Predictable Differences in Surface Soil Organic Carbon Storage across Landcover Types around Ísafjörður, Iceland

It is unclear how soil carbon varies by landcover type in areas with discontinuous and heterogenous vegetation cover in the Icelandic subarctic. Understanding which landcover types store the most C is important for understanding regional surface C inventory and for making decisions about optimal land use for C sequestration and storage. This study investigates the differences in soil C storage between different vegetation cover types in the Westfjords of northwestern Iceland. The three dominant landcover types in the Westfjords include heathlands, wetlands, and unvegetated areas. When compared across these three landcover types, surface soil C, bulk density, and soil moisture follow predictable patterns that vary between vegetated and unvegetated landcover. Heathland and wetland soils were consistently statistically similar in physical and chemical characteristics. Wetland and heathland had the highest surface soil C at 0.05 ± 0.02 g C cm3 and 0.06 ± 0.01 ± g C cm3 respectively, while unvegetated areas had a significantly lower mean surface soil C of 0.03 ± 0.009 g C cm3 . This trend flipped for bulk density, with wetland and heathland soils having similar mean bulk densities of 0.48 ± 0.36 g- soil cm3 , and 0.39 ± 0.14 g-soil cm3, while unvegetated soils had a much higher mean bulk density of 1.11 ± 0.63 g-soil cm3 . The similarities between heathland and wetland areas lay the groundwork for future regional surface soil C inventories that take into account patchy landcover type. Additionally, this pattern is important to consider in the context of land conservation and strategically altering land to sequester and store C.