Poster presented by Adam E Altrichter at Ecological Society of America's 2010 Meeting in Pittsburg, PA.

1. Influence of Snow Packs on Soil Biota and Biogeochemical
Patterns in Polar Desert Soils
1 1 1 2 3
Altrichter , AE, KM Geyer , JE Barrett , MN Gooseff , C Takacs-Vesbach
1Virginia Polytechnic Institute and State University, Blacksburg, VA
INTRODUCTION RESULTS
This project seeks to understand the influence of seasonal melting of snow packs on distribution
of biota, biogeochemisty, hydrologic processes and permafrost dynamics.
QUESTIONS
• What effects does enhanced water availability have on soil biogeochemical cycling and
microbial diversity and distribution?
Courtesy of B. J. Adams, BYU
• Over what spatial scales do snow pack dynamics influence soil processes and
communities?
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 The nematode Eudorylaimus spp. is rarely found outside
widespread metazoans) of areas of elevated moisture in the Dry Valleys, for
example stream and lake margins. Eudorylaimus was
• Liquid water is a primary limitation to the assembly and activity of biological communities more abundant in soils adjacent to snow packs relative to
• Snow is patchily distributed by winter katabatic winds more distant position of the transects, likely due to higher
• Only during the short austral summer do snow packs melt moisture availability and reduced salinity.
• Snow packs provide potential water resource for
Microbial Biomass (mg C/kg Dry Soil)
− Permafrost recharge
− Biological activity
− Biogeochemical processes
EXPERIMENTAL DESIGN ANALYSIS Near-pack environments show greater The shallower depths of the active
• Austral summer 2009-2010 • Gravimetric water content variability in soil moisture, demonstrating the layer in soils adjacent to snow packs
• 18 snow packs in Wright and Taylor Valley • Soil geochemistry source and insulating properties of the snow demonstrate the combined influence
• 3 replicate transect per pack spanning subnivian − pH, Conductivity packs. Soils beyond the influence of snow of elevated water content and
to exposed soils − Anions packs (red line) exhibit lower water content insulative properties of snow packs
• 3 sampling periods to capture seasonal variation − TOC, TN than within the zone of influence of the packs. on permafrost dynamics.
• Collected surface soils (<10cm), measured depth • Biota
of active layer − Microbial biomass Regional variation in Distance from Edge of Pack (m)
− Nematode abundance landscape age contributes
Microbial biomass exhibits the greatest variability in
to the differences in salt
near pack environments and is generally lower in soils
composition and
more distant from the pack.
concentrations among
sites, while the influence
of snow pack on soil CONCLUSIONS
properties is evident in the • Subnivian soils have elevated water content
spread of observations • Subnivian soils have shallow active layers relative to
within individual sites. exposed soils.
• Snow packs contribute to variation in major anion
concentration
TABLE 1. F statistic and significance levels of main effects and interactions from ANOVA of soil • Subnivian soils host a nematode species typically
properties in subnivian environments. Site by site differences accounted for most of the found in or near aquatic habitats
variation in most soil properties (ex: TOC, TN, microbial biomass). However water content, • In continuing work we are examining variation in the
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. microbial communities inhabiting subnivian
environments
Three transects were established at • Snow packs may act as “resource islands” for soil
each snow pack, radiating outward from biota in this harsh environment.
subnivian to exposed soils.
ACKNOWLEDGEMENTS
National Science Foundation ANT - 0838922
References United States Antarctic Program
1Cary, et al. 2010. On the rocks: the microbiology of Antarctic Dry Valley soils. Nature 8: 129-138.
Raytheon Polar Services
2Fountain, et al. 1999. Physical controls on the Taylor Valley ecosystem, Antarctica. BioScience 49: 961-971.
VT ERG Technician Bobbie Niederlehner
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. 2 Pennsylvania State University 3 University of New Mexico
*ANOVA P ≤ 0.05, ** P ≤ 0.01, *** P ≤ 0.001