Assessing Biological Impacts of Land Reclamation in a Mining Region in Canada: Effects of Dolomitic Lime Applications on Forest Ecosystems and Microbial Phospholipid Fatty Acid Signatures

Abstract

The ability of an ecosystem to withstand serious disturbances may depend in part on the diversity of the system, with soil microbiological communities being coupled to their associated vegetation. The main objectives of the present study were (1) to determine the association between soil microbial diversity, abundance, and activities with diversity and sustainability of remediated mining-damaged ecosystems in Northern Ontario, and (2) to assess the effects of dolomitic lime applications on aboveground and belowground biodiversity and community structures. Results revealed that liming increases soil pH, cation exchange capacity (CEC), forest tree species diversity and abundance, and the overall ecosystem health even 25 to 35 years after dolomite applications. The mean Shannon index value was significantly higher in limed compared to unlimed sites. Tree species richness was 4.0, 6.0, and 7.7 for unlimed, limed, and reference sites, respectively. Overall, the mean health index revealed a significant improvement in population health in limed sites (index score = 7) compared to unlimed areas (index score = 4). Soil microbial biomass and respiration were also increased by liming. Surprisingly, the main component of soil microbial biomass in limed, unlimed, and reference sites within the vicinity of the restored lands was bacteria (mostly Gram (−). Significant difference was also observed between limed, unlimed, and reference sites for arbuscular mycorrhizal fungi, Gram (−) bacteria, Gram (+) bacteria, anaerobe, and actinomycetes abundance. The ratios between fungi and bacteria and among other phospholipid fatty acid (PLFA) measures were extremely low suggesting that the targeted region is still under environmental stress. No apparent associations among soil microbial biomass, soil respiration, and forest plant diversity or abundance were observed. Soil pH levels and organic matter amounts and quality appear to be the main factors affecting these parameters. Molecular analysis of main tree species within the impacted region revealed no change in genetic variation among plant populations on either limed or unlimed lands contaminated with metals over two generations.