Abstract
Although restoration ecology has developed rapidly as a scientific discipline, there are still considerable gaps in integrating above-and belowground linkages between plants and their associated soil microbial communities into restoration efforts. However, understanding these linkages may assist in improving restoration success. The aim of this study was to assess how post-mining soil stockpile age affects plant biomass and soil microbial activity, particularly plant root symbionts such as rhizobia and arbuscular mycorrhizal fungi (AMF). We grew a legume species Acacia saligna (Fabaceae) in 1, 2, 3, 5 and 10 year old stockpile soils collected from a sand mine near Perth, Western Australia under controlled glasshouse conditions. We assessed whether plant biomass, specific root length (SRL) and root diameter (D) decrease with stockpile age. Furthermore, we investigated how stockpile age affected the distribution and the number of effective nodules, nodule biomass and AMF colonization in roots. Results revealed that plant biomass was the lowest and SRL was the highest in plants grown in oldest soils. Soil age had a negligible effect on rhizobial abundance. Colonization of AMF significantly increased with stockpile age suggesting that AMF spores and hyphae are present in old stockpiles. Thus, plants were not constrained by the absence of rhizobial and AMF propagules in old soils. However, our results revealed that plants grown in oldest soils were overall smallest but invested most into producing long and thin roots that had highest AMF colonization rates suggesting that these plants were plausibly struggling for growth in oldest stockpiles.