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 constitute 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 woodpeckers 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 competition 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 thorny 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 quantities 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 associated with osage orange trees.
The seeds are well liked by other rodents also. In late fall and winter after the "hedge balls" 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 accumulate at the base of the tree trunk. The seeds probably constitute the one most important winter food of the fox squirrel. The tufted titmouse also relies to a large extent on the seeds for its winter food. Being unable to shred the bulky hedge balls 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 titmouse.