Fig. 1.

a Bigleaf maple (Acer macrophyllum) litter (foreground) on the floor of a temperate, North American, Pacific Northwest forest. Indian plum (Oemleria cerasiformis) and sword fern (Polystichum munitum) grow up through the litter. These leaves may have fallen from the mature bigleaf maple tree (seen here as a moss-covered, large trunk on the left), but bigleaf maple litter is also found in stands with the dominant overstory tree, ectomycorrhizal Douglas fir (Pseudotsuga menziesii; dark horizontal branches of Douglas fir are shown just to the right of the bigleaf maple trunk). b Arbuscular mycorrhizal (AM) fungus-like spore with associated hyphae as well as other fungus hyphae in bigleaf maple litter. Leaf veins also are visible. Litter was cleared and stained with Trypan blue and then viewed with light microscopy at 400 × . c Nonmetric multidimensional ordination of predominant arbuscular mycorrhizal fungi amplified from leaf litter and adjacent soil samples. Fungal communities amplified from litter and soil were distinct from each other (p = 0.004, Table S4). SSU sequence data were resampled to 114 sequences/sample. Samples with fewer sequences were dropped from this analysis. Full dataset (pre-rarefaction) is available in Table S2