Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2010
Publication Date: 5/1/2011
Publication URL: http://handle.nal.usda.gov/10113/53938
Citation: Wick, A.F., Merrill, S.D., Toy, T.J., Liebig, M.A. 2011. Effect of soil depth and topographic position on plant productivity and community development on 28-year old reclaimed mine lands. Journal of Soil and Water Conservation. 66(3):201-211. Interpretive Summary: Determination of adequate topsoil replacement depths following surface mining has been an ongoing issue in reclamation research. Several short-term studies were initiated using soil wedge designs in the 1970's and 1980's to make recommendations to mining companies for soil replacement depths; however, assessment of these recommendations for long-term sustainability has become an important topic within the last decade. This study was undertaken in 2003 to understand plant-soil dynamics after 28 years of vegetation establishment on various replaced soil depths. The ultimate goal was to determine if original recommendations should be altered to address long-term sustainability. Results obtained in this study were compared directly to previous results from a 1979 study conducted at this location. Plots originally seeded to aggressive cool season species showed lower diversity after 28 years than plots seeded to less aggressive species such as alfalfa or Russian wildrye. There was also a weaker dependence of plant productivity on soil depth/topographic position and a slight shift to higher production values on deeper soil depths across all subsoil types in 2003 compared to 1979. This is attributed to the following: (a) changes to plant communities from the originally seeded monocultures utilizing surface soil water early in the growing season to more diverse communities which require soil water later in the season and deeper in the profile, and (b) depth of soil development increased with returned subsoil depth, supporting the shift of increased plant productivity with soil depth in 2003. In summary, replaced soil depths should be determined based on soil stabilization and initial establishment of diverse, sustainable plant communities to reduce invasion of undesirable plant species.
Technical Abstract: Reclamation research has shifted from short- to long-term assessment of mine land reclamation management strategies, wherein previously established study sites are revisited. In this study, we assessed long-term (28 yr) relations among re-established plant communities (production and diversity), replaced soil depth following mining (0.2 to 1.4 m), and slope position (5% north slope, 2% south) for three different subsoil types (A, B, C; characterized by 43%, 23%, and 14% clay, respectively) on a previously established soil wedge experiment in North Dakota. Non-native seeded species such as crested wheatgrass (Agropyron cristatum) and smooth brome (Bromus inermus) had nearly 50% persistence after 28 yr, while less aggressive seeded species, such as Russian wildrye (Psathyrostachys juncea) and alfalfa (Medicago sativa), were more susceptible to invasion by other species leading to greater plant community diversity (H’ = 1.348, 1.717, respectively). The most significant plant productivity response to soil depth/topographic position was observed on subsoil C on the south facing 2% slope (R2 = 0.43; P = 0.03). The two soil parameters measured in this study (electrical conductivity and pH) indicated mine soil profile development through time for both slope position and subsoil type. Specific relations observed in this long-term study were more difficult to identify compared to earlier short-term studies conducted on this site, providing strong evidence that replaced soil depths should be determined based on soil stabilization and initial establishment of diverse, sustainable plant communities to reduce invasion of undesirable plant species.