The Role of Biological Soil Crusts in Nitrogen Cycling and Soil Stabilization in Kangerlussuaq, West Greenland

Abstract

Biological soil crusts (biocrusts) naturally coexist with vascular plants in many dryland ecosystems. Although most studies of dryland biocrusts have been conducted in warm deserts, dryland biocrusts also exist in the Arctic, where they may be an important source of nitrogen (N) and carbon (C) to nutrient-limited environments. In Kangerlussuaq, Greenland, wind-driven soil erosion has created a heterogeneous landscape where biocrusts dominate distinct patches of soil but are absent from the surrounding shrub and graminoid tundra. Prior to this study, little was known about the physical development and nutrient cycling of west Greenland biocrusts and their role in maintaining landscape heterogeneity. We characterized the physical properties, lichen assemblages, and nutrient concentrations of biocrusts and underlying soils along gradients in biocrust development and age. We found that biocrusts took 180 ± 40 years to fully develop and that biocrusts became thicker and soil penetration resistance increased as they developed. The N-fixing lichen Stereocaulon sp. was found throughout the study region at all stages of biocrust development. Natural 15N abundance suggests that Stereocaulon sp. obtains about half of its N from biological fixation and that some biologically fixed N is incorporated into the underlying soils over time. Although the N and C concentrations of underlying soils increased slightly with biocrust development, nutrient concentrations under the most developed biocrusts remained low compared to the surrounding vegetated tundra. Our results suggest that biocrusts are a persistent feature and play an important role in maintaining the high spatial heterogeneity of the Kangerlussuaq terrestrial landscape.