Experimental Alteration of Plant Canopy and the Effects on Cryoturbation Regime Anja Kade, Donald Walker Institute of Arctic Biology University of Alaska Fairbanks
Frost Boils in Alaskan Arctic Tundra Howe Island, AK Patterned, circular landforms of northern tundra areas Non-sorted circles in loess landscapes of northern Alaska Sorted circles in areas with coarser material 1-3 m in diameter Caused by differential frost heave High content of ice lenses Minimal vegetation cover Great thaw depth Organic matter Mineral soil Inter- Boil Frost Boil
Frost-Boil Ecosystem Vegetation OM nutrients Cryoturbation Soil disturbance insulation insulation disturbance
Objective Vegetation Soil Cryoturbation To study the influence of the plant canopy and different plant functional types on cryoturbation regime.
Hypotheses _ Plant Cover + Soil-Surface Temperature SUMMER + Soil-Surface Temperature _ WINTER Cryoturbation Activity (Frost Heave & Thaw Depth)
Study Area Prudhoe Bay Sagwon Hills North Slope, Alaska Sagwon Hills (60 miles south of Prudhoe Bay) Mean July Temp.: 7ºC Erect dwarf-shrub bioclimatic subzone Frost-boil vegetation: small mosses, fruticose lichens, forbs
Frost-Boil Treatments Vegetation removal What influence does the lack of plant canopy have on thermal insulation and cryoturbation parameters of frost boils? Vegetation removal & transplanting sedge seedling How do vascular plants with an extensive root system (Eriophorum vaginatum) affect cryoturbation activity? Vegetation removal & transplanting moss carpet What effect does an insulating moss carpet have on cryoturbation activity? Control
Methods: Vegetation Removal Stripping off vegetation mat Exposing mineral soil
Methods: Graminoid Transplants Collecting Eriophorum vaginatum seedlings Transplanting seedlings at 10 cm intervals
Methods: Moss Carpet Collection of moss slabs from surrounding area Transplanting 10-15 cm thick moss slabs
Methods: Rebar and Toothpicks to measure frost heave and to monitor soilsurface stability
Finished Plots Control Removal Graminoids Moss Carpet
Response Variables Frost heave Movement of ground around rebar Thaw depth Insertion of probe through active layer Soil moisture Spot measurements of upper 6 cm of soil with Theta probe Soil temperature In situ measurements with data loggers at 2 cm depth in the soil and at 2 cm above soil surface Soil-surface stability Percentage of tilted or expelled toothpicks Snow depth
Winter in Sagwon November 2002 April 2003
Preliminary Results cm 14 12 10 8 6 4 2 Frost Heave (mid July - mid November 2002) a Removal ab Graminoid b Moss b Control cm 76 74 72 70 68 66 64 62 a Removal Thaw Depth (early September 2002) ab Graminoid b Moss a Control 0 60 Frost heave Thaw depth
Preliminary Results 48 47 46 45 44 43 42 41 40 39 38 c Soil Moisture (early September 2002) bc a Soil temperature Soil moisture ab % water (volumetric soil moisture) Removal Graminoid Moss Control 8 7 6 5 4 3 2 1 0 Soil Temperature (mid August 2002; at 1 cm depth) a a c b degrees C Removal Graminoid Moss Control
Preliminary Results Cryoturbation parameters: Frost heave was increased by vegetation removal. Thaw depth was decreased by moss carpet. Soil parameters: Summer soil-temperature was increased by vegetation removal and graminoid treatment. It was decreased by moss carpets. Soil moisture was decreased by vegetation removal.
Discussion and Conclusion Cryoturbation activity seems to be closely linked to insulation through plant canopy. Why was thaw depth not affected by vegetation removal, and why did frost heave show no response to the moss carpet? Frost boils seem to have an imprint on their cryoturbation regime and remember their past more time might be required to alter all cryoturbation variables experimentally.