Corrales Adriana, Mangan Scott A, Turner Benjamin L, Dalling James W
Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana-Champaign, IL, 61801, USA.
Department of Biology, Washington University in St. Louis, St. Louis, MO, 63130, USA.
Ecol Lett. 2016 Apr;19(4):383-92. doi: 10.1111/ele.12570. Epub 2016 Feb 1.
Tropical forests are renowned for their high diversity, yet in many sites a single tree species accounts for the majority of the individuals in a stand. An explanation for these monodominant forests remains elusive, but may be linked to mycorrhizal symbioses. We tested three hypotheses by which ectomycorrhizas might facilitate the dominance of the tree, Oreomunnea mexicana, in montane tropical forest in Panama. We tested whether access to ectomycorrhizal networks improved growth and survival of seedlings, evaluated whether ectomycorrhizal fungi promote seedling growth via positive plant-soil feedback, and measured whether Oreomunnea reduced inorganic nitrogen availability. We found no evidence that Oreomunnea benefits from ectomycorrhizal networks or plant-soil feedback. However, we found three-fold higher soil nitrate and ammonium concentrations outside than inside Oreomunnea-dominated forest and a correlation between soil nitrate and Oreomunnea abundance in plots. Ectomycorrhizal effects on nitrogen cycling might therefore provide an explanation for the monodominance of ectomycorrhizal tree species worldwide.
热带森林以其高度的生物多样性而闻名，但在许多地方，单一树种在一片林分中占个体的大多数。对于这些单优势种森林的解释仍然难以捉摸，但可能与菌根共生有关。我们测试了外生菌根促进巴拿马山地热带森林中墨西哥奥瑞木（Oreomunnea mexicana）树木占优势的三种假说。我们测试了接入外生菌根网络是否能改善幼苗的生长和存活，评估了外生菌根真菌是否通过积极的植物-土壤反馈促进幼苗生长，并测量了奥瑞木是否降低了无机氮的有效性。我们没有发现证据表明奥瑞木从外生菌根网络或植物-土壤反馈中受益。然而，我们发现奥瑞木占优势的森林外部土壤硝酸盐和铵浓度比内部高三倍，并且在样地中土壤硝酸盐与奥瑞木丰度之间存在相关性。因此，外生菌根对氮循环的影响可能为全球外生菌根树种的单优势现象提供一种解释。
