Effect of Neutralizing Treatments Using a Waste-lime and Oyster Mix on the Growth of Pinus densiflora Seedlings and Herbaceous Vegetation in the Acid Soil of an Abandoned Metal Mine

The objective of this study was to select a proper mixing ratio of soil neutralizer (waste-lime and oyster mix) by assessing treatment effect on the root collar diameter (RCD) growth of Pinus densiflora seedlings, the inflow of herbaceous vegetation from the forest edge, and soil characteristics in the acid soil of abandoned metal mines to increase carbon uptake. The mixing ratios of the soil neutralizer were 0.6%, 1.0%, 1.2%, and 1.6% in comparison with the soil weight. All soil neutralizer treatments promoted RCD growth and survival of P. densiflora seedlings and the inflow of herbaceous vegetation from the forest edge. In addition, soil pH was improved by the soil neutralizer treatment. Treatment with 1.6% soil neutralizer resulted in increased RCD growth of P. densiflora seedlings, total population of herbaceous plants from around the forest, TOC, and total N. In this study, the mixing ratio showed a positive correlation with RCD growth and survival of P. densiflora seedlings, the inflow of herbaceous vegetation, soil pH, and TOC. The results of this study indicated that treatment with soil neutralizer at a ratio of 1.6% is applicable for rehabilitation in this abandoned metal mine considering the growth of P. densiflora seedlings and herbaceous vegetation, soil chemical characteristics, and economic feasibility. However, it is necessary to conduct field experiments to select a proper mixing ratio of soil neutralizers to apply in other abandoned metal mines.