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Understanding and predicting large-scale ecological responses to global environmental change requires comparative studies across geographic scales with coordinated efforts and standardized methodologies. We designed, applied and assessed standardized protocols to measure tundra herbivory at three spatial scales: plot, site (habitat), and study area (landscape). The plot and site-level protocols were tested in the field during summers 2014-2015 at eleven sites, nine of them comprising warming experimental plots included in the International Tundra Experiment (ITEX). The study area protocols were assessed during 2014-2018 at 24 study areas across the Arctic. Our protocols provide comparable and easy-to-implement methods for assessing the intensity of invertebrate herbivory within ITEX plots and for characterizing vertebrate herbivore communities at larger spatial scales. We discuss methodological constraints and make recommendations for how these protocols can be used and how sampling effort can be optimized to obtain comparable estimates of herbivory, both at ITEX sites and at large landscape scales. The application of these protocols across the tundra biome will allow characterizing and comparing herbivore communities across tundra sites and at ecologically relevant spatial scales, providing an important step towards a better understanding of tundra ecosystem responses to large-scale environmental change. CGB was funded by the Estonian Research Council (grant IUT 20-28), and the European Regional Development Fund (Centre of Excellence EcolChange). JDMS was supported by the Research Council of Norway (262064). OG and LB were supported by the French Polar Institute (program “1036 Interactions”) and PRC CNRS Russie 396 (program “ICCVAT”). DSH, NL, MAG, JB and JDR were supported by the Natural Sciences and Engineering Research Council (Canada). NL, MAG, JB and JDR were supported by the Polar Continental Shelf Program. NL was supported by the Canada Research Chair program and the Canada Foundation for Innovation. NL and JB were supported by Environment Canada and Polar Knowledge Canada. NL and MAG were supported by the Government of Nunavut, the Igloolik Community, and Université de Moncton. NL, MAG and JB were supported by the Northern Scientific Training Program. JMA was funded by Carl Tryggers stiftelse för vetenskaplig forskning and Qatar Petroleum (QUEX-CAS-QP-RD-18_19). IHM-S was funded by the UK Natural Environmental Research Council Shrub Tundra (NE/M016323/1) grant. ISJ was funded by the University of Iceland Research Fund. Fieldwork in Yamal peninsula (Erkuta, Sabetta and Belyi) for DE, NS and AS was supported by the Russian Foundation for Basic Research (No: 18-05-60261 and No: 18-54-15013), Fram Centre project YaES (No: 362259), the Russian Center of Development of the Arctic, and the “Yamal-LNG” company. Fieldwork in Utqiaġvik was supported by the U.S. Fish and Wildlife Service. Fieldwork in Svalbard was supported by the Norwegian Research Council (AFG No: 246080/E10), the Norwegian Polar Institute, Climate-ecological Observatory for Arctic Tundra – COAT, the Svalbard Environmental protection fund (project number 15/20), and the University Centre in Svalbard (UNIS) and the AB-338/AB-838 students of 2018. Sampling at Billefjorden was supported by GACR 17- 20839S.

Despite increasing evidence that large northern lakes are rapidly changing due to climate change, descriptive baseline studies of their physicochemical properties are largely lacking, limiting our ability to detect or predict change. This study represents a comprehensive scientific assessment of the limnology of Yukon’s largest lake: Lhù’ààn Mân’ (Kluane Lake), an important waterbody for local and First Nation communities, and key habitat for trout and salmon. Water sample and instrument data generated throughout 2015 describe distinct regions within the lake and their respective seasonal variability. A deep, glacially-influenced southern basin was characterized by cold, turbid, poorly stratified, unproductive, and nutrient-poor conditions; a shallower northwestern region (Tthe Kaala Daagur (Brooks/Little Arm)) was warmer, fully mixed, and more productive; a northeast region (’Ùha K’ènji (Talbot/Big Arm)) was clear and stratified with intermediate depth, temperature, productivity, and nutrient concentrations; and a central region had intermediate physicochemical conditions relative to the other three. This variability demonstrates the need for adequate spatial (within lake) and temporal (between seasons) monitoring of large northern lakes. In 2016, glacier recession within the watershed resulted in diversion of the lake’s primary inflow (‘A’ą̈y Chù’ (Slims River)). Our results, when used together with Indigenous knowledge, form a historical reference that enables assessments of the potential ecological consequences to Lhù’ààn Mân’.

Concentrated resources or hotspots, within an individual's usual home range may be strong determinates of movement behavior. We evaluated the patterns of mineral lick use by a population of mountain goats Oreamnos americanus displaying high site fidelity at two mineral licks along the Trans-Canada Highway in the Rocky Mountains, British Columbia, Canada. Access to these mineral licks was characterized by deliberate and repetitive movements into marginal habitat. We describe the patterns of mineral lick use over decadal, seasonal and daily periods by using dendrochronological analysis of trampling scars along mountain goat trails, movements determined from GPS collar locations, and camera traps placed along trails and at mineral licks, respectively. Our findings suggest that mountain goats have strong trans-generational behavioral traditions and that they predictably access mineral licks using the same trails, seasons and daily patterns. Differences in the patterns of mineral lick visitation between males and females may be related to reproductive and nutritional status, while their nocturnal use appears to be a response to disturbance at the mineral licks. Understanding how animals adjust their behavior in response to highly localized resource hotspots outside their usual home range can provide valuable information for the management of these critical habitat features and the wider conservation of mountain goat populations.

The climate of high midlatitude mountains appears to be warming faster than the global average, but evidence for such elevation-dependent warming (EDW) at higher latitudes is presently scarce. Here, we use a comprehensive network of remote meteorological stations, proximal radiosonde measurements, downscaled temperature reanalysis, ice cores, and climate indices to investigate the manifestation and possible drivers of EDW in the St. Elias Mountains in subarctic Yukon, Canada. Linear trend analysis of comprehensively validated annual downscaled North American Regional Reanalysis (NARR) gridded surface air temperatures for the years 1979–2016 indicates a warming rate of 0.028°C a−1 between 5500 and 6000 m above mean sea level (MSL), which is ~1.6 times larger than the global-average warming rate between 1970 and 2015. The warming rate between 5500 and 6000 m MSL was ~1.5 times greater than the rate at the 2000–2500 m MSL bin (0.019°C a−1), which is similar to the majority of warming rates estimated worldwide over similar elevation gradients. Accelerated warming since 1979, measured by radiosondes, indicates a maximum rate at 400 hPa (~7010 m MSL). EDW in the St. Elias region therefore appears to be driven by recent warming of the free troposphere. MODIS satellite data show no evidence for an enhanced snow albedo feedback above 2500 m MSL, and declining trends in sulfate aerosols deposited in high-elevation ice cores suggest a modest increase in radiative forcing at these elevations. In contrast, increasing trends in water vapor mixing ratio at the 500-hPa level measured by radiosonde suggest that a longwave radiation vapor feedback is contributing to EDW.

The effects of climate change appear to be amplified in mountains compared with lowland areas, with rapid changes in plant community composition, soil properties, and increased substrate for biological development following retreat of glaciers. Associated soil gaseous fluxes in alpine ecosystems contribute to the global balance of greenhouse gases, but methane and carbon dioxide soil fluxes and their controls are not well known. We used a dynamic closed-chamber method to measure methane and carbon dioxide fluxes along a successional gradient during the peak growing season in the North Selkirk Mountains, British Columbia, Canada. Soil physico-chemical properties, vegetation cover, and topographic variables were quantified to determine mechanisms influencing these fluxes. Mean methane uptake ranged from − 155 µg CH4-C m− 2 h−1 in well vegetated sites to zero in recently deglaciated terrain. Soil total carbon (TC) and water content were the primary drivers of methane uptake. Sites with TC greater than 4% and moisture below 0.22 water fraction by volume (w.f.v) corresponded to the strongest methane sinks. Increased vegetation cover and relatively drier soil conditions, anticipated with future climate change, suggest that methane uptake may increase in these alpine ecosystems.

