Evidence that saprotrophic fungi mobilise carbon and mycorrhizal fungi mobilise nitrogen during litter decomposition

With improvements in molecular techniques, identification of taxa in mycorrhizal ecology has expanded from fruitbodies to mycorrhizal roots to extraradical hyphae (Anderson & Cairney, 2004). These molecular techniques are, in general, equally applicable to saprotrophic fungi, although this important functional group has received relatively little focus in community studies (Allmer et al., 2006). Only a few studies have examined the spatial patterns of ectomycorrhizal fungi in soil profiles, and no studies have examined similar patterns for saprotrophic fungi. In this issue of New Phytologist (pp. 611–620), Lindahl et al. reported on the spatial patterns of ectomycorrhizal and saprotrophic fungi from soil profiles in a Pinus sylvestris forest in Sweden, and compared those patterns with patterns of bulk carbon:nitrogen ratios, 15N content and radiocarbon (as a proxy for age). As expected, each of these parameters increased with depth in soil profiles. The authors also reported a striking separation of the ectomycorrhizal and the saprotrophic communities, with the surface litter layer strongly dominated by saprotrophic fungi and the deeper horizons strongly dominated by ectomycorrhizal fungi. This physical separation implies that these fungal types also play separate roles in the carbon and nitrogen cycles by exploiting discrete pools of litter