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Rising temperatures amplify biogenic volatile organic compound (VOC) emissions from Arctic vegetation, causing feedbacks to the climate system. Changes in climate also alter plant physiology and vegetation composition, all of which can influence VOC emissions. Moreover, leaf development and biotic stresses cause highly variable emissions during the growing season. Therefore, linking VOC emissions with plant traits and tracking responses to climate change might provide better understanding of VOC emission regulation under future conditions. We measured VOC emissions and other plant traits in dwarf birch (Betula glandulosa) at two elevations in Narsarsuaq, South Greenland. The measurements were performed in warming experiments that have run since 2016. We collected VOCs using the branch enclosure method from early June until late July 2019 (n = 200). Emissions of green leaf volatiles (GLVs), oxygenated monoterpenes (oMTs), and homoterpenes followed a seasonal trend. VOC emission rates and the diversity of the VOC blend decreased at the end of the measurement period. Differences in VOC emission rates between elevations were pronounced early in the season. Majority of the traits did not explain the variation in VOC emissions. We show strong seasonal variability in VOC emissions within the growing season, which is likely driven by leaf phenology. While the diversity of VOCs was greater at the milder low-elevation site, VOC emission rates were higher or similar at the harsher high-elevation site, showing stronger VOC emission potentials than previously assumed. Seasonal variations in the emissions of VOCs are crucial for accurate predictions of current and future VOC emissions from arctic ecosystems., Rising temperatures amplify biogenic volatile organic compound (VOC) emissions from Arctic vegetation, causing feedbacks to the climate system. Changes in climate also alter plant physiology and vegetation composition, all of which can influence VOC emissions. Moreover, leaf development and biotic stresses cause highly variable emissions during the growing season. Therefore, linking VOC emissions with plant traits and tracking responses to climate change might provide better understanding of VOC emission regulation under future conditions. We measured VOC emissions and other plant traits in dwarf birch (Betula glandulosa) at two elevations in Narsarsuaq, South Greenland. The measurements were performed in warming experiments that have run since 2016. We collected VOCs using the branch enclosure method from early June until late July 2019 (n = 200). Emissions of green leaf volatiles (GLVs), oxygenated monoterpenes (oMTs), and homoterpenes followed a seasonal trend. VOC emission rates and the diversity of the VOC blend decreased at the end of the measurement period. Differences in VOC emission rates between elevations were pronounced early in the season. Majority of the traits did not explain the variation in VOC emissions. We show strong seasonal variability in VOC emissions within the growing season, which is likely driven by leaf phenology. While the diversity of VOCs was greater at the milder low-elevation site, VOC emission rates were higher or similar at the harsher high-elevation site, showing stronger VOC emission potentials than previously assumed. Seasonal variations in the emissions of VOCs are crucial for accurate predictions of current and future VOC emissions from arctic ecosystems.

Plants release a complex blend of volatile organic compounds (VOCs) in response to stressors. VOC emissions vary between contrasting environments and increase with insect herbivory and rising temperatures. However, the joint effects of herbivory and warming on plant VOC emissions are understudied, particularly in high latitudes, which are warming fast and facing increasing herbivore pressure. We assessed the individual and combined effects of chemically mimicked insect herbivory, warming, and elevation on dwarf birch (Betula glandulosa) VOC emissions in high-latitude tundra ecosystems in Narsarsuaq, South Greenland. We hypothesized that VOC emissions and compositions would respond synergistically to warming and herbivory, with the magnitude differing between elevations. Warming increased emissions of green leaf volatiles (GLVs) and isoprene. Herbivory increased the homoterpene, (E)-4,8-dimethyl-1,3,7-nonatriene, emissions, and the response was stronger at high elevation. Warming and herbivory had synergistic effects on GLV emissions. Dwarf birch emitted VOCs at similar rates at both elevations, but the VOC blends differed between elevations. Several herbivory-associated VOC groups did not respond to herbivory. Harsher abiotic conditions at high elevations might not limit VOC emissions from dwarf birch, and high-elevation plants might be better at herbivory defense than assumed. The complexity of VOC responses to experimental warming, elevation, and herbivory are challenging our understanding and predictions of future VOC emissions from dwarf birch-dominated ecosystems., Plants release a complex blend of volatile organic compounds (VOCs) in response to stressors. VOC emissions vary between contrasting environments and increase with insect herbivory and rising temperatures. However, the joint effects of herbivory and warming on plant VOC emissions are understudied, particularly in high latitudes, which are warming fast and facing increasing herbivore pressure. We assessed the individual and combined effects of chemically mimicked insect herbivory, warming, and elevation on dwarf birch (Betula glandulosa) VOC emissions in high-latitude tundra ecosystems in Narsarsuaq, South Greenland. We hypothesized that VOC emissions and compositions would respond synergistically to warming and herbivory, with the magnitude differing between elevations. Warming increased emissions of green leaf volatiles (GLVs) and isoprene. Herbivory increased the homoterpene, (E)-4,8-dimethyl-1,3,7-nonatriene, emissions, and the response was stronger at high elevation. Warming and herbivory had synergistic effects on GLV emissions. Dwarf birch emitted VOCs at similar rates at both elevations, but the VOC blends differed between elevations. Several herbivory-associated VOC groups did not respond to herbivory. Harsher abiotic conditions at high elevations might not limit VOC emissions from dwarf birch, and high-elevation plants might be better at herbivory defense than assumed. The complexity of VOC responses to experimental warming, elevation, and herbivory are challenging our understanding and predictions of future VOC emissions from dwarf birch-dominated ecosystems.

