Reduction in snow depth negatively affects decomposers but impact on decomposition rates is substrate dependent

Decomposition of organic matter in high latitude biomes makes a significant contribution to global fluxes of nutrients and carbon and is expected to accelerate due to climate change. The majority of studies have focused on decomposition during the growing season, but winter climate is expected to change dramatically. Furthermore, knowledge of the drivers of organic matter decomposition, such as litter chemical composition, has primarily been tested across the growing season so it is unknown whether these drivers are also important during the winter. Given that the depth of snow cover insulates the sub-nivean climate from the much colder air, it is an important control on winter decomposition and is expected to be influenced by climate change, we experimentally manipulated snow cover to simulate impacts of different winter precipitation scenarios on soil processes. Our results show that despite snow reduction negatively affecting decomposer abundance (by 99%) and bulk soil respiration (by 47%), litter decomposition rates showed little to no response. Furthermore, variation in winter decomposition rates among litter types was unrelated to nutrient status, indicating that our current understanding of drivers of litter decomposition may not hold during winter months. Despite very large reductions in decomposer fauna due to snow removal, litter decomposition rates were not consistently responsive, indicative of decoupled responses of soil organisms and soil processes to winter climate change.