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.本研究针对安大略省东北部绕行湖矿（Detour Lake Mine）复垦田间试验内的早期演替植物群落组成展开评估，并与森林参考场地及历史复垦场地开展对比分析。本次复垦田间试验共设置8种改良剂处理组合，涵盖燕麦（作为冬季冻死型覆盖作物）、肥料、生物固体（biosolids）、泥炭及其复合处理方案。本研究的目标为：（1）探究土壤改良剂（soil amendments）对矿山剥离物（mine overburden）中植物功能群定植与生长的影响；（2）筛选可最优支撑植物群落定植与生长的改良剂属性，使构建的植物群落趋近基线参考场地。 目前，外来物种与优势木本植物群落的存在，是造成森林高地、低地参考场地与所有复垦场地之间差异的最主要变异来源。与外来物种类似，禾草类植物（graminoids）在森林高地参考场地中未被检出。禾草类植物群落的组成差异，可解释森林参考场地与所有复垦场地间的大部分变异。 肥料与泥炭的累积施用提升了各改良剂处理组中外来物种与禾草类植物的α多样性（alpha diversity），该两类植物功能群的α多样性均高于森林参考场地。在改良剂处理组中，养分处理组的外来物种与禾草类α多样性初始阶段更高，但至2019年，各改良剂处理组间的外来物种或禾草类α多样性已无显著差异。 研究结果表明，通过肥料或生物固体施用养分，可在复垦单元的第1年提升禾草类植物的α多样性与丰度。同时，研究证实历史复垦场地与改良剂处理组内的维管植物（vascular plant）群落组成，均与森林参考场地并不相似。改良剂处理场地内的植物群落可归类为早期演替群落，而历史复垦场地则以外来草本豆科植物占主导。 尽管如此，结果显示相较于泥炭基处理组，基于肥料与生物固体的处理组所形成的维管植物群落（不含木本物种）与森林参考场地更为相似。仍需开展进一步研究与长期监测，以明确哪种改良剂处理可最优支撑趋近森林参考场地的植物群落。此外，此类未来研究可考虑纳入受野火影响及采伐后的林分作为额外参考场地，以更好地捕捉严重扰动环境下可能的植物群落演替轨迹。