Hewitt Rebecca E, Chapin F Stuart, Hollingsworth Teresa N, Taylor D Lee
Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK, USA.
USDA Forest Service, Pacific Northwest Research Station, Boreal Ecology Cooperative Research Unit, Fairbanks, AK, USA.
Mol Ecol. 2017 Jul;26(14):3826-3838. doi: 10.1111/mec.14143. Epub 2017 May 18.
Root-associated fungi, particularly ectomycorrhizal fungi (EMF), are critical symbionts of all boreal tree species. Although climatically driven increases in wildfire frequency and extent have been hypothesized to increase vegetation transitions from tundra to boreal forest, fire reduces mycorrhizal inoculum. Therefore, changes in mycobiont inoculum may potentially limit tree-seedling establishment beyond current treeline. We investigated whether ectomycorrhizal shrubs that resprout after fire support similar fungal taxa to those that associate with tree seedlings that establish naturally after fire. We then assessed whether mycobiont identity correlates with the biomass or nutrient status of these tree seedlings. The majority of fungal taxa observed on shrub and seedling root systems were EMF, with some dark septate endophytes and ericoid mycorrhizal taxa. Seedlings and adjacent shrubs associated with similar arrays of fungal taxa, and there were strong correlations between the structure of seedling and shrub fungal communities. These results show that resprouting postfire shrubs support fungal taxa compatible with tree seedlings that establish after wildfire. Shrub taxon, distance to the nearest shrub and fire severity influenced the similarity between seedling and shrub fungal communities. Fungal composition was correlated with both foliar C:N ratio and seedling biomass and was one of the strongest explanatory variables predicting seedling biomass. While correlative, these results suggest that mycobionts are important to nutrient acquisition and biomass accrual of naturally establishing tree seedlings at treeline and that mycobiont taxa shared by resprouting postfire vegetation may be a significant source of inoculum for tree-seedling establishment beyond current treeline.
与根系相关的真菌，尤其是外生菌根真菌（EMF），是所有北方树种的关键共生体。尽管据推测，气候驱动导致的野火频率和范围增加会促使植被从苔原向北方森林转变，但火灾会减少菌根接种体。因此，菌根共生体接种体的变化可能会限制当前树线以外树木幼苗的建立。我们调查了火灾后重新萌发生长的外生菌根灌木所支持的真菌类群是否与火灾后自然生长的树木幼苗所关联的真菌类群相似。然后，我们评估了共生菌根的身份是否与这些树木幼苗的生物量或营养状况相关。在灌木和幼苗根系上观察到的大多数真菌类群是外生菌根真菌，还有一些深色有隔内生真菌和石楠类菌根真菌类群。幼苗和相邻灌木与相似的真菌类群阵列相关联，并且幼苗和灌木真菌群落的结构之间存在很强的相关性。这些结果表明，火灾后重新萌发生长的灌木支持与野火后生长的树木幼苗相容的真菌类群。灌木类群、到最近灌木的距离和火灾严重程度影响了幼苗和灌木真菌群落之间的相似性。真菌组成与叶片碳氮比和幼苗生物量均相关，并且是预测幼苗生物量的最强解释变量之一。虽然这些结果是相关性的，但它们表明，共生菌根对于树线处自然生长的树木幼苗的养分获取和生物量积累很重要，并且火灾后重新萌发生长的植被所共有的共生菌根类群可能是当前树线以外树木幼苗建立的重要接种体来源。