18 pages, 5 figures, supplementary data https://doi.org/10.1016/j.biocon.2021.109175.-- The data supporting the findings of this study are available in the Supplementary Materials (Appendix 3–5, Table A3-A5). Raw datasets (where available) and results summary tables for each analysis of human mobility and empirical datasets are deposited in a github repository: https://github.com/rjcommand/PAN-Environment, The global lockdown to mitigate COVID-19 pandemic health risks has altered human interactions with nature. Here, we report immediate impacts of changes in human activities on wildlife and environmental threats during the early lockdown months of 2020, based on 877 qualitative reports and 332 quantitative assessments from 89 different studies. Hundreds of reports of unusual species observations from around the world suggest that animals quickly responded to the reductions in human presence. However, negative effects of lockdown on conservation also emerged, as confinement resulted in some park officials being unable to perform conservation, restoration and enforcement tasks, resulting in local increases in illegal activities such as hunting. Overall, there is a complex mixture of positive and negative effects of the pandemic lockdown on nature, all of which have the potential to lead to cascading responses which in turn impact wildlife and nature conservation. While the net effect of the lockdown will need to be assessed over years as data becomes available and persistent effects emerge, immediate responses were detected across the world. Thus initial qualitative and quantitative data arising from this serendipitous global quasi-experimental perturbation highlights the dual role that humans play in threatening and protecting species and ecosystems. Pathways to favorably tilt this delicate balance include reducing impacts and increasing conservation effectiveness, The Canada Research Chairs program provided funding for the core writing team. Field research funding was provided by A.G. Leventis Foundation; Agence Nationale de la Recherche, [grant number ANR-18-32–0010CE-01 (JCJC PEPPER)]; Agencia Estatal de Investigaci; Agência Regional para o Desenvolvimento da Investigação Tecnologia e Inovação (ARDITI), [grant number M1420-09-5369-FSE-000002]; Alan Peterson; ArcticNet; Arkadaşlar; Army Corp of Engineers; Artificial Reef Program; Australia's Integrated Marine Observing System (IMOS), National Collaborative; Research Infrastructure Strategy (NCRIS), University of Tasmania; Australian Institute of Marine Science; Australian Research Council, [grant number LP140100222]; Bai Xian Asia Institute; Batubay Özkan; BC Hydro Fish and Wildlife Compensation Program; Ben-Gurion University of the Negev; Bertarelli Foundation; Bertarelli Programme in Marine Science; Bilge Bahar; Bill and Melinda Gates Foundation; Biology Society of South Australia; Boston University; Burak Över; California State Assembly member Patrick O'Donnell; California State University Council on Ocean Affairs, Science & Technology; California State University Long Beach; Canada Foundation for Innovation (Major Science Initiative Fund and funding to Oceans Network Canada), [grant number MSI 30199 for ONC]; Cape Eleuthera Foundation; Centre National d'Etudes Spatiales; Centre National de la Recherche Scientifique; Charles Darwin Foundation, [grant number 2398]; Colombian Institute for the Development of Science and Technology (COLCIENCIAS), [grant number 811–2018]; Colombian Ministry of Environment and Sustainable Development, [grant number 0041–2020]; Columbia Basin Trust; Commission for Environmental Cooperation; Cornell Lab of Ornithology; Cultural practices and environmental certification of beaches, Universidad de la Costa, Colombia, [grant number INV.1106–01–002-15, 2020–21]; Department of Conservation New Zealand; Direction de l'Environnement de Polynésie Française; Disney Conservation Fund; DSI-NRF Centre of; Excellence at the FitzPatrick Institute of African Ornithology; Ecology Project International; Emin Özgür; Environment and Climate Change Canada; European Community: RTD programme - Species Support to Policies; European Community's Seventh Framework Programme; European Union; European Union's Horizon 2020 research and innovation programme, Marie Skłodowska-Curie, [grant number 798091, 794938]; Faruk Eczacıbaşı; Faruk Yalçın Zoo; Field research funding was provided by King Abdullah University of Science and Technology; Fish and Wildlife Compensation Program; Fisheries and Oceans Canada; Florida Fish and Wildlife Conservation Commission, [grant numbers FWC-12164, FWC-14026, FWC-19050]; Fondo Europeo de Desarrollo Regional; Fonds québécois de la recherche nature et technologies; Foundation Segré; Fundação para a Ciência e a Tecnologia (FCT Portugal); Galapagos National Park Directorate research, [grant number PC-41-20]; Gordon and Betty Moore Foundation, [grant number GBMF9881 and GBMF 8072]; Government of Tristan da Cunha; Habitat; Conservation Trust Foundation; Holsworth Wildlife Research Endowment; Institute of Biology of the Southern Seas, Sevastopol, Russia; Instituto de Investigación de Recursos Biológicos Alexander von Humboldt; Instituto Nacional de Pesquisas Espaciais (INPE), Brazil; Israeli Academy of Science's Adams Fellowship; King Family Trust; Labex, CORAIL, France; Liber Ero Fellowship; LIFE (European Union), [grant number LIFE16 NAT/BG/000874]; María de Maeztu Program for Units of Excellence in R&D; Ministry of Science and Innovation, FEDER, SPASIMM,; Spain, [grant number FIS2016–80067-P (AEI/FEDER, UE)]; MOE-Korea, [grant number 2020002990006]; Mohamed bin Zayed Species Conservation Fund; Montreal Space for Life; National Aeronautics and Space Administration (NASA) Earth and Space Science Fellowship Program; National Geographic Society, [grant numbers NGS-82515R-20]; National Natural Science Fund of China; National Oceanic and Atmospheric Administration; National Parks Board, Singapore; National Science and Technology Major Project of China; National Science Foundation, [grant number DEB-1832016]; Natural Environment Research Council of the UK; Natural Sciences and Engineering Research Council of Canada (NSERC), Alliance COVID-19 grant program, [grant numbers ALLRP 550721–20, RGPIN-2014-06229 (year: 2014), RGPIN-2016-05772 (year: 2016)]; Neiser Foundation; Nekton Foundation; Network of Centre of Excellence of Canada: ArcticNet; North Family Foundation; Ocean Tracking Network; Ömer Külahçıoğlu; Oregon State University; Parks Canada Agency (Lake Louise, Yoho, and Kootenay Field Unit); Pew Charitable Trusts; Porsim Kanaf partnership; President's International Fellowship Initiative for postdoctoral researchers Chinese Academy of Sciences, [grant number 2019 PB0143]; Red Sea Research Center; Regional Government of the Azores, [grant number M3.1a/F/025/2015]; Regione Toscana; Rotary Club of Rhinebeck; Save our Seas Foundation; Science & Technology (CSU COAST); Science City Davos, Naturforschende Gesellschaft Davos; Seha İşmen; Sentinelle Nord program from the Canada First Research Excellence Fund; Servizio Foreste e Fauna (Provincia Autonoma di Trento); Sigrid Rausing Trust; Simon Fraser University; Sitka Foundation; Sivil Toplum Geliştirme Merkezi Derneği; South African National Parks (SANParks); South Australian Department for Environment and Water; Southern California Tuna Club (SCTC); Spanish Ministry for the Ecological Transition and the Demographic Challenge; Spanish Ministry of Economy and Competitiveness; Spanish Ministry of Science and Innovation; State of California; Sternlicht Family Foundation; Suna Reyent; Sunshine Coast Regional Council; Tarea Vida, CEMZOC, Universidad de Oriente, Cuba, [grant number 10523, 2020]; Teck Coal; The Hamilton Waterfront Trust; The Ian Potter Foundation, Coastwest, Western Australian State NRM; The Red Sea Development Company; The Wanderlust Fund; The Whitley Fund; Trans-Anatolian Natural Gas Pipeline; Tula Foundation (Hakai Institute); University of Arizona; University of Pisa; US Fish and Wildlife Service; US Geological Survey; Valencian Regional Government; Vermont Center for Ecostudies; Victorian Fisheries Authority; VMRC Fishing License Fund; and Wildlife Warriors Worldwide, With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S

