Nagati Mélissande, Roy Mélanie, Desrochers Annie, Manzi Sophie, Bergeron Yves, Gardes Monique
UQAT-UQAM Industrial Chair in Sustainable Forest Management, Forest Research Institute, University of Québec in Abitibi-Témiscamingue, Rouyn-Noranda, QC, Canada.
UMR5174, Laboratory Evolution and Biological Diversity, Centre National de la Recherche Scientifique - IRD, Université Paul Sabatier, Toulouse, France.
Front Plant Sci. 2019 Jul 18;10:932. doi: 10.3389/fpls.2019.00932. eCollection 2019.
Succession is generally well described above-ground in the boreal forest, and several studies have demonstrated the role of interspecific facilitation in tree species establishment. However, the role of mycorrhizal communities for tree establishment and interspecific facilitation, has been little explored. At the ecotone between the mixed boreal forest, dominated by balsam fir and hardwood species, and the boreal forest, dominated by black spruce, several stands of trembling aspen can be found, surrounded by black spruce forest. Regeneration of balsam fir seems to have increased in the recent decades within the boreal forest, and it seems better adapted to grow in trembling aspen stands than in black spruce stands, even when located in similar abiotic conditions. As black spruce stands are also covered by ericaceous shrubs, we investigated if differences in soil fungal communities and ericaceous shrubs abundance could explain the differences observed in balsam fir growth and nutrition. We conducted a study centered on individual saplings to link growth and foliar nutrient concentrations to local vegetation cover, mycorrhization rate, and mycorrhizal communities associated with balsam fir roots. We found that foliar nutrient concentrations and ramification indices (colonization by mycorrhiza per length of root) were greater in trembling aspen stands and were positively correlated to apical and lateral growth of balsam fir saplings. In black spruce stands, the presence of ericaceous shrubs near balsam fir saplings affected ectomycorrhizal communities associated with tree roots which in turn negatively correlated with N foliar concentrations. Our results reveal that fungal communities observed under aspen are drivers of balsam fir early growth and nutrition in boreal forest stands and may facilitate ecotone migration in a context of climate change.
北方森林地上部分的演替通常已有充分描述，多项研究表明种间促进作用在树木物种建立过程中发挥的作用。然而，菌根群落对树木建立和种间促进作用的影响却鲜有探索。在以香脂冷杉和硬木树种为主的北方混交林与以黑云杉为主的北方森林的交错带，可以发现几处山杨幼林，周围环绕着黑云杉林。近几十年来，北方森林内香脂冷杉的更新似乎有所增加，而且即使处于相似的非生物条件下，它似乎在山杨林中比在黑云杉林中更适合生长。由于黑云杉林也被石南科灌木覆盖，我们研究了土壤真菌群落和石南科灌木丰度的差异是否能够解释在香脂冷杉生长和营养方面观察到的差异。我们开展了一项以单个幼树为中心的研究，将生长和叶片养分浓度与当地植被覆盖、菌根侵染率以及与香脂冷杉根系相关的菌根群落联系起来。我们发现，山杨林中叶片养分浓度和分枝指数（每根长度的菌根侵染率）更高，并且与香脂冷杉幼树的顶端和侧向生长呈正相关。在黑云杉林中，香脂冷杉幼树附近石南科灌木的存在影响了与树根相关的外生菌根群落，进而与叶片氮浓度呈负相关。我们的研究结果表明，在山杨林下观察到的真菌群落是北方森林中香脂冷杉早期生长和营养的驱动因素，并且在气候变化背景下可能促进交错带的迁移。
