Microtopographic controls on ecosystem functioning in the Arctic Coastal Plain

[1] The investigation of the microtopographic controls on thermal and hydrologic conditions of the soil and consequently the carbon dynamics from Arctic regions is of major importance. Ecosystem respiration (ER) between microsites of the same tundra type could differ more than ER in different tundra types even at different latitudes. In this study we investigated the microtopographic effect on soil temperature, thaw depth, pH, oxidation reduction potential (ORP), electrical conductivity (EC), dissolved CO2, vegetation types, and ER rates from different features forming the low-center polygon structure. Most of these environmental variables significantly differ particularly between areas with higher elevation (polygon rims) and with lower elevation (low-center polygons). Polygon rims presented the lowest water table and showed the lowest thaw depth and the highest ER (a seasonal average of 1 μmol CO2 m−2 s−1), almost double than the ER in the low-center polygons (a seasonal average of 0.6 μmol CO2 m−2 s−1). The microtopographic gradient from polygon rims to low-centers led to a very consistent pattern in pH, EC, ORP and dissolved CO2, with low-centers presenting the highest pH, the highest EC, the highest dissolved CO2, and the lowest ORP. Based on vegetation measurements, we also showed that microtopography controls the lateral flow of organic matter, and that vascular plant material accumulates as litter in the lower elevation areas, possibly contributing to the higher dissolved CO2 in the low-center polygons. Microtopography, and the ramifications discussed here, should be considered when evaluating landscape scale environmental controls on carbon dynamics in the Arctic.

[1]  David L. Verbyla,et al.  Shrinking ponds in subarctic Alaska based on 1950–2002 remotely sensed images , 2006 .

[2]  S. Hagemann,et al.  Vulnerability of Permafrost Carbon to Climate Change: Implications for the Global Carbon Cycle , 2008 .

[3]  W. Oechel,et al.  Methane fluxes during the initiation of a large‐scale water table manipulation experiment in the Alaskan Arctic tundra , 2009 .

[4]  W. D. Billings,et al.  VEGETATIONAL CHANGE AND ICE-WEDGE POLYGONS THROUGH THE THAW-LAKE CYCLE IN ARCTIC ALASKA , 1980 .

[5]  Jeffrey M. Welker,et al.  Temperature and Microtopography Interact to Control Carbon Cycling in a High Arctic Fen , 2008, Ecosystems.

[6]  W. Oechel,et al.  Energy and trace-gas fluxes across a soil pH boundary in the Arctic , 1998, Nature.

[7]  R. Rhew,et al.  Methyl halide and methane fluxes in the northern Alaskan coastal tundra , 2007 .

[8]  Sini Niinistö,et al.  Comparison of different chamber techniques for measuring soil CO2 efflux , 2004 .

[9]  Marco Caccianiga,et al.  Accelerated thawing of subarctic peatland permafrost over the last 50 years , 2004 .

[10]  W. D. Billings,et al.  Influence of water table and atmospheric CO/sub 2/ concentration on the carbon balance of arctic tundra , 1984 .

[11]  F. Chapin,et al.  Permafrost and the Global Carbon Budget , 2006, Science.

[12]  L. D. Hinzman,et al.  Disappearing Arctic Lakes , 2005, Science.

[13]  W. Oechel,et al.  Carbon balance in tussock tundra under ambient and elevated atmospheric CO2 , 1990, Oecologia.

[14]  G. L. Hutchinson,et al.  Chamber measurement of surface‐atmosphere trace gas exchange: Numerical evaluation of dependence on soil, interfacial layer, and source/sink properties , 2000 .

[15]  Jerry Brown,et al.  Tundra Soils Formed over Ice Wedges, Northern Alaska1 , 1967 .

[16]  W. Oechel,et al.  Landscape-Scale CO 2 , H 2 O Vapour and Energy Flux of Moist-Wet Coastal Tundra Ecosystems over Two Growing Seasons , 1997 .

[17]  J. Titus,et al.  Vertical zonation of Sphagnum mosses along hummock-hollow gradients , 1983 .

[18]  Tim R. Moore,et al.  THE INFLUENCE OF WATER TABLE LEVELS ON METHANE AND CARBON DIOXIDE EMISSIONS FROM PEATLAND SOILS , 1989 .

[19]  A. W. Damman.  Distribution and movement of elements in ombrotrophic peat , 1978 .

[20]  W. Oechel,et al.  Change in Arctic CO2Flux Over Two Decades: Effects of Climate Change at Barrow, Alaska , 1995 .

[21]  Steven F. Oberbauer,et al.  Responses of CO2 flux components of Alaskan Coastal Plain tundra to shifts in water table , 2010 .

