Kessler Michael, Güdel Ramona, Salazar Laura, Homeier Jürgen, Kluge Jürgen
Institute of Systematic Botany, University of Zurich, Zollikerstrasse 107, 8008, Zurich, Switzerland,
Oecologia. 2014 Jul;175(3):887-900. doi: 10.1007/s00442-014-2941-7. Epub 2014 Apr 10.
Mycorrhizal fungi are crucial for the ecological success of land plants, providing their hosts with nutrients in exchange for organic C. However, not all plants are mycorrhizal, especially ferns, of which about one-third of the species lack this symbiosis. Because the mycorrhizal status is evolutionarily ancestral, this lack of mycorrhizae must have ecological advantages, but what these advantages are and how they affect the competitive ability of non-mycorrhizal plants under natural conditions is currently unknown. To address this uncertainty, we studied terrestrial fern assemblages and species abundances as well as their mycorrhization status, leaf nutrient concentration and relative annual growth along an elevational gradient in the Ecuadorian Andes (500-4,000 m). We surveyed the mycorrhizal status of 375 root samples belonging to 85 species, and found mycorrhizae in 89% of the samples. The degree of mycorrhization decreased with elevation but was unrelated to soil nutrients. Species with mycorrhizae were significantly more abundant than non-mycorrhizal species, but non-mycorrhizal species had significantly higher relative growth and concentrations of leaf N, P, Mg, and Ca. Our study thus shows that despite lower abundances, non-mycorrhizal fern species did not appear to be limited in their growth or nutrient supply relative to mycorrhizal ones. As a basis for future studies, we hypothesize that non-mycorrhizal fern species may be favoured in special microhabitats of the forest understory with high soil nutrient or water availability, or that the ecological benefit of mycorrhizae is not related to nutrient uptake but rather to, for example, pathogen resistance.
菌根真菌对于陆地植物在生态上的成功至关重要，它们为宿主提供养分以换取有机碳。然而，并非所有植物都有菌根，尤其是蕨类植物，约三分之一的蕨类物种缺乏这种共生关系。由于菌根状态在进化上是祖先状态，这种缺乏菌根的情况必然具有生态优势，但这些优势是什么以及它们如何在自然条件下影响非菌根植物的竞争能力目前尚不清楚。为了解决这种不确定性，我们沿着厄瓜多尔安第斯山脉（500 - 4000米）的海拔梯度研究了陆生蕨类植物组合、物种丰度以及它们的菌根状态、叶片养分浓度和相对年生长情况。我们调查了属于85个物种的375个根样本的菌根状态，发现89%的样本中有菌根。菌根化程度随海拔升高而降低，但与土壤养分无关。有菌根的物种比无菌根的物种明显更为丰富，但无菌根的物种具有明显更高的相对生长率以及叶片氮、磷、镁和钙的浓度。因此，我们的研究表明，尽管丰度较低，但相对于有菌根的蕨类物种，无菌根的蕨类物种在生长或养分供应方面似乎并未受到限制。作为未来研究的基础，我们推测无菌根的蕨类物种可能在森林林下土壤养分或水分供应充足的特殊微生境中更具优势，或者菌根的生态益处与养分吸收无关，而是与例如抗病性等有关。
