Physical and chemical analyses were carried out on soil samples collected from treatment and control plots at the three DIRT sites (HF, PA, WI). Not all analyses were performed on all samples.
List of samples and analyses:
HF 1990: %C, %N
HF 1991: %C, %N, Db, pH, d13C,
d
15N
HF 1995: All analyses listed below. Only 3 of the 6 control
plots were sampled.
WI 1997: All analyses listed below.
Analytical Methods
d13C:
expressed as positive or negative deviation from the PDB standard
d15N:
expressed as positive or negative deviation from the atmospheric
standard
Bulk Density: Fresh weight of soil divided by core volume. For
details see soil sampling information for individual sites.
Ash-Free Dry Weight (%): [(oven-dry weight - ashed weight)/oven
dry weight ]* 100. For details see soil sampling
information for individual sites.
Elemental Analyzer %C: %C determined with Perkin-Elmer 2400
Elemental Analyzer
Elemental Analyzer %N: %N determined with Perkin-Elmer 2400
Elemental Analyzer
Soil carbon and nitrogen content: mineral soil: g/m2: %C or %N
* Db (g/cm3) * 105 cm3.
Oea soil: mass (g) of sample scaled from template size up to
m2 ground area.
Exchangeable cations and acidity: Robarge and Fernandez. (see
references)
Data:
Abbreviation Description Study Site Harvard Forest (HF), Bousson Forest (PA),
U. of Wisconsin Arboretum (WI) Site WI soils only: Noe Woods, Wingra Woods,
Curtis Prairie Year Year soils were collected Depth Oea organic horizon, 0-10 cm mineral
soil, 10-15 cm mineral soil Treatment Treatment (2X, C, OX, T, TOX,
O/A-less) Plot Plot number Rep Replicate sample from plot Cosm# Unique sample number d13C Delta 13C d15N Delta 15N Db (g/cc) Bulk Density Soil wt per m2 HF 1995: used sample weight to calculate
mass/area for Oea soils, because Db was not measured
directly. Mineral soil: soil mass is calculated as Db *
105 Mg/ha Soil mass Mg/ha Ash-Free DW (%) % Ash-free Dry Weight Ash-Free C est (%) Estimated %Ash-free %carbon; calculated
as (% ash free dry weight)/2 Elem An C (%) %C determined by Elemental
Analyzer Elem An N (%) %N determined by Elemental
Analyzer C:N Ratio of %C/%N C cont (g/m2) Soil carbon content, g C per
m2 ground area N cont (g/m2) Soil nitrogen content, g C per
m2 ground area Exch Ca (cmolc/kg) Exchangeable calcium, centimoles of
charge per kg dry weight soil Exch Mg (cmolc/kg) Exchangeable magnesium, centimoles of
charge per kg dry weight soil Exch K (cmolc/kg) Exchangeable potassium, centimoles of
charge per kg dry weight soil Exch Na (cmolc/kg) Exchangeable sodium, centimoles of charge
per kg dry weight soil Exch bases (cmolc/kg) Sum of exchangeable cations, centimoles
of charge per kg dry weight soil Exch Al (cmolc/kg) Exchangeable aluminum, centimoles of
charge per kg dry weight soil Exch H+ (cmolc/kg) Exchangeable acidity, centimoles of
charge per kg dry weight soil Total Acidity (cmolc/kg) Exchangeable acidity + exchangeable
aluminum CEC (cmolc/kg) Sum of exchangeable bases and
acidity Base Sat (% of CEC) (Exchangeable bases* 100)/CEC pH See method for pH [H+] The inverse log of pH d
13C d
15N
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