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Fungal feedbacks on global change Kathleen Treseder Jennifer Lansing Nathan Choi Univ. of California Irvine
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Fungal communities shift in response to environmental change Elevated CO 2 Elevated CO 2 Nitrogen deposition Nitrogen deposition Plant distributions Plant distributions Disturbance Disturbance Land use change Land use change e.g. Grogan et al. 2000; Lilleskov et al. 2002
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Fungal feedbacks Fungalgroups Ecosystemfunction Globalchange
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Fungalgrowth Soil CO2 release Globalwarming + + +
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Fungal feedbacks ? EctomycorrhizaeSaprotrophs ? ?
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? Ectomycorrhizae Lignin degraders Cellulose degraders Sugar degraders ? ?
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Fungal feedbacks Soil CO2 release Globalwarming ? ? ?
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Warming more pronounced at higher latitudes John Walsh & Amanda Lynch °C
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Forest fires increasing in Alaska Kasischke & Stocks, 2000
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Models: decomposition increases in the first few decades after burning
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Better conditions for decomposers? Fire scar Mature forest
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Does fire affect all fungal groups equally? Ectomycorrhizal fungi Saprotrophic fungi
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Hypotheses Fire alters the species composition of fungi Fire alters the species composition of fungi Fungal species specialize in use of different organic compounds in the soil Fungal species specialize in use of different organic compounds in the soil Shifts in fungal community composition may alter the decomposition rate of different organic pools Shifts in fungal community composition may alter the decomposition rate of different organic pools
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Fire chronosequence 3-yr15-yr 47-yr80-yr
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Experimental design Six 50-m long transects in each site Six 50-m long transects in each site Surveyed each week during 2002 growing season Surveyed each week during 2002 growing season Collected 6,146 sporocarps Collected 6,146 sporocarps
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Sporocarp biomass varied among sites
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Species composition varied Site * species: P < 0.001
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15 N indicated ectomycorrhizal versus saprotrophic species Cortinarius sp A Cortinarius sp B Cortinarius sp C Hebeloma crustuliniforme Lactarius torminosus Leccinum insigne Leccinum scabrum Russula brevipes Russula sp A Russula sp B Russula sp C Russula sp D Gloeophyllum sepiarium Lycoperdon sp Psilocybe sp P = 0.021
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Ectomycorrhizal fungi peaked at intermediate succession
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Are saprotrophs specializing on different compounds?
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Approach: Radiocarbon isotopes Atmospheric 14 C (‰)
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Saprotrophs displayed widely different signatures
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Calculating abundance of different functional groups Ages of C used: Ages of C used: 0 to 4 years 0 to 4 years 5 to 14 years 5 to 14 years >50 years >50 years Total sporocarp weight for each functional group Total sporocarp weight for each functional group
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Saprotrophic groups shifted across sites
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Dead wood common in younger sites
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Hypotheses Fire alters the species composition of fungi Fungal species specialize in use of different organic compounds in soil Shifts in fungal community composition may alter the decomposition rate of different organic pools
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Hypotheses Fire alters the species composition of fungi Fungal species specialize in use of different organic compounds in soil Shifts in fungal community composition may alter the decomposition rate of different organic pools
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Fire OrganicmatterSaprotrophiccommunity Decomposition of available carbon pools Host plant growth altered shifted Ectomycorrhizalabundance + + projected
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Acknowledgements China Hanson Katie Turner Sue Trumbore Julianna Fessenden UC Davis Stable Isotope Facility Keck AMS Facility, UCI NSF (EAR-0433918, DEB-0430111) China Hanson Katie Turner Sue Trumbore Julianna Fessenden UC Davis Stable Isotope Facility Keck AMS Facility, UCI NSF (EAR-0433918, DEB-0430111)
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