Vegetation Control with Nonchemical Methods

Some weeds lend themselves reasonably well to removal without chemicals. Alder more than 2 inches in diameter can be killed fairly well by cutting at the ground line from mid-June to mid-August. Smaller stems are more likely to sprout at any time. Fungi complement the cutting to help kill stumps if done in summer. Alders cut at other times are likely to sprout vigorously. Most other western Oregon and Washington hardwoods sprout if cut at any time; chemical treatment improves results.

Grazing intensively This method can, in some circumstances, remove palatable herbs and certain brush species (not scotch broom, however). Great care is required when grazing among conifers to keep animals out of plantations when trees are actively growing. Grazing is among the most difficult methods of control because weed removal must be relatively complete to provide significant benefits, and this degree of control is difficult to achieve without animal damage to trees. However, intensive pasturing of a cut-over hardwood stand for the two years immediately after logging will remove or reduce vigor of many of the sprouting brush species and may help simplify the weeding job to herb removal only. However, herbs may recover too quickly for this procedure to do the whole job of site preparation.

The need to reduce cover to very low levels means the livestock will not gain weight well in programs such as this. If they are not grazed to this intensity, some supplemental weeding will be necessary, either with paper mulch or herbicides.

Paper mulch This method has had success comparable to that of grass herbicides. In southwestern Oregon, and near the state's Willamette Valley, mulch paper should be at least 9 sq ft (3 ft x 3 ft). On coastal areas and in western Washington, 4 sq ft (2 ft x 2 ft) should be adequate. Mulch paper should be fiber-reinforced, laminated Kraft paper with an asphalt core for adequate durability. Mulch paper must be well weighted on all four corners, or pinned to the ground. Clear plastic will not work. Black plastic will work and is lightweight but difficult to handle.

Mechanical tillage Using heavy equipment to till forest soil has limited value on cutover land because of stumps, logs, and other obstacles. Recent trials of large subsoil or ripping equipment have shown promise on compacted soil and clay soils with restricted drainage, leading to easier planting and better root development. The procedure is not a truly effective weed control measure, however, and usually should be preceded or followed by an herbicide application to postpone weed development. If vegetation is controlled in spring before summer tillage, less horsepower/energy is required for the tillage. In a sense, this is a practical "greener" approach to tillage. Mechanical tillage is still energy-intensive.

In some circumstances, scarification with a bulldozer is feasible. Use toothed or conventional blades to remove brush on gentle topography. Do this when soil is very dry to minimize damage. Combining partial scarification with chemicals often offers the advantages of both procedures. In any event, keep soil compaction to a minimum. The operator should anticipate that scarification may set up a seedbed for an entirely new weed problem that can compromise results. Follow-up weed control is often needed. Burn or scatter piles of brush to improve plantability and reduce animal damage.