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) .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). Of the original population of tussocks, 264 were harvested in 2011. For tussocks with > 25 tillers, 25 tillers were collected for measurements of biomass/tiller. For tussocks with ≤ 25 tillers, all of the tillers were used for these measurements. Samples were dried for 48 hr at 65°C, and weighed. Total mass of the sample was divided by number of tillers to give mass/tiller.

After weighing, the dried samples were processed for stable isotope analysis at the Stable Isotope Facility of the University of California at Davis. Sample preparation followed SIF-recommended protocols (http://stableisotopefacility.ucdavis.edu/13cand15nsamplepreparation.html). The tissue was ground in a ball mall and four mg were weighed into a tin capsule and sent to the facility. The SIF analyzed the sample. for 13C and 15N using a PDZ Europa ANCA-GSL elemental analyzer connected to a PDZ Europa 20-20 continuous flow isotope ratio mass spectrometer. Stable isotope ratios (δ13C and δ15N) are reported relative to Vienna PeeDee Belemnite and air, respectively.

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 with additional support from NSF-BSR-9024188.
Mass per tiller data are incorporated in a ms. submitted to Botany. Nutrient and stable isotope data are still unpublished.