Table_3_Plant Genotype Influences Physicochemical Properties of Substrate as Well as Bacterial and Fungal Assemblages in the Rhizosphere of Balsam Poplar.PDF

Abandoned unrestored mines are an important environmental concern as they typically remain unvegetated for decades, exposing vast amounts of mine waste to erosion. Several factors limit the revegetation of these sites, including extreme abiotic and unfavorable biotic conditions. However, some pioneer tree species having high levels of genetic diversity, such as balsam poplar (Populus balsamifera), can naturally colonize these sites and initiate plant succession. This suggests that some tree genotypes are likely more suited for acclimation to the conditions of mine wastes. In this study, we selected two contrasting mine waste storage facilities (waste rock from a gold mine and tailings from a molybdenum mine) from the Abitibi region of Quebec (Canada), on which poplars were found to have grown naturally. First, we assessed in situ the impact of vegetation presence on each mine waste type. The presence of balsam poplars improved soil health locally by modifying the physicochemical properties (e.g., higher nutrient content and pH) of the mine wastes and causing an important shift in their bacterial and fungal community compositions, going from lithotrophic communities that dominate mine waste environments to heterotrophic communities involved in nutrient cycling. Next, in a greenhouse experiment we assessed the impact of plant genotype when grown in these mine wastes. Ten genotypes of P. balsamifera were collected locally, found growing either at the mine sites or in the surrounding natural forest. Tree growth was monitored over two growing seasons, after which the effects of genotype-by-environment interactions were assessed by measuring the physicochemical properties of the substrates and the changes in microbial community assembly. Although substrate type was identified as the main driver of rhizosphere microbiome diversity and community structure, a significant effect due to tree genotype was also detected, particularly for bacterial communities. Plant genotype also influenced aboveground tree growth and the physicochemical properties of the substrates. These results highlight the influence of balsam poplar genotype on the soil environment and the potential importance of tree genotype selection in the context of mine waste revegetation.

未修复的废弃矿山是一类重要的环境关切议题，这类场地往往数十年无法形成植被覆盖，致使大量矿山废弃物暴露于侵蚀作用之下。诸多因素制约了此类场地的植被恢复，其中包括极端非生物条件与不利的生物环境。然而，部分遗传多样性较高的先锋树种——例如香脂杨（balsam poplar，*Populus balsamifera*）——能够自然定植于此类场地并启动植物演替过程。这表明部分树木基因型或许更适配矿山废弃物的生长环境。本研究选取了加拿大魁北克省阿比蒂比地区两处特征迥异的矿山废弃物存储场地：一处为金矿废石，另一处为钼矿尾矿——经调查，这两处场地均自然生长有杨树。首先，我们针对两种矿山废弃物类型，原位评估了植被定植对其产生的影响。香脂杨的定植可通过改良矿山废弃物的理化性质（如提升养分含量与pH值）在局部改善土壤健康状况，并促使其细菌与真菌群落结构发生显著转变——从主导矿山废弃物环境的化能自养群落，转向参与养分循环的异养群落。其次，我们通过温室盆栽实验，评估了树木基因型在上述矿山废弃物中生长时的影响效应。我们于当地采集了10个香脂杨基因型的样本，这些样本分别采自矿山场地及其周边的天然林。我们对树木生长进行了两个生长季的监测，随后通过测定基质的理化性质与微生物群落组装的变化，评估了基因型与环境的交互作用效应。尽管基质类型被确定为根际微生物群落多样性与结构的主要驱动因子，但我们同样检测到树木基因型带来的显著影响，尤其在细菌群落层面。树木基因型同时对地上部分生长与基质的理化性质产生了调控作用。本研究结果凸显了香脂杨基因型对土壤环境的调控作用，以及在矿山废弃物植被恢复实践中筛选适宜树木基因型的潜在价值。