Soil reconstruction after mining fails to restore soil function in an Australian arid woodland

Abstract

The biogeochemical properties of soils drive ecosystem function and vegetation dynamics, and hence soil restoration after mining should aim to reinstate the soil properties and hydrological dynamics of remnant ecosystems. The aim of this study is to assess soil structure in two vegetation types in an arid ecosystem, and to understand how these soil properties compare to a reconstructed soil profile after mining. In an arid ecosystem in southeast Australia, soil samples were collected at five depths (to 105 cm) from remnant woodland and shrubland sites, and sites either disturbed or totally reconstructed after mining. We assessed soil physico-chemical properties and microbial activity. Soils in the remnant arid ecosystem had coarse-textured topsoils that overlay clay horizons, which allows water to infiltrate and avoid evaporation, but also slows drainage to deeper horizons. Conversely, reconstructed soils had high sand content at subsoil horizons and high bulk density and compaction at surface layers (0-20 cm). Reconstructed soils had topsoils with higher pH and electrical conductivity. The reconstructed soils did not show increased microbial activity with time since restoration. Overall, the reconstructed soil horizons were not organized in a way that allowed rainfall infiltration and water storage, as is imperative to arid-zone ecosystem function. Future restoration efforts in arid ecosystems should focus on increasing sand content of soils near the surface, to reduce evaporative water loss and improve soil quality and plant health.

Restoration ecophysiology: an ecophysiological approach to improve restoration strategies and outcomes in severely disturbed landscapes

“…Following mine closure, entire soil profiles may be reconstructed using topsoil, subsoil, and waste materials. These substrates may be dramatically different in structure and function compared to natural systems (Bradshaw 1997; Duncan et al 2020). Altered soil properties may cause significant declines in plant performance, including low nutrient availability (Cross et al 2019), reduced soil biological activity (Birnbaum et al 2017), soil contamination by heavy metals (Bradshaw 1997), compaction (Rokich et al 2001), and altered hydrology (Enright & Lamont 1992).…”

Stockpiling disrupts the biological integrity of topsoil for ecological restoration

“…This is likely due to a loss of soil structure and compaction during stripping and stockpiling, which could impede water infiltration and root penetration (Rokich et al 2001;Strohmayer 1999). It is possible this change in bulk density could impact plant growth, and soil compaction is indeed a challenge for plant (Duncan et al 2020;Koch 2007;Rokich et al 2001). However, it is unlikely that this effect is fully responsible for observed differences in our experiment given that soils were all sieved prior to potting (further disturbing soil structure), plants were continuously well-watered, and we observed no evidence that root penetration was impeded in any of the pots.…”

Biocrust Amendments to Topsoils Facilitate Biocrust Restoration in a Post-mining Arid Environment

“…A strong driver of the focus on rehabilitating biocrust is the generally low success rate of dryland restoration ( Ravi et al, 2010 ; Cortina et al, 2011 ). Restoration efforts have tended to focus primarily on putting vascular plants back into ecosystems ( Sheoran et al, 2010 ; Vallejo et al, 2012 ), overlooking the role that biocrusts play in soil function and structure, and the hydrological function of soils ( Duncan et al, 2020 ). The current study aims to test the use of biocrust slurry inoculation and the use of psyllium for improving the reestablishment of biocrusts after mining in an arid landscape in southwest New South Wales, Australia.…”