Contributions of ectomycorrhizal fungal mats to forest soil respiration

[摘要] Distinct aggregations of fungal hyphae and rhizomorphs, or "mats", formedby some genera of ectomycorrhizal (EcM) fungi are common features of soilsin coniferous forests of the Pacific Northwest. We measured in siturespirationrates of Piloderma mats and neighboring non-mat soils in an old-growth Douglas-firforest in western Oregon to investigate whether there was higher respirationfrom mats, and to estimate mat contributions to total soil respiration. Wefound that areas where Piloderma mats colonized the organic horizon often had highersoil surface flux than non-mats, with the relative increase in respirationaveraging 16% across two growing seasons. Both soil physical factors andbiochemistry were related to the higher surface flux of mat soils. When soilmoisture was high, soil CO₂ production was concentrated intonear-surface soil horizons where mats tend to colonize, resulting in greaterapparent differences in respiration between mat and non-mat soils.Respiration rates were also correlated with the activity of chitin-degradingsoil enzymes. This finding supports the notion that the abundance of fungalbiomass in EcM mats is an important driver of C and N cycling. We foundPiloderma mats present across 57% of the exposed soil, and use this value toestimate a respiratory contribution from mats at the stand-scale of about9% of total soil respiration. The activity of EcM mats, which includesboth EcM fungi and microbial associates, appeared to constitute asubstantial portion of total soil respiration in this old-growth Douglas-firforest.

[学科分类] 地球化学与岩石