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Spatial variability in soil biogeochemistry and biodiversity in periglacial landscapes of the McMurdo Dry Valleys, Antarctica. Jeb Barrett Ross Virginia Dartmouth College Diana Wall Colorado State University. Spatial variability in soil biogeochemistry and biodiversity. Questions: - PowerPoint PPT Presentation
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Spatial variability in soil biogeochemistry and biodiversity in periglacial landscapes of the McMurdo Dry Valleys, Antarctica.
Jeb BarrettRoss Virginia
Dartmouth College
Diana Wall
Colorado State University
Spatial variability in soil biogeochemistry and biodiversitySpatial variability in soil biogeochemistry and biodiversity
Questions:Questions:What are the appropriate scales for studying spatial What are the appropriate scales for studying spatial variability in soil ecosystems? variability in soil ecosystems?
What are the opportunities for predictive modeling and What are the opportunities for predictive modeling and mapping?mapping?
Is there opportunity to use polygons as a unit for scaling soil Is there opportunity to use polygons as a unit for scaling soil biology and biogeochemistry?biology and biogeochemistry?
Is the spatial heterogeneity in soil biota and chemistry Is the spatial heterogeneity in soil biota and chemistry linked to the process of polygon and soil development?linked to the process of polygon and soil development?
Patterned ground formations near Commonwealth Glacier, Taylor Valley.
Importance of understanding spatial patterning
-Scaling issues
-Inferring mechanism from spatial correlations
Dry Valley Soil Ecology: Life in the active layerDry Valley Soil Ecology: Life in the active layer
Vertical distribution of organic matter, salts and biota.Vertical distribution of organic matter, salts and biota.Nematodes -Powers et al. 1996Nematodes -Powers et al. 1996Soil chemistry - Burkins et al. 2001, Barrett unpublishedSoil chemistry - Burkins et al. 2001, Barrett unpublished
Horizontal distribution of biodiversity and biogeochemistryHorizontal distribution of biodiversity and biogeochemistrySampling design/stratificationSampling design/stratificationInfluence of polygons on biota and biogeochemistryInfluence of polygons on biota and biogeochemistryVariation among multiple scalesVariation among multiple scalesPredicative soil habitat modeling (Spatial?) Predicative soil habitat modeling (Spatial?)
Algal mats and moss beds
Lithic environments Invertebrates
Antarctic Soil EcosystemsAntarctic Soil Ecosystems
0.3 m
13C (‰)
1
5N
(‰
)
Fryxell - Ross Sea drift 12-20 KY
Hoare - Ross Sea drift 12-20 KY
Taylor-Bonney drift 75-98 KY
Mummy - Taylor III drift 200-210 KY
Source Materials:
EDOM: Endolithic derived organic matter.
LDOM: Lacustrine derived organic matter
MDOM: Marine derived organic matter SDOM: Soil microalgae derived organic matter.
Burkins et al. 2000, Barrett et al. in preparation
Stable isotope composition of Dry Valley soils
-25
-20
-15
-10
-5
0
5
10
15
-35 -30 -25 -20 -15 -10
MDOM
LDOM
EDOM
SDOM
Beacon Valley -Taylor IV drift 2-8 MY
Life in the active layer: Vertical distribution of soil biota
Re-plotted from Powers et al. 1996
0
5
10
15
20
25
30
0 200 400 600 800 1000 1200
# of live organisms per
soil depth
Soil Organic Carbon (%)
0
5
10
15
20
25
30
0.00 0.01 0.02 0.03 0.04 0.05
Extractable NO3- (PPM-N)
0
5
10
15
20
25
30
0.00 0.01 0.10 1.0 10 100 1000 10000
So
il d
epth
cm
Fryxell Hoare
Bonney Beacon
Life in the active layer: vertical distribution of soil organic carbon and nitrate
Burkins et al. 2000 and
Barrett and Virginia unpublished
Scaling Units
• Valleys
• Lake basins
• Patterned ground formations
Polygons
Polygons
Nested Experimental DesignNested Experimental Design
Taylor ValleyTaylor Valley3 Lake Basins3 Lake Basins
FryxellFryxellHoareHoareBonneyBonney
3 Polygon clusters per basin3 Polygon clusters per basin
3 Adjacent polygons per cluster3 Adjacent polygons per cluster