This is a manuscript version of an article published as: Haines, J.A., Nason, S.E., Skurdal, A.M.M., Bourchier, T., Boutin, S., Taylor, R.W., McAdam, A.G., Lane, J.E., Kelley, A.D., Humphries, M.M., Gorrell, J.C., Dantzer, B., Coltman, D.W., & Hämäläinen, A. (2020). Sex- and context-specific associations between personality and a measure of fitness but no link with life history traits. Animal Behaviour, 167, 23-29. https://doi.org/10.1016/j.anbehav.2020.06.013 The Canadian Rocky Mountains are one of the few places on Earth where the spatial genetic structure of wide-ranging species has been relatively unaffected by anthropogenic disturbance. We characterized the spatial genetic structure of Rocky Mountain bighorn sheep (Ovis canadensis canadensis Shaw, 1804) in the northern portion of their range. Using microsatellites from 1495 individuals and mitochondrial DNA sequences from 188 individuals, we examined both broad- and fine-scale spatial genetic structure, assessed sex-biased gene flow within the northern portion of the species range, and identified geographic patterns of genetic diversity. We found that broad-scale spatial genetic structure was consistent with barriers to movement created by major river valleys. The fine-scale spatial genetic structure was characterized by a strong isolation-by-distance pattern, and analysis of neighborhood size using spatial autocorrelation indicated gene flow frequently occurred over distances of up to 100 km. However, analysis of sex-specific spatial autocorrelation and analysis of mitochondrial haplotype distributions failed to detect any evidence of sex-biased gene flow. Finally, our analyses reveal decreasing genetic diversity with increasing latitude, consistent with patterns of post-glacial recolonization of the Rocky Mountains. Post-print version This is an author supplied, accepted manuscript version of an article published as: Deakin, S., Gorrell, J.C., Kneteman, J., Hik, D.S., Jobin, R.M., & Coltman, D.W. (2020). Spatial genetic structure of Rocky Mountain bighorn sheep (Ovis canadensis canadensis) at the northern limit of their native range. Canadian Journal of Zoology, 98(5), 317-330. DOI: 10.1139/cjz-2019-0183 Canadian Journal of Zoology is available online at: http://www.nrcresearchpress.com/journal/cjz, and this article is available at: http://dx.doi.org/10.1139/cjz-2019-0183. https://viurrspace.ca/bitstream/handle/10613/23294/Gorrell.CJZ.pdf?sequence=3

Methane (CH4) is a strong greenhouse gas with a global warming potential 23 times larger than that of carbon dioxide. Characterizing ecosystems as either sources or sinks for methane and their magnitudes informs on biosphere contributions to the global CH4 budget and to warming of the atmosphere. We quantified methane fluxes for the first time in a neotropical alpine páramo (Valle de Los Conejos, Chirripó Massif, Costa Rica) and examined the relationships of these fluxes with topography, soil moisture and vegetation, during the transition from dry to rainy season. Using closed chambers and laser spectroscopy, we measured soil CH4 and CO2 fluxes across a field site encompassing: a grassy plain as well as a plain, a gentle slope and a plateau dominated by a dwarf bamboo (Chusquea subtessellata Hitchcock). We found that the páramo landscape acts as a sink for CH4 [−53.1 ± 29.6 (mean ± SE) µg C m−2 hr−1]. Of the four field areas, the grassy plain was on average the strongest CH4 sink, likely because this soil profile had no drainage restrictions and was well aerated. By contrast, in the slope and plateau, a heavily-consolidated subsurface layer was shown to perch water, increasing surface soil moisture and limiting CH4 uptake. Conversely, in certain parts of the plain, where Chusquea grew vigorously in discrete, tall patches, we found intense CH4 uptake beneath these patches. Within the Chusquea plain, these hot spots of CH4 uptake localized under the tall Chusquea had double the uptake rates than outside these patches, with even greater uptake than the average in the grassy plain. Our results show that CH4 uptake in the páramo is driven by moisture interacting with impeding soil layers, vegetation and topography. El metano (CH4) es un gas de efecto invernadero fuerte con un potencial de calentamiento global 23 veces mayor que el del dióxido de carbono. Caracterizar los ecosistemas como fuentes o sumideros de metano y sus magnitudes informa sobre las contribuciones de la biosfera al presupuesto global de CH4 y al calentamiento de la atmósfera. Cuantificamos los flujos de metano por primera vez en un páramo alpino neotropical (Valle de Los Conejos, Macizo Chirripó, Costa Rica) y examinamos las relaciones de estos flujos con la topografía, la humedad del suelo y la vegetación, durante la transición de la estación seca a la lluviosa. Usando cámaras cerradas y espectroscopía láser, medimos los flujos de CH4 y CO2 del suelo a través de un sitio de campo que abarca: una llanura cubierta de hierba, así como una llanura, una pendiente suave y una meseta dominada por un bambú enano (Chusquea subtessellata Hitchcock). Encontramos que el paisaje de páramo actúa como sumidero de CH4 [−53,1 ± 29,6 (media ± SE) µg C m − 2 hr − 1]. De las cuatro áreas de campo, la llanura cubierta de hierba fue en promedio el sumidero de CH4 más fuerte, probablemente porque este perfil de suelo no tenía restricciones de drenaje y estaba bien aireado. Por el contrario, en la ladera y la meseta, se demostró que una capa subterránea muy consolidada se posa en el agua, lo que aumenta la humedad del suelo en la superficie y limita la absorción de CH4. Por el contrario, en ciertas partes de la llanura, donde Chusquea creció vigorosamente en parches altos y discretos, encontramos una absorción intensa de CH4 debajo de estos parches. Dentro de la llanura de Chusquea, estos puntos calientes de absorción de CH4 localizados debajo de la alta Chusquea tenían el doble de tasas de absorción que fuera de estos parches, con una absorción aún mayor que el promedio en la llanura cubierta de hierba. Nuestros resultados muestran que la absorción de CH4 en el páramo es impulsada por la interacción de la humedad con las capas del suelo, la vegetación y la topografía que obstaculizan. Universidad Nacional, Costa Rica Universidad de Costa Rica, Costa Rica University of Alberta, Canada Simon Fraser University, Canada Agricultural University of Iceland, Iceland Escuela de Química

Summary Climate warming is predicted to alter ecological boundaries in high-latitude ecosystems including the elevational or latitudinal extent of tall shrubs in Arctic and alpine tundra. Over 60 studies from 128 locations around the tundra biome have investigated shrub expansion in tundra ecosystems; however, only six studies test whether shrublines are actually advancing up hill-slopes or northward into tundra where tall shrubs are currently absent. We test the hypothesis that willow shrublines have expanded to higher elevations in relation to climate across a 50 x 50 km area in the Kluane Region of the southwest Yukon Territory, Canada by surveying of 379 shrubs at 14 sites and sampling of 297 of the surveyed shrubs at 10 sites. We compared growth and recruitment to climate variables to test the climate sensitivity of shrub increase using annual radial growth analysis, age distributions and repeat field surveys to estimate the current rate of shrubline advance. We found consistent and increasing rates of recruitment of alpine willows, with estimates of faster advancing shrublines on shallower hill-slopes. Mortality was extremely low across the elevation gradient. Aspect, elevation and species identity did not explain variation in recruitment patterns, suggesting a regional factor, such as climate, as the driver of the observed shrubline advance. Annual radial growth of willows was best explained by variation in summer temperatures, and recruitment pulses by winter temperatures. Measured recruitment rates are ˜20 ± 5 individuals per hectare per decade (mean ± SE) and measured rates of increased shrub cover of ˜5 ± 1% per decade (mean ± SE) measured at the Pika Camp site between field surveys in 2009 and 2013. Our results suggest that shrubline will continue to advance over the next 50 years, if growing conditions remain suitable. However, if future conditions differ between summer and winter seasons, this could lead to contrasting trajectories for recruitment versus growth, and influence the vegetation change observed on the landscape. Synthesis. Our findings in the context of a review of the existing literature indicate that elevational and latitudinal shrublines, like treelines, are advancing in response to climate warming; however, the trajectories of change will depend on the climate drivers controlling recruitment versus growth. This article is protected by copyright. All rights reserved.

