Arctic patterned‐ground ecosystems: A synthesis of field studies and models along a North American Arctic Transect

Abstract

Arctic landscapes have visually striking patterns of small polygons, circles, and hummocks. The linkages between the geophysical and biological components of these systems and their responses to climate changes are not well understood. The “Biocomplexity of Patterned Ground Ecosystems” project examined patterned‐ground features (PGFs) in all five Arctic bioclimate subzones along an 1800‐km trans‐Arctic temperature gradient in northern Alaska and northwestern Canada. This paper provides an overview of the transect to illustrate the trends in climate, PGFs, vegetation, n‐factors, soils, active‐layer depth, and frost heave along the climate gradient. We emphasize the thermal effects of the vegetation and snow on the heat and water fluxes within patterned‐ground systems. Four new modeling approaches build on the theme that vegetation controls microscale soil temperature differences between the centers and margins of the PGFs, and these in turn drive the movement of water, affect the formation of aggradation ice, promote differential soil heave, and regulate a host of system properties that affect the ability of plants to colonize the centers of these features. We conclude with an examination of the possible effects of a climate warming on patterned‐ground ecosystems.

New Multicentury Evidence for Dispersal Limitation during Primary Succession

“…Greater cover of cryptogams in circles may reflect greater cryoturbation in circles than in forelands (Klaus et al 2013), resulting in greater turnover of vascular plant mass and opening up space for cryptogams. Greater belowground biomass in circles may reflect the small particle size of circle soils, produced by the upwelling of fine sediments in the centers of circles (Walker et al 2008). Our results for belowground biomass were in the same range as those from another primary succession sequence (Uselman et al 2007).…”

“…Soil C content increased with succession, typical for both forelands (Hodkinson et al 2003;Nakatsubo et al 2005;Tanner et al 2013) and circles (Walker et al 2008). The presence of soil C in young overburden might be attributable to preglacial organic matter that dominates soil C in soils !50 years old in an Austrian foreland (Bardgett et al 2007).…”

“…In glacial forelands, the chronosequence spans some kilometers (Hodkinson et al 2003;Nakatsubo et al 2005;Robbins and Matthews 2009), but in sorted circles, the successional chronosequence spans several meters (Kessler and Werner 2003;Haugland and Beatty 2005;Walker et al 2008). Thus, propagules need to disperse several kilometers on forelands but only a few meters on circles.…”

“…A1, A2 and tables A1, A2 are available online), which comprise a gradient of time since disturbance from newly exposed, cryogenically mixing soils in the center to older, more stable soils at the edge (Klaus et al 2013). Sorted circles occur within glacial forelands, as well as outside them, and are a widespread geomorphic feature of high latitudes (Kessler and Werner 2003;Haugland and Beatty 2005;Walker et al 2008). Successional sequences on sorted circles are similar to those on glacial forelands, comprising a gradient from cyanobacterial crusts near the center to evergreen plants at the edge (Haugland and Beatty 2005;Walker et al 2008;Makoto and Klaminder 2012).…”

Spatial distribution of pingos in northern Asia

“…Knowledge about the spatial distribution, morphometry, and statistical characteristics of a population of such landforms allows for conclusions on geological, geomorphological, hydrological, and cryological conditions during past and present times. Many detailed studies exist on the spatial distribution and spatial statistics of periglacial landforms such as rock glaciers (Esper-Angillieri, 2009), cryoplanation terraces (Nelson, 1998), solifluction features (Matsuoka, 2001), patterned ground (Walker et al, 2008), palsas (Luoto and Seppälä, 2002), pingos (Mackay, 1962), and thermokarst lakes and basins (Hinkel et al, 2005) in various polar regions. Increasingly, more recent studies make intense use of spatial analysis tools within Geographical Information System (GIS) software, allowing for the study of large digital datasets in combination with various environmental data.…”