\<description\>
\<markdown\>## Experimental design:
The 1996 LTER moist acidic tussock (96LMAT) site was set up in 1996. The experimental design is four blocks of 5 x 20 meter plots with randomly assigned treatments within each block. Each plot is separated by a 2 meter walkway.
These plots received annual fertilization (the first week of June) with the following plot abbreviations and treatment amounts. (Note that Nitrogen was applied as NH4NO3 from 2006 -2011. From 2012 to 2022 nitrogen was added half as NH4Cl and half as NaNO3. The exception being the NH4 alone and NO3 alone where NH4CL and NaNO3 has been used since 2006.)
- F10 (10 g/m2 Nitrogen and 5 g/m2 Phosphorous (as triple superphosphate))
- F5 (5 g/m2 N and 2.5 g/m2 P)
- F2 (2 g/m2 N and 1 g/m2 P).
- F1 (1 g/m2 N and 0.5 g/m2 P)
- F.5 (.5 g/m2 N and 0.25 g/m2 P)
- NH4 (5 g/m2 N and 2.5 g/m2 P)
- NO3 (5 g/m2 N and 2.5 g/m2 P)
## Sampling Description:
In this harvest only plots from Blocks 1-3 Control, F2, F5, F10 were harvested.
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. 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.)
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.
## Root biomass Sampling Method.
Samples for soil analyses and roots were collected immediately adjacent to each quadrat harvested for above-ground biomass, with 5 quadrats collected per plot (i.e., 5 quadrats per treatment per block). For each sample, a single ca. 8 x 8 cm column of soil was collected using a serrated knife to the depth of the thawed portion of the soil. The soil column was separated into 3 layers (organic layer, transition layer and mineral layer), based on a visual distinction between the layers, and the height measured for each. The organic layer is rich in organic material, including dead and decaying plant material, with little visible mineral soil. The transition layer is also rich in organic material, but contains a significant proportion of clay, based on soil texture and color. The mineral layer is primarily clay-dominated mineral soil, with little visible organic material.
After each soil column was separated into the 3 soil layers, columns were trimmed using a serrated knife or scissors to 5 cm x 5 cm x soil depth. Roots were collected from each soil segment, with the method depending on the soil layer. Further, it is difficult to separate living from recently senesced roots. We focused on collecting roots that were not visibly decomposing and maintained their structure during soil processing. For the organic and transition layer, the organic-rich soil was manually pulled apart, with all visible roots removed using forceps. Transition layers which contained especially high proportions of mineral soil, were processed in a similar method to the mineral layer. For the mineral layer, clay was dispersed in water inside a 1mm sieve, and flatting roots removed. Clay dispersion and root removal continued until all clay had passed through the sieve. Visible roots were then picked out of any organic material that had collected on the bottom of the sieve.
As roots were collected, they were separated into two size classes: Coarse (> 2mm diameter) and Fine (< 2 mm diameter). Roots were further separated into species for species that are easily identifiable (Eriophorum vaginatum Carex bigelowii) and into categories for others (Other graminoids, All other species). All roots were rinsed free of soil before drying at 50C for a minimum of 3 days. Roots were weighed for each category and quadrat, and weights scaled to area and volume as necessary.
## Summary of root biomass method
- 5 quadrats were collected per treatment per block
- Soil column was separated into 3 layers: organic layer, transition layer & mineral layer
- For each layer, slab of soil cut with bread knife or scissors to 5 cm x 5 cm x depth of the soil layer
- All visible roots were collected from each soil segment, with the method depending on the soil layer
- Organic & Transition layer: Soil was manually pulled apart, and visible roots removed using forceps
- Mineral layer: clay was dispersed in water inside a 1mm sieve, and floating roots removed. Clay dispersion and root removal continued until all clay had passed through the sieve. Visible roots were then picked out of the organic matter that had collected on the bottom of the sieve. Very mineral-rich transition layers were also processed in this way.
- It is very difficult to tell living from recently senesced roots. We focused on collecting roots that were not visibly decomposing and maintained their structure easily.
- Once roots were collected, they were separated into size classes: Coarse (> 2mm diameter) and Fine (< 2 mm diameter).
- Roots were separated by species where possible: EriVag, CarBig, OtherGraminoids, OtherSpecies
- All roots were rinsed free of soil before drying.
- Roots were dried (50C for min 3 days) and weighed. Root mass and Volume of soil sampled were summed across all 5 quadrats within each treatment/block
\</markdown\>
\</description\>
