Factors affecting soil biogeochemical development in the glacier foreland of Midtre Lovenbreen, Svalbard

Climate change has caused significant receding of glaciers, exposing the ice-free land surfaces. These newly exposed lands are regarded as the best place for studying soil development along the chronosequence. However, the biogeochemical properties of the de-glaciated soils are not only affected by time but also by parent materials, surrounding environments, and geomorphological disturbances. We aim to understand soil biogeochemical development considering various soil-forming factors in the glacier foreland of Midtre Lovénbreen, Svalbard. Total 38 sampling points were selected considering soil age, X, Y coordinates, slope, wind, and glacial-fluvial runoff. We analyzed vegetation and soil parameters as follows: vegetation frequency; normalized difference vegetation index (NDVI); soil organic carbon (SOC), total nitrogen (TN) and total phosphorus (TP) contents; particle size distribution; soil pH; electrical conductivity (EC); K, Ca, Na and Mg contents. To better understand the quality of SOM in early soil development, we separated the SOC and TN into a free-light (FLF), silt/clay-associated (Silt+Clay), and sand-sized (Sand) fractions. As a result, the SOC and TN contents increased significantly with increasing soil age, which was highly correlated with the frequency of S. oppositifolia and S. polaris, and NDVI. Consistently, the FLF, consisting of plant-derived organic matter, showed a higher proportion with increasing soil age. Our findings confirmed that the expansion of vegetation cover significantly contributed to the chronological accumulation of SOM on the surface soil. Meanwhile, higher TP content and EC in the young-soil sites in the top 5-cm depth than the older-soil sites were probably due to the subglacial materials remaining after the glacier retreated. In the old-soil sites, biogeochemical materials originating from the parent bedrocks (TP and Mg) or the sea-salt deposition (Na and K) were higher in the subsoil and topsoil, respectively. Moreover, we found that glacial-fluvial runoff could delay soil development by reducing SOC, TN, clay, EC, and vegetation cover. Therefore, we suggest that soil development in the glacier foreland can be affected not only by the chronological changes but also by parent materials, surrounding environments, and geomorphological disturbances.