Effects of Livestock
Livestock importantly affected the trend of succession. The tendency of grazing animals to hold back the forest by stripping the foliage from young trees and killing them is selective, however; the several kinds of trees differ in their tolerance to browsing and in their palatability to animals. The kind of animal and the season and intensity of use also have important bearing on the ultimate effect. Several kinds of shrubs and small trees seem to be especially susceptible to damage by browsing; chinquapin oak, crab-apple, plum, hazel, dogwood, prickly ash, and paw paw were found to be either absent entirely from the parts of the woodland that were heavily used by stock, or much scarcer than they were on adjacent unbrowsed areas. Some woody plants that are even more susceptible may have been completely eliminated by browsing.
In the thirties when most of the woodland area was fenced off and protected from grazing, three wooded hillside areas of a few acres each, were maintained as connecting strips between the pastures of the hilltops and those of the bottomlands. These areas were utilized only at certain seasons, but by 1948 the effect of trampling and heavy browsing by livestock was conspicuous. Herbaceous ground vegetation was almost lacking and low woody vegetation was also scarce, in contrast to the parts of the woodland that were adjacent but separated by fences that excluded livestock. The contrast was perhaps heightened along the fences because the animals tended to follow along the fence lines and their effects were concentrated there.
Table 4.—Numbers of Young Trees of Various Kinds and Sizes in 1954 on a .919-acre Area Consisting of Six Hillside Strips Each 20 Feet Wide. Each Strip Was Equally Divided by a Fence Line, Excluding Livestock from One Side During the Period 1934 (Approximately) to 1948.
 | ||||||
| Less than ½-inch stem diameter | ½-inch to 4-inch stem diameter | 5-inch to 12-inch stem diameter | ||||
| Total Number | Percent- age in browsed half | Total Number | Percent- age in browsed half | Total Number | Percent- age in browsed half | |
| | | | | | |
| Dogwood | 556 | 52.1 | 1058 | 16.4 | ||
| Redbud | 40 | 42.5 | 102 | 5.9 | ||
| Elm | 30 | 76.7 | 189 | 27.6 | 99 | 47.5 |
| Hackberry | 131 | 39.7 | 206 | 13.1 | 5 | 20.0 |
| Plum | 26 | 77.0 | 35 | 22.8 | 1 | 100.0 |
| Crab-apple | 11 | 100.0 | 46 | 37.0 | ||
| Red haw | 1 | 100.0 | 33 | 48.5 | 9 | 75.8 |
| Walnut | 7 | 28.6 | 32 | 43.7 | 26 | 61.5 |
| Honey locust | 2 | 100.0 | 20 | 15.0 | 11 | 27.3 |
| Osage orange | 1 | 100.0 | 7 | 57.1 | 2 | 50.0 |
| Shagbark hickory | 3 | 100.0 | 42 | 73.8 | 44 | 40.9 |
| Chestnut oak | 26 | 30.8 | 24 | 58.2 | ||
| Chinquapin oak | 12 | 100.0 | 1 | 100.0 | ||
| Coffee-tree | 11 | 18.1 | 8 | 12.5 | ||
| Ailanthus | 6 | 33.3 | 65 | 26.1 | 3 | 100.0 |
| Black oak | 5 | 40.0 | 7 | 16.6 | ||
| American ash | 21 | 100.0 | 3 | 33.3 | ||
| Paw paw | 12 | 61 | 27.8 | |||
| | | | | | |
In 1954 ten-foot wide strips were sampled on both sides of the fences. For both browsed and unbrowsed samples, the strips had a total length of 4000 feet, each representing an area of .919 acres. [Table 4] contrasts the number of young trees per acre on the browsed and unbrowsed areas, grouped in several size classes. In general the saplings up to one-fourth inch in diameter were those that had become established in the five growing seasons since browsing was discontinued and both areas were protected. For this size group the numbers were approximately equal, being slightly higher on the browsed strips. However, in the size group of ½ inch to 4 inches in stem diameter, the trees were nearly three times as abundant on the unbrowsed areas, and most trees within this size range must have become established within the time of differing treatments. The disparity in numbers was great for hackberry, redbud, elm and dogwood which made up the bulk of the saplings. In the size range 5 to 12 inches most trees antedated the fence, and the unbrowsed portion had only a few more than the portion that had been browsed.
On the formerly browsed areas clumps of gooseberry bushes were conspicuous and were computed to cover 3.81 per cent of the area sampled, versus 2.87 per cent on the unbrowsed area. These thorny bushes seem to be resistant to browsing, and elsewhere have been noted in abundance in woodlands heavily used by livestock. The elimination of competing undergrowth by browsers may be a factor favoring development of gooseberry clumps. The trend was just the opposite for fragrant sumac, which was computed to cover 1.94 per cent of the browsed sample versus 3.23 per cent of the unbrowsed sample. Greenbrier (Smilax tamnoides hispida) was most abundant on the unbrowsed strips, with seven large clumps, and 56 smaller clumps (10 stems or fewer) as contrasted with five large clumps and 32 smaller clumps on the browsed strips. There were 32 grapevines (Vitis vulpina) on the unbrowsed strips and only seven on those that were browsed.