EXPERIMENTAL DESIGN AND METHODS: (B.Kaye)

SAMPLE METHODS:
Toolik 2003
Samples of top 3 most abundant species in each plot were collected near flux plots on August 8th. C-N leaves were collected 2-2.5 weeks after last round of fluxing was completed.

C-N analysis was done on these leaves by Lorna Street at the University of Edinburgh in the fall of 2003.

Toolik/Imnavait 2004
Leaf samples were collected of the predominate 2-5 species in each flux plot. Leaf samples from the plot (or near the plot) were collected within a few days of the date that the plot was fluxed. Sometimes one group of leaves was collected to represent a group of plots when plots were from the same treatment group and vegetation type and were close together.

These leaves were ground in 2005/2006 at MBL and analyzed for C-N content by Brooke Kaye.

2003 C-N analysis
Leaf samples for C:N analysis from 2003 were processed in 2003 by Lorna Street at the University of Edinburgh, UK. Samples were ground and analysed for carbon and nitrogen concentration using CE-440 Elemental Analyser (North Chelmsford MA, USA).

2005 C-N analysis
Samples from 2004-2005 were ground and analyzed between October 2005 and April 2006 by Brooke Kaye at the Ecosystems Center in Woods Hole, MA.

Samples were briefly re-dried at 60oC (24 hours) and put in a dessicator. Smaller samples (less than ~0.3 grams, depending on leaf size) were ground for approximately one minute in the Wig-L-Bug in the grinding room at the Marine Biological Lab. Larger samples (larger than ~0.3 grams, depending on leaf size) were ground in the Retsch MM200 double grinder for approximately three minutes, or until samples were finely powdered with no remaining visible plant fibers. If leaves still had petioles attached I removed the petioles with scissors and discarded them before grinding the leaf sample. All ground samples were stored in plastic 20ml scint vials until C-N analysis could be done.

For C-N analysis, tins were packed with 3-4 milligrams of powdered leaves. One tin was packed for every sample type. Every 10th sample had a replicate sample packed from it in order to check the reproducibility of values and the uniformity of the ground sample, this is indicated by an R in the column "rep?"

After prep samples were run, leaves were analyzed in auto-run mode (non-filter type samples). After every 10 samples a blank tin and a K-factor (standard - Acetinilide) were run to check accuracy of values. Samples were run on a Perkins Elmer CHNS/O Series II analyzer, owned by the Ecosystems Center and maintained by Don Burnette in 2005/2006.

COMMENTS:

FOR MORE INFORMATION CONTACT: Gus Shaver, The Ecosystems Center, Woods Hole, MA, 02543, USA

REFERENCE CITATIONS: van Wijk M.T., Williams M. and Shaver G (2005) Tight coupling between leaf area index and foliage N content in arctic plant communities. Oecologia 142:421-427

OTHER DATA FILES TO REFERENCE:
2003-2009gsflux.dat. CO2 and H2O flux data.
2004-2009gscoversp.dat. Percent cover of flux plots by species.
2004-2009gscoverft.dat. Percent cover of flux plots by functional type.
2003-2009gsGPSandveg.dat. GPS locations and description of vegetation for flux plots.
2003-2009gscurveparameters.dat Best fit parameters describing the light response curves measured on each plot.
2003-2009gssoiltemp.dat. Soil temperature and volumetric water content for flux plots.
2003gspointframe.dat. Point intercept sampling of vegetation within flux plots 2003
2003-2009gsharvest.dat. Leaf area, biomass and CHN analysis by species for each harvest.
2003-2009gsharvestLAI-N.dat. Total LAI, Foliar N and NDVI for 20cm x 20cm harvests.

FORMAT OF DATA FILE: ASCII

See Methods.