Abstract
We examined the response of mycorrhizal fungi to free-air CO2 enrichment (FACE) and nitrogen (N) fertilization in a warm temperate forest to better understand potential influences over plant nutrient uptake and soil carbon (C) storage. In particular, we hypothesized that mycorrhizal fungi and glomalin would become more prevalent under elevated CO2 but decrease under N fertilization. In addition, we predicted that N fertilization would mitigate any positive effects of elevated CO2 on mycorrhizal abundance. Overall, we observed a 14% increase in ectomycorrhizal (ECM) root colonization under CO2 enrichment, which implies that elevated CO2 results in greater C investments in these fungi. Arbuscular mycorrhizal (AM) hyphal length and glomalin stocks did not respond substantially to CO2 enrichment, and effects of CO2 on AM root colonization varied by date. Nitrogen effects on AM fungi were not consistent with our hypothesis, as we found an increase in AM colonization under N fertilization. Lastly, neither glomalin concentrations nor ECM colonization responded significantly to N fertilization or to an N-by-CO2 interaction. A longer duration of N fertilization may be required to detect effects on these parameters.
Highlights
Humans are augmenting concentrations of CO2 in the atmosphere by burning fossil fuels, clearing forests, and converting land to intensive agricultural systems (Schimel et al 1995)
We examined the dynamics of ECM fungi and arbuscular mycorrhizal (AM) fungi in soils of a loblolly pine plantation exposed to free-air CO2 enrichment and N fertilization
We found that the proportion of root length colonized by ECM fungi increased in response to elevated CO2
Summary
Humans are augmenting concentrations of CO2 in the atmosphere by burning fossil fuels, clearing forests, and converting land to intensive agricultural systems (Schimel et al 1995). Atmospheric enrichment of CO2 tends to enhance net primary production (NPP) and biomass of land plants (DeLucia et al 1999; Wang 2007) which could lead to sequestration of anthropogenic C emissions in terrestrial pools (van Veen et al 1991; Gorissen 1996; Ineson et al 1996). Microbial symbionts such as mycorrhizal fungi can contribute to C sequestration by increasing nutrient uptake by plants to sustain higher NPP levels. This compound could represent a globally significant pool of C that might be altered under global change (Treseder and Turner 2007)
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