Correlation between soil development and native plant growth in forest restoration after surface mining

Recovery of soil conditions in ecosystems that have been modified by human activities can happen in time, but empirical data indicating how soil development influences plant growth are limited. Here, we studied the changes in 23 properties of jarrah-forest soils restored after bauxite mining (1.5, 7, 22 years post-restoration) and their correlative effects on the growth of bossiaea, a plant that grows in the jarrah-forest of Western Australia. We found that physico-chemical and biological properties of restored soils were different compared with properties of unmined soils, and were correlated with time post-restoration. In turn, biomass produced by bossiaea seedlings was correlated with time post-restoration. Differential correlative effects of restored soils properties translated into higher biomass produced by bossiaea in soils aged 22 years compared with biomass produced in younger soils and in unmined soils. Biomass variation of bossiaea seedlings grown in restored soils was matched to the physico-chemical and biological properties of the soils to detect correlative effects of individual soil properties on plant growth. We found that biomass produced by bossiaea seedlings was positively correlated with the number of bacterial-feeding nematodes in soils, a likely consequence of increased microbial biomass, and with the rate of CO2 produced by microbial respiration of phenolic compounds. Our data suggest recovery of physico-chemical and key biological properties of soil through restoration after bauxite mining, but overall, at 22 years soils were not recovered to reference conditions. Our study has implications for restoration projects aiming to promote soil development in addition to plant growth