Satellite-derived land surface temperature (skin temperature) provides invaluable information for data-sparse high elevation and Arctic regions. However, the relationship between satellite-derived clear-sky skin temperature and various downscaled air temperature products for snow covered sub-Arctic alpine regions remain poorly understood, such that trend analysis or air temperature product integration is difficult. We compared monthly average air temperatures from two independent downscaled temperature products to MODIS Land Surface Temperature (LST) and air temperature at nine meteorological stations situated above tree-line in the southwest Yukon, Canada, between May and August 2008 for a full range of snow cover fractions. We found that both downscaled products generally agreed with LST for the low elevation, snow-free, vegetation classes. However, a systematic cold bias in Average LST emerged for snow fractions greater than approximately 40%, and this bias increased in magnitude as snow cover increased. In these situations the downscaled air temperatures were 5–7 °C warmer than Average LST for snow fractions of > 90%, and this pattern was largely independent of the number of measurements of LST within a month. Maximum LST was similar to average air temperatures for high snow fractions, but Minimum LST was colder by 10 °C or more for all snow fractions. Consequently, the average of Maximum and Minimum LST produces the cold bias, compared to air temperature, for high snow cover fractions. Air temperature measured at nine meteorological monitoring stations located between elevations of 1408–2690 m, on land cover classes Barren, Sparsely Vegetated or Permanent Snow and Ice, confirmed the cold bias results when incorporating Minimum LST in monthly averages. For snow fractions of 40%, the average LST bias became strongly negative at − 4.5 °C, and the RMSE increased to 6.1 °C, whereas the downscaled products bias and RMSE were similar to those from snow fractions of

Public engagement is essential to the procedural and substantive sustainability of environmental assessment. Public hearings present the lowest barrier to entry for public participation, but these forums face competing political pressures for conducting appropriate public engagement within an expeditious process. Repositories of public hearing testimony provide a source of primary data for examining these public engagement issues during environmental assessments. However, the time and resources required may be prohibitive for conducting the kind of in-depth qualitative analyses that are commonly used. Automated content analysis (ACA) techniques can provide a rapid, replicable, inductive, and systematic way to examine public hearing transcripts, consisting of the critical development and application of computer programming scripts that synthesize evidence from extensive document sets. This case illustration demonstrates the potential utility of ACA, based on the examination of two public hearings, ...

Invertebrate herbivores depend on external temperature for growth and metabolism. Continued warming in tundra ecosystems is proposed to result in increased invertebrate herbivory. However, empirical data about how current levels of invertebrate herbivory vary across the Arctic is limited and generally restricted to a single host plant or a small group of species, so predicting future change remains challenging. We investigated large-scale patterns of invertebrate herbivory across the tundra biome at the community level and explored how these patterns are related to long-term climatic conditions and year-of-sampling weather, habitat characteristics, and aboveground biomass production. Utilizing a standardized protocol, we collected samples from 92 plots nested within 20 tundra sites during summer 2015. We estimated the community-weighted biomass lost based on the total leaf area consumed by invertebrates for the most common plant species within each plot. Overall, invertebrate herbivory was prevalent at low intensities across the tundra, with estimates averaging 0.94% and ranging between 0.02 and 5.69% of plant biomass. Our results suggest that mid-summer temperature influences the intensity of invertebrate herbivory at the community level, consistent with the hypothesis that climate warming should increase plant losses to invertebrates in the tundra. However, most of the observed variation in herbivory was associated with other site level characteristics, indicating that other local ecological factors also play an important role. More details about the local drivers of invertebrate herbivory are necessary to predict the consequences for rapidly changing tundra ecosystems. - 2019, Springer-Verlag GmbH Germany, part of Springer Nature. This study is a contribution of the Herbivory Network ( https://herbivory.lbhi.is ). SIR and DSH were supported by the Natural Sciences and Engineering Research Council of Canada (RGPNS-305471); ICB was supported by a postdoctoral fellowship funded by the Icelandic Research Fund (Rannsóknasjóður, Grant nr 152468–051) and AXA Research Fund (15-AXA-PDOC-307); JMA was supported by Carl Tryggers Stiftelse för Vetenskaplig Forskning (Sweden) and Qatar Petroleum; MVK and VZ were supported by the Academy of Finland (Project 276671); AS and NS were supported by the Grant of Russian fund for basic research (18-05-60261); Field work on Bylot Island was supported by the Natural Sciences and Engineering Research Council of Canada, the network of Center of excellence ArcticNet, and the Polar Continental Shelf Program to GG and EL; SK and the Burntpoint Creek Research Station was supported by the Waterfowl, Wetlands and Far North research unit of the Ontario Ministry of Natural Resources and Forestry, with assistance from K. Bennet, R. Brook, and L. Pollock; O. Krasheninnikova assisted with the collection plant samples on Erkuta; SS was partly supported by a state assignment of the Institute of Plant and Animal Ecology UB RAS; DDE was supported by a Grant to JO from the Swedish Research Council Formas 2012–1039, 2012–230, 2015–1091 and a Grant to DDE from Gunnar and Ruth Björkmans fund for botanical research in northern Sweden; Sampling in Svalbard was conducted during an UNIS field course (ISJ); JSP was supported by the WSL Institute for Snow and Avalanche Research, and an INTERACT Transnational Access Research Grant; Research at Toolik Field Station by ALA was supported by National Science Foundation Grants DEB 102683 to support the Arctic LTER and OPP 0908502; JDMS was supported by the Research Council of Norway (262064); C. Brachmann assisted with Fig. 1 ; H.C. Proctor and B.A. Keddie assisted with gall damage determination. Scopus

Pollination is an ecosystem function of global importance. Yet, who visits the flower of specific plants, how the composition of these visitors varies in space and time and how such variation translates into pollination services are hard to establish. The use of DNA barcodes allows us to address ecological patterns involving thousands of taxa that are difficult to identify. To clarify the regional variation in the visitor community of a widespread flower resource, we compared the composition of the arthropod community visiting species in the genus Dryas (mountain avens, family Rosaceae), throughout Arctic and high-alpine areas. At each of 15 sites, we sampled Dryas visitors with 100 sticky flower mimics and identified specimens to Barcode Index Numbers (BINs) using a partial sequence of the mitochondrial COI gene. As a measure of ecosystem functioning, we quantified variation in the seed set of Dryas. To test for an association between phylogenetic and functional diversity, we characterized the structure of local visitor communities with both taxonomic and phylogenetic descriptors. In total, we detected 1,360 different BINs, dominated by Diptera and Hymenoptera. The richness of visitors at each site appeared to be driven by local temperature and precipitation. Phylogeographic structure seemed reflective of geological history and mirrored trans-Arctic patterns detected in plants. Seed set success varied widely among sites, with little variation attributable to pollinator species richness. This pattern suggests idiosyncratic associations, with function dominated by few and potentially different taxa at each site. Taken together, our findings illustrate the role of post-glacial history in the assembly of flower-visitor communities in the Arctic and offer insights for understanding how diversity translates into ecosystem functioning.

