View
101
Download
0
Category
Preview:
Citation preview
Influence of Snow Packs on Soil Biota and Biogeochemical
Patterns in Polar Desert SoilsAltrichter1, AE, KM Geyer1, JE Barrett1, MN Gooseff2, C Takacs-Vesbach3
1Virginia Polytechnic Institute and State University, Blacksburg, VA
INTRODUCTIONThis project seeks to understand the influence of seasonal melting of snow packs on distribution
of biota, biogeochemisty, hydrologic processes and permafrost dynamics.
MCMURDO DRY VALLEYS2
• Largest ice-free area on Antarctic continent
• Mean daily temperatures: -16 C to -21 C
• Mean annual precipitation: <10 cm
• Simple biotic communities comprised of very few invertebrate taxa (e.g. nematodes are the most abundant and
widespread metazoans)
• Liquid water is a primary limitation to the assembly and activity of biological communities
• Snow is patchily distributed by winter katabatic winds
• Only during the short austral summer do snow packs melt
• Snow packs provide potential water resource for
− Permafrost recharge
− Biological activity
− Biogeochemical processes
EXPERIMENTAL DESIGN• Austral summer 2009-2010
• 18 snow packs in Wright and Taylor Valley
• 3 replicate transect per pack spanning subnivian
to exposed soils
• 3 sampling periods to capture seasonal variation
• Collected surface soils (<10cm), measured depth
of active layer
QUESTIONS• What effects does enhanced water availability have on soil biogeochemical cycling and
microbial diversity and distribution?
• Over what spatial scales do snow pack dynamics influence soil processes and
communities?
Three transects were established at
each snow pack, radiating outward from
subnivian to exposed soils.ACKNOWLEDGEMENTS
National Science Foundation ANT - 0838922
United States Antarctic Program
Raytheon Polar Services
VT ERG Technician Bobbie Niederlehner2 Pennsylvania State University 3 University of New Mexico
References1Cary, et al. 2010. On the rocks: the microbiology of Antarctic Dry Valley soils. Nature 8: 129-138.2Fountain, et al. 1999. Physical controls on the Taylor Valley ecosystem, Antarctica. BioScience 49: 961-971.3Gooseff, et al. 2003. Snow-patch influence on soil biogeochemical processes and invertebrate distribution in the McMurdo Dry Valleys, Antarctica. Arct Antarct Alp Res35: 91-99.
RESULTS
ANALYSIS• Gravimetric water content
• Soil geochemistry
− pH, Conductivity
− Anions
− TOC, TN
• Biota
− Microbial biomass
− Nematode abundance
The shallower depths of the active
layer in soils adjacent to snow packs
demonstrate the combined influence
of elevated water content and
insulative properties of snow packs
on permafrost dynamics.
The nematode Eudorylaimus spp. is rarely found outside
of areas of elevated moisture in the Dry Valleys, for
example stream and lake margins. Eudorylaimus was
more abundant in soils adjacent to snow packs relative to
more distant position of the transects, likely due to higher
moisture availability and reduced salinity.
Microbial biomass exhibits the greatest variability in
near pack environments and is generally lower in soils
more distant from the pack.
CONCLUSIONS• Subnivian soils have elevated water content
• Subnivian soils have shallow active layers relative to
exposed soils.
• Snow packs contribute to variation in major anion
concentration
• Subnivian soils host a nematode species typically
found in or near aquatic habitats
• In continuing work we are examining variation in the
microbial communities inhabiting subnivian
environments
• Snow packs may act as “resource islands” for soil
biota in this harsh environment.
Courtesy of B. J. Adams, BYU
Mic
rob
ial B
iom
ass (
mg
C/k
g D
ry S
oil)
Distance from Edge of Pack (m)Regional variation in
landscape age contributes
to the differences in salt
composition and
concentrations among
sites, while the influence
of snow pack on soil
properties is evident in the
spread of observations
within individual sites.
Near-pack environments show greater
variability in soil moisture, demonstrating the
source and insulating properties of the snow
packs. Soils beyond the influence of snow
packs (red line) exhibit lower water content
than within the zone of influence of the packs.
*ANOVA P ≤ 0.05, ** P ≤ 0.01, *** P ≤ 0.001
TABLE 1. F statistic and significance levels of main effects and interactions from ANOVA of soil
properties in subnivian environments. Site by site differences accounted for most of the
variation in most soil properties (ex: TOC, TN, microbial biomass). However water content,
active layer depths and major anion exhibited the most variation across transect positions
indicating a significant influence of snow pack on surface microclimate and geochemistry.
Recommended