Regional Ecosystem Soil Hydraulics Project aims to improve the access and representation of soil water potential data across the diverse ecosystems and sites that are actively contributing to AmeriFlux Network.
Regional Ecosystem Soil Hydraulics Project aims to improve the access and representation of soil water potential data across the diverse ecosystems and sites that are actively contributing to AmeriFlux Network.

Site: US-WCr (Willow Creek)

Site Contact:

Ankur Desai - University of Wisconsin

Jonathan Thom - University of Wisconsin

Paul Schramm - University of Wisconsin

Site Location

Photo of samples during the soaking process
Photo of samples during the soaking process

Soil Texture

Methods:

Soil texture is measured using a combination of the Hydrometer method and wet sieving. The hydrometer method is used to calculate the clay fraction; the wet sieving is used to calculate the sand fraction, and the silt fraction is calculated by difference. The soil is initially tested for organic matter and pretreated with hydrogen peroxide if organic matter content is greater than 1.5%. After pretreatment (if needed), soil is dispersed with a solution of sodium hexametaphosphate to then measure the clay content by the Hydrometer method. Once the clay fraction is measured, the dispersed sample is wet sieved to 53µm to collect and dry the sand fraction in an oven at 105 Celsius degrees. With the sand fraction calculated, the silt fraction can be calculated by difference. Fine root biomass (defined as roots < 2mm in diameter) is estimated by picking from the soil and placing the soil in a sieve. After that, the roots are rinsed and dried in an oven at 65 Celsius degrees. Once roots are dried, they are weighed.

Sample Summary for Soil Texture
Site Plot Depth [cm] Clay [%] Silt [%] Sand [%] Root Mass [g] Bulk Den [kg m-3]
US-WCR E001 0 17.4 23.4 59.3 0.430 1.20
US-WCR E001 10 14.1 22.3 63.6 0.470 1.50
US-WCR E001 50 12.6 14.5 72.8 0.110 1.50
US-WCR N001 0 17.0 18.0 65.0 0.800 0.73
US-WCR N001 10 16.7 29.1 54.3 0.480 1.20
US-WCR N001 50 8.8 20.6 70.6 0.020 1.50
US-WCR S001 0 15.2 26.9 57.9 0.660 0.85
US-WCR S001 10 12.7 26.2 61.1 0.067 1.10
US-WCR S001 50 12.6 21.2 66.2 0.003 1.50
US-WCR W001 0 13.3 45.3 41.4 0.980 0.84
US-WCR W001 10 15.5 35.8 48.7 0.320 1.20
US-WCR W001 50 11.3 23.5 65.1 0.200 1.40
Depth Summary for Soil Texture: Median and Stdev (\(\sigma\))
Site Depth [cm] Clay [%] Silt [%] Sand [%] Root Mass [g] Bulk Den [kg m-3] Clay \(\sigma\) Silt \(\sigma\) Sand \(\sigma\) Root Mass \(\sigma\) Bulk Den \(\sigma\)
US-WCR 0 16.10 25.15 58.6 0.730 0.84 1.9 12.0 10.0 0.230 0.210
US-WCR 10 14.80 27.65 57.7 0.390 1.20 1.7 5.7 6.7 0.190 0.160
US-WCR 50 11.95 20.90 68.4 0.064 1.50 1.8 3.8 3.6 0.092 0.027
Site Summary for Soil Texture: Median and Stdev (\(\sigma\))
Site Clay [%] Silt [%] Sand [%] Root Mass [g] Bulk Den [kg m-3] Clay \(\sigma\) Silt \(\sigma\) Sand \(\sigma\) Root Mass \(\sigma\) Bulk Den \(\sigma\)
US-WCR 13.7 23.45 62.35 0.37 1.2 2.6 8.3 9 0.32 0.28

Soil Water Retention Curves

Van Genuchten Equation for soil water retention curves

\[ \theta=\theta_{r}+\left(\theta_{s}-\theta_{r}\right)\left[1+(\alpha \psi)^{n}\right]^{-(1-\frac{1}{n})} \]

Van Genuchten Equation for soil water retention curves #updated with Dennis derivation

\[ \psi=\frac{\sqrt[n]{\left(\frac{\theta-\theta{r}}{\theta_{s}-\theta{r}}\right)^{n /(n-1)}-1}}{\alpha} \]

Methods:

