Winter warming as an important co-driver for Betula nana growth in western Greenland during the past century

Growing season conditions are widely recognized as the main driver for tundra shrub radial growth, but the effects of winter warming and snow remain an open question. Here, we present a more than 100 years long Betula nana ring-width chronology from Disko Island in western Greenland that demonstrates a highly significant and positive growth response to both summer and winter air temperatures during the past century. The importance of winter temperatures for Betula nana growth is especially pronounced during the periods from 1910-1930 to 1990-2011 that were dominated by significant winter warming. To explain the strong winter importance on growth, we assessed the importance of different environmental factors using site-specific measurements from 1991 to 2011 of soil temperatures, sea ice coverage, precipitation and snow depths. The results show a strong positive growth response to the amount of thawing and growing degree-days as well as to winter and spring soil temperatures. In addition to these direct effects, a strong negative growth response to sea ice extent was identified, indicating a possible link between local sea ice conditions, local climate variations and Betula nana growth rates. Data also reveal a clear shift within the last 20 years from a period with thick snow depths (1991-1996) and a positive effect on Betula nana radial growth, to a period (1997-2011) with generally very shallow snow depths and no significant growth response towards snow. During this period, winter and spring soil temperatures have increased significantly suggesting that the most recent increase in Betula nana radial growth is primarily triggered by warmer winter and spring air temperatures causing earlier snowmelt that allows the soils to drain and warm quicker. The presented results may help to explain the recently observed 'greening of the Arctic' which may further accelerate in future years due to both direct and indirect effects of winter warming.

[1]  T. Wigley,et al.  On the Average Value of Correlated Time Series, with Applications in Dendroclimatology and Hydrometeorology , 1984 .

[2]  J. Johnstone,et al.  DEVELOPMENTAL PLASTICITY ALLOWS BETULA NANA TO DOMINATE TUNDRA SUBJECTED TO AN ALTERED ENVIRONMENT , 2001 .

[3]  S. Rumpf,et al.  Idiosyncratic Responses of High Arctic Plants to Changing Snow Regimes , 2014, PloS one.

[4]  W. Mohn,et al.  Long‐term experimental manipulation of climate alters the ectomycorrhizal community of Betula nana in Arctic tundra , 2011 .

[5]  D. Inouye,et al.  Effects of climate change on phenology, frost damage, and floral abundance of montane wildflowers. , 2008, Ecology.

[6]  Christian Zang,et al.  Dendroclimatic calibration in R: The bootRes package for response and correlation function analysis , 2013 .

[7]  Sonja Wipf,et al.  A review of snow manipulation experiments in Arctic and alpine tundra ecosystems , 2010 .

[8]  M. Sturm,et al.  The evidence for shrub expansion in Northern Alaska and the Pan‐Arctic , 2006 .

[9]  Marc Macias-Fauria,et al.  Eurasian Arctic greening reveals teleconnections and the potential for structurally novel ecosystems , 2012 .

[10]  E. Cook,et al.  Tree-ring standardization and growth-trend estimation , 1990 .

[11]  Donald A. Walker,et al.  The Circumpolar Arctic Vegetation Map: AVHRR-derived base maps, environmental controls, and integrated mapping procedures , 2002 .

[12]  B. Elberling,et al.  The importance of winter in annual ecosystem respiration in the High Arctic: effects of snow depth in two vegetation types , 2010 .

[13]  C. Tucker,et al.  Dynamics of aboveground phytomass of the circumpolar Arctic tundra during the past three decades , 2012 .

[14]  Steven F. Oberbauer,et al.  Plot-scale evidence of tundra vegetation change and links to recent summer warming. , 2012 .

[15]  S. Wipf,et al.  Advanced snowmelt causes shift towards positive neighbour interactions in a subarctic tundra community , 2006 .

[16]  J. Guiot,et al.  The Bootstrapped Response Function , 1991 .

[17]  Gaius R Shaver,et al.  Plant functional types do not predict biomass responses to removal and fertilization in Alaskan tussock tundra , 2008, The Journal of ecology.

[18]  Jon Holmgren,et al.  Snow-Shrub Interactions in Arctic Tundra: A Hypothesis with Climatic Implications , 2001 .

[19]  T. Wilbanks,et al.  Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change , 2007 .

[20]  S. Alberts,et al.  Developmental plasticity , 2018, Evolution, medicine, and public health.

[21]  Donald A. Walker,et al.  The Circumpolar Arctic vegetation map , 2005 .

[22]  J. Kollmann,et al.  Growth response to climatic change over 120 years for Alnus viridis and Salix glauca in West Greenland , 2015 .

[23]  Elisabeth J. Cooper,et al.  Deeper snow alters soil nutrient availability and leaf nutrient status in high Arctic tundra , 2015, Biogeochemistry.

[24]  Meteorological trends (1991–2004) at Arctic Station, Central West Greenland (69°15'N) in a 130 years perspective , 2006 .

[25]  Martin Hallinger,et al.  Establishing a missing link: warm summers and winter snow cover promote shrub expansion into alpine tundra in Scandinavia. , 2010, The New phytologist.

