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Climate change may alter nutrient cycling in Arctic soils and plants. Deeper snow during winter, as well as summer warming, could increase soil temperatures and thereby the availability of otherwise limiting nutrients such as nitrogen (N). We used fences to manipulate snow depths in Svalbard for 9 consecutive years, resulting in three snow regimes: 1) Ambient with a maximum snow depth of 35 cm, 2) Medium with a maximum of 100 cm and 3) Deep with a maximum of 150 cm. We increased temperatures during one growing season using Open Top Chambers (OTCs), and sampled soil and vascular plant leaves throughout summer 2015. Labile soil N, especially inorganic N, during the growing season was significantly greater in Deep than Ambient suggesting N supply in excess of plant and microbial demand. However, we found no effect of Medium snow depth or short-term summer temperature increase on soil N, presumably due to minor impacts on soil temperature and moisture. The temporal patterns of labile soil N were similar in all snow regimes with high concentrations of organic N immediately after snowmelt, thereafter dropping towards peak growing season. Concentrations of all N forms increased at the end of summer. Vascular plants had high N at the start of growing season, decreasing as summer progressed, and leaf N concentrations were highest in Deep , corresponding to the higher soil N availability. Short-term summer warming was associated with lower leaf N concentrations, presumably due to growth dilution. Deeper snow enhanced labile soil organic and inorganic N pools and plant N uptake. Leaf 15N natural abundance levels (δ15N) in Deep indicated a higher degree of utilization of inorganic than organic N, which was especially pronounced in mycorrhizal plants. • Enhanced snow regimes cause high amounts of labile soil N during growing season. • Common tundra plants acquire more N in enhanced than in ambient snow regimes. • Common tundra plants acquire more inorganic N in enhanced snow regimes. [ABSTRACT FROM AUTHOR]

In arctic and subarctic regions, rapid climate changes enhance biogenic volatile organic compound (BVOC) emissions from vegetation, with potentially significant influence on atmospheric processes. However, the seasonal and diel patterns of bidirectional exchange (flux) of BVOCs remain poorly studied in these regions. Here, we deployed a proton-transfer-reaction time-of-flight mass spectrometer (PTR-TOF-MS) to investigate ecosystem-level BVOC fluxes over a growing season in a subarctic tundra heath in Abisko, Northern Sweden, and to quantify BVOC emissions from two widespread dwarf shrubs in the high latitudes, Salix myrsinites and Betula nana. As expected, ecosystem fluxes of short-chained oxygenated compounds (e.g., methanol, acetaldehyde and acetone) and terpenoids (e.g., isoprene, monoterpenes and sesquiterpenes) followed different seasonal and diel patterns. For the short-chained oxygenated compounds, net emissions dominated and peaked in the early growing season, while net deposition occurred sporadically, particularly at night. In contrast, terpenoids were almost exclusively emitted from the ecosystem, with maxima occurring in the peak growing season. At the branch level, these compound groups were emitted from both S. myrsinites and B. nana in clear diel patterns with high emissions during the day. S. myrsinites was dominated by isoprene emissions whilst B. nana was dominated by terpene emissions. Methanol, acetaldehyde and acetone were emitted at comparable levels and similar patterns from both species. Both ecosystem fluxes and branch emissions responded exponentially to enclosure temperature and depended on light levels. Compared to the BVOC emission models, however, the temperature responses were steeper for isoprene, monoterpenes, methanol and acetone, but weaker for sesquiterpenes. Apart from the well-known compounds, many other BVOCs, such as some carbonyls and nitrogen-containing compounds, were emitted from both the ecosystem and plants with significant contributions to the season variation in ecosystem fluxes. Overall, our study highlights the complexity of subarctic ecosystem BVOC fluxes, which vary both seasonally and diurnally. Vegetation composition changes triggered by climate change will shift BVOC composition, with important implications for atmospheric processes and local climate. • Ecosystem- and branch-level BVOC fluxes were measured using PTR-TOF-MS. • Net emissions dominated subarctic ecosystem BVOC fluxes. • Net deposition occurred mainly at night for few oxygenated short-chain compounds. • Large seasonal and species differences occurred in emission rates and composition. • Temperature responses for many BVOCs were stronger than previously assumed. [ABSTRACT FROM AUTHOR]

Corrigendum to Mörsdorf et al. (2019) "Deepened winter snow significantly influences the availability and forms of nitrogen taken up by plants in High Arctic tundra" [Soil Biology & Biochemistry 135 222-234] 1 Daily averages of soil temperatures across all plots within respective treatments, in a depth of approx. one cm below soil surface. "T" represents plots within snow regimes that were temperature enhanced during summer, using OTCs. [Extracted from the article]