Forest Road Revegetation: Effects of Seeding and Soil Amendments

Ecological Restoration, Vol. 21, No. 3, 2003 ISSN 1522-4740 E-ISSN 1543-4079 ©2003 by the Board of Regents of the University of Wisconsin System. Roads are a prevalent component of forested landscapes throughout the United States, and their effects on forested ecosystems are numerous. Roads are known to cause habitat loss and fragmentation, which can directly alter plant and animal species composition (Andrews 1990, Auerbach and others 1997). They also affect natural disturbance regimes and hydrology with wideranging impacts on ecosystem functioning (Hobbs and Huenneke 1992, Swift and Burns 1999). About 435,000 miles (700,350 km) of road dissect U.S. Forest Service lands (USDA Forest Service 1999). New Forest Service road management policy attempts to reverse the adverse ecological impacts associated with roads on national forest lands by decommissioning unneeded forest roads and restoring their ecological processes (USDA Forest Service 2001). Natural recovery of roads is often impaired by highly compacted soils (Knapp 1992, Kamaruzaman 1996), so some form of rehabilitation is necessary to restore ecological processes. Although general information exists on the benefits of various road rehabilitation options (Cotts and others 1991, Luce 1997, Bagley 1998, Walker and Powell 1999), regionally specific information may be needed for effective results. No studies have been conducted in the ponderosa pine (Pinus ponderosa) forests of northern Arizona that address the effectiveness of road rehabilitation practices. Efforts to rehabilitate roads in the region range from simply blocking road entrances to ripping and seeding. This latter activity requires the use of bulldozers that drag rock rippers or subsoilers through the soil in order to reduce soil compaction, increase soil moisture, and improve seedbed conditions by breaking up soil clods and increasing the amount of pore space between them (Miles and Froehlich 1988, Cotts and others 1991). Seeding after ripping takes advantage of the decompacted soil and may facilitate natural regeneration by reducing surface erosion and improving soil structure (Swift and Burns 1999). Rapidly establishing and maintaining native plant communities on decommissioned forest roads is vital because until adequate plant cover is established, ripping alone provides only temporary and marginal improvements in soil structure (Luce 1997). Vegetative cover on roads can improve soil structure by increasing soil organic matter (Greacen and Sands 1980), reducing erosion (Swift 1984, 1986), and restoring the habitat lost from road construction. Successful revegetation may also help to keep roads closed by reducing their visibility. This is particularly important in the ponderosa pine forests of northern Arizona where the relatively open forest structure and moderate terrain makes it difficult to keep roads closed to vehicle use. Studies in other regions have found that the addition of soil amendments, specifically topsoil (Cotts and others 1991, Claassen and Zasoski 1993, Holmes 2001) Forest Road Revegetation: Effects of Seeding and Soil Amendments