ops of the hills.

The 90-acre study area consists of a valley bordered on the north by a
wooded slope and on the southeast by another wooded slope adjacent to a
narrow hilltop, east of which is another wooded slope. The area is thus
an alternating series of three wooded slopes and two grass-covered,
relatively level areas.

The wooded slopes rise from the valley for about 125 feet at a grade of
approximately 16 per cent. There is a sharp increase in grade to 36 per
cent 100 feet below the top of the hills. A natural terrace 50 feet to
100 feet wide parallels the hilltop at the base of the 36 per cent
incline.

The vegetation of the northwest-facing wooded slopes has been described
by Packard (1956). It consists of American elm (_Ulmus americana_),
shagbark hickory (_Carya ovata_), chestnut oak (_Quercus
muehlenbergii_), black oak (_Quercus velutina_), and black walnut
(_Juglans nigra_), in that order of dominance. Honey locust (_Gleditsia
triacanthos_) and hackberry (_Celtis occidentalis_) are also present.
Shrubs and herbs of the lower story include greenbriar (_Smilax
hispida_), wild grape (_Vitis vulpina_), Virginia creeper
(_Parthenocissus quinquefolia_), coralberry (_Symphoricarpos
orbiculatus_), gooseberry (_Ribes missouriense_), bluegrass (_Poa
pratensis_), sedges (_Carex_ sp.), poison ivy (_Rhus radicans_), and
white snakeroot (_Eupatorium rugosum_).

The flat hilltops are covered by a mixture of grasses and forbs but are
dominated by awnless brome (_Bromus inermis_). Foxtail (_Setaria
glauca_), false redtop (_Triodia flava_), and panic grass (_Panicum
clandestinum_) also occur commonly. Awnless brome is dominant in the
valley (Pl. 46, fig. 1; Pl 47, fig. 2) except in the eastern end where
bluegrass is dominant (Pl. 45).

Near the tops and bottoms of the slopes barbed wire fences separate the
woodlands from the grasslands, which were grazed until 1948. The
borderline between woods and grasslands is well defined but woody
plants are rapidly encroaching into the grasslands. Young Osage orange
(_Maclura pomifera_), American elm, and hackberry are common trees
encroaching on the grasslands. The edge vegetation between woods and
fields (Pls. 45 and 47) includes smooth sumac (_Rhus glabra_),
coralberry and wild plum (_Prunus americana_). The lowland edges are
characterized by blackberry (_Rubus argutus_), greenbriar and
elderberry (_Sambucus canadensis_). Plates 45, 46 and 47 all show local
habitat in situatio