Plant-herbivore interactions are central to the functioning of tundra ecosystems, but their outcomes vary over space and time. Accurate forecasting of ecosystem responses to ongoing environmental changes requires a better understanding of the processes responsible for this heterogeneity. To effectively address this complexity at a global scale, coordinated research efforts, including multi-site comparisons within and across disciplines, are needed. The Herbivory Network was established as a forum for researchers from Arctic and alpine regions to collaboratively investigate the multifunctional role of herbivores in these changing ecosystems. One of the priorities is to integrate sites, methodologies, and metrics used in previous work, to develop a set of common protocols and design long-term geographically-balanced, coordinated experiments. The implementation of these collaborative research efforts will also improve our understanding of traditional human-managed systems that encompass significant portions of the sub-Arctic and alpine areas worldwide. A deeper understanding of the role of herbivory in these systems under ongoing environmental changes will guide appropriate adaptive strategies to preserve their natural values and related ecosystem services.

Alpine and Arctic land cover can present a challenge for the validation of satellite-derived albedo measurements due, in part, to the complex terrain and logistical difficulty of accessing these regions. We compared measurements of albedo on transects from northern mountain land covers (snowfield, glacier ice, tundra, saline silt river delta) and over a large elevation range to the coincident 8-day MODIS (MCD43) albedo product. We also compared field measurements at snow covered sites to the coincident daily MODIS (MOD10A1) snow albedo product. For each transect, we measured a range of albedo values, with the least variability on the silt river delta (range = 0.084) and the largest over mid-elevation glacier ice (range = 0.307). The highest elevation snowfield (0.170) had nearly the same range of albedo values as tundra (0.164). The MODIS shortwave White Sky Albedo product (MCD43A3) was highly correlated with the field transect albedo (R 2 = 0.96), with a Root Mean Square Error (RMSE) of 0.061. The MODIS shortwave Black Sky Albedo product was similarly correlated with field transects (R 2 = 0.96; RMSE = 0.063). These results indicate that remote observation of albedo over snow covered and alpine terrain is well constrained and consistent with other studies. Albedo varied by ∼15% both spatially and temporally for the high elevation snowfields at the point in the season where albedo variation should be at its minimum. There were several instances where MCD43A3 albedo was not produced over snow and was instead classified as cloud covered, despite field observations of cloud free skies. There were also several instances where daily MOD10A1 albedo was produced during the coincident 8-day period at these locations. This suggests that the cloud mask in the MCD43 product is overly conservative over snow. Spatial variation in albedo within the MODIS grid cell (500 m), especially for snow and glacier ice, combined with the uncertainty associated with positional accuracy of MODIS, indicates that the accuracy of MODIS albedo will be dependent on both land cover type and the period of observation.

Aim: Understanding the forces shaping biodiversity patterns, particularly for groups of organisms with key functional roles, will help predict the responses of ecosystems to environmental changes. ...

Arctic warming is resulting in reduced snow cover and increased shrub growth, both of which have been associated with altered land surface-atmospheric feedback processes involving sensible heat flux, ground heat flux and biogeochemical cycling. Using field measurements, we show that two common Arctic shrub species (Betula glandulosa and Salix pulchra), which are largely responsible for shrub encroachment in tundra, differed markedly in albedo and that albedo of both species increased as growing season progressed when measured at their altitudinal limit. A moveable apparatus was used to repeatedly measure albedo at six precise spots during the summer of 2012, and resampled in 2013. Contrary to the generally accepted view of shrub-covered areas having low albedo in tundra, full-canopy prostrate B. glandulosa had almost the highest albedo of all surfaces measured during the peak of the growing season. The higher midsummer albedo is also evident in localized MODIS albedo aggregated from 2000 to 2013, which displays a similar increase in growing-season albedo. Using our field measurements, we show the ensemble summer increase in tundra albedo counteracts the generalized effect of earlier spring snow melt on surface energy balance by approximately 40%. This summer increase in albedo, when viewed in absolute values, is as large as the difference between the forest and tundra transition. These results indicate that near future (

Natural resource development is accelerating in the circumpolar region, raising questions about the balance between potential economic benefits for northern indigenous peoples with the risks of increasing long-standing health inequities. New communication tools are needed to document and synthesize complex and diverse evidence of health impacts in a context relevant for natural resource management. Our research examines the perspectives of circumpolar experts on Geographic Information Systems (GIS) as a platform to synthesize and communicate scientific and indigenous knowledge. Thirty policy makers, academic researchers, and community-level practitioners participated in semi-structured interviews examining indigenous community health, natural resource management, and the use of GIS within Arctic and subarctic communities. Qualitative analysis of the interview transcripts for key themes indicated that the majority of circumpolar experts supported employing GIS to facilitate more extensive collaboration with indigenous communities and to produce higher quality data outputs for decision-making forums. To ensure GIS enables natural resource development decision-making to improve the social and economic welfare of indigenous people, experts recommended increasing communities’ access to technology and training, community stewardship of data, utilizing data for ongoing monitoring of development impacts, and coordinating cumulative impact monitoring within regions. Findings focus on circumpolar natural resource management in jurisdictions with a mandate for public participation, with relevance to improving accountability to indigenous populations in other regions.

Altres ajuts europeus: P.A.W. was additionally supported by the European Union Fourth Environment and Climate Framework Programme (Project Number ENV4-CT970586)P.A.W. was additionally supported by the European Union Fourth Environment and Climate Framework Programme (Project Number ENV4-CT970586). The tundra is warming more rapidly than any other biome on Earth, and the potential ramifications are far-reaching because of global feedback effects between vegetation and climate. A better understanding of how environmental factors shape plant structure and function is crucial for predicting the consequences of environmental change for ecosystem functioning. Here we explore the biome-wide relationships between temperature, moisture and seven key plant functional traits both across space and over three decades of warming at 117 tundra locations. Spatial temperature-trait relationships were generally strong but soil moisture had a marked influence on the strength and direction of these relationships, highlighting the potentially important influence of changes in water availability on future trait shifts in tundra plant communities. Community height increased with warming across all sites over the past three decades, but other traits lagged far behind predicted rates of change. Our findings highlight the challenge of using space-for-time substitution to predict the functional consequences of future warming and suggest that functions that are tied closely to plant height will experience the most rapid change. They also reveal the strength with which environmental factors shape biotic communities at the coldest extremes of the planet and will help to improve projections of functional changes in tundra ecosystems with climate warming.

The above mentioned article was originally scheduled for publication in the special issue on Ecology of Tundra Arthropods with guest editors Toke T. Høye . Lauren E. Culler. Erroneously, the article was published in Polar Biology, Volume 40, Issue 11, November, 2017. The publisher sincerely apologizes to the guest editors and the authors for the inconvenience caused.

Land degradation and extensive soil erosion are serious environmental concerns in Iceland. Natural processes associated with a harsh climate and frequent volcanic activity have shaped Icelandic landscapes. However, following human settlement and the introduction of livestock in the 9th century the extent of soil erosion rapidly escalated. Despite increased restoration and afforestation efforts and a considerable reduction in sheep numbers during the late 20th century, many Icelandic rangelands remain in poor condition. A deeper understanding of the ecology of these dynamic landscapes is needed, and state-and-transition models (STMs) can provide a useful conceptual framework. STMs have been developed for ecosystems worldwide to guide research, monitoring and management, but have been used at relatively small spatial scales and have not been extensively applied to high-latitude rangelands. Integrating the best available knowledge, we develop STMs for rangelands in Iceland, where sheep grazing is often regarded as a main driver of degradation. We use STMs at a country-wide scale for three time periods with different historical human influence, from pre-settlement to present days. We also apply our general STM to a case study in the central highlands of Iceland to illustrate the potential application of these models at scales relevant to management. Our STMs identify the set of possible states, transitions and thresholds in these ecosystems and their changes over time, and suggest increasing complexity in recent times. This approach can help identify important knowledge gaps and inform management efforts and monitoring programmes, by identifying realistic and achievable conservation and restoration goals., I. C. B. was supported by a postdoctoral fellowship funded by theIcelandic Research Fund (Rannsóknasjóður, grant 152468‐051) andAXA Research Fund (15‐AXA‐PDOC‐307). D. S. H. recieved supportfrom the Natural Sciences and Engineering Research Council (Canada),and ISJ from the University of Iceland Research Fund.

