One of the most recognizable was to track change is to look for changes in the cover of plant species.

Tundra is treeless by definition.  We generally think of tundra as low in stature (short plants), with lots of open space.  The open space is generally covered by mosses and lichens. 

The generalization described above was true when we started measuring, but as the data show, it is much less true today. 

There are many ways to sample vegetation.  Here we show results using a point frame, where all encounters under the 100 cross hairs are recorded, along with their height and live or dead status.  This is a common method for low stature vegetation such as tundra or grasslands. 

The graphs below show the cover of plants over time.  The years when the vegetation was sampled is listed on the x-axis.

The Atqasuk and Utqiaġvik Grids span many moisture types but are predominantly moist acidic tundra. 

The control and warmed sites are locations with long-term experimental warming.

If you look across years you will see that the cover of vascular plants has increased greatly, going from less than 50% at most locations to as much as 150% at the Atqasuk Grid.  You might ask how you can have more than 100%, remember we measure every encounter therefore it is possible to have more than one layer of plants at a point. 

Related Papers

Elmendorf, S.C., G.H.R. Henry, R.D. Hollister, R.G. Björk, A.D. Bjorkman, T.V. Callaghan, L.S. Collier, E.J. Cooper, J.H.C. Cornelissen, T.A. Day, A.M. Fosaa, W.A. Gould, J. Grétarsdóttir, J. Harte, L. Hermanutz, D.S. Hik, A. Hofgaard, F. Jarrad, I.S. Jónsdóttir, F. Keuper, K. Klanderud, J.A. Klein, S. Koh, G. Kudo, S.I. Lang, V. Loewen, J.L. May, J. Mercado, A. Michelsen, U. Molau, I.H. Myers-Smith, S.F. Oberbauer, S. Pieper, E. Post, C. Rixen, C.H. Robinson, N.M. Schmidt, G.R. Shaver, A. Stenström, A. Tolvanen, Ø. Totland, T. Troxler, C.-H. Wahren, P.J. Webber, J.M. Welker, and P.A. Wookey. 2012a. Global assessment of experimental climate warming on tundra vegetation: Heterogeneity over space and time. Ecology Letters 15:164–175. 10.1111/j.1461-0248.2011.01716.x.

Elmendorf, S.C., G.H.R. Henry, R.D. Hollister, R.G. Björk, N. Boulanger-Lapointe, E.J. Cooper, J.H.C. Cornelissen, T.A. Day, E. Dorrepaal, T.G. Elumeeva, M. Gill, W.A. Gould, J. Harte, D.S. Hik, A. Hofgaard, D.R. Johnson, J.F. Johnstone, I.S. Jónsdóttir, J.C. Jorgenson, K. Klanderud, J.A. Klein, S. Koh, G. Kudo, M. Lara, E. Lévesque, B. Magnússon, J.L. May, J.A. Mercado-Dı´az, A. Michelsen, U. Molau, I.H. Myers-Smith, S.F. Oberbauer, V.G. Onipchenko, C. Rixen, N. Martin Schmidt, G.R. Shaver, M.J. Spasojevic, Þ.E. Þórhallsdóttir, A. Tolvanen, T. Troxler, C.E. Tweedie, S. Villareal, C.-H. Wahren, X. Walker, P.J. Webber, J.M. Welker, and S. Wipf. 2012b. Plot-scale evidence of tundra vegetation change and links to recent summer warming. Nature Climate Change 2:453–457. 10.1038/nclimate1465.

Harris, J.A., R.D. Hollister, T.F. Botting, C.E. Tweedie, K.R. Betway, J.L. May, R.T.S. Barrett, J.A. Leibig, H.L. Christoffersen, S.A. Vargas, M. Orejel, and T.L. Fuson. 2022. Understanding the climate impacts on decadal vegetation change in northern Alaska. Arctic Science 8:878–898. 10.1139/as-2020-0050.

Hollister, R.D., J.L. May, K.S. Kremers, C.E. Tweedie, S.F. Oberbauer, J.A. Liebig, T.F. Botting, R.T. Barrett, and J.L. Gregory. 2015. Warming experiments elucidate the drivers of observed directional changes in tundra vegetation. Ecology and Evolution 5:1881–1895. 10.1002/ece3.1499.

Hollister, R.D., P.J. Webber, and C.E. Tweedie. 2005. The response of Alaskan arctic tundra to experimental warming: Differences between short- and long-term responses. Global Change Biology 11:525–536. 10.1111/j.1365-2486.2005.00926.x.

Walker, M.D., C.H. Wahren, R.D. Hollister, G.H.R. Henry, L.E. Ahlquist, J.M. Alatalo, M.S. Bret-Harte, M.P. Calef, T.V. Callaghan, A.B. Carroll, H.E. Epstein, I.S. Jónsdóttir, J.A. Klein, B. Magnusson, U. Molau, S.F. Oberbauer, S.P. Rewa, C.H. Robinson, G.R. Shaver, K.N. Suding, C.C. Thompson, A. Tolvanen, O. Totland, P.L. Turner, C.E. Tweedie, P.J. Webber, and P.A. Wookey. 2006. Plant community responses to experimental warming across the tundra biome. Proceedings of the National Academy of Sciences of the United States of America 103:1342–1346. 10.1073pnas.0503198103.