Plant Community Structure within a Reclamation Field Trial and Forested Reference Sites in a Post-Mine Environment

Early successional plant community assemblage within a reclamation field trial at the Detour Lake Mine in northeastern Ontario is assessed, and compared with reference forested and historically reclaimed sites. The reclamation field trial examines eight amendment treatment combinations that include treatments with a winter kill cover crop of oats, fertilizer, biosolids, peat, and combinations thereof. The objectives of this study are to: (1) Investigate how soil amendments influence plant functional group establishment and growth in mine overburden; and (2) Explore the amendment properties that best support the establishment and growth of a plant community that resembles the baseline reference sites. Currently, the presence of non-native species and a dominant woody plant community explains the largest proportion of variance between the forested upland and lowland reference sites and all reclaimed sites. Similar to non-native species, graminoids were absent from the upland forested reference sites. The difference in the graminoid community explains much of the variance between the forested reference sites and all reclaimed sites. The cumulative additions of fertilizer and peat increased alpha diversity of non-native and graminoid plants within the amendment treatments, which had greater alpha diversity of these plant functional groups than the forested reference sites. Within the amendment treatments, non-native and graminoid alpha diversity was initially greater in the nutrient treatments, but by 2019 there was no significant difference in non-native or graminoid alpha diversity between amendment treatments. The results indicate that applications of nutrients through fertilizer or biosolids may increase graminoid alpha diversity and abundance within reclamation units in year 1. The results also confirm that the vascular plant community composition present within the historically reclaimed sites and amendment treatments does not resemble the forested reference sites. The plant community present within the amendment treatment sites is best described as early successional, with the presence of non-native herbaceous legumes dominating the historically reclaimed sites. Despite this, the results indicate that fertilizer and biosolids-based treatments have developed a vascular plant community, excluding woody species that is more similar to the forested reference sites than the peat-based treatments. Further research and long-term monitoring are needed to determine which amendment treatment will best support a plant community that resembles the forested reference sites. In addition, future studies of this nature might consider including wildfire affected and post-harvested forest stands as additional reference sites, to better capture possible plant community trajectories of a severely disturbed environment.