PARENT SESSION
Wednesday, August 9, 1:30-5:00 pm
COS 64 - Carbon and nitrogen dynamics
Ballroom E, Ballroom Level, Cook Convention Center
Presiders: J Baron and M Santana
Increased ectomycorrhizal fungal abundance after long-term fertilization and warming of two arctic tundra ecosystems.
Clemmensen, Karina*,1, Michelsen, Anders1, Jonasson, Sven1, Shaver, Gaius2, 1 University of Copenhagen, Denmark, Copenhagen, Denmark2 The Ecosystems Center, Marine Biology Laboratory, Woods Hole, Woods Hole, MA
ABSTRACT- Shrub abundance is expected to increase with enhanced temperature and nutrient availability in the Arctic, and associated changes in abundance of ectomycorrhizal (EM) fungi could be a key link between plant responses and longer-term changes in soil organic matter storage. This study quantifies the response in EM fungal abundance to long-term warming and fertilization in two arctic ecosystems with contrasting responses of the EM shrub Betula nana. We used ergosterol as a biomarker for living fungal biomass in roots and organic soil and ingrowth bags to estimate EM mycelial production. Natural abundance of 15Nitrogen and 13Carbon confirmed the EM-saprotrophic divide in fungal sporocarps and validated the EM origin of mycelia in the ingrowth bags. At both sites, fertilization increased EM mycelial production and fungal biomass in the soil, and warming increased both measures at one site. This was partly caused by increased dominance of EM plants and partly by direct stimulation of EM mycelial growth. We conclude that cycling of carbon and nitrogen through EM fungi will increase when strongly nutrient limited arctic ecosystems are exposed to a warmer and more nutrient rich environment. This has potential consequences for belowground litter quality and quantity and for accumulation of organic matter in arctic soils.
Key words: arctic tundra, mycorrhizal fungal ingrowth bags, soil organic matter storage