Content and quality of soil organic matter in topsoils under different tundra vegetation in central Spitsbergen (High Arctic)

Permafrost-affected soils contain a large amount of soil organic matter (SOM) which may become easily available to microbial decomposition due to climate warming. Despite numerous studies conducted on SOM in permafrostaffected soils, our knowledge about its quantity and chemistry requires further enhancement in the central part of Spitsbergen, due to a lack of detailed studies in this area. Especially, very little is known about the link between soil and vegetation in the High Arctic region. The main aim of this study was to determine the quantity and chemistry of SOM in the topsoil horizons of permafrost-affected soils covered with different tundra vegetation types in the vicinity of Longyearbyen (central Spitsbergen). Four types of tundra (pioneer tundra, arctic meadow, wet moss tundra, and heath tundra) were selected for this study. The obtained results indicate that the highest mean content of total organic carbon (TOC, 24.22 %) and total nitrogen (TN, 0.79 %) occurred in topsoils covered with heath tundra, while clearly lower mean contents of TOC and TN were noted in topsoils under wet moss tundra (5.96 %, 0.37 %, respectively), arctic meadow (3.40 %, 0.19 %, respectively), and pioneer vegetation (2.56 %, 0.21 %, respectively). The obtained FTIR-ATR spectroscopy results indicated significant differences in the chemical composition of SOM under different types of tundra. The highest mean value of the aromatic C/aliphatic C ratio (1632/2928 ratio) was noted for topsoils covered with arctic meadow (2.82). On the other hand, the lowest mean value of aromatic C/aliphatic C ratio for SOM was obtained for topsoils covered with heath tundra (0.81). This indicated that SOM in topsoils under heath tundra vegetation is characterized by a higher content of aliphatic compounds in relation to aromatic compounds. Moreover, both soil texture and soil pH significantly affected the content and quality of SOM in the studied topsoils.