Organic Soil Layer Data for 1992, 1998, 1999, 2002, 2004 and 2006

for the Walker Branch Throughfall Displacement Experiment (TDE)

1.1 Document Title: TDE forest floor organic layer data
1.2 Revision Date:  9 June 2008
1.3 Document Summary:  Pre- (1992) and multiple year post-treatment mineral element data for TDE soils
1.4 Sponsor: Office of Biological and Environmental Research, U. S. DOE

2.1 Investigator and data set contact:

Mats J. Fröberg (
Department of Soil Science
SLU - Sveriges Lantbruksuniversitet
SLU PO Box 7001, SE-75007
Uppsala, Sweden


Paul J. Hanson (
Environmental Sciences Division
Oak Ridge National Laboratory
P.O. Box 2008, Building 1062
Oak Ridge, TN 37831-6422
2.2 Title Of Investigation:
Walker Branch Throughfall Displacement Experiment (TDE)


Organic layer mass and element data for all three treatment areas of the TDE site before (1992) and after (1998, 1999, 2002, 2004, and 2006)  chronic precipitation manipulations initiated in July of 1993.


From Frobert et al. 2008: 

    Organic horizons were sampled throughout the study period using identical methods in late January 1992 (pre-treatment), and February of 1999, 2002, 2004, and 2006. General sampling locations were designated in protected areas of each treatment plot along upper, middle and lower slope transects in undisturbed areas, away from foot traffic. Repeated collections within each of the designated sampling areas were done in a sub-area that had never been previously sampled due to the consumptive nature of the organic layer measurements. Sampling for each campaign was undertaken at 5 locations per transect in each treatment area for a total of 15 sampling locations for each of the wet, ambient, and dry treatment areas. 

    Organic horizons were sampled within 0.25 m2 circular plots. Coarse twigs and large pieces of non-foliar litter were collected first followed by the separation of the components of the O horizon (Oi, Oe, Oa). The C stocks of the Oe and Oa horizons are presented together, because the Oe or Oa horizons were too thin or difficult to separate in a replicable manner. All organic horizon samples were immediately oven dried for 48 hours (70 °C) and dry mass was determined. The organic horizon samples were subsequently coarse ground in a large Wiley mill without further separations (i.e., fine roots of the Oa horizon were not removed). Sub-samples of the homogenized coarse-ground material were further ground to 20 mesh in a Tecator Cyclotec sample mill (Tecator, Herndon, VA) prior to the evaluation of C and other element concentrations.

    All dried soil samples were archived in sealed glass containers for simultaneous analysis of all pre- and post treatment samples in 2006. Dry samples of organic horizons and soil were analyzed for total C and N on a LECO CN-2000 (LECO Corporation, St. Joseph, Michigan) using secondary standards traceable to NIST reference materials. Element analysis was preformed by microwave-acid digestion with digests being analyzed by ICP emissions spectrograph (Thermo Jarell -Ash model 61E ICP).

    Data for the organic and mineral soils are presented as both dry mass and carbon content per unit soil area."

The 1998 and 1999 data include replicate samples.


Data are provided in comma delimeted csv files where the first line includes the variable names and subsequent lines include the following data by year.

6.1 Variable, Definition, and Units (as appropriate)

Column 1 = Year
Column 2 = Month -  Month of Sampling
Column 3 = Y = position up and down the hill slope.
Column 4 = X = position across the hill side.

Column 5 = TMT = Treatments of the TDE experiment
1 = wet
2 = ambient
3 = dry

Column 6 = Layer
Oi  = recognizable litter layer
Oe = fragmented litter layer
Oa = humus litter layer
Twigs = woody materials within the litter less than 1" in diameter.

Column 7 = MassDM, dry mass of the layer, gd.m. m-2
Column 8 = C, carbon, %
Column 9 = MassC, dry mass of carbon per layer,  gC m-2
Column 10 =  N, nitrogen, %
Column 11 = CN, C to N ratio, unitless
Column 12 = P, phosphorus, %
Column 13 = K, potassium, %
Column 14 = Ca, calcium, %
Column 15 = Mg, magnesium, %
Column 16 = B, boron, ppm
Column 17 = Fe, iron, ppm
Column 18 = Mn, manganese, ppm
Column 19 = Zn, zinc, ppm

6.2 Number of Records: 8079 individual mass or element measurements.

6.3 Missing data: Yes, represented by blank or empy cells between commas.

6.4 Related Data Sets:  Data sets on mineral layer elements over time for the TDE are also archived. 

No known errors other than missing samples. 


8.1 Limitations of the data
Element analyses are not available for the 1992 samples ruined by rodents, and were not attempted for the 1998 samples (still archived).

8.2 Known Problems With The Data

8.3 Usage Guidance:


Fröberg M, Hanson PJ, Todd DE, Johnson DW (2008) Evaluation of effects of sustained decadal precipitation manipulations on soil carbon stocks.  Biogeochemistry (in press).

Johnson DW, Todd DE Jr, Hanson PJ (2008) The effects of throughfall manipulation on soil nutrient status: results of 12 years of sustained wet and dry treatments. Global Change Biology 14:1661-1675.


Click on the following text to view the column delminited data for the listed year.
Once open the files can exported as text files with the 'Save As' command.