Relieving soil compaction to reclaim Appalachian forests
July 29, 2014
What happens to the soil in a strip-mined coal site after all the coal is gone? Due to processes put in place in the 1970’s, what were wooded hillsides before mining have become open grass fields or brush land. The Appalachian coal states are pockmarked with hundreds of thousands of old mine sites. Rarely do the sites return to their original forested state.
Starting in the 1970’s, the conventional clean up practice was to replace the dislodged soil and rock using very large and heavy dump trucks. The next step was to thoroughly smooth out the area, making several passes with a bulldozer. Then the site was planted with fast growing, competitive grasses. The use of heavy equipment packed the soil in an unnatural way. The end result was heavily compacted soil and ecological stalemate.
Soil is a dynamic structure that contains soil particles and billions of soil microbes—living creatures that don’t respond well to compaction and lack of oxygen. Soil compaction damages soil structure, making it almost impossible for native plant roots to access nutrients and water.
The typical shrubby grasslands of a conventionally reclaimed mining site don’t evolve the way a native forest does. The non-native grasses outcompete sapling trees, so the trees can’t grow. These areas fragment Appalachian hardwood forests and have inferior habitats for wildlife. They don’t provide high quality ecosystem services like watershed protection and carbon storage as well as a mature forest can.
In the last few decades, a coalition of groups under the Appalachian Regional Reforestation Initiative (ARRI) have pushed to change the status quo of mine reclamation. They promote the Forestry Reclamation Approach (FRA). The FRA is a method for restoring sites to their original forestland as they are mined. The basic tenant of the FRA? Do not compact the soil.
“You have to know and care about soils when restoring ecosystems,” says Mary Beth Adams. Adams is a research soil scientist with the USDA Forest Service in West Virginia. There are countless “legacy” mine sites, or sites that were mined decades ago, that have been sitting in a state of limbo. In order to restore these areas, the soil needs some breathing room. Adams studies how to heal soils in order to regenerate native forests.
“Healthy forests require healthy soils,” she says, “What you want is a soil that provides moisture, aeration, and a reasonable level of acidity. When a soil is really compacted it doesn’t hold water well. The first step to reforesting these areas is to relieve the compaction by ripping the soil.”
Soil ripping is almost as violent as mining itself. “It’s like plowing but much deeper,” says Adams, “Often sites have very large boulders. You can feel the ground shake”. The goal is to loosen the soil so that it allows roots to flourish. Then, native species like red spruce are planted in the furrows. “It’s a success story when the trees survive. Once established, they can then improve the quality of the soil,” says Adams. In a healthy forest, nutrients are cycled back into the soil through plant decay and litter.
The timeframe for re-establishing a native forest varies and depends on the type of trees planted. Mixed hardwoods take less time to develop than the high elevation trees, like red spruce. “For a fully functional forest it could take several decades,” says Adams, “But we haven’t been doing this long enough to know how to define ‘fully restored.’ There are a lot of natural processes to consider, including the right soil conditions.”
In the last four years, 97 legacy mine sites in all seven Appalachian coal states were reclaimed using the Forestry Reclamation Approach. “It takes partnerships to make reforestation happen,” says Adams. “It’s not inexpensive and it’s not always obvious where the funding will come from.” Encouraging reforestation as a post-mining land use requires cooperation from a host of people, including regulators, landowners and mine operators. “The [newer] Forestry Reclamation Approach is all based on research in the last 25 to 30 years,” says Adams “The conventional reclamation practices have been the standard since the 1970’s.” FRA represents a new, best management practice for mine land reforestation.
To Adams and groups like ARRI, the million-plus acres of compacted soil present an opportunity. “Forest reclamation takes a given situation and creates something from it. There are some incredible potentials for these sites,” she says, “They needn't just be brushy fields.” Reclaiming them back to their original states will provide habitat for wildlife, and improve the soil’s ability to do all the things it naturally does: provide a place for plants to grow, clean water, store carbon, and many other ecosystem services.