Responses of Nitrogen Transformation Processes in Arctic Organic Soil to Snow Cover Depth Variation

초록

Winter snow accumulation insulates Arctic soils, maintaining relatively warm soil temperatures despite low air temperatures and allowing microbial activity to occur in unfrozen soils. However, climate change is altering snow precipitation patterns, potentially affecting winter microbial processes and soil organic matter storage. Nitrogen availability during winter is particularly important for supporting spring plant growth, yet winter nitrogen dynamics in Arctic regions remain relatively understudied. In particular, gross nitrogen transformation rates, which capture both nitrogen production and consumption processes, remain less extensively studied than net nitrogen measurements that reflect only the net balance. This study aimed to investigate how soil nitrogen transformation processes in Arctic organic soil respond to varying winter snow cover conditions. Soil samples were incubated at ?20°C, 0°C, and 5°C to simulate winter environments associated with different levels of snow accumulation. To account for the influence of spring snowmelt on soil moisture, soil water-holding capacity was adjusted to 30%, 60%, and 100% at 5°C, and samples were incubated for 10 days. Gross nitrogen transformation rates were quantified using ¹?N isotope labeling combined with inorganic nitrogen extraction and isotopic analysis. To access nitrogen immobilization and gaseous losses, microbial biomass and N₂O emissions were measured using the chloroform fumigation-extraction method, and gas chromatography, respectively. This study enhances our understanding of nitrogen production and consumption processes by quantifying gross nitrogen transformation in Arctic soil under changing winter conditions associated with warming. Furthermore, by improving preditions of nitrogen availability not only during winter but also for subsequent spring plant growth, this work contributes to advancing ecosystem models of Arctic.