Transcript HIGH LATTITUDE SOILS: INDICATORS OF GLOBAL CHANGE

Taylor Mills
Zachary Davies
GEOG 4401/5401 Soils Geography
Fall 2007 – Univ of Colorado, Boulder
STUDY SITES
 McMurdo Dry Valleys,
Antarctica
 Arctic, Brooks Range,
Alaska
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
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
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
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
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
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
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
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?
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
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, have
received 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
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
Control
Fertlilizer
Increased nutrients in upper soil
Horizons
Arctic ecosystem extremely nutrient limited
 Most Vascular plant species are mycorrhizal
 Increase of nutrients = decrease mycorrhizas
Fig. 1 Percentage of ectomycorrhizal colonization of Betula roots
in 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=6
blocks). Bars with the same letters are not significantly different
[Tukey’s honestly significant difference (HSD) test, P <0.05]
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
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
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: 10431048.
 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: 23772391.