Rapid warming in northern ecosystems is simultaneously influencing plants, herbivores and the interactions among them. Recent studies suggest that herbivory could buffer plant responses to environmental change, but this has only been shown for vertebrate herbivores so far. The role of invertebrate herbivory in tundra ecosystems is often overlooked, but can be relevant in determining the structure and dynamics of tundra plant communities and may also affect how plants respond to warming. Invertebrate herbivores are also likely to respond more rapidly to warming than vertebrates because their behaviour and life cycles strongly depend on temperature. We investigated the effects of current season warming on Arctic moth caterpillars, their herbivory rates, and the subsequent responses of two common tundra plants, Salix arctica and Dryas octopetala. We manipulated both herbivore presence and temperature in a full-factorial field experiment at two elevations, using enclosures and passive warming chambers. Changes in temperature achieved through elevation and/or experimental warming directly affected caterpillars, herbivory and the responses of plants. Caterpillars performed worse (higher respiration rates and lower growth rates) in warmer, lower elevation plots and shifted their diets towards more nutritious foods, such that the relative intensity of herbivory changed for the two studied plants. Within-season responses of both forage plant species were weak, but invertebrate herbivores affected the responses of plants to elevation or experimental warming. Our results suggest that increased temperatures can reduce the performance of cold-adapted invertebrate herbivores, with potential consequences to the longer term responses of tundra plants to warming due to changes in herbivory rates and selective foraging.

Decreasing spring snow cover may amplify Arctic warming through the snow albedo feedback. To examine the impact of snowmelt on increasing temperature we used a 5,000 m elevation gradient in Yukon, Canada, extending from valley-bottom conifer forests, through middle elevation tundra, to high elevation icefields, to compare validated downscaled reanalysis air temperature patterns across elevational bands characterized by different patterns of spring snowmelt. From 2000 to 2014 we observed surface warming of 0.01 °C/a·1,000 m in May (0.14 °C/a at 1,000 m to 0.19 °C/a at 5,000 m), and uniform cooling of 0.09 °C/a in June at all elevations. May temperature trends across elevationally dependent land cover types were highly correlated with each other despite large variations in albedo and snow cover trends. Furthermore, a clear dependency of infrared skin temperature on snow cover mediated albedo decline was observed in tundra, but this was insufficient to influence average diurnal air temperature. We observed negative June temperature trends which we attribute to increasing daytime cloud cover because albedo and snow cover trends were unchanging. We conclude that 8-day and monthly averaged Spring air temperature trends are responding to a synoptic external forcing that is much stronger than the snow albedo feedback in sub-Arctic mountains.

Risky in the tropics It is well known that diversity increases toward the tropics. Whether this increase translates into differences in interaction rates among species, however, remains unclear. To simplify the problem, Roslin et al. tested for predation rates by using a single approach involving model caterpillars across six continents. Predator attack rates were higher toward the equator, but only for arthropod predators. Science , this issue p. 742

Chronic, low intensity herbivory by invertebrates, termed background herbivory, has been understudied in tundra, yet its impacts are likely to increase in a warmer Arctic. The magnitude of these changes is however hard to predict as we know little about the drivers of current levels of invertebrate herbivory in tundra. We assessed the intensity of invertebrate herbivory on a common tundra plant, the dwarf birch (Betula glandulosa-nana complex), and investigated its relationship to latitude and climate across the tundra biome. Leaf damage by defoliating, mining and gall-forming invertebrates was measured in samples collected from 192 sites at 56 locations. Our results indicate that invertebrate herbivory is nearly ubiquitous across the tundra biome but occurs at low intensity. On average, invertebrates damaged 11.2% of the leaves and removed 1.4% of total leaf area. The damage was mainly caused by external leaf feeders, and most damaged leaves were only slightly affected (12% leaf area lost). Foliar damage was consistently positively correlated with mid-summer (July) temperature and, to a lesser extent, precipitation in the year of data collection, irrespective of latitude. Our models predict that, on average, foliar losses to invertebrates on dwarf birch are likely to increase by 6–7% over the current levels with a 1 °C increase in summer temperatures. Our results show that invertebrate herbivory on dwarf birch is small in magnitude but given its prevalence and dependence on climatic variables, background invertebrate herbivory should be included in predictions of climate change impacts on tundra ecosystems. This study is a joint contribution of the Herbivory Network (http://herbivory.biology.ualberta.ca) and the Network for Arthropods of the Tundra (NeAT; https://tundraarthropods.wordpress.com/). Dwarf birch distribution maps were kindly provided by Kyle Joly. Sample collection during 2014 was facilitated by INTERACT (http://www.eu-interact.org/). ICB was supported by a postdoctoral fellowship funded by the Icelandic Research Fund (Rannsóknasjóður, grant nr 152468-051) and AXA Research Fund (15-AXA-PDOC-307); MtB and EK were supported by the Nordic Centre of Excellence TUNDRA, funded by the Norden Top-Level Research Initiative ‘‘Effect Studies and Adaptation to Climate Change’’; EMS and KAB were supported by COAT (Climate-ecological Observatory of the Arctic Tundra); AB was supported by MOBILITY PLUS (1072/MOB/2013/0) and the Polish-American Fulbright Commission; CGB was supported by IUT 20-28, EcolChang e Center of Excellence; BCF and TK were supported by the Academy of Finland (project 256991); MMPDH was supported by The Netherlands Organization for Scientific Research (NWO-ALW, VIDI grant 864.09.014); DSH was supported by the Natural Sciences and Engineering Research Council of Canada; AH was supported by the Research Council of Norway (grant 244557/E50); JL was funded by the German Research Foundation DFG (project WI 2680/8-1); MM-F was supported by a NERC IRF fellowship NE/L011859/1; SN was supported by the Villum foundation’s Young Investigator Programme (VKR023456); JS was supported by Kempestiftelserna and the Research Foundation Flanders (FWO); AS and NS were supported by the grant of RFBR (project 16-44-890108), grant of UB of RAS (project 15-15-4-35) and IEC “Arctic” of Yamal Government Department of Science and Innovation; LES and PAW were supported by the UK Natural Environment Research Council (NERC) grant NE/K000284/1; MVK and VZ were supported by the Academy of Finland (project 276671). Scopus

Water conservation is a critical aspect affecting the survival, distribution and abundance of terrestrial arthropods. In this study we investigate mechanisms of dehydration tolerance of the native, flightless fly, Calycopteryx moseleyi, inhabiting contrasting environments at two localities in the Kerguelen Islands. We compare the survival abilities and management of body water content of adult flies from two different ecophenotypes when exposed to conditions of low relative humidity. Our results suggest a broad plasticity in the responses of C. moseleyi to desiccation, showing distinct local adaptations to environmental conditions.

