Land cover and landform-based upscaling of soil organic carbon stocks on the Brøgger Peninsula, Svalbard

Abstract

In this study we assess the total storage, landscape distribution, and vertical partitioning of soil organic carbon (SOC) stocks on the Brøgger Peninsula, Svalbard. This type of high Arctic area is underrepresented in SOC databases for the northern permafrost region. Physico-chemical, elemental, and radiocarbon (14 C) dating analyses were carried out on thirty-two soil profiles. Results were upscaled using both a land cover classification (LCC) and a landform classification (LFC). Both LCC and LFC approaches provide weighted mean SOC 0-100 cm estimates for the study area of 1.0 ± 0.3 kg C m −2 (95% confidence interval) and indicate that about 68 percent of the total SOC storage occurs in the upper 30 cm of the soil, and about 10 percent occurs in the surface organic layer. Furthermore, LCC and LFC upscaling approaches provide similar spatial SOC allocation estimates and emphasize the dominant role of "vegetated area" (4.2 ± 1.6 kg C m −2) and "solifluction slopes" (6.7 ± 3.6 kg C m −2) in SOC 0-100 cm storage. LCC and LFC approaches report different and complementary information on the dominant processes controlling the spatial and vertical distribution of SOC in the landscape. There is no evidence for any significant SOC storage in the permafrost layer. We hypothesize, therefore, that the Brøgger Peninsula and similar areas of the high Arctic will become net carbon sinks, providing negative feedback on global warming in the future. The surface area that will have vegetation cover and incipient soil development will expand, whereas only small amounts of organic matter will experience increased decomposition due to active-layer deepening.

Regional and local scale variations in soil organic carbon stocks in West Greenland

“…Generally, topsoil SOCS are controlled by vegetation cover because most Arctic plants root within the upper 25–30 cm ( Iversen et al., ). Vegetation varies in its spatial distribution and portions affecting the spatial distribution of SOCS in Arctic environments ( Elberling et al., ; Horwath Burnham and Sletten , ; Palmtag et al., ; Siewert et al., ; Wojcik et al., ). In SISI, VEG1 predominantly covers west‐ and northwest‐facing locations where plant growth might be restricted by constant onshore winds and high direct solar radiation.…”

“…In LU4, SOCS are highest at 50–100 cm, which might be connected a thick active layer since the isolating effect of sites with low‐growing vegetation is less than on sites with shrub vegetation leading to deep thawing and relocation of SOC in LU4. Besides cryoturbation, SOCS can also be high in the subsoil caused by buried organic material which was deposited or covered by slope processes related to various topographic positions within different landscape patterns ( Palmtag et al., , ; Wojcik et al., ).…”

“…In general, landscape and landform classifications are common approaches to address the horizontal and vertical distribution of SOCS ( Siewert et al., ; Palmtag et al., ; Wojcik et al., ). Further, such classifications are suitable to represent local patterns like accumulation areas with additional input of SOC (as in SISI) or lower SOCS on convex shaped moraines (as in RUSS).…”

“…On a local scale, vegetation and topography influence SOCS distribution in Greenland ( Ozols and Broll , ; Jensen et al., ; Elberling et al., ; Horwath Burnham and Sletten , ; Henkner et al., ) and also in other Arctic environments ( Palmtag et al., , ; Siewert et al., , ; Wojcik et al., ). The topography affects both the local and the regional climate, thaw depth of the active layer, deflation, erosion by water and related accumulation processes ( Van Tatenhove and Olesen , ; Müller et al., ).…”

“…Katabatic winds take control in east–west direction, with more arid and colder conditions close to the ice margin over distances of some hundred meters to a few kilometers ( Müller et al., ). In addition, topsoil SOCS are connected to distribution pattern of vegetation and soil moisture ( Henkner et al., ), whereas slope processes, cryoturbation and active layer thickness affect the vertical distribution of SOC in the subsoil ( Bockheim , ; Palmtag et al., , ; Siewert et al., , ; Wojcik et al., ). However, vegetation pattern and the soil water regime are related to topographic positions as well ( Elberling et al., ), mainly determined by the local Holocene deglaciation history resulting in moraines stretching across valleys from north to south ( Henkner et al., ).…”