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• 1. [Article] Water track modification of soil ecosystems in the Lake Hoare basin, Taylor Valley, Antarctica

  Water tracks are zones of high soil moisture that route shallow groundwater down-slope, through the active layer and above the ice table. A water track in Taylor Valley, McMurdo Dry Valleys, was analysed ...

  Citation × Citation Citation Abstract Copy Title: Water track modification of soil ecosystems in the Lake Hoare basin, Taylor Valley, Antarctica Author: Levy, Joseph S., Fountain, Andrew G., Gooseff, Michael N., Barrett, John E., Vantreese, Robert, Welch, Kathleen A., Lyons, W. Berry, Nielsen, Uffe N., Wall, Diana H. Year: 2013 Water tracks are zones of high soil moisture that route shallow groundwater down-slope, through the active layer and above the ice table. A water track in Taylor Valley, McMurdo Dry Valleys, was analysed for surface hydrogeological, geochemical, and biological characteristics in order to test the hypothesis that water tracks provide spatial structure to Antarctic soil ecosystems by changing the physical conditions in the soil environment within the water tracks from those outside the water tracks. The presence of the water track significantly affected the distribution of biotic and abiotic ecosystem parameters: increasing soil moisture, soil salinity, and soil organic matter within the water track relative to soils outside the water track, and reducing soil phosphate, soil pH, and the population of nematodes and other invertebrates in water track soils relative to off track soils. These results suggest that water tracks are distinct and extreme ecological zones in Taylor Valley that provide long-range (kilometre to multikilometre) structure to Antarctic hillslope ecosystems through physical control on soil moisture and solute content. Contrary to expectations, these high soil-moisture sites are not hotspots for faunal biological activity because high soil salinity makes them suitable habitats for only the most halo-tolerant organisms Title: Water track modification of soil ecosystems in the Lake Hoare basin, Taylor Valley, Antarctica Author: Levy, Joseph S., Fountain, Andrew G., Gooseff, Michael N., Barrett, John E., Vantreese, Robert, Welch, Kathleen A., Lyons, W. Berry, Nielsen, Uffe N., Wall, Diana H. Year: 2013 Water tracks are zones of high soil moisture that route shallow groundwater down-slope, through the active layer and above the ice table. A water track in Taylor Valley, McMurdo Dry Valleys, was analysed for surface hydrogeological, geochemical, and biological characteristics in order to test the hypothesis that water tracks provide spatial structure to Antarctic soil ecosystems by changing the physical conditions in the soil environment within the water tracks from those outside the water tracks. The presence of the water track significantly affected the distribution of biotic and abiotic ecosystem parameters: increasing soil moisture, soil salinity, and soil organic matter within the water track relative to soils outside the water track, and reducing soil phosphate, soil pH, and the population of nematodes and other invertebrates in water track soils relative to off track soils. These results suggest that water tracks are distinct and extreme ecological zones in Taylor Valley that provide long-range (kilometre to multikilometre) structure to Antarctic hillslope ecosystems through physical control on soil moisture and solute content. Contrary to expectations, these high soil-moisture sites are not hotspots for faunal biological activity because high soil salinity makes them suitable habitats for only the most halo-tolerant organisms Close

• 2. [Article] Biogeochemical Stoichiometry of Antarctic Dry Valley Ecosystems

  Among aquatic and terrestrial landscapes of the McMurdo Dry Valleys, Antarctica, ecosystem stoichiometry ranges from values near the Redfield ratios for C:N:P to nutrient concentrations in proportions ...

  Citation × Citation Citation Abstract Copy Title: Biogeochemical Stoichiometry of Antarctic Dry Valley Ecosystems Author: Barrett, John E., Virginia, Ross A., Lyons, W. Berry, McKnight, Diane M., Priscu, John Charles, Doran, Peter T., Fountain, Andrew G., Wall, Diana H., Moorhead, D. L. Year: 2007 Among aquatic and terrestrial landscapes of the McMurdo Dry Valleys, Antarctica, ecosystem stoichiometry ranges from values near the Redfield ratios for C:N:P to nutrient concentrations in proportions far above or below ratios necessary to support balanced microbial growth. This polar desert provides an opportunity to evaluate stoichiometric approaches to understand nutrient cycling in an ecosystem where biological diversity and activity are low, and controls over the movement and mass balances of nutrients operate over 10–10⁶ years. The simple organisms (microbial and metazoan) comprising dry valley foodwebs adhere to strict biochemical requirements in the composition of their biomass, and when activated by availability of liquid water, they influence the chemical composition of their environment according to these ratios. Nitrogen and phosphorus varied significantly in terrestrial and aquatic ecosystems occurring on landscape surfaces across a wide range of exposure ages, indicating strong influences of landscape development and geochemistry on nutrient availability. Biota control the elemental ratio of stream waters, while geochemical stoichiometry (e.g., weathering, atmospheric deposition) evidently limits the distribution of soil invertebrates. We present a conceptual model describing transformations across dry valley landscapes facilitated by exchanges of liquid water and biotic processing of dissolved nutrients. We conclude that contemporary ecosystem stoichiometry of Antarctic Dry Valley soils, glaciers, streams, and lakes results from a combination of extant biological processes superimposed on a legacy of landscape processes and previous climates. Title: Biogeochemical Stoichiometry of Antarctic Dry Valley Ecosystems Author: Barrett, John E., Virginia, Ross A., Lyons, W. Berry, McKnight, Diane M., Priscu, John Charles, Doran, Peter T., Fountain, Andrew G., Wall, Diana H., Moorhead, D. L. Year: 2007 Among aquatic and terrestrial landscapes of the McMurdo Dry Valleys, Antarctica, ecosystem stoichiometry ranges from values near the Redfield ratios for C:N:P to nutrient concentrations in proportions far above or below ratios necessary to support balanced microbial growth. This polar desert provides an opportunity to evaluate stoichiometric approaches to understand nutrient cycling in an ecosystem where biological diversity and activity are low, and controls over the movement and mass balances of nutrients operate over 10–10⁶ years. The simple organisms (microbial and metazoan) comprising dry valley foodwebs adhere to strict biochemical requirements in the composition of their biomass, and when activated by availability of liquid water, they influence the chemical composition of their environment according to these ratios. Nitrogen and phosphorus varied significantly in terrestrial and aquatic ecosystems occurring on landscape surfaces across a wide range of exposure ages, indicating strong influences of landscape development and geochemistry on nutrient availability. Biota control the elemental ratio of stream waters, while geochemical stoichiometry (e.g., weathering, atmospheric deposition) evidently limits the distribution of soil invertebrates. We present a conceptual model describing transformations across dry valley landscapes facilitated by exchanges of liquid water and biotic processing of dissolved nutrients. We conclude that contemporary ecosystem stoichiometry of Antarctic Dry Valley soils, glaciers, streams, and lakes results from a combination of extant biological processes superimposed on a legacy of landscape processes and previous climates. Close