Gynaephora groenlandica (Wocke) (Lepidoptera: Erebidae) is a cold-adapted species, whose life history traits are dictated by cold and short Arctic summers. We used a recently discovered alpine tundra population in southwestern Yukon, Canada to investigate local adaptations to habitats with different environmental conditions (alpine versus Arctic). Using cafeteria-type experiments and field observations we examined the diet breadth of alpine populations of G. groenlandica beringiana Schmidt and Cannings, and compared these to published data on High Arctic populations of G. groenlandica groenlandica and to the closely related G. rossii Curtis. Gynaephora groenlandica beringiana appears to have a broader diet than High Arctic populations, but similar to that exhibited by alpine populations of G. rossii. Such trends could emerge from reduced synchrony between herbivores and their host plants in less extreme environments, and possibly from a reduced incidence of parasitoids in the life cycle of these populations. Our findings indicate the larval host plant plasticity of G. groenlandica in different environments, and are relevant to predictions regarding the fate of these populations under climate warming scenarios. Resume—Gynaephora groenlandica (Wocke) (Lepidoptera: Erebidae) est une espece adaptee au froid, dont les traits d'histoire de vie sont dictes par des etes Arctiques froids et courts. Nous avons utilise une population de toundra alpine recemment decouverte dans le sud-ouest du Yukon (Canada) pour etudier les adaptations locales a des environnements differents (alpins vs. arctiques). Utilisant des experiences de type « cafeteria » et des observations de terrain, nous avons examine l'amplitude alimentaire de populations alpines de G. groenlandica beringiana Schmidt and Cannings, et nous les avons comparees aux donnees publiees sur des populations deG.groenlandicadu Haut Arctique et des populations de G. rossii Curtis, espece qui lui est etroitement apparentee. Gynaephora groenlandica beringiana semble avoir une amplitude alimentaire plus large que celle de populations du Haut Arctique, mais similaire a celle de populations alpines de G. rossii. De telles tendances pourraient resulter d'une synchronisation reduite entre herbivores et leurs plantes hotes dans des environnements alpins, moins extremes, et eventuellement d'une incidence plus reduite des parasitoides dans le cycle de vie de ces populations. Nos resultats indiquent la plasticite du choix de la plante hote par la chenille de G. groenlandica dans des environnements differents. Ces resultats ont une importance pour des predictions quant a l'avenir de ces populations sous des scenarios de rechauffement climatique.

Changes in the density of small mammal populations can alter their genetic diversity and structure over time. Repeated density declines may gradually erode a population’s genetic variability, and ultimately undermine its long-term viability. We investigated changes in the genetic diversity and structure of a fluctuating collared pika (Lagomorpha: Ochotona collaris) population over 12 years. There are concerns that the long-term persistence of the collared pika is at risk due to climate change, as pika populations are sensitive to environmental variability and inhabit a region undergoing particularly rapid warming. The study population declined abruptly during 2000 and 2003; however, it subsequently recovered and failed to show any genetic signature of having undergone a bottleneck. There was also no evidence for widespread inbreeding before or after the population declines. Using a spatial autocorrelation analysis, we also documented positive fine-scale genetic structure (

Environment Canada meteorological station hourly sampled air temperatures Tair at four stations in the southwest Yukon were used to identify cloud contamination in the Moderate Resolution Imaging Spectroradiometer (MODIS) Terra clear-sky daytime land surface temperature (LST) and emissivity daily level-3 global 1-km grid product (MOD11A1, Collection 5) that is not flagged by the MODIS quality algorithm as contaminated. The additional cloud masking used qualitative ground-based sky condition observations, collected at two of the four stations, and coincident MODIS quality flag information. The results indicate that air temperature observed at a variety of discrete spatial locations having different land cover is highly correlated with MODIS LST collected at 1-km grid spacing. Quadratic relationships between LST and air temperature, constrained by ground observations of “clear” sky conditions, show less variability than relationships found under “mainly clear” and “mostly cloudy” sky conditions, and the more clouds observed in the sky coincides with a decreasing y intercept. Analysis of MODIS LST and its associated quality flags show a cold bias (0°C). Analysis of two observation stations shows that unidentified clouds in MODIS LST are between 13% and 17%, a result that agrees well with previous studies. Analysis of daytime values is important because many processes are dependent on daylight and maximum temperature. The daytime clear-sky LST–Tair relationship observed for the good-quality confirmed cloud-free-sky MODIS LST quality flag can be used to discriminate cloud-contaminated grid cells beyond the standard MODIS cloud mask.

Global warming and increasing human activity are altering northern ecosystems. In these strongly seasonal environments, small herbivorous mammals may have a significant role in determining the trajectory of ecosystem transitions from one state to another. Arctic ground squirrels Urocitellus parryii are a key component of northern terrestrial food webs and are considered ecosystem engineers, exerting a large impact on their habitat through bioturbation. We review and synthesize diverse information about current and past distribution and density of arctic ground squirrels, their physiology and ecological interactions with other species. Factors that appear to affect the distribution and abundance of arctic ground squirrels include increasing temperatures, changes in flooding probability, permafrost thaw, shifting phenology, habitat change, new predators and invasive diseases. Increases in the distribution and density of arctic ground squirrels in northern latitudes and high altitudes could accelerate ecosystem change through facilitation of disturbance-tolerant species, while decreases in southern and milder climates could remove an important agent of disturbance and prey item. Despite their pervasive ecological influence throughout most of their range, arctic ground squirrels are underrepresented in ecological research, based on a comparison of the number of publications about arctic ground squirrels with the number about other species of the same genus, and about other arctic herbivores. The widespread distribution of arctic ground squirrels, along with their potential to exacerbate and alter trajectories of ecosystem change under global warming, makes them a valuable indicator of ecosystem change and therefore a candidate for increased monitoring.

In tundra ecosystems, bryophytes influence soil processes directly and indirectly through interactions with overstory shrub species. We experimentally manipulated moss cover and measured seasonal soil properties and processes under two species of deciduous shrubs with contrasting canopy structures, Salix planifolia pulchra and Betula glandulosa-nana complex. Soil properties (seasonal temperature, moisture and C:N ratios) and processes (seasonal litter decomposition and soil respiration) were measured over twelve months. Shrub species identity had the largest influence on summer soil temperatures and soil respiration rates, which were higher under Salix canopies. Mosses were associated with lower soil moisture irrespective of shrub identity, but modulated the effects of shrubs on winter soil temperatures and soil C:N ratios so that moss cover reduced differences in soil winter temperatures between shrub species and reduced C:N ratios under Betula but not under Salix canopies. Our results suggest a central role of mosses in mediating soil properties and processes, with their influence depending on shrub species identity. Such species-dependent effects need to be accounted for when forecasting vegetation dynamics under ongoing environmental changes.

Some of the most rapidly changing ecosystems on our planet are located in the polar regions (IPCC 2007; Turner et al. 2009; SWIPA 2011). In some areas of the Arctic and Antarctic, atmospheric temperatures are rising at rates more than double the global average. In addition, there are other direct human impacts on polar regions such as pollution, exploitation and development. Polar ecosystems and the biodiversity they support are already responding to this change and it is expected that even more profound impacts will occur this century. Compounding the risk to polar biodiversity is the fact that many polar ecosystems have limited functional redundancy; in the event of the loss of a single keystone species, they may potentially be exposed to cascading effects and complete ecosystem restructuring (Post et al. 2009). Rapid climate change affecting the polar regions will also have profound physical and ecological consequences for the rest of the planet since the ice-covered Arctic Ocean, the Antarctic contine...

Temperature is increasing at unprecedented rates across most of the tundra biome. Remote-sensing data indicate that contemporary climate warming has already resulted in increased productivity over much of the Arctic, but plot-based evidence for vegetation transformation is not widespread. We analysed change in tundra vegetation surveyed between 1980 and 2010 in 158 plant communities spread across 46 locations. We found biome-wide trends of increased height of the plant canopy and maximum observed plant height for most vascular growth forms; increased abundance of litter; increased abundance of evergreen, low-growing and tall shrubs; and decreased abundance of bare ground. Intersite comparisons indicated an association between the degree of summer warming and change in vascular plant abundance, with shrubs, forbs and rushes increasing with warming. However, the association was dependent on the climate zone, the moisture regime and the presence of permafrost. Our data provide plot-scale evidence linking changes in vascular plant abundance to local summer warming in widely dispersed tundra locations across the globe. © 2012 Macmillan Publishers Limited. All rights reserved.