[26]  C. Tucker,et al.  Circumpolar Arctic Tundra Vegetation Change Is Linked to Sea Ice Decline , 2010 .

[27]  F. Babst,et al.  Continuously missing outer rings in woody plants at their distributional margins , 2012 .

[28]  L. Gough,et al.  Differential physiological responses to environmental change promote woody shrub expansion , 2013, Ecology and evolution.

[29]  Gaku Kudo,et al.  Global assessment of experimental climate warming on tundra vegetation: heterogeneity over space and time. , 2012, Ecology letters.

[30]  N. Schmidt,et al.  Reconstructing Century-long Snow Regimes Using Estimates of High Arctic Salix arctica Radial Growth , 2006 .

[31]  W. Oechel,et al.  Observational Evidence of Recent Change in the Northern High-Latitude Environment , 2000 .

[32]  J. Welker,et al.  Winter Biological Processes Could Help Convert Arctic Tundra to Shrubland , 2005 .

[33]  G. Henry,et al.  Tundra plants and climate change: the International Tundra Experiment (ITEX) , 1997 .

[34]  G. Liston,et al.  Changing snow and shrub conditions affect albedo with global implications , 2005 .

[35]  E. Schulze,et al.  Atlas of Stem Anatomy in Herbs, Shrubs and Trees , 2013, Springer Berlin Heidelberg.

[36]  B. Elberling,et al.  High nitrous oxide production from thawing permafrost , 2010 .

[37]  B. Elberling,et al.  Erratum: High nitrous oxide production from thawing permafrost , 2010 .

[38]  F. Stuart Chapin,et al.  Responses of Arctic Tundra to Experimental and Observed Changes in Climate , 1995 .

[39]  E. Cooper.  Warmer Shorter Winters Disrupt Arctic Terrestrial Ecosystems , 2014 .

[40]  R. Holmes.  Computer-Assisted Quality Control in Tree-Ring Dating and Measurement , 1983 .

[41]  Holger Gärtner,et al.  Temperature modulates intra-plant growth of Salix polaris from a high Arctic site (Svalbard) , 2013, Polar Biology.

[42]  B. Forbes,et al.  Russian Arctic warming and ‘greening’ are closely tracked by tundra shrub willows , 2010 .

[43]  D. Morgan,et al.  Differential physiological responses to central leptin overexpression in male and female rats , 2017, Journal of neuroendocrinology.

[44]  Christian Zang,et al.  treeclim: an R package for the numerical calibration of proxy‐climate relationships , 2015 .

[45]  J. Schimel,et al.  Increased snow depth affects microbial activity and nitrogen mineralization in two Arctic tundra communities , 2004 .

[46]  F. Serre-Bachet,et al.  Identification, presentation and interpretation of event years and pointer years in dendrochronology. , 1990 .

[47]  J. Francis,et al.  The Arctic Amplification Debate , 2006 .

[48]  S. Hobbie,et al.  Luxury consumption of soil nutrients: a possible competitive strategy in above‐ground and below‐ground biomass allocation and root morphology for slow‐growing arctic vegetation? , 2003 .

[49]  U. Molau,et al.  Onset of flowering and climate variability in an alpine landscape: a 10-year study from Swedish Lapland. , 2005, American journal of botany.

[50]  Paul Grogan,et al.  Deeper Snow Enhances Winter Respiration from Both Plant-associated and Bulk Soil Carbon Pools in Birch Hummock Tundra , 2007, Ecosystems.

[51]  G. Henry,et al.  Spatial Variability of the Dominant Climate Signal in Cassiope tetragona from Sites in Arctic Canada , 2011 .

[52]  M. Bret-Harte,et al.  Vegetation responses in Alaskan arctic tundra after 8 years of a summer warming and winter snow manipulation experiment , 2005 .

[53]  Andrew G. Bunn,et al.  A dendrochronology program library in R (dplR) , 2008 .

[54]  Roger A. Pielke,et al.  Modelled changes in arctic tundra snow, energy and moisture fluxes due to increased shrubs , 2002 .

[55]  J. Buring,et al.  Observational Evidence , 1993, Annals of the New York Academy of Sciences.

[56]  G. Schaepman‐Strub,et al.  What are the main climate drivers for shrub growth in Northeastern Siberian tundra , 2011 .

[57]  S. Simard,et al.  Below-ground carbon transfer among Betula nana may increase with warming in Arctic tundra. , 2011, The New phytologist.

[58]  Wenjun Chen,et al.  Effects of observed and experimental climate change on terrestrial ecosystems in northern Canada: results from the Canadian IPY program , 2012, Climatic Change.

[59]  F. Stuart Chapin,et al.  Species composition interacts with fertilizer to control long-term change in tundra productivity , 2001 .

[60]  Keith R. Briffa,et al.  Basic chronology statistics and assessment , 1990 .

[61]  J. Box.  Survey of Greenland instrumental temperature records: 1873–2001 , 2002 .