With more than 850,000 kilometers of road on federal land and many of these roads classified as surplus to management, the United States Forest Service identifies road decommissioning as a key strategy for the protection and restoration of critical ecological services provided by the National Forest system. After a rain-on-snow event resulted in road associated landslides across the on the Clearwater National Forest (CNF) in Northern Idaho, CNF and their partner, the Nez Perce Tribe (NPT) began a road removal program. Now in the 10th year of work, CNF and NPT have removed over 966 km of roads through a prescription of recontour. As the program evolves into a holistic restoration program, questions have emerged about the benefits of different road treatments especially whether an abandoned, but re-vegetated, road (passive) provides similar ecohydrologic functions as a removed road (active recontour). Specific questions include: 1) How do plant functional groups change over a restoration age gradient? 2) What are the effects of different road treatments (passive versus active) on infiltration rates over time? 3) What ecosystem properties and processes explain these differences? Road recontour involves complete removal of the road prism and incorporates organic layer material from adjacent unroaded slopes; because of this we expected the recontoured roads to have ecohydrologic characteristics closer to unroaded areas. In summer 2008, we established 20, 150-m linear transects on recontoured roads forming a restoration age gradient (Yr 1 to Yr 10), 5 transects on abandoned roads, and 6 transects in never roaded areas. We collected plant functional group data every meter, measured infiltration rates every 5 meters, and collected soil samples at depth from 5 soil pits per transect. We characterized soil physical properties and measured soil organic matter (SOM), total carbon (TC) and total nitrogen (TN).
Results/Conclusions Infiltration rates on recontoured roads increase with restoration age and, while variable, are on average greater than on abandoned roads. In addition, rooting depth was limited to the upper 10 cm on abandoned roads, whereas rooting depth on recontoured roads and never-roaded areas were below the limits of excavation. Finally, results show substantial differences in distribution of soil organic matter (SOM) across road treatment types, with SOM nearly two times greater on recontoured roads than on abandoned, revegetated roads. Limitation on rooting depth and difference in SOM suggest that the compaction from road building and traffic still exists after 50 years of passive restoration.
