RESEARCH ARTICLE Soil moisture dynamics and restoration of self-sustaining native vegetation ecosystem on an open-cut coal mine Michael R. Ngugi 1,2 , Victor J. Neldner 1 , David Doley 3 , Brano Kusy 4 , Darren Moore 4 , Christian Richter 4 Post-mining landscape reconstruction on open-cut coal mines aims to support restoration of self-sustaining native vegetation ecosystems that in perpetuity require no extra inputs relative to unmined analogs. Little is known about the soil moisture retention capacity of the limited layer of topsoil replaced (often <30 cm deep), impacts of deep ripping of the profle, and the combined impacts of these on plant available water during the mine restoration process. We examined changes in soil moisture parameters (soil water potential, , and soil water content, ) daily using automated soil sensors installed at 30 and 45 – 65 cm depths on mine restoration sites aged between 3 and 22 years and on adjacent remnant vegetation sites following heavy rainfall events at Meandu mine, southeast Queensland, Australia. Consistent patterns in soil moisture attributes were observed among rehabilitated sites with generally marked differences from remnant sites. Remnant site soil profles had generally higher  after drying than rehabilitated sites and maintained high  for extended periods after rain events. There was a relatively rapid decline of  on reconstructed soil profles compared with remnant sites although the times of decline onset varied. This response indicated that vegetation restoration sites released soil moisture more rapidly than remnant sites but the rate of drying decreased with increasing rehabilitation age and increased with increasing tree stem density. The rapid drying of mine rehabilitated sites may threaten the survival of some remnant forest species, limit tree growth, and delay restoration of self-sustaining native ecosystem. Key words: macropore drainage, mine rehabilitation, mine revegetation, novel ecosystems, vegetation restoration Implications for Practice • Our results suggest that the thin layer of replaced topsoil overlying deep overburden with limited organic carbon content on reconstructed sites explains low water retention and rapid drying of soil profle. Restoration objectives should ensure that soil depth is suitable for the targeted ecosystem. • Replacement of 20 – 30 cm of topsoil followed by deep rip- ping to 70–80 cm depth prior to seeding exposes coarse overburden material and facilitates greater water loss through deep drainage. To avoid this, the depth of ripping should be reduced to less than the depth of the applied soil layer. • Pre-mining soil stripping should stockpile and replace all topsoil and subsoil separately to maximize plant available water, nutrients, and organic matter on the reconstructed soil profles. Introduction Surface mineral extraction is a short-term land use activity with the potential to cause severe long-term land degradation. As a consequence, rehabilitation of mined land in Australia and in many other nations is now a legislative requirement (Holl 2002; Commonwealth of Australia 2006). Under the Queensland Environmental Protection Act 1994 (Qld Govern- ment 2015), the goal of this rehabilitation process is either to restore an ecosystem similar in structure and function to the pre-existing ecosystem or a self-sustaining native ecosystem similar to unmined land use adjacent a mine site (Chambers et al. 1994; Ward 2000; Bell 2001; Commonwealth of Australia 2006; Doley et al. 2012; Audet et al. 2013a; Doley & Audet 2013; DEHP 2014). The natural process of soil development takes many thou- sands of years, producing soil horizons of varying character- istics that support unique vegetation types (Bradshaw 1997; Mckenzie et al. 2004; Quideau et al. 2013). This soil profle Author contributions: CR, JN, DM, MN conceived and designed the research; DM installed sensors; BK summarized sensor data; MN, DD analyzed the data; MN, JN, DD wrote frst draft; DD, MN, JN, CR, DM, BK edited the manuscript. 1 Department of Science, Information Technology and Innovation, Queensland Herbar- ium, Mt Coot-tha Road, Toowong, Qld 4066, Australia 2 Address correspondence to M. R. Ngugi, email michael.ngugi@dsitia.qld.gov.au 3 Centre for Mined Land Rehabilitation, Sustainable Minerals Institute, The University of Queensland, Brisbane, Qld 4072, Australia 4 Digital Productivity and Services Flagship, CSIRO, QCAT, 1 Technology Ct, Pullen- vale, Qld 4069, Australia © 2015 Society for Ecological Restoration doi: 10.1111/rec.12221 Supporting information at: http://onlinelibrary.wiley.com/doi/10.1111/rec.12221/suppinfo September 2015 Restoration Ecology Vol. 23, No. 5, pp. 615–624 615