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Plant functional group influences arbuscular mycorrhizal fungal abundance and hyphal contribution to soil CO2 efflux in temperate grasslands

Gui, Weiyang, Ren, Haiyan, Liu, Nan, Zhang, Yingjun, Cobb, Adam B., Wilson, Gail W. T., Sun, Xiao, Hu, Jian, Xiao, Yan, Zhang, Fengge, Yang, Gaowen
Plant and soil 2018 v.432 no.1-2 pp. 157-170
C3 plants, C4 plants, aboveground biomass, botanical composition, carbon, carbon dioxide, ecosystems, field experimentation, forbs, grasses, grasslands, growing season, hyphae, mowing, mycorrhizal fungi, plant communities, roots, seasonal variation, soil, soil respiration, vesicular arbuscular mycorrhizae
BACKGROUND AND AIMS: Arbuscular mycorrhizal (AM) fungi are abundant in grassland ecosystem. We assessed AM hyphal contributions to soil CO₂ efflux across plant functional groups to better quantify AM fungal influences on soil carbon dynamics. METHODS: We conducted a field experiment using in-growth mesocosms to partition soil CO₂ efflux from roots, AM hyphae, and free-living soil microbes associated with C₃ grasses, C₄ grasses, forbs, and diverse plant communities from May to August in 2017. RESULTS: AM hyphae contributed <10% to total soil respiration in forb communities and diverse plant communities but accounted for as much as 32% in C₃ grasses. Plant functional groups differed in hyphal production efficiencies (the ratio of AM hyphal length to aboveground biomass), with the lowest in C₃ grasses (0.47 ± 0.15 m g⁻¹) and the greatest in forbs (3.27 ± 0.55 m g⁻¹). Mowing reduced hyphal production efficiency of C₄ grasses and forbs but did not affect total soil respiration. AM hyphal and microbial respiration peaked at the middle of the growing season, however there was no significant seasonal variation in root respiration. CONCLUSION: AM hyphal respiration is an important pathway of carbon flux from plants to atmosphere. Shifts in plant community composition can influence soil carbon processes by regulating hyphal production and respiration.