1 transect per polygon. Samples collected at:1 transect per polygon. Samples collected at:0, 0.2, 0.4, 0.6, 0.8, 1, 2, 4, and ~6 m from cracks0, 0.2, 0.4, 0.6, 0.8, 1, 2, 4, and ~6 m from cracks
Barrett et al. 2004. Ecology
soil organic carbon
y = 0.01x + 0.18
R 2 = 0.790.00
0.05
0.10
0.15
0.20
0.25
0.30
0 1 2 3 4 5 6
total soil nitrogen
y = 0.002x + 0.026
R 2 = 0.91
0.00
0.01
0.02
0.03
0.04
0.05
0 1 2 3 4 5 6
distance from polygon edge (m)
(g kg-1) (g kg-1)
> >
Soil biogeochemical properties Soil biogeochemical properties
in Taylor Valley sand-wedge polygonsin Taylor Valley sand-wedge polygons
Barrett et al. 2004. Ecology
soil mositure
0.00
0.30
0.60
0.90
1.20
1.50
1.80
0 1 2 3 4 5 6
Soil conductivity
y = 454.42x0.13
R2 = 0.68
0
200
400
600
800
1000
0 1 2 3 4 5 6
distance from polygon edge (m)
(% by weight) (S cm-1)
> >
Soil biogeochemical properties Soil biogeochemical properties
in Taylor Valley sand-wedge polygonsin Taylor Valley sand-wedge polygons
Barrett et al. 2004. Ecology
S. lindsayae, live
0
200
400
600
800
1000
1200
1400
0 1 2 3 4 5 6
Mortality (dead/ living)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
0 1 2 3 4 5 6
distance from polygon edge (m)
Scottnema Eudorylaimus
Ind
ivid
ual
s kg
-1 (
OD
WE
)
distance from polygon edge (m)
Soil nematode communitiesSoil nematode communities
in Taylor Valley sand-wedge polygonsin Taylor Valley sand-wedge polygons
Barrett et al. 2004. Ecology
Polygons cracks are unfavorable habitats
Low organic matter, low salt, high moisture and chlorophyll a content.
Mechanical disturbance?
Scaling Units?
• Valleys
• Hydrological basins
• Polygons
Proportion of 2
contributed by landscape scales
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
pH E.C. soil
water
SIC TN SOC Chl.a Eudor. Scott.
par
tial
r 2
basin polygon
VARIABILITY IN SOIL PROPERTIES OVER NESTED SCALES WITHIN TAYLOR VALLEY
Barrett et al. 2004. Ecology
Dry Valley Spatial Variability
• Polygons influence soil biogeochemisty and biodiversity , but …
• biogeochemcial properties vary most at scales> 10 km(among lake basins).
Mechanism?Till provenance?
Surface age?
Microclimaterelative humiditysoil moisture
0
2000
4000
6000
8000
Beacon Arena Wright Victoria Taylor
Upper
MiddleLower
soil salinity (uS cm-1)
0.00
0.25
0.50
0.75
Beacon Arena Wright Victoria Taylor
soil organic carbon (g kg-1)
0
1000
2000
3000
4000
5000
Beacon Arena Wright Victoria Taylor
Scottnema (#'s kg soil-1)
Broader scales?Broader scales?
data from Courtright et al. 2001 and Barrett and Virginia unpublished data.
NA NA
NA NA
Logistic Regression Probability Models
P is the probability of an outcome (0,1)
log(P)ixi iixiiiiixiii … +
for example:In a survey of 500 samples collected from the DV’s
log(P of Scottnema)soil water) + 2.1(pH) – 0.003 (E.C.) +
p = 0.0001, R2 = 0.75
0.0
0.2
0.4
0.6
0.8
1.0
6 7 8 9 10soil pH
0.0
0.2
0.4
0.6
0.8
1.0
0 0.2 0.4 0.6 0.8 1
soil organic C (g C kg-1)
Scottnema
Eudorylaimus
Multi-taxa communities
NS
Logistic Probability Models
ConclusionsConclusions
Strong scale-dependant links between spatial patterns of Strong scale-dependant links between spatial patterns of biodiversity and biogeochemistry.biodiversity and biogeochemistry.
Soil biology and biogeochemical properties vary over Soil biology and biogeochemical properties vary over multiple scales associated with:multiple scales associated with:
• continuous spatial gradients across polygonscontinuous spatial gradients across polygons
• discontinuous variability among basins discontinuous variability among basins
What do we (soil scientists) have to gain from understanding biodiversity in the dry valleys?
What do we (ecologists) have to gain from understanding periglacial dynamics?
Mechanisms?Polygon development
SortingMechanical disturbance
GeographicMicroclimateTill age and provenance
Barrett, J. E., D. H. Wall, R. A. Virginia, A. N. Parsons, L. E. Powers, and M. B. Burkins. 2004. Biogeochemical parameters and constraints on the structure of soil biodiversity. Ecology 85: In press.