The Effects of Vegetation Succession and Landscape on the Evolution of Soil Properties: A Chronosequence Study Along the Proglacial Area of Skaftafellsjökull Glacier, SE Iceland

Abstract:

On young soils developing along the recessional path left by the Skaftafellsjökull glacier, SE-Iceland, we investigated the soil development, vegetation succession and landscape representing an age chronosequence of 120 years. In total, 54 sampling sites were distributed along three moraines representing surfaces exposed for 8, 65 and 120 years. For comparison, soil samples were collected from nearby birch woodlands, representing soils in a mature ecosystem likely to establish on the moraines in the future.

The youngest moraines were sparsely vegetated with only 10% cover of mosses and grasses. The plant cover increased to 67% after 120 years, and was characterized by mosses (38%), dwarf shrubs (20%) and low growing birch (3.5%). Consequently, the soil formed over 120 years contained 1.1 kg C m^-2 in the surface layer (0-10 cm), or about one third of the 3.2 kg C m^-2 in soil under the woodlands. The N stock was estimated at 0.06 kg N m^-2after 120 yrs, almost one fourth of that under the woodlands. The data suggest that landscape affects vegetation establishment and in turn, both landscape and vegetation affect soil development. Thus, concentrations of soil organic carbon (SOC), N and noncrystalline oxalate extractable Al and Fe were higher within depressions than on ridges and slopes.

The comparison of SOC stock in the moraine-derived soils with that under the birch woodlands showed that the young proglacial soils still have a large potential to accrete SOC within the developing pedosphere. With the observed accrual rate of 9.1 g C m^-2 yr^-1in the top 10 cm, it may take the moraine soils an additional 220 yrs to accrue SOC stocks comparable with those under the birch forest. Given the fact that all Icelandic glaciers are receding, assessing SOC sequestration in new soil formation may be important to off-setting some of anthropogenic emissions.

The research is funded by the University of Iceland Doctoral Fund, the University of Iceland Trust Fund, the Landsvirkjun‘s Energy Research Fund, the Friends of Vatnajökull Fund, the Icelandic Research Fund (no. 120211021) and Targeted Investment in Excellence, Climate, Water and Carbon Project, C-MASC, OSU, USA.

Keywords: Soil organic carbon, nitrogen, soil development, chronosequence, plant colonization, vegetation succession, glacier forefield, Skaftafellsjökull, Iceland.