Active‐Layer Hydrology in Nonsorted Circle Ecosystems of the Arctic Tundra

Patterned-ground features are common throughout arctic tundra ecosystems and develop as a result of intricate relationships among climate, hydrology, vegetation, and soil processes. Changes in the annual energy budget induced by climatic warming could likely affect the arctic freeze‐thaw cycles, altering biogeochemistry and soil processes, which in turn could change the patterned-ground ecosystem. In this study, we concentrate on the hydrology of the nonsorted circle system, an example of arctic tundra patterned ground in a relatively stable condition. Our objective was to model the processes governing liquid water movement in the active layer during freezing in order to identify the driving forces that alter the balance within this system. Our model simulations demonstrate that water redistributes within the active layer during freezing as an indirect result of horizontal differences in soil temperature. Soil surface insulation (such as that imposed by vegetation or snow) causes preferential ice accumulation in adjacent noninsulated areas, which inhibits vegetation from colonizing these areas. Both lower soil freezing rates and increased vegetation on nonsorted circles reduce water movement to the center of these features, potentially altering the equilibrium condition of these systems.

[1]  A. Michelsen,et al.  Mineralization and distribution of nutrients in plants and microbes in four arctic ecosystems: responses to warming , 2002, Plant and Soil.

[2]  Donald A. Walker,et al.  Soil climate and frost heave along the Permafrost/Ecological North American Arctic Transect , 2006 .

[3]  W. Krantz,et al.  A mechanism for differential frost heave and its implications for patterned-ground formation , 2003, Journal of Glaciology.

[4]  J. Melillo,et al.  Plant performance and soil nitrogen mineralization in response to simulated climate change in subarctic dwarf shrub heath , 1999 .

[5]  James K. Mitchell,et al.  Fundamentals of soil behavior , 1976 .

[6]  J. Baker,et al.  The Soil Freezing Characteristic: Its Measurement and Similarity to the Soil Moisture Characteristic , 1996 .

[7]  F. Stuart Chapin,et al.  Responses of Arctic Tundra to Experimental and Observed Changes in Climate , 1995 .

[8]  F. Chapin,et al.  Analyzing the functional type concept in arctic plants using a dynamic vegetation model , 2001 .

[9]  F. Stuart Chapin,et al.  A TRANSIENT, NUTRIENT‐BASED MODEL OF ARCTIC PLANT COMMUNITY RESPONSE TO CLIMATIC WARMING , 2000 .

[10]  D. Walker,et al.  Greening of arctic Alaska, 1981–2001 , 2003 .

[11]  F. Chapin,et al.  Evidence and Implications of Recent Climate Change in Northern Alaska and Other Arctic Regions , 2004 .

[12]  M. Celia,et al.  A General Mass-Conservative Numerical Solution for the Unsaturated Flow Equation , 1990 .

[13]  Masaru Mizoguchi,et al.  Water Flow and Heat Transport in Frozen Soil , 2004 .

[14]  Barrie Maxwell,et al.  2 – Arctic Climate: Potential for Change under Global Warming , 1992 .

[15]  M. Sturm,et al.  The evidence for shrub expansion in Northern Alaska and the Pan‐Arctic , 2006 .

[16]  O. Ippisch.  Coupled transport in natural porous media , 2001 .

[17]  J. Walsh.  The elusive Arctic warming , 1993, Nature.

[18]  Steven F. Oberbauer,et al.  Plant community responses to experimental warming across the tundra biome , 2006, Proceedings of the National Academy of Sciences of the United States of America.

[19]  F. Chapin,et al.  Role of Land-Surface Changes in Arctic Summer Warming , 2005, Science.

[20]  L. A. Richards.  Capillary conduction of liquids through porous mediums , 1931 .

[21]  William B. Krantz,et al.  A Generalized Secondary Frost Heave Model , 1994, SIAM J. Appl. Math..

[22]  A. L. Washburn.  CLASSIFICATION OF PATTERNED GROUND AND REVIEW OF SUGGESTED ORIGINS , 1956 .

[23]  Van Genuchten,et al.  A closed-form equation for predicting the hydraulic conductivity of unsaturated soils , 1980 .

[24]  Kevin O'Neill,et al.  Exploration of a Rigid Ice Model of Frost Heave , 1985 .

[25]  Daniel Hillel,et al.  Applications of soil physics , 1980 .

[26]  R. D. Miller,et al.  11 – Freezing Phenomena in Soils , 1980 .

[27]  W. Gould,et al.  Frost‐boil ecosystems: complex interactions between landforms, soils, vegetation and climate , 2004 .

[28]  Tammo S. Steenhuis,et al.  Heat and Moisture Transfer in a Partly Frozen Nonheaving Soil1 , 1986 .

[29]  Thomas Foken,et al.  Evaluation of six parameterization approaches for the ground heat flux , 2007 .

[30]  C. Tucker,et al.  Increased plant growth in the northern high latitudes from 1981 to 1991 , 1997, Nature.

[31]  P. H. Groenevelt,et al.  On the Interaction of Water and Heat Transport in Frozen and Unfrozen Soils: I. Basic Theory; The Vapor Phase1 , 1974 .