Aboveground plant and belowground stem biomass were measured in moist acidic and moist non-acidic tussock tundra experimental plots. Treatments at the acidic site include control and nitrogen (N) plus phosphorus (P) amendments; treatments at the non-acidic site include N, P, N+P, greenhouse warming, and greenhouse+N+P.
Note: Version 8 corrected an error where Carex vaginata was listed twice under treatment of "Nitrogen Phosphorus". The tissues with 8 quadrats were "Greenhouse" treatment.
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Plots at the acidic site (MAT) were set up in July 1996 on extra 5 x 20 meters plots within the four block design of the 1989 LTER acidic tussock experimental plots. On each plot a 5x10 meter section was fenced with large mesh (4-inch square mesh) and within this fence a 5x5-meter plot was fenced with a small mesh (1/2-inch square mesh). In each block two fenced plots were setup: a plot with no fertilizer and a plot with annual fertilization (NP) treatments of 10 g/m2 Nitrogen (as NH4NO3) and 5 g/m2 Phosphorous (as triple superphosphate). In this biomass harvest only the control unfenced (NFCT) and NP unfenced (NFNP) treatments were sampled. Plots at the non-acidic site (MNT) were setup in July 1997. Three replicate blocks were established with the following annual treatments in 5 x 20 m plots: control (CT), nitrogen added (N), phosphorus added (P) and N and P (NP) in the same amounts as described for the MAT site. Two replicate blocks were established with a greenhouse treatment (GH) and a greenhouse fertilized treatment (GHNP). Greenhouses are annually set up in late May or early June and removed in the end of August or early September.
Notes: Cassiope tetragona was not separated into leaves and stems prior to drying and weighing; “new stems” includes new leaves and “old stems” includes old leaves.
Calculations: Tissue mass data are expressed in g/quadrat (400 cm2). Multiply by 25 to get g/m2.
Reference Citations: Gough, L. and S.E. Hobbie. 2003. Responses of moist non-acidic arctic tundra to altered environment: productivity, biomass, and species richness. Oikos 103:204-216.
Sampling Description. Biomass quadrats, size 20x20 cm, were taken from each site. Four quadrats were randomly located along line transects in each of the replicate blocks of each treatment. Aboveground biomass is considered "within" the quadrat if it is associated with a meristem that is within the quadrat. Quadrats were sorted within 24 hours into species and then into tissue type. All aboveground biomass and belowground stems (rhizomes) were saved; roots were discarded. The samples were dried at 50-70 degrees C in a drying oven and after several days weighed to nearest milligram. Details are given in Shaver and Chapin (Ecological Monographs, 61(1), 1991, pg. 1-31.)
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