Can graminoids used for mine tailings revegetation improve substrate structure?

Abstract

The seeding of agronomic graminoid species that are tolerant to the compacted and low aeration conditions associated with mine tailings allows for rapid cover of mine waste, which in turn controls erosion. These graminoids can be used as primer-species on mine tailings to improve the rooting of other plant species, which may not tolerate soil compaction and low aeration. Tailings colonization by graminoid roots could improve ecological filters such as low air-filled porosity and elevated bulk density. The effect of above- and below-ground development of graminoid species used for hay-field seeding on the macroporosity and density of gold mine tailings was studied under controlled conditions as well as in situ. All of the graminoid species tested improved the macroporosity of the tailings after only 2 months of growth under greenhouse conditions, but had no effect on the density of the tailings. The perennial Bromus inermis Leyss. was most efficient in improving the macroporosity of tailings, having greater root diameter, biomass, and volume. The annual Avena sativa L. also produced high root biomass and length, which improved the macroporosity of the tailings. However, under field conditions, graminoids had low cover and no effect on macroporosity, which highlights that their growth should be improved to make them usefull as primer-plants.