Soil carbon storage and respiration potential across a landscape age and climate gradient in western Greenland
Abstract
The soil formation state factors proposed by Hans Jenny (climate, organisms, relief, parent material, time) explain many soil characteristics, yet geological controls on biological carbon cycling are not well represented in regional carbon models. Landscape age, for instance, can directly affect the quantity and quality of soil organic carbon, which are key determinants of the temperature sensitivity of soil organic matter (SOM) to decomposition. Temperature control of SOM decomposition is of particular importance in Arctic soils, which contain nearly half of global belowground organic carbon and have a permafrost thermal regime that straddles the freeze-thaw threshold. We investigated soil carbon storage and respiration potential across a west Greenland transect, and related the landscape carbon patterns to regional variation in climate and landscape age. The four study sites capture a range in: landscape age from 180 years on the inland Little Ice Age moraine near Kangerlussuaq to ~10,000 years at the coastal sites near Sisimiut and Nuuk, mean annual air temperatures from -5.7 to -1.4 °C, and mean annual precipitation from 149 to 752 mm. At each site, we collected surface and mineral samples from nine soil pits within similar vegetation cover and relief classes. We measured total organic carbon and nitrogen though elemental analysis, and incubated soils at 4 °C and field capacity moisture for 175 day to measure carbon dioxide production from which we derived soil respiration potential. We hypothesized that soil carbon storage and respiration potential would be greatest at the sites with the oldest landscape age. Soil carbon content was more than four times greater at the 10,000 year sites (Nuuk = 24.03%, Sisimiut = 17.34%) than the inland sites (Ørkendalen = 3.49%, LIA = 0.05%). Carbon quality decreased across the age gradient, as measured by a nearly two-fold increase in C:N ratio from the youngest and driest to the oldest and wettest soils (LIA = 12.2, Nuuk = 22.8). While soil respiration rates were significantly highest in the surface soils at the wettest coastal site, we observed high variation in respiration potential indicating that small-scale variation in carbon quality and other soil properties is high. This study informs our understanding of regional variation of carbon storage and turnover in western Greenland and provides important information for the parameterization of landscape scale models of soil carbon dynamics in the Arctic tundra.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.B31C0409B
- Keywords:
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- 0428 BIOGEOSCIENCES Carbon cycling;
- 0475 BIOGEOSCIENCES Permafrost;
- cryosphere;
- and high-latitude processes;
- 0486 BIOGEOSCIENCES Soils/pedology;
- 0439 BIOGEOSCIENCES Ecosystems;
- structure and dynamics