Active layer thermal regime at different vegetation covers at Lions Rump, King George Island, Maritime Antarctica Ivan C.C. Almeida a,b, ⁎, Carlos Ernesto G.R. Schaefer b , Raphael B.A. Fernandes b , Thiago T.C. Pereira c,b , Alexandre Nieuwendam d , Antônio Batista Pereira e a Instituto Federal Norte de Minas Gerais, Campus Januária, Fazenda São Geraldo, CEP 39480-000 Januária, MG, Brazil b INCT-Criosfera, Departamente de Solos, Universidade Federal de Viçosa, Av. PH Rolfs, CEP 36570-000 Viçosa, MG, Brazil c Universidade do Estado de Minas Gerais, Av. Prof. Mário Palmério, 1001 Frutal, MG, Brazil d Centro de Estudos Geográficos-IGOT, Universidade de Lisboa, Portugal e INCT-APA, Universidade Federal do Pampa, Campus São Gabriel, Av. Antônio Trilha, Centro, CEP 97300-000 São Gabriel, RS, Brazil abstract article info Article history: Received 4 March 2013 Received in revised form 24 March 2014 Accepted 31 March 2014 Available online 12 April 2014 Keywords: Soil thermal regime Climate change Cryosol Permafrost n-F index Climate change impacts the biotic and abiotic components of polar ecosystems, affecting the stability of perma- frost, active layer thickness, vegetation, and soil. This paper describes the active layer thermal regimes of two ad- jacent shallow boreholes, under the same soil but with two different vegetations. The study is location in Lions Rump, at King George Island, Maritime Antarctic, one of the most sensitive regions to climate change, located near the climatic limit of Antarctic permafrost. Both sites are a Turbic Cambic Cryosol formed on andesitic basalt, one under moss vegetation (Andreaea gainii, at 85 m a.s.l.) and another under lichen (Usnea sp., at 86 m a.s.l.), located 10 m apart. Ground temperature at same depths (10, 30 and 80 cm), water content at 80 cm depth and air temperature were recorded hourly between March 2009 and February 2011. The two sites showed sig- nificant differences in mean annual ground temperature for all depths. The lichen site showed a higher soil tem- perature amplitude compared to the moss site, with ground surface (10 cm) showing the highest daily temperature in January 2011 (7.3 °C) and the lowest daily temperature in August (-16.5 °C). The soil temper- ature at the lichen site closely followed the air temperature trend. The moss site showed a higher water content at the bottommost layer, consistent with the water-saturated, low landscape position. The observed thermal buff- ering effect under mosses is primarily associated with higher moisture onsite, but a longer duration of the snow- pack (not monitored) may also have influenced the results. Active layer thickness was approximately 150 cm at low-lying moss site, and 120 cm at well-drained lichen site. This allows to classify these soils as Cryosols (WRB) or Gelisols (Soil Taxonomy), with evident turbic features. © 2014 Elsevier B.V. All rights reserved. 1. Introduction A more precise knowledge on the distribution and properties of Ant- arctic permafrost is essential for the cryosphere and life sciences, since it will represent a major control on ecosystem modification following climate-induced changes (Vieira et al., 2010). Permafrost, defined as any subsurface earth materials remaining below 0 °C for more than two years, may be profoundly affected by global warming. Permafrost- affected soils normally present an active layer, which is defined as the portion of soil which experiences seasonal thawing and freezing (Brown et al., 2000). The regional climate is a first-order control on permafrost thermal regime, with local microclimate further affecting ground surface tem- peratures, and therefore, the thermal state of the permafrost at meso- and microscales. Permafrost temperatures and distribution depend on climatic and topographic factors, such as air temperature, solar radia- tion, and snow cover, as related to aspect, slope angle and altitude (Luetschg et al., 2004). At a local scale, ground surface and permafrost temperatures are affected by the characteristics of the snowpack, the type and height of vegetation, moisture content in the ground, topogra- phy, the geothermal flux, and the thermal diffusivity of the earth materials (Judge, 1973). Hence, permafrost and vegetation are key envi- ronmental components and both are sensitive to climate change (Guglielmin et al., 2008), particularly where permafrost has a discontin- uous distribution (Burgess et al., 2000), as in the case of Maritime Antarctica (Bockheim et al., 2013) where Lions Rump is located. Mari- time Antarctica has been increasingly recognized as a key region for monitoring climate change (Cannone et al., 2006; Vieira et al., 2010; Bockheim et al., 2013). Geomorphology 225 (2014) 36–46 ⁎ Corresponding author. E-mail addresses: ivan.almeida@ifnmg.edu.br (I.C.C. Almeida), carlos.schaefer@ufv.br (C.E.G.R. Schaefer), raphael@ufv.br (R.B.A. Fernandes), torresthiago@yahoo.com.br (T.T.C. Pereira), alexandretn@gmail.com (A. Nieuwendam), anbatistape@gmail.com (A.B. Pereira). http://dx.doi.org/10.1016/j.geomorph.2014.03.048 0169-555X/© 2014 Elsevier B.V. All rights reserved. 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