The soil water retention curves (SWRC) were measured using two instruments to best represent both the wet and dry ends of the SWRC. 1) Saturated soils were put onto METER Group HyProp and water was allowed to slowly evaporate while measuring soil tensions and soil mass. Measurements spanned two- fourteen days depending on soil texture. 2) Unsaturated soils were removed from HyProp and two subset samples were selected and transferred to WP4C sample containers where they were measured repeatedly until soils reached -15 MPa. Data from WP4C and HyProp were compiled to form SWRC spanning entire spectrum of soil moisture conditions. Previous curves were generated using a nonlinear least squares model. This Version 2 utilized a Bayesian approach, with a confidence interval of 90%.

Van Genutchen Model Parameters
Site Depth_cm \(\theta{s}\) \(\theta{r}\) \(\alpha\) n \(\sigma\) \(\theta{s}\) \(\sigma\) \(\theta{r}\) \(\sigma\) \(\alpha\) \(\sigma\) n
US-WCR 0 0.5861998 -0.0059220 307.5499 1.236730 0.0047135 0.0050409 30.06466 0.0080127
US-WCR 10 0.4940269 -0.0070947 289.4118 1.229110 0.0038809 0.0037772 26.13369 0.0072949
US-WCR 50 0.4269822 0.0088812 260.9532 1.259155 0.0027925 0.0109400 21.57182 0.0198871
Site Level Van Genutchen Model Parameters
Site \(\theta{s}\) \(\theta{r}\) \(\alpha\) n \(\sigma\) \(\theta{s}\) \(\sigma\) \(\theta{r}\) \(\sigma\) \(\alpha\) \(\sigma\) n
US-WCR 0.502403 -0.0013785 285.9716 1.241665 0.0037956 0.006586 25.92339 0.0117316

Saturated Hydraulic Conductivity

Methods:

The soil saturated hydraulic conductivity (KSAT) is measured from samples that have been saturated for 24-48 hours. Saturated soils samples were put into METER Group KSAT and measured using falling head approaches. Each sample was measured 3-7 times aiming to capture consistent measurements for each sample. These replicated measurements were summarized for analysis of KSAT. Soil bulk densities were estimated using soil mass (g) inside the 250 mL rings. The estimates of KSAT are inherently noisy as roots, rocks, and macropores produce preferential flow pathways, we have aimed to reduce this uncertainty by only using the best measurements for analysis. We have used Grade A measurements in all summaries and analysis. Grade A measurements are defined as cores meeting the following QAQC criteria: sample bulk density within 1.5 standard deviations of the median bulk densities for each soil depth, measurements reaching a 0.99 R2 correlation, and individual observations within METER Group’s listed measurement ranges (i.e., 0.01 < KSat [cm d-1] < 5000).

## [1] "List of samples meeting A criteria being within 1.5 standard deviations from the median bulk density"
##  [1] "US-WCR_E001_050" "US-WCR_N001_000" "US-WCR_N001_010" "US-WCR_N001_050"
##  [5] "US-WCR_S001_000" "US-WCR_S001_010" "US-WCR_S001_050" "US-WCR_W001_000"
##  [9] "US-WCR_W001_010" "US-WCR_W001_050"
## [1] "List of samples meeting B criteria being outside 1.5 standard deviations from the median bulk density"
## [1] "US-WCR_E001_000" "US-WCR_E001_010"
Core Summary for Saturated Hydraulic Conductivty (Grade A cores and measurements only)
Site Plots Depth [cm] Median KSat [m s-1] Min KSat [m s-1] Max KSat [m s-1] StDev KSat [m s-1]
US-WCR E001 50 6.30e-06 5.20e-06 6.80e-06 7.00e-07
US-WCR N001 0 5.37e-04 5.37e-04 5.37e-04 0.00e+00
US-WCR N001 10 2.44e-04 2.07e-04 2.73e-04 2.58e-05
US-WCR N001 50 3.88e-05 3.10e-05 4.07e-05 4.30e-06
US-WCR S001 0 3.77e-04 3.34e-04 4.51e-04 3.94e-05
US-WCR S001 10 2.87e-05 2.68e-05 3.26e-05 2.30e-06
US-WCR S001 50 8.40e-06 8.20e-06 1.00e-05 8.00e-07
US-WCR W001 0 2.16e-04 2.01e-04 2.29e-04 1.02e-05
US-WCR W001 10 9.74e-05 8.61e-05 1.27e-04 1.49e-05
US-WCR W001 50 3.21e-05 2.83e-05 3.34e-05 2.40e-06
Depth Summary for Saturated Hydraulic Conductivty
Site Depth [cm] Median KSat [m s-1] Min KSat [m s-1] Max KSat [m s-1] StDev KSat [m s-1] StErr KSat [m s-1]
US-WCR 0 3.77e-04 2.01e-04 5.37e-04 0.0001088 5.44e-05
US-WCR 10 8.61e-05 2.68e-05 2.73e-04 0.0000987 4.94e-05
US-WCR 50 8.20e-06 5.20e-06 4.07e-05 0.0000140 7.00e-06
Median Site Saturated Hydraulic Conductivty
Site Median KSat [m s-1] Min KSat [m s-1] Max KSat [m s-1] StDev KSat [m s-1] StErr KSat [m s-1]
US-WCR 3.1e-05 5.2e-06 0.000537 0.0001287 3.22e-05

