Coal mining involves removing and dumping large quantities of waste material (overburden) that often contain high concentrations of heavy metals, low nutrients, and low pH. Innumerable acres and sites throughout Appalachia contain now-abandoned overburden with legacy effects of acidic drainage and materials to adjacent streams and groundwater, depauperate soils and vegetation, and subsequent decline in biodiversity. Furthermore, the sites appear desolate and bleak in the landscape due to the exposed, rocky, gray overburden. Since most of these abandoned sites are grandfathered prior to the Surface Mining Control and Reclamation Act (SMCRA) of 1977, as amended, stabilization, vegetation, and reclamation are not required, despite their significant environmental impacts. The goal of this project is to identify low-cost, effective means of using vegetation to stabilize abandoned coal mine overburden. In this study, we investigated the first-year (July) growth and physiological responses of a combination of plants [little bluestem (Schizachyrium scoparium), annual ryegrass (Lolium rigidum), strip mine seed mix, and lavender (Lavandula angustifolia and L. grosso)] with inexpensive amendments (lime, straw, mycorrhizal fungi, all, or none) in a fully replicated, multifactorial experimental planting on overburden. In addition to measuring plant height and density, we also measured chlorophyll content, fluorescence, and photosynthetic light response.
Results/Conclusions
Amendments had a significant (p=0.011) effect on the tallest plant height, with significantly (p<0.05) taller plants in the combination and lime treatments than in the straw treatment; the largest positive effect was for the legume partridge pea (Chamaecrista fasciculata; p=0.008). However, amendments have not yet affected plant density (p=0.266), with no significant (p>0.477) pairwise differences. While mean chlorophyll content (336 mg m-2) was similar across plant species (p=0.24), amendments had a significant (p=0.002) effect, with lime and mycorrhizae contributing to significantly higher chlorophyll content and straw reducing chlorophyll content below the effect of the control treatment. Yet light-acclimated variable chlorophyll fluorescence (Fv’/Fm’) was not significantly affected by amendment type (p=0.082). Respiration rate (Rd, p=0.704), light compensation point (LCP, p=0.942), and light-saturated net photosynthesis rate (Asat, p=0.484) were not affected by amendment; although not significant, these rates were consistently highest in plots that contained mycorrhizae and lowest in the straw plots. Although no choice of plant treatments appeared best, lime and mycorrhizae consistently improved plant growth, chlorophyll content, and metabolic function, while straw inhibited plant success. Pretreatment with lime and mycorrhizae could improve colonization, and thus stabilization, of barren abandoned coal mine overburden throughout Appalachia.