Hillslope Runoff and Soil Erosion Following Reforestation in the Copper Basin, Tennessee, USA



The landscape of the 130 km2 Copper Basin, in the southeastern USA, became extremely degraded during more than a century of logging, mining, acidification, grazing, and fire. In the twentieth century, the Copper Basin became the focus of a series of reforestation programs and is now largely tree-covered again. To investigate the effects of over 50 years of reforestation efforts, we developed a space-for-time substitution and conducted rainfall simulation experiments in ‘forest’ patches of various ages, at sites remaining unvegetated, and at forested reference sites outside the basin. At 59 sites, we monitored surface runoff and sediment detachment rates during 30-minute rainfall simulation experiments; and at 54 of those sites, we determined soil organic matter content. Then, we measured litter and observed soils at 25 of the sites, and measured soil respiration at a site in each age zone. The results demonstrate that soil erosion by sediment detachment decreases within a decade following reforestation. Recently reforested sites have soils with significantly less organic matter and have higher runoff rates than forests more than 50 years old. The long-term persistence of low infiltration rates suggests that, at sites where the A and B soil horizons and the biological health of the soil have been lost, restoration of the hydrologic function of a landscape by reforestation may require centuries.