially fond of them. Red-bellied woodp.e.c.k.e.rs have been seen storing them. Migrating flocks of robins may utilize them as a major food source temporarily. White-footed mice and woodrats store them and eat them.

#Morus rubra.#--Red mulberry is moderately common in certain heavily wooded areas, especially the lower parts of north slopes. A few are present on wooded hilltops. Most of the trees are between ten and twenty feet tall, and generally die before growing larger. Red mulberry is present in most woodlands of eastern Kansas and is seemingly distributed by birds. It is never an important component of woodlands in the area. Catbirds (_Dumetella carolinensis_) and wood thrushes (_Hylocichla mustelina_) especially have been noted frequenting the vicinity of mulberry trees in fruit. Probably many other kinds of birds utilize the fruits to some extent.

#Maclura pomifera.#--Osage orange was not a member of the original flora, but early settlers in Kansas valued it for windbreaks and fence posts, and they made extensive plantings. Presumably it was introduced onto the area of the present study in the eighteen sixties. At the present time it occurs throughout the woodland, with scattered mature trees and many young trees on the former pastures. This aggressive invader spread despite frequent cutting, and now plays an important part in the ecology of the area. Most of the larger trees have been cut one or more times, but have regenerated from stump sprouts with multiple stems and spreading habit. The tough and durable wood is useful for fence posts. The growth rate is slow, similar to that of oaks and elms.

Osage orange is intolerant of fire and is easily killed by scorching.

It is damaged by browsing, and cannot grow in deep shade. It is drought resistant. Mortality was light during the drought period of 1952-1954, although many of the trees were growing on poor soil in the hotter and drier sites.

Where there are stands of mixed hardwoods, osage orange is relatively scarce and tends to be on or near the edges of the stands. The osage orange trees growing in compet.i.tion with oaks, elms and hickories may have tall, slender trunks and narrow crowns, in contrast with the spreading habit of those growing in more open sites. In the woodlands small and medium-sized trees are scarce and there is hardly any reproduction. Obviously the osage orange, like honey locust became established in the forests when the stands were more open, probably after cutting of the large trees. In contrast to the meager reproduction in shaded sites is the abundant crop of young saplings along edges of fields adjacent to woods or about isolated osage orange trees. Evidently the tree does not become established readily on bluestem prairie. On a hillside adjoining the northwest corner of the Reservation, long subjected to heavy grazing, osage orange dominates, but just across the fence on the Reservation side, it is almost absent. This area had been maintained as bluestem prairie until about 1934 by occasional burning and since then had partly grown up into thickets in which dogwood, and saplings of elm and hackberry were abundant.

The dense th.o.r.n.y branches provide shelter and nesting sites for many kinds of animals. On this area the cardinal utilizes it for nesting sites more frequently than any other kind of tree. Some nests were so well protected by the thorns that they could scarcely be reached.

Indigo buntings, field sparrows, and yellow-billed cuckoos also use these trees or young saplings for nesting sites.

In the forties, when the woodrat was common on the area, its local distribution seemed to be determined mainly by the osage orange. Many houses of the woodrat were built around old stumps at the bases of large, spreading osage orange trees. Frequently the houses were in the main crotch of a tree two to eight feet from the ground.

Characteristically the rats used horizontal or gently inclined, low branches of the tree as runways to and from the house. In summer and early autumn these rats stored foliage of the osage orange in large quant.i.ties in chambers adjacent to the nest. The seeds also provided an important food source. During the period 1948 to 1951 the woodrat population steadily decreased, and one by one the houses in osage orange trees were deserted, until the small surviving population of woodrats was limited to hilltop rock outcrops not a.s.sociated with osage orange trees.

The seeds are well liked by other rodents also. In late fall and winter after the "hedge b.a.l.l.s" have fallen, fox squirrels visit the trees and shred the fruits to gain access to the seeds. Over periods of weeks heaps of the shredded refuse acc.u.mulate at the base of the tree trunk. The seeds probably const.i.tute the one most important winter food of the fox squirrel. The tufted t.i.tmouse also relies to a large extent on the seeds for its winter food. Being unable to shred the bulky hedge b.a.l.l.s itself, it depends almost entirely on the seeds in fruits torn open by the squirrel but not fully utilized by it. At times when the ground and trees are snow-covered, making unavailable most other food sources, the osage orange seeds gleaned from refuse heaps in the sheltered feeding places of the squirrels are probably of critical importance to the t.i.tmouse.

The cottontail and white-footed mouse also eat the seeds.

#Plata.n.u.s occidentalis.#--Sycamores are few and scattered on the area, but those present seem to be holding their own if not gaining in numbers. They include some of the largest trees on the Reservation.

The most typical habitat is along rocky ravines on wooded slopes.

Occasional trees are scattered through the woods away from ravines on slopes of north, east, or west exposures, or on hilltop edges, providing strong evidence that these areas were more open at the time the sycamore seedlings became established. Cutting of the mature trees in the original forest and subsequent grazing might have created the conditions favorable for their establishment. Many saplings have sprung up in the fallow hilltop fields that were formerly cultivated.

Many of the larger sycamores have cavities and these are inhabited by various animals. A large sycamore in a ravine below a pond had a cavity in its base within which a racc.o.o.n reared its litter of young one summer. At other times this same cavity was inhabited by woodrats and by fox squirrels. Seemingly this cavity was the habitat of a certain chigger which was found on both the squirrels and the woodrat.

Red-bellied woodp.e.c.k.e.rs excavated a cavity high on this same tree trunk, in which they reared their brood.

Several large sycamores died as a result of the c.u.mulative effect of drought in the summers of 1952, 1953 and 1954, but many others survived.