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HIGH LATTITUDE SOILS: INDICATORS OF GLOBAL CHANGE

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HIGH LATTITUDE SOILS: INDICATORS OF GLOBAL CHANGE

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    1. HIGH LATTITUDE SOILS: INDICATORS OF GLOBAL CHANGE ? Taylor Mills Zachary Davies

    2. STUDY SITES McMurdo Dry Valleys, Antarctica Arctic, Brooks Range, Alaska

    3. MCMURDO FACTS Located at 77°30'S 163°00'E Largest ice free area of Antarctica Harshest ecosystem on earth Lowest species diversity on earth Primarily dominated by Nematodes and algae

    4. GLOBAL COOLING…? Mcmurdo dry valleys have been cooling over the past 50 years Cooler temperatures lead to dryer soil Less melt water = fewer streams Soil water consistently frozen

    5. PRESERVING SOIL HYDROLOGY FOR FUTURE GENERATIONS Past climate influences current soil characteristics Colder drier = less PP = less organic matter deposits Organic matter is energy source for current soil organisms

    6. PRESERVING SOIL HYDROLOGY FOR FUTURE GENERATIONS Cycle of lake expansion and desiccation recharges soil OM Little to no PP in the soil itself Deposition of organic matter is either aeolian or lake deposits

    7. SUMMARY OF COOLING EFFECT ON MCMURDO DRY LAKES Reduces amount of liquid water Lowers soil moisture Prevents formation of lakes and ponds Greatly reduces inputs of organic matter into the soil Decreases soil organism diversity and richness

    8. Arctic LTER Implications of Global Warming on the Tussock tundra North Slope of the Brooks range in Alaska

    9. Why Study Tundra Ecosystem? Global warming is predicted to be most pronounced at high Latitudes One-third of the global soil carbon pool is stored in northern latitudes Changes in carbon storage in these areas could have a large effect on global warming

    10. Effects of Global Warming on Arctic Terrestrial Ecosystem Increase plant litter and SOM Change in soil Carbon storage Loss of Mycorrhizal Change in Soil Acidity Positive feedback on Global Warming?

    11. Plant Litter Temperatures are expected to increase 1-4 degrees in Arctic ecosystems Bio mass Production -increase of plant litter and SOM -increased C stored aboveground by stimulating plant productivity and by shifting species composition from slow-growing species to more productive shrubs that accumulate C in long-lived woody biomass

    12. -litter from shrubs decomposes more slowly than the graminoid litter they replace, so conversion to shrub tundra was thought to slow decomposition and increase ecosystem C accumulation Decomposition Increased nutrient availability stimulated the decomposition of old litter in deep soil layers, leading to loss via mineralization and leaching of dissolved organic C The rate of decomposition was greater than the increase in production Net loss of 2,000g C m-2 from the ecosystem

    13. Increased nutrients in upper soil Horizons Arctic ecosystem extremely nutrient limited Most Vascular plant species are mycorrhizal Increase of nutrients = decrease mycorrhizas

    14. Soil Acidity Arctic region dominated by Moist Arctic Tundra including permafrost High soil moisture leaches cations resulting in high soil acidity The increase of organic matter will lead to greater soil acidity -OM forms soluble complexes with non-acid nutrient cations which can than be leached - OM source of H+ ions as OM contains numerous acid functional groups from which these Ions can dissociate Further reduction of Cation Exchange Capacity

    15. Summary Global Warming Effects -Increase in Biomass and SOM -Greater increase in decomposition than production leading to decrease Carbon in soil Loss of Symbiotic relationship between mycorrhizal fungi and vascular plant roots Increase of acidity

    16. Hmmmmm? Will loss of Carbon stores further global warming creating a positive feedback mechanism? What will happen to terrestrial vegetation with the loss of mycorrhizal fungi and increasing soil acidity?

    17. Sources Urcelay C, Bret-Harte MS, Diaz S, et al. Mycorrhizal colonization mediated by species interactions in arctic tundra  OECOLOGIA 137 (3): 399-404 NOV 2003 Mack MC, Schuur EAG, Bret-Harte MS, et al. Ecosystem carbon storage in arctic tundra reduced by long-term nutrient fertilization  NATURE 431 (7007): 440-443 SEP 23 2004 Adams G. A. and Wall D. H. (2000) Biodiversity above and below the surface of soils and sediments: linkages and implications for global change, Bioscience, 50: 1043-1048. Wolters V., Silver W. L., Bignell D. E., Coleman D. C., Lavelle P., van der Putten W., deRuiter P. C., Rusek J., Wall D. H., Wardle D. A., Brussaard L., Dangerfield J.M., Brown V. K., Giller K. E., Hooper D. U., Sala O. E., Tiedje J. M., and vanVeen J. A. (2000) Global change effects on above and below ground biodiversity in terrestrial ecosystems: interactions and implications for ecosystem functioning , Bioscience, 50: 1089-1099. Burkins, M.B., R.A. Virginia, C.P. Chamberlain and D.H. Wall (2000) The Origin of Soil Organic Matter in Taylor Valley, Antarctica: A Legacy of Climate Change, Ecology, 81: 2377-2391.

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