[22]  Jed O. Kaplan,et al.  Trace gas exchange in a high‐Arctic valley: 1. Variationsin CO2 and CH4 Flux between tundra vegetation types , 2000 .

[23]  D. Mortensen,et al.  Increasing atmospheric carbon dioxide: possible effects on arctic tundra , 1983, Oecologia.

[24]  M. Sommerkorn.  Micro-topographic patterns unravel controls of soil water and temperature on soil respiration in three Siberian tundra systems , 2008 .

[25]  Kenneth M. Hinkel,et al.  Spatial Extent, Age, and Carbon Stocks in Drained Thaw Lake Basins on the Barrow Peninsula, Alaska , 2003 .

[26]  Line Rochefort,et al.  Response of vegetation and net ecosystem carbon dioxide exchange at different peatland microforms following water table drawdown , 2006 .

[27]  Walter C. Oechel,et al.  Recent change of Arctic tundra ecosystems from a net carbon dioxide sink to a source , 1993, Nature.

[28]  W. Oechel,et al.  Light-stress avoidance mechanisms in a Sphagnum-dominated wet coastal Arctic tundra ecosystem in Alaska. , 2011, Ecology.

[29]  M. Torre Jorgenson,et al.  Abrupt increase in permafrost degradation in Arctic Alaska , 2006 .

[30]  W. Oechel,et al.  Reduction of iron (III) and humic substances plays a major role in anaerobic respiration in an Arctic peat soil , 2010 .

[31]  R. S. Clymo.  Ion Exchange in Sphagnum and its Relation to Bog Ecology , 1963 .

[32]  K. Ramesh Reddy,et al.  Biogeochemistry of Wetlands: Science and Applications , 2008 .

[33]  M. Ohlson,et al.  Rate of Peat Increment in Hummock and Lawn Communities on Swedish Mires during the Last 150 Years , 1991 .

[34]  T. Moore.  PLANT PRODUCTION, DECOMPOSITION, AND CARBON EFFILUX IN A SUBARCTIC PA'ITERNED FEN , 1989 .

[35]  R. S. Clymo.  Sphagnum-dominated peat bog: a naturally acid ecosystem , 1984 .

[36]  Donatella Zona,et al.  Characterization of the carbon fluxes of a vegetated drained lake basin chronosequence on the Alaskan Arctic Coastal Plain , 2009 .

[37]  J. Canadell,et al.  Soil organic carbon pools in the northern circumpolar permafrost region , 2009 .

[38]  C. Freeman,et al.  Fluxes of CO2, CH4 and N2O from a Welsh peatland following simulation of water table draw-down: Potential feedback to climatic change , 1992 .

[39]  Leslie A. Morrissey,et al.  Methane emissions from Alaska Arctic tundra: An assessment of local spatial variability , 1992 .

[40]  Kenneth M. Hinkel,et al.  Morphometric and spatial analysis of thaw lakes and drained thaw lake basins in the western Arctic Coastal Plain, Alaska , 2005 .

[41]  F. Chapin,et al.  Soil Temperature and Nutrient Cycling in the Tussock Growth Form of Eriophorum Vaginatum , 1979 .

[42]  George L. Vourlitis,et al.  The effects of water table manipulation and elevated temperature on the net CO2 flux of wet sedge tundra ecosystems , 1998 .

[43]  Douglas L. Kane,et al.  Hydrologic and thermal properties of the active layer in the Alaskan Arctic , 1991 .

[44]  L. C. Bliss,et al.  6 – Plant Succession, Competition, and the Physiological Constraints of Species in the Arctic , 1992 .

[45]  Kenji Yoshikawa,et al.  Shrinking thermokarst ponds and groundwater dynamics in discontinuous permafrost near council, Alaska , 2003 .

[46]  Keith M. Hussey,et al.  Tundra Relief Features near Point Barrow, Alaska , 1966 .

[47]  F. Nelson,et al.  The circumpolar active layer monitoring (calm) program: Research designs and initial results , 2000 .

[48]  S. Verma,et al.  Soil surface CO2 flux in a Minnesota peatland , 1992 .

[49]  W. Oechel,et al.  The effect of soil moisture and thaw depth on CH4 flux from wet coastal tundra ecosystems on the north slope of Alaska , 1993 .

[50]  T. Lindholm,et al.  Moisture conditions in hummocks and hollows in virgin and drained sites on the raised bog Laaviosuo, southern Finland , 1984 .

[51]  Keith M. Hussey,et al.  The Oriented Lakes of Arctic Alaska , 1962, The Journal of Geology.

[52]  W. D. Billings,et al.  ROOT GROWTH, RESPIRATION, AND CARBON DIOXIDE EVOLUTION IN AN ARCTIC TUNDRA SOIL* , 1977 .