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.