SAND DUNES AND MISCELLANEOUS 89 



small twigs and buds. In the Kaibab National Forest in Arizona and 

 in portions of Pennsylvania deer have done so much harm to the forest 

 that permission has been granted to shoot does or to reduce the deer 

 herds. Beavers do considerable damage by girdling or felling trees, 

 chiefly the poplar and aspen groups. They may destroy an entire 

 stand adjacent to their dams by raising the water level and flooding 

 timbered areas. This has occurred in parts of the Rocky Mountains 

 and in the Adirondacks in New York. 



Porcupines gnaw and girdle the bark of standing trees, particularly 

 in lodgepole pine in the Northern Rocky Mountains and in the Lake 

 States. Rabbits eat buds and small branches and even the bark of 

 some species. In England, rabbit hunts are frequently conducted prior 

 to the reforestation of many areas. Squirrels eat seeds and fruits, 

 as well as young shoots and buds. Pike, in 1934, reported that squir- 

 rels girdled the main stems of ponderosa pine trees at 10 to 20 feet 

 from the tops of trees, 4 to 7 inches in d.b.h. Mice have eaten con- 

 siderable quantities of seed, particularly those stored in nursery ware- 

 houses. They also gnaw and destroy the bark of seedlings and young 

 trees. Birds have caused relatively little damage. In fact, they con- 

 tribute very helpfully by destroying large quantities of insect enemies. 

 Birds also aid in the dissemination of seeds, particularly on burned 

 areas, and on old fields in the South and East. 



12. SAND DUNES AND MISCELLANEOUS 



Sand dunes have done considerable damage, particularly along the 

 Pacific, Atlantic, and Gulf Coasts, in several sections of the Rocky 

 Mountains, notably in Colorado, as well as along the shores of the 

 Great Lakes and in other sections. France has expended millions of 

 dollars for the fixation of sand dunes and prevention of shifting sands, 

 notably in the Landes region of southwestern France, where a veritable 

 desert waste was converted into a profitable forest and a prosperous 

 settled section. 



Erosion has come to be considered a national problem. Both sheet 

 and gully erosion have inflicted enormous damage in many parts of 

 the country. This subject is briefly described in connection with the 

 work of the Soil Conservation Service. Avalanches, landslides, and 

 floods have been very destructive in restricted localities. Forest. fires 

 have added to the injuries inflicted by these phenomena. Extreme cold, 

 especially sudden drops in temperature, has caused frost cracks in 

 many sections in the northern part of the country. These are long 

 splits in the stems of trees resulting from the rapid contraction of the 



