Abstract
Abstract. Surface coal mining in the eastern USA disturbs hundreds of hectares of land every year and removes valuable and ecologically diverse eastern deciduous forests. Reclamation involves restoring the landscape to approximate original contour, replacing the topsoil, and revegetating the site with trees and herbaceous species to a designated post-mining land use. Re-establishing an ecosystem of ecological and economic value as well as restoring soil quality on disturbed sites are the goals of land reclamation, and microbial properties of mine soils can be indicators of restoration success. Reforestation plots were constructed in 2007 using weathered brown sandstone or unweathered gray sandstone as topsoil substitutes to evaluate tree growth and soil properties at Arch Coal's Birch River mine in West Virginia, USA. All plots were planted with 12 hardwood tree species and subplots were hydroseeded with a herbaceous seed mix and fertilizer. After 6 years, the average tree volume index was nearly 10 times greater for trees grown in brown (3853 cm3) compared to gray mine soils (407 cm3). Average pH of brown mine soils increased from 4.7 to 5.0, while gray mine soils declined from 7.9 to 7.0. Hydroseeding doubled tree volume index and ground cover on both mine soils. Hydroseeding doubled microbial biomass carbon (MBC) on brown mine soils (8.7 vs. 17.5 mg kg−1), but showed no effect on gray mine soils (13.3 vs. 12.8 mg kg−1). Hydroseeding also increased the ratio of MBC to soil organic C in both soils and more than tripled the ratio for potentially mineralizable nitrogen (PMN) to total N. Brown mine soils were a better growth medium than gray mine soils and hydroseeding was an important component of reclamation due to improved biochemical properties and microbial activity in mine soils.
Highlights
Surface mining in the eastern USA disturbs hundreds of hectares of land by removing ecologically diverse eastern deciduous forests, resulting in the disruption and degradation of underlying soil resources
Detailed annual results of tree survival and growth on the site have been previously reported (Wilson-Kokes et al, 2013b). These data showed that after six growing seasons (2007–2012), tree survival was significantly higher in brown mine soil treatments compared to gray mine soils www.soil-journal.net/1/621/2015/
Average tree volume index was significantly higher for trees grown in brown mine soils compared to gray mine soils after 6 years and hydroseed treatment doubled the tree volume index on both mine soils (Table 3)
Summary
Surface mining in the eastern USA disturbs hundreds of hectares of land by removing ecologically diverse eastern deciduous forests, resulting in the disruption and degradation of underlying soil resources. The brown sandstone substitute materials have a pH from 4.5 to 5.5 compared to the gray sandstone materials with a pH of 7.5 to 8.0 (Wilson-Kokes et al, 2013a, b) These low pH conditions in brown mine soil are more conducive to tree growth, while the higher pH of gray mine soils is better for many seeded grasses (Zipper et al, 2013). Both mine soils tend to contain high levels of rock fragments, which translates into poor water-holding capacity and poor nutrient relations in these topsoil substitutes (Haering et al, 2004). The temporal dynamics of the physical, chemical, and biochemical properties of topsoil substitutes following reclamation are not sufficiently understood
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