Soil carbon development in the recently deglaciated foreland of Midtre Lovenbreen, Spitsbergen

Abstract

Global warming is leading the rapid retreat of glaciers in the high Arctic, exposing new land. The accumulation of soil organic carbon (SOC) in the proglacial environment is initiated after microorganisms and plants settle down. Studies in glacier forelands have mostly focused on the chronosequential changes in soil, plants, and microorganisms following glacier recession. However, the quantity and rate of SOC accumulation over the glacier foreland are affected not only by time but also by several environmental factors. Furthermore, proglacial land is dynamically reworked by runoff activity of glacier streams. However, those influences have not yet been thoroughly investigated. Therefore, we were aiming to understand the distribution pattern of SOC and to estimate the SOC stock and carbon (C) storage in different soil fractions from the foreland of the Midtre Lovenbreen, Spitsbergen, Norway (79°N, 12°W). We considered the deglaciated years and several environmental factors such as microtopography, runoff activity, etc. as influencing factors on SOC. A total of 36 sampling points were selected to collect soil for 0-30 cm depth, and vegetation was surveyed from 93 points. The SOC stock was estimated from concentration of SOC and bulk density calculated from soil texture. Soil were fractionated based on density and size. The SOC stock for 30 cm depth ranged from 1.5 to 15.4 Mg/ha in the foreland of Midtre Lovenbreen. The SOC content among 5-10, 10-20, and 20-30 cm was not different, neither was there any variance in bulk density through all depths. Thus, SOC stock was closely related to the SOC content of the top soil (0-5 cm). Among several vegetation-related parameters, the sum of vascular plants' frequency showed the highest correlation with the SOC content of top soil and SOC stock. However, intestingly, there was no correlation between the SOC stock and soil age. The active and intermittent runoff sites showed significantly lower SOC content compared to sites with no runoff. Glacier/snow meltwater would have washed out previously established vegetation and accumulated SOC. We are currently using multivariate statistics to deal with quantitative and qualitative data, and are scrutinizing the relationship between SOC stock and environmental variables acquired from DEM and remote sensing data in-depth as the next step. Furthermore, we are analyzing C contents in each soil fractions to scrutinize soil C development in the glacier foreland. Through an understanding of the relationship between SOC content/stock and environmental parameters, it will be possible to quantify and predict SOC distribution in recently deglaciated soil.