214 



TIMBER RESOURCES FOR AMERICA'S FUTURE 



In many parts of the country, liimber com- 

 panies are now gearing their operations to salvag- 

 ing insect-killed timber. Added access roads are 

 needed to make this large amount of salvable 

 timber more readUy available and in some cases 

 added mill capacity is necessary. 



THE IMPACT OF ANIMAL DAMAGE 

 ON TIMBER GROWTH 



Many kinds of wildlife, as well as domestic 

 cattle, sheep, and hogs, damage timber. The com- 

 bined effect of these animals and birds can be the 

 limiting factor in successful regeneration of some 

 timber stands. In almost all cases where impor- 

 tant damage to timber was caused by animals, 

 such damage was the result of excessively dense 

 populations. 



The total growth impact of animal damage on 

 commercial forest land in 1952 is estimated at 

 1,009 million cubic feet of growing stock, including 

 2,722 million board-feet of sawtimber (table 113). 

 This damage constitutes 9 percent of the total 

 impact to growing stock, and 6 percent of the im- 

 pact to S9wtimber. Only a little is direct tree 

 mortality, 93 percent being due to unsatisfactory 

 reproduction and inhibited growth (fig. 72). 

 About 86 percent of the animal impact on growing 

 stock and 90 percent of the impact on sawtimber 

 occurred in the North (table 114). 



Map^ Kinds of Animals Impede 

 Growth and Regeneration 



The nature of damage by animals varies in 

 different parts of the country. In the Southwest, 

 the loss of forest values caused by the grazing of 

 domestic animals, partially from browsing of 

 seedlings but primarily from site deterioration on 

 overgrazed lands, is a serious problem in some 

 localities. Browsing by livestock is common in 

 many parts of the South. Such damage also 

 occurs through the use of farm woodlots bj^ dairy 

 cattle, particularly in the North. Livestock in 

 some areas have not only injured and destroyed 

 many young trees by browsing and trampling, but 

 excessive use has accelerated erosion, resulting in 

 lowered site qualitj^ through loss of soil, increased 

 soil temperatures, and more rapid losses of soil 

 moisture. 



In the South, hogs have prevented thousands of 

 acres from restocking naturally to longleaf pine. 

 Hogs eat the roots of seedlings, destroying both 

 planted and natural stock. 



Big-game damage is caused primarily by deer, 

 but in a few limited areas, principally in the 

 West, elk and moose have seriously damaged 

 aspen reproduction and conifers through excessive 

 browsing. Forest damage by deer occurs prin- 

 cipally in the Lake States, the Middle and North 



Atlantic States, and in the Rocky Mountains. 

 It is ordinarily greatest in the North during the 

 winter, when snow confines deer herds to small 

 areas, but in areas with excessively high deer 

 populations, summer range has also been affected. 



Deer sometimes interfere mth the establish- 

 ment of forest reproduction by browsing the 

 terminal shoots and side branches. Continued 

 heavj^ browsing can result in deterioration of 

 timber stands through the elimination of the more 

 palatable species and dominance of species that 

 are less palatable. An example is the transition 

 from maple and ash to blue beech, ironw'ood, and 

 beech in man}^ areas in the Middle Atlantic States. 

 Less common is the damage caused by big-game 

 animals through bark peeling and antler rubbing. 



In the Olympic Peninsula of western Washing- 

 ton, in western Oregon, and in California, bears 

 damage or kill young timber during spring and 

 early summer hj stripping bark and eating the 

 succulent cambium layer. It has been estimated 

 that one California lumber company has recently 

 been suffering bear damage of 700 to 900 board- 

 feet per acre per year over 53,000 acres. Damage 

 tends to be concentrated in small areas and is 

 serious only in second-grow'th stands. 



Rabbits damage commercial forest stands mainlj^ 

 in the Lake States, New^ England, and in the 

 Pacific Northw^est. Thej^ clip shoots and nip off 

 or girdle the main stems of reproduction, thus 

 retarding stand establishment and causing forked 

 stems and bushy trees. Where rabbits are numer- 

 ous they are a serious threat to the success of 

 Douglas-fir and pine plantations in the Pacific 

 Northwest and in California. 



Porcupine damage occurs mainly in the West 

 and the North, and mostlj- in the \vinter, when 

 porcupines feed on the inner bark and cambium 

 layer of young pines and northern hardwoods. 

 The}^ girdle small trees near the ground, but on 

 larger trees they feed in the upper portion of the 

 bole. The principal damage consists of partial 

 or complete girdling of the trunk and branches. 

 Some saplings and poles are killed outright. 

 Often growth is reduced and manj" trees are de- 

 formed or weakened and made susceptible to 

 insects and disease. 



Tliroughout their range, beavers kill trees for 

 food and build dams that flood stands. The 

 damage, how'ever, is usually limited to small areas 

 and is not an important factor in timber manage- 

 ment. 



Forest tree seeds, particularly of conifers, are 

 important food for manj" small mammals and 

 birds, and the impact on establishment of tree 

 reproduction can be severe. The most widespread 

 and important seed-eating mammals are the 

 white-footed mice, tree squirrels, and chipmunks, 

 but there are many others. Many species of 

 birds also feed on tree seeds. Tree squirrels are 

 particularly heavy consumers of coniferous seeds 



