Analysis of Soil Microbial Diversity and Activities in Mining Reclaimed Lands in Northern Ontario (Canada): Association with Plant Population Structure.

The ability of an ecosystem to withstand serious disturbances may depend in part on the diversity of the system. There is evidence that soil biotic communities are 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 mining – damaged ecosystems in Northern Ontario; and 2) to assess the effects of soil liming on above and below ground biodiversity and community structures. Results from different analyses revealed that liming increases forest trees diversity and abundance and the overall ecosystem health even 25 to 35 years after dolomic 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 PLFA measures were extremely low suggesting that the targeted region is still under environmental stress. No associations among soil microbial biomass, soil respiration, and forest plant diversity or  abundance were observed. Soil pH and organic matter appear to be the main factors affecting these parameters. However, molecular analysis of main tree species within the targeted region revealed no change in genetic variation among plant populations from limed, unlimed lands contaminated with metals over two generations.