Observations of changes in phenology have provided some of the strongest signals of the effects of climate change on terrestrial ecosystems. The International Tundra Experiment (ITEX), initiated in the early 1990s, established a common protocol to measure plant phenology in tundra study areas across the globe. Today, this valuable collec-tion of phenology measurements depicts the responses of plants at the colder extremes of our planet to experimental and ambient changes in temperature over the past decades. The database contains 150 434 phenology observations of 278 plant species taken at 28 study areas for periods of 1–26 years. Here we describe the full data set to increase the visibility and use of these data in global analyses and to invite phenology data contributions from underrepresented tundra locations. Portions of this tundra phenology database have been used in three recent syntheses, some data sets are expanded, others are from entirely new study areas, and the entirety of these data are now available at the Polar Data Catalogue (https://doi.org/10.21963/13215).

Snow is an important driver of ecosystem processes in cold biomes. Snow accumulation determines ground temperature, light conditions, and moisture availability during winter. It also affects the growing season’s start and end, and plant access to moisture and nutrients. Here, we review the current knowledge of the snow cover’s role for vegetation, plant-animal interactions, permafrost conditions, microbial processes, and biogeochemical cycling. We also compare studies of natural snow gradients with snow experimental manipulation studies to assess time scale difference of these approaches. The number of tundra snow studies has increased considerably in recent years, yet we still lack a comprehensive overview of how altered snow conditions will affect these ecosystems. Specifically, we found a mismatch in the timing of snowmelt when comparing studies of natural snow gradients with snow manipulations. We found that snowmelt timing achieved by snow addition and snow removal manipulations (average 7.9 days advance and 5.5 days delay, respectively) were substantially lower than the temporal variation over natural spatial gradients within a given year (mean range 56 days) or among years (mean range 32 days). Differences between snow study approaches need to be accounted for when projecting snow dynamics and their impact on ecosystems in future climates.

This is the third in a planned series of data papers presenting modelled vector distributions produced during the ECDC and EFSA funded VectorNet project. The data package presented here includes those Culicoides vectors species first modelled in 2015 as part of the VectorNet gap analysis work namely C. imicola, C. obsoletus, C. scoticus, C. dewulfi, C. chiopterus, C. pulicaris, C. lupicaris, C. punctatus, and C. newsteadi. The known distributions of these species within the Project area (Europe, the Mediterranean Basin, North Africa, and Eurasia) are currently incomplete to a greater or lesser degree. The models are designed to fill the gaps with predicted distributions, to provide a) first indication of vector species distributions across the project geographical extent, and b) assistance in targeting surveys to collect distribution data for those areas with no field validated information. The models are based on input data from light trap surveillance of adult Culicoides across continental Europe and surrounding regions (71.8°N –33.5°S, – 11.2°W – 62°E), concentrated in Western countries, supplemented by transect samples in eastern and northern Europe. Data from central EU are relatively sparse.

1. Species richness is unrivalled as the most reported biodiversity metric in ecological and conservation research. Unfortunately, species richness ignores the scale-dependency of biodiversity. 2. We propose the metric uniquity, a quantitative and spatially scalable measure of uniqueness of a site based on a species-by-site matrix and a site-by-habitat type classification with area weights for habitat types correcting for sampling biases. 3. An example of uniquity is presented using vascular plant data from 130 sites representing a larger region (Denmark). We demonstrate the importance of the scale parameter of uniquity for the prediction of independent uniqueness indices calculated from species distribution data and the number of recorded red listed species. 4. We compare the performance of uniquity with the performance of the indices Local Contribution to Beta Diversity (LCBD) and Range Rarity Richness (RRR), and we investigate its sensitivity to small sample size and poorly resolved habitat classification. 5. We assess the performance of the uniquity metric applied to DNA metabarcoding data for plants, fungi and eukaryotes from the same set of study sites. 6. Uniquity is a strong predictor of site uniqueness based on national distribution data and also correlates neatly with the observed number of red listed species. Uniquity based on DNA metabarcoding corresponds well with the number of red listed species observed. 7. Perspective: Uniquity is generally applicable to biotas sampled with comparable effort, including field inventories, trap sampling, and DNA metabarcoding data. To our knowledge uniquity is the first index of uniqueness that explicitly considers spatial scale and sampling biases, while simultaneously accepting non-annotated DNA-data as input. Based on our study we offer general recommendations for further use and testing of uniquity as conservation value metric., 1. Species richness is unrivalled as the most reported biodiversity metric in ecological and conservation research. Unfortunately, species richness ignores the scale-dependency of biodiversity.2. We propose the metric uniquity, a quantitative and spatially scalable measure of uniqueness of a site based on a species-by-site matrix and a site-by-habitat type classification with area weights for habitat types correcting for sampling biases.3. An example of uniquity is presented using vascular plant data from 130 sites representing a larger region (Denmark). We demonstrate the importance of the scale parameter of uniquity for the prediction of independent uniqueness indices calculated from species distribution data and the number of recorded red listed species.4. We compare the performance of uniquity with the performance of the indices Local Contribution to Beta Diversity (LCBD) and Range Rarity Richness (RRR), and we investigate its sensitivity to small sample size and poorly resolved habitat classification.5. We assess the performance of the uniquity metric applied to DNA metabarcoding data for plants, fungi and eukaryotes from the same set of study sites.6. Uniquity is a strong predictor of site uniqueness based on national distribution data and also correlates neatly with the observed number of red listed species. Uniquity based on DNA metabarcoding corresponds well with the number of red listed species observed.7. Perspective: Uniquity is generally applicable to biotas sampled with comparable effort, including field inventories, trap sampling, and DNA metabarcoding data. To our knowledge uniquity is the first index of uniqueness that explicitly considers spatial scale and sampling biases, while simultaneously accepting non-annotated DNA-data as input. Based on our study we offer general recommendations for further use and testing of uniquity as conservation value metric.