Sex-biased dispersal is common in mammals, and in most species, the majority of dispersers are juvenile males. However, which sex typically disperses in a species will ultimately be determined by the costs and benefits of dispersal for each sex. These are partly determined by a species’ mating system, with female-defence polygyny being strongly associated with male-biased dispersal. The few mammal species without sex-biased dispersal have been predicted to have a monogamous or polygynandrous mating system and levels of intraspecific competition that affect males and females equally. North American pikas may meet these criteria. Using microsatellite data from a decade of population monitoring, we examined the mating system and dispersal habits of the collared pika, Ochotona collaris, an asocial alpine-dwelling lagomorph. While their behaviour suggests they are monogamous or polygynous, parentage analyses revealed that the pikas were primarily polygynandrous. As predicted, there was no difference in the average distance dispersed by the two sexes, most likely because the costs and benefits of dispersal do not differ between males and females in this species. Since levels of inbreeding in the population were low, we also determined whether the pikas chose mates based on genetic dissimilarity, and whether they decreased the inbreeding coefficients of their offspring by going on forays to mate with animals other than their neighbours. Pikas did not restrict themselves to mating with their neighbours, but the average relatedness coefficients between pairs that produced offspring did not differ from the average relatedness coefficients expected under a model of random mate choice.

Environmental variation in mountainous regions can impose major differences in demography and physiology on animal populations that occupy a large elevation range. This variation can be both predictable and unpredictable. In the south-western Yukon, arctic ground squirrel (AGS) populations occur all the way from the forested valley bottoms to the alpine meadows and, in so doing, experience a wide range of predation risk, forage quality and exposure to weather variables. To assess how AGS integrate these factors and respond to them, we measured fecal glucocorticoid metabolites (FCM) as an index of the stress axis on four sites at different elevations. We first validated the enzyme immunoassay with a hormonal challenge protocol and a simulated predator stressor. AGS show a strong diurnal pattern in FCM levels, with peaks at mid-day and a marked increase in response to adrenocorticotropic hormone and the simulated predator and a decline in response to dexamethasone. The lag time between the challenge and its reflection in the feces was 4–12 h. Using this method in our field studies, we found that FCM levels decreased as the active season progressed; however, specific patterns differed among sites. We hypothesized that the early season peak in FCM levels followed by the general decline was due to brief, intense early season breeding, followed by the necessity of AGS to increase mass in preparation for hibernation. Although we found no clear, single explanation for the different FCM patterns among sites, we hypothesized that differences in seasonal climate and adverse weather may be major factors affecting FCM levels. The environment was markedly different between years, with 2008 being colder and wetter than 2009 and this was associated with AGS in 2008 having much higher FCM levels in general than 2009. We found that population density and visibility may also contribute. In conclusion, AGS live in a mosaic of habitats and each population is faced with a variety of environmental stressors; how they cope and respond to these stressors may not depend on a single factor but the complete aggregate of these stressors.

35 Abstract Understanding the sensitivity of tundra vegetation to climate warming is critical to forecasting future biodiversity and vegetation feedbacks to climate. In situ warming experiments accelerate climate change on a small scale to forecast responses of local plant communities. Limitations of this approach include the apparent site-specificity of results and uncertainty about the power of short-term studies to anticipate longer term change. We address these issues with a synthesis of 61 experimental warming studies, of up to 20 years duration, in tundra sites worldwide. The response of plant groups to warming often differed with ambient summer temperature, soil moisture and experimental duration. Shrubs increased with warming only where ambient temperature was high, whereas graminoids increased primarily in the coldest study sites. Linear increases in effect size over time were frequently observed. There was little indication of saturating or accelerating effects, as would be predicted if negative or positive vegetation feedbacks were common. These results indicate that tundra vegetation exhibits strong regional variation in response to warming, and that in vulnerable regions, cumulative effects of long-term warming on tundra vegetation - and associated ecosystem consequences - have the potential to be much greater than we have observed to date.

When phenotypic change occurs over time in wildlife populations, it can be difficult to determine to what degree it is because of genetic effects or phenotypic plasticity. Here, we assess phenotypic changes over time in horn length and volume of thinhorn sheep (Ovis dalli) rams from Yukon Territory, Canada. We considered 42 years of horn growth from over 50,000 growth measurements in over 8000 individuals. We found that weather explained a large proportion of the annual fluctuation in horn growth, being particularly sensitive to spring weather. Only 2.5% of variance in horn length growth could be explained by an individual effect, and thus any genetic changes over the time period could only have had a small effect on phenotypes. Our findings allow insight into the capacity for horn morphology to react to selection pressures and demonstrate the overall importance of climate in determining growth.

The acoustic environment, composed in part by the vocalizations of sympatric animals, is a major source of information and can be used to fine-tune behavioural decisions. Active assessment of alarm calls within and between mammal species is not fully understood. We explored the behavioural responses of collared pikas to con- and heterospecific vocalizations, in order to determine whether they selectively attend to these calls. Pikas increased their vigilance after playback of alarm calls of heterospecific mammals (marmots and ground squirrels), but responded most strongly to conspecific calls. While responses to playback calls of their own, of neighbours and of a stranger did not differ, pikas did discriminate between individual callers in a habituation-discrimination experiment. The ability to make use of information from different sources in their acoustic environment likely facilitates pikas’ behavioural decisions that affect foraging, predator avoidance and nepotism.

We investigated whether plant interaction intensity in a subarctic-alpine meadow is important for determining community structure and species abundance. Using two common species as phytometers, we measured interaction intensity using a neighbor removal approach. Eight biotic and abiotic variables known to influence species abundance and community structure were measured, with regression trees used to examine how plant interactions and the biotic and abiotic variables were related to species evenness, richness, and phytometer spatial cover. A range of interactions was present, with both strong competition and facilitation present over small-scale abiotic and biotic gradients. Despite the variation in interaction intensity, it was generally unrelated to either community structure or phytometer cover. In other words, plant interactions were intense in many cases but were not important to community structure. This may be due to the prevalence of clonal species in this system and the influence of previous year's interactions on plant survival and patterns of community structure. These results also suggest how conflicting theories of the role of competition in unproductive environments may be resolved. Our findings suggest that plant interactions may be intense in reducing individual growth, while simultaneously not important in the context of community structure. Plant interactions need to be viewed and tested relative to other factors and stresses to accurately evaluate their importance in plant communities, with continued differentiation between the intensity of plant interactions and their relative importance in communities.

Understanding geographic call variation can resolve evolutionary and behavioural questions, yet the factors influencing divergent acoustic signals remain poorly understood in mammals. We explored call variation between collared pikas in Yukon and Alaska and American pikas in Alberta, and between individuals within a population of collared pikas. Classification trees were used to determine the extent of call divergence between populations and the elements of calls driving these differences. Pika populations had significant differences in call structure, and individual pikas were classified to their correct populations with up to 94% accuracy. To investigate possible mechanisms responsible for interspecific variability, we tested the acoustic adaptation hypothesis by using a playback experiment to explore whether American and collared pika calls transmit with less degradation across their own species' habitat than the habitat of their congener. We found no support for the acoustic adaptation hypothesis. Geographic call variation in these two species of pikas likely reflects genetic divergence, and may be a result of separate evolutionary histories. We calculated the potential for individual coding for both time and frequency measurements of calls. High frequency harmonics showed greater between- than within-individual variation, and may act as sources of information regarding individual identity.

We developed primers for eight polymorphic microsatellite loci isolated from the collared pika, Ochotona collaris, and also tested nine loci previously developed for the American pika, O. princeps, for use in O. collaris. Forty-six individuals from an O. collaris population in the southern Yukon were genotyped using all 17 loci. The average number of alleles per locus was six and the average observed heterozygosity was 0.59. All loci were tested for use in four Asian pika species and all but two loci amplified reliably in these species.