Are your seedlings being buried?

Certain sites are difficult to regenerate after clear cutting or wildfire. Heat anddrought are well recognized as limiting factors on many such areas, but another factoraffecting regeneration—gravitational movement of soil and debris on slopes--is seldomconsidered. Removal of vegetative cover can greatly accelerate soil sloughing on steepsites, and planted or -natural seedlings may be covered or uprooted.
Although downslope movement of soil material and other debris such as rocks, litter,and slash is not as obvious as the gullies and alluvial deposits caused by surface runoff,it may be much more widespread.- It occurs during all seasons but is most intense in thesummer as dry grivel and in the fall as debris moved by frost heaving and heavy rains.In some areas deer have also accelerated this type of erosion by trampling warm southslopes during the spring.
The extent of the problem is not known. However, gravitational movement of soiland debris appears to occur most commonly on steep south slopes (fig. 1) where a dense vegetative cover may have held the soil in a position greater than its natural angle ofrepose. When the vegetative cover is removed and the soil surface is disturbed, move-ment begins. This sequence of events has been observed on the west side of the CascadeRange and in the Coast Ranges of Oregon.
A study of planted 2-0 and 3-0 Douglas-fir seedlings on a south-exposed, 50-percentslope showed 3-0 stock survived better, primarily because its larger size made it morecapable of resisting sloughing.1 As observed in that study, ". . . 23 percent of the 2-0 and8 percent of the 3-0 trees were lost by the end of the first growing season because ofsurface movement--soil, rock particles, litter, and rotten wood either covered or up-rooted them." A later planting of incense-cedar and ponderosa and sugar pines in thesame vicinity suffered heavy damage from debris movement between November, whenthe trees were planted, and bud bursting time in May. Almost two-thirds of the treeswere partially or completely covered (fig. 2).
Some measures can be taken to avoid excessive damage to planted trees from soiland debris movement. Planting spots should be chosen carefully to include the flattestmicrosites such as occur above stumps and uprooted trees. Trees should be plantednear the outside edges of benches or scalped spots in areas subject to sloughing; treesplanted on the inside of benches are especially vulnerable to covering. Trees could beplanted beneath stumps, well-anchored rocks, or other objects which would help divertmoving debris from the tree. Large stock appears to be superior to small stock in resist-ing debris.
Studies of slope, aspect, and soil are needed where gravitational movement is amajor problem. Special methods of treatment are necessary to insure a new stand onareas where debris movement is a hazard to regeneration: Some possibilities include:(a) temporary cover to stabilize the soil, (b) preparatory measures such as furrowing,(c) fertilization to increase early growth of planted trees, and (d) leaving slash unburnedon steep, unstable slopes.