ABSTRACT
The potential increased development of extraradical hyphae in arbuscular mycorrhizal associations results in more fungal biomass for faunal consumption. For example, Lundquist et al. (1999) reported that the incorporation of fresh rye shoots into soil increased that number of bacterial and fungal-feeding nematodes, but that the FDA-active (live) fungal hyphal length did not increase significantly. There is thus probably a balance between a system being able to produce fungal biomass and the rate at which it is consumed by organisms in the next trophic level. The amount of overall accretion of soil carbon therefore is a balance between what carbon enters and is retained in a “slow” turnover pool and that which enters a “fast” turnover pool. Klironomos and Kendrick (1996), Klironomos and Ursic (1998), and Klironomos et al. (1999), however, have evidence to suggest that these fungi are less favored food sources for soil fauna than saprotrophic fungi. As a number of these fungi produce the glycoprotein glomalin (Wright and Upadhyaya, 1996), Treseder and Allen (2000) calculate that glomalin could
account for 30-60% of the carbon in undisturbed soils. An increase in the glomalin content of grassland soils under long-term exposure to elevated CO2 (Rillig et al., 2000) suggests a secondary function of carbon storage in the increased development of soil stability due to aggregate formation. This carbon is somewhat protected in soil aggregates and could be regarded as a potential long-term carbon sink.
