to extramatrical mycelium depending on fungal taxa, nutrient availability, and the age of the associated mycorrhizas. Much of the carbon allocated to extramatrical mycelium accumulates as fungal biomass, making up an estimated one-third of the total microbial biomass and one-half of the total dissolved organic carbon in some forest soils. Carbon also supports the production of sporocarps and sclerotia, with various taxa investing differentially in these structures rather than in the proliferation of extramatrical mycelium. Carbon acquisition also goes toward the production of fungal exudates. Extramatrical hyphae excrete a range of compounds into the soil matrix, accounting for as much as 40% of total carbon usage. These exudates are released primarily at the growing front, and are used in functions such as mineralization and homeostasis. Many researchers have attempted projections of the role that extramatrical mycelium may play in carbon sequestration. Although estimates of the life span of individual ectomycorrhizas very considerably, turnover is generally considered on a scale of months. After death, the presence ectomycorrhizas on root tips, may increase the rate of root decomposition for some fungal taxa. Besides host plant death and mycorrhizal turnover, rates of carbon sequestration may also be affected by disturbances in the soil, which cause sections of the extramatrical mycelium to become severed from the host plant. Such disturbances, such as those caused by animal disruption, mycophagous invertebrates or habitat destruction, may have a notable impact on turnover rates. These variables make it difficult to estimate the turnover rates of mycorrhizal biomass in forest soils and the relative contribution of extramatrical mycelium to carbon sequestration. Mycelial networks The presence of long-distance extramatrical hyphae may affect forest health via the formation of common mycelial networks, in which hyphal connections form between plant hosts and can facilitate the transfer of carbon and nutrients between hosts. Mycelial networks may also be responsible for facilitating the transport of allelopathic chemicals from the supplying plant directly to the rhizosphere of other plants. Ectomycorrhizal fungi increase primary production in host plants, with multi trophic effects. In this way, extramatrical mycelium is important to the maintenance of soil food webs, supplying a significant nutritive source to invertebrates and microorganisms. Mineral access Enzyme production The enzymatic activities of ectomycorrhizal fungi are highly variable between species. These differences are correlated with exploration type (particularly the presence or absence of rhizomorphs) rather than lineage or host association- suggesting that similar morphologies of extraradical