Stefani Franck, Beguin Julien, Paré David, Morency Marie-Josée, Martineau Christine, Fortin J André, Thiffault Nelson, Séguin Armand
Agriculture and Agri-Food Canada, Ottawa Research and Development Centre, Ottawa, ON, Canada.
Institut de recherche sur les forêts, Université du Québec en Abitibi-Témiscamingue, Rouyn-Noranda, QC, Canada.
Front Plant Sci. 2023 May 3;14:1122445. doi: 10.3389/fpls.2023.1122445. eCollection 2023.
Reforestation of degraded lands in the boreal forest is challenging and depends on the direction and strength of the plant-soil feedback (PSF).
Using a gradient in tree productivity (null, low and high) from a long-term, spatially replicated reforestation experiment of borrow pits in the boreal forest, we investigated the interplay between microbial communities and soil and tree nutrient stocks and concentrations in relation to a positive PSF induced by wood mulch amendment.
Three levels of mulch amendment underlie the observed gradient in tree productivity, and plots that had been amended with a continuous layer of mulch 17 years earlier showed a positive PSF with trees up to 6 m tall, a closed canopy, and a developing humus layer. The average taxonomic and functional composition of the bacterial and fungal communities differed markedly betweenlow- and high-productivity plots. Trees in high-productivity plots recruited a specialized soil microbiome that was more efficient at nutrient mobilization and acquisition. These plots showed increases in carbon (C), calcium (Ca), nitrogen (N), potassium (K), and phosphorus (P) stocks and as well as bacterial and fungal biomass. The soil microbiome was dominated by taxa from the fungal genus Cortinarius and the bacterial family Chitinophagaceae, and a complex microbial network with higher connectivity and more keystone species supported tree productivity in reforested plots compared to unproductive plots.
Therefore, mulching of plots resulted in a microbially mediated PSF that enhances mineral weathering and non-symbiotic N fixation, and in turn helps transform unproductive plots into productive plots to ensure rapid restoration of the forest ecosystem in a harsh boreal environment.
北方森林退化土地的重新造林具有挑战性，且取决于植物 - 土壤反馈（PSF）的方向和强度。
利用北方森林中借土坑长期空间重复造林实验中树木生产力的梯度（无、低和高），我们研究了微生物群落与土壤以及树木养分储量和浓度之间的相互作用，这些与木质覆盖物改良诱导的正向PSF相关。
三个水平的覆盖物改良构成了观察到的树木生产力梯度的基础，17年前用连续一层覆盖物改良的地块显示出正向PSF，树木高达6米，树冠封闭，腐殖质层正在形成。低生产力和高生产力地块之间细菌和真菌群落的平均分类和功能组成存在显著差异。高生产力地块中的树木招募了一个专门的土壤微生物群，其在养分动员和获取方面更有效。这些地块的碳（C）、钙（Ca）、氮（N）、钾（K）和磷（P）储量以及细菌和真菌生物量都有所增加。土壤微生物群以真菌属丝膜菌属和细菌科几丁质ophagaceae的分类群为主，与非生产性地块相比，具有更高连通性和更多关键物种的复杂微生物网络支持了造林地块的树木生产力。
因此，地块覆盖导致了微生物介导的PSF，增强了矿物风化和非共生固氮，进而有助于将非生产性地块转变为生产性地块，以确保在恶劣的北方环境中森林生态系统的快速恢复。
