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.

本研究对安大略省东北部迂回湖矿（Detour Lake Mine）的复垦田间试验内的早期演替植物群落组成开展评估，并与参考林地及历史复垦场地进行对比。该复垦田间试验共设置8种改良剂组合处理，涵盖燕麦冬季覆盖作物、肥料、生物固体、泥炭及其复合施用方案。本研究的目标为：（1）探究土壤改良剂对矿山排土场中植物功能群建植与生长的影响机制；（2）筛选可最佳支撑与基线参考场地相似植物群落建植与生长的改良剂属性。

目前，非本土物种与优势木本植物群落的存在，是造成高地林地、低地参考林地与所有复垦场地间群落差异的最主要变量来源。与非本土物种类似，禾本科植物（graminoids）在高地林地参考场地中未出现；禾本科植物群落的差异，亦是导致林地参考场地与所有复垦场地间群落差异的核心因素。

改良剂处理组中，肥料与泥炭的累积施用提升了非本土植物与禾本科植物的α多样性（alpha diversity），且该两类植物功能群的α多样性显著高于林地参考场地。在改良剂处理组内，养分施用处理组的非本土植物与禾本科植物α多样性初始更高，但至2019年，不同改良剂处理组间的非本土植物或禾本科植物α多样性已无显著差异。

研究结果表明，在复垦单元中，通过肥料或生物固体施加养分可在第1年提升禾本科植物的α多样性与个体多度。本研究同时证实，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，均与林地参考场地存在显著差异。改良剂处理场地内的植物群落可被归类为早期演替群落，而历史复垦场地则以非本土草本豆科植物占绝对优势。

尽管如此，结果显示，相较于泥炭基改良处理，以肥料与生物固体为基础的改良处理所形成的维管植物群落（排除木本物种），与林地参考场地的群落组成更为相似。

仍需开展进一步研究与长期监测，以确定哪种改良剂处理能够最佳支撑与林地参考场地相似的植物群落。此外，此类未来研究可考虑将受野火影响与采伐后的林分作为额外参考场地，以更好地捕捉严重干扰环境下植物群落的潜在演替轨迹。