In 1980-1982, six transplant gardens were established along a latitudinal gradient in interior Alaska from Eagle Creek, AK, in the south to Prudhoe Bay, AK, in the north (Shaver et al. 1986, Bennington et al. 2012) .Three sites, Toolik Lake (TL), Sagwon (SAG), and Prudhoe Bay (PB) are north of the continental divide and the remaining three, Eagle Creek (EC), No Name Creek (NN), and Coldfoot (CF), are south of the continental divide. Each garden consisted of 10 individual tussocks transplanted back to their home-site, as well as 10 individuals from each of the other transplant sites (n = 10; 6 populations x 6 sites x 10 replicates = 360 total individuals).

For each E. vaginatum tussock sampled, transparent impressions were created of the widest abaxial surface of three haphazardly chosen leaves using clear nail polish. The nail polish peels were mounted on glass slides under clear plastic tape for viewing with a light microscope. Stomata were viewed at 50 × magnification and photographed after which AxioVision software (ver. 3.1, Carl Zeiss Vision Imaging Systems, Germany) was used to digitally manipulate the photos. Because stomata in monocots are arranged in linear rows or files, one file was chosen from each leaf impression and an area (minimum= 0.05 mm 2 , maximum = 0.25 mm 2 ), determined by the quality of the peel and/or the availability of undamaged portions, was delineated around it, oriented in the same direction as the file and including the adjacent, stomata-freearea. All the stomata within this area were counted as an estimate of stomatal density (SD) for the leaf. Only stomata in one location per leaf were counted as within-leaf variation in density tended to be very low compared to between-leaf variation. Stomatal length (SL) was expressed as the length in micrometers of the guard cells on a closed stomate at the same magnification. Stomatal density and length are important determinants of stomatal conductance. According to theory (Brown and Escombe 1900, Franks and Beerling, 2009 ): Conductance (C) =(SD * Pore Area)/Effective Pore Depth. Effective pore depth is assumed to be relatively constant across stomata within E. vaginatum and pore area is assumed to be proportional to SL 2 . Thus, an index of conductance is calculated as C = SD*SL2 .

In 14-19 July 2011, the temperature of each tussock was taken by inserting a digital thermometer 10 cm into the top of each tussock.

Bennington CC, Fetcher N, Vavrek MC, Shaver GR, Cummings KJ, McGraw JB. 2012. Home site advantage in two long-lived arctic plant species: results from two 30-year reciprocal transplant studies. Journal of Ecology 100:841-851

Brown , H. T., F. Escombe. 1900. Static diffusion of gases and liquids in relation to the assimilation of carbon and translocation in plants. Philosophical Transactions of the Royal Society of London, B, Biological Sciences 193: 223– 291.

Fetcher, N., and G. R. Shaver. 1990. Environmental sensitivity of ecotypes as a potential influence on primary productivity. American Naturalist 136:126-131.

Franks , P. J., D. J. Beerling. 2009. Maximum leaf conductance driven by CO2 effects on stomatal size and density over geologic time. Proceedings of the National Academy of Sciences, USA 106 : 10343 – 10347 .

Peterson, C. A. , N. Fetcher, J. B. Mcgraw , and C. C. Bennington. 2012. Clinal variation in stomatal characteristics of an arctic sedge, Eriophorum vaginatum (Cyperaceae). American Journal of Botany 99: 1–10.

Shaver GR, Fetcher N, Chapin FS 1986. Growth and flowering in Eriophorum vaginatum - Annual and latitudinal variation. Ecology 67:1524-1535

Notes:
Funding for this research was provided by National Science Foundation grant ARC-0908936.
Stomatal data are incorporated in Peterson et al. 2012.