Plants establishing in environments that are marginal for growth could be particularly sensitive to mycorrhizal associations. We investigated ectomycorrhizal colonization and its significance for young conifers growing at, or above, their normal limits for growth, in the alpine-treeline ecotone. * Colonization of seedlings (<1 yr old) and juveniles (2- to 10-yr-old) of Picea engelmannii and Abies lasiocarpa by Cenococcum geophilum was determined in a field study, and effects of Cenococcum on Picea seedling ecophysiology were investigated in a glasshouse. * Colonization by Cenococcum was c. 20-fold greater for juveniles than seedlings, and approximately 4-fold greater adjacent compared with approximately 7 m away from trees. Juveniles of Picea were more colonized at timberline than Abies, and the opposite relationship was observed in forest. Colonization enhanced seedling water potential, but not phosphorus concentrations or photosynthesis. * These landscape and age-dependent variations in colonization correspond well with known variations in conifer physiology and establishment near timberline. Facilitation of seedling establishment by older trees at alpine-treeline may include a below-ground, mycorrhizal component that complements previously reported effects of trees on the microclimate and ecophysiology of seedlings.
摘要
在生长条件处于边缘状态的环境中定植的植物可能对菌根共生关系特别敏感。我们研究了外生菌根的定殖情况及其对生长在高山树线交错带、处于或高于其正常生长极限的针叶树幼苗的意义。* 在一项田间研究中测定了土生空团菌对恩氏云杉和大果冷杉1年生以下幼苗以及2至10年生幼树的定殖情况，并在温室中研究了土生空团菌对云杉幼苗生理生态学的影响。* 土生空团菌对幼树的定殖率比幼苗高约20倍，在距离树木约1米处比距离约7米处高约4倍。云杉幼树在树线处的定殖率高于冷杉，而在森林中观察到的情况则相反。定殖提高了幼苗的水势，但对磷浓度或光合作用没有影响。* 这些定殖情况在景观和年龄上的差异与树线附近针叶树生理和定植的已知差异非常吻合。高山树线处 older trees 对幼苗定植的促进作用可能包括一个地下菌根成分，它补充了先前报道的树木对幼苗小气候和生理生态学的影响。
