Jeb Barrett Ross Virginia Dartmouth College Diana Wall Colorado State University

1. 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

2. Spatial variability in soil biogeochemistry and biodiversity Questions: What are the appropriate scales for studying spatial variability in soil ecosystems? Is the spatial heterogeneity in soil biota and chemistry linked to the process of polygon and soil development? • Is there opportunity to use polygons as a unit for scaling soil biology and biogeochemistry? What are the opportunities for predictive modeling and mapping?

3. Patterned ground formations near Commonwealth Glacier, Taylor Valley. Importance of understanding spatial patterning -Scaling issues -Inferring mechanism from spatial correlations

4. Dry Valley Soil Ecology: Life in the active layer Vertical distribution of organic matter, salts and biota. Nematodes -Powers et al. 1996 Soil chemistry - Burkins et al. 2001, Barrett unpublished Horizontal distribution of biodiversity and biogeochemistry Sampling design/stratification Influence of polygons on biota and biogeochemistry Variation among multiple scales Predicative soil habitat modeling (Spatial?)

5. Antarctic Soil Ecosystems 0.3 m Algal mats and moss beds Lithic environments Invertebrates

6. Stable isotope composition of Dry Valley soils 15 Fryxell - Ross Sea drift 12-20 KY 10 Hoare - Ross Sea drift 12-20 KY MDOM 5 Taylor-Bonney drift 75-98 KY LDOM 0 Mummy - Taylor III drift 200-210 KY 15N (‰) Beacon Valley -Taylor IV drift 2-8 MY -5 -10 Source Materials: EDOM: Endolithic derived organic matter. LDOM: Lacustrine derived organic matter MDOM: Marine derived organic matter SDOM: Soil microalgae derived organic matter. EDOM -15 -20 SDOM -25 -35 -30 -25 -20 -15 -10 13C (‰) Burkins et al. 2000, Barrett et al. in preparation

7. Life in the active layer: Vertical distribution of soil biota Re-plotted from Powers et al. 1996

8. Fryxell Hoare Bonney Beacon Life in the active layer: vertical distribution of soil organic carbon and nitrate Soil Organic Carbon (%) Extractable NO3- (PPM-N) 0.00 0.01 0.02 0.03 0.04 0.05 0.00 0.01 0.10 1.0 10 100 1000 10000 0 0 5 5 10 10 Soil depth cm 15 15 20 20 25 25 30 30 Burkins et al. 2000 and Barrett and Virginia unpublished

9. Scaling Units • Valleys • Lake basins • Patterned ground formations Polygons Polygons

10. Nested Experimental Design Taylor Valley 3 Lake Basins Fryxell Hoare Bonney Barrett et al. 2004. Ecology 3 Polygon clusters per basin 3 Adjacent polygons per cluster 1 transect per polygon. Samples collected at: 0, 0.2, 0.4, 0.6, 0.8, 1, 2, 4, and ~6 m from cracks

11. Soil biogeochemical properties in Taylor Valley sand-wedge polygons (g kg-1) (g kg-1) > > distance from polygon edge (m) Barrett et al. 2004. Ecology

12. Soil biogeochemical properties in Taylor Valley sand-wedge polygons 1000 (mS cm-1) (% by weight) Soil conductivity 800 600 400 0.13 y = 454.42x 200 2 R = 0.68 0 > > 0 1 2 3 4 5 6 distance from polygon edge (m) Barrett et al. 2004. Ecology

13. 1400 S. lindsayae, live 1200 1.6 Mortality (dead/ living) 1000 1.4 800 1.2 600 1.0 400 0.8 200 0.6 0 0.4 0 1 2 3 4 5 6 0.2 0.0 0 1 2 3 4 5 6 distance from polygon edge (m) Scottnema Eudorylaimus Soil nematode communities in Taylor Valley sand-wedge polygons Individuals kg-1 (ODWE) distance from polygon edge (m) Barrett et al. 2004. Ecology

14. Polygons cracks are unfavorable habitats Low organic matter, low salt, high moisture and chlorophyll a content. Mechanical disturbance?

15. Scaling Units? • Valleys • Hydrological basins • Polygons

16. VARIABILITY IN SOIL PROPERTIES OVER NESTED SCALES WITHIN TAYLOR VALLEY 0.70 2 Proportion of s 0.60 contributed by landscape scales 2 0.50 r 0.40 partial 0.30 0.20 0.10 0.00 pH E.C. soil SIC TN SOC Chl.a Eudor. Scott. water basin polygon Barrett et al. 2004. Ecology

17. 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? Microclimate relative humidity soil moisture

18. Broader scales? NA NA 5000 -1 Scottnema (#'s kg soil ) 4000 3000 2000 1000 NA NA 0 Beacon Arena Wright Victoria Taylor data from Courtright et al. 2001 and Barrett and Virginia unpublished data.

19. Logistic Regression Probability Models P is the probability of an outcome (0,1) log(P) = a + bixi+ biixii + biiixiii … + e • for example: • In a survey of 500 samples collected from the DV’s • log(P of Scottnema)= -16.7 + 1.12(soil water) + 2.1(pH) – 0.003 (E.C.) + e • p = 0.0001, R2 = 0.75

20. NS Logistic Probability Models

21. Conclusions Strong scale-dependant links between spatial patterns of biodiversity and biogeochemistry. • Soil biology and biogeochemical properties vary over multiple scales associated with: • continuous spatial gradients across polygons • discontinuous variability among basins

22. Mechanisms? Polygon development Sorting Mechanical disturbance Geographic Microclimate Till age and provenance What do we (ecologists) have to gain from understanding periglacial dynamics? What do we (soil scientists) have to gain from understanding biodiversity in the dry valleys?

23. 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.