Variations in glomalin-related soil protein in Vicia faba rhizosphere depending upon interactions among mycorrhization, daytime and/or nighttime elevated CO2 levels

Relationships between glomalin-related soil protein (GRSP) and soil organic carbon, total nitrogen or enzyme activity are unknown under the combined effects of varying daytime/nighttime elevated CO2 (eCO(2)) levels and arbuscular mycorrhizal fungi (AMF). We demonstrated that daytime, nighttime, and dual daytime/nighttime eCO(2) levels could significantly increase AMF mycorrhization, soil organic carbon, total nitrogen, easily extractable, difficultly extractable and total GRSP in AMF soil. Under daytime eCO(2), soil total nitrogen was significantly decreased in non-AMF soil, while mycorrhization alleviated soil nitrogen limitation. Nighttime and dual daytime/nighttime eCO(2) significantly increased beta-glucosidase and protease activities in AMF and non-AMF soils. With greater eCO(2) effects in AMF than in non-AMF soils, GRSPs positively related to mycorrhization, soil organic carbon, total nitrogen, and beta-glucosidase activity. Under the circumstance of global CO2 rising, besides mycorrhization, the combined effects of varying, non-steady-state daytime and nighttime eCO(2), play important