Taylor Mills Zachary Davies GEOG 4401/5401 Soils Geography Fall 2007 – Univ of Colorado, Boulder
Dec 22, 2015
Taylor MillsZachary Davies
GEOG 4401/5401 Soils GeographyFall 2007 – Univ of Colorado, Boulder
STUDY SITESMcMurdo Dry
Valleys, AntarcticaArctic, Brooks
Range, Alaska
MCMURDO FACTSLocated at 77°30'S
163°00'E Largest ice free area
of AntarcticaHarshest ecosystem
on earthLowest species
diversity on earth Primarily dominated
by Nematodes and algae
GLOBAL COOLING…?
Mcmurdo dry valleys have been cooling over the past 50 years
Cooler temperatures lead to dryer soilLess melt water = fewer streamsSoil water consistently frozen
PRESERVING SOIL HYDROLOGY FOR FUTURE GENERATIONSPast climate
influences current soil characteristicsColder drier = less
PP = less organic matter deposits
Organic matter is energy source for current soil organisms
PRESERVING SOIL HYDROLOGY FOR FUTURE GENERATIONS Cycle of lake
expansion and desiccation recharges soil OMLittle to no PP in the
soil itselfDeposition of
organic matter is either aeolian or lake deposits
SUMMARY OF COOLING EFFECT ON MCMURDO DRY LAKES
Reduces amount of liquid waterLowers soil moisturePrevents formation of lakes and pondsGreatly reduces inputs of organic matter into
the soilDecreases soil organism diversity and richness
Implications of Global Warming on the Tussock tundra
North Slope of the Brooks range in Alaska
Why Study Tundra Ecosystem?Global warming is predicted to be most pronounced at high
LatitudesOne-third of the global soil carbon pool is stored in northern
latitudesChanges in carbon storage in these areas could have a large
effect on global warming
Effects of Global Warming on Arctic Terrestrial EcosystemIncrease plant litter and SOMChange in soil Carbon storageLoss of MycorrhizalChange in Soil AcidityPositive feedback on Global Warming?
Plant LitterTemperatures are expected to increase 1-4 degrees in Arctic
ecosystemsBio 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
Figure 1 Effect of fertilization on vascular plant aboveground net primary production (ANPP) in tundra. Fertilized plots in moist acidic tundra near Toolik Lake, Alaska, havereceived 10 g Nm22 yr21 and 5 g Pm22 yr21 since 1981.
-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
DecompositionIncreased 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
Control Fertlilizer
Increased nutrients in upper soil HorizonsArctic ecosystem extremely nutrient limitedMost Vascular plant species are mycorrhizalIncrease of nutrients = decrease mycorrhizas
Fig. 1 Percentage of ectomycorrhizal colonization of Betula rootsin the tussock tundra, Alaska, under different treatments: control(C), fertilizer addition (F), Ledum removal (LR), Ledum removal+fertilizer addition (LR+F). Error bars indicate +1 SE (n=6blocks). Bars with the same letters are not significantly different[Tukey’s honestly significant difference (HSD) test, P <0.05]
Soil AcidityArctic region dominated by Moist Arctic Tundra including
permafrostHigh soil moisture leaches cations resulting in high soil acidityThe 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
SummaryGlobal 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
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?
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.