All measurements used in the tables are defined as cores meeting QAQC criteria, i.e., “Grade A” within 1.5 standard deviations of the median bulk densities for each soil depth, measurements reaching a 0.99 R2 correlation, and individual observations within METER Group’s listed measurement ranges (i.e., 0.01 < KSat [cm d-1] < 5000). Saturated hydraulic conductivity of clay-rich soils is often outside the measurement range of the lab-based KSAT sensors.

Data Files:

Site Meta Data

US-WCR_Metadata.xlsx

Soil Texture

US-WCR Soil Texture.csv

Root Biomass

WCR Root Biomass.xlsx

Complete Soil Water Retention Curves

[1] “US-WCR_E001-000.xlsx” “US-WCR_E001-010.xlsx” [3] “US-WCR_E001-050.xlsx” “US-WCR_N001-000.xlsx” [5] “US-WCR_N001-010.xlsx” “US-WCR_N001-050.xlsx” [7] “US-WCR_S001-000.xlsx” “US-WCR_S001-010.xlsx” [9] “US-WCR_S001-050.xlsx” “US-WCR_W001-000.xlsx” [11] “US-WCR_W001-010.xlsx” “US-WCR_W001-050.xlsx”

Saturated Hydraulic Conductivity

[1] “KSAT_measurement_US-WCR_E001_000_001.csv” [2] “KSAT_measurement_US-WCR_E001_000_002.csv” [3] “KSAT_measurement_US-WCR_E001_000_003.csv” [4] “KSAT_measurement_US-WCR_E001_000_004.csv” [5] “KSAT_measurement_US-WCR_E001_000_005.csv” [6] “KSAT_measurement_US-WCR_E001_000_006.csv” [7] “KSAT_measurement_US-WCR_E001_010_001.csv” [8] “KSAT_measurement_US-WCR_E001_010_002.csv” [9] “KSAT_measurement_US-WCR_E001_010_003.csv” [10] “KSAT_measurement_US-WCR_E001_010_004.csv” [11] “KSAT_measurement_US-WCR_E001_010_005.csv” [12] “KSAT_measurement_US-WCR_E001_010_006.csv” [13] “KSAT_measurement_US-WCR_E001_050_001.csv” [14] “KSAT_measurement_US-WCR_N001_000_001.csv” [15] “KSAT_measurement_US-WCR_N001_000_002.csv” [16] “KSAT_measurement_US-WCR_N001_000_003.csv” [17] “KSAT_measurement_US-WCR_N001_000_004.csv” [18] “KSAT_measurement_US-WCR_N001_010_001.csv” [19] “KSAT_measurement_US-WCR_N001_010_002.csv” [20] “KSAT_measurement_US-WCR_N001_010_003.csv” [21] “KSAT_measurement_US-WCR_N001_010_004.csv” [22] “KSAT_measurement_US-WCR_N001_050_001.csv” [23] “KSAT_measurement_US-WCR_N001_050_002.csv” [24] “KSAT_measurement_US-WCR_S001_000_001.csv” [25] “KSAT_measurement_US-WCR_S001_000_002.csv” [26] “KSAT_measurement_US-WCR_S001_000_003.csv” [27] “KSAT_measurement_US-WCR_S001_000_004.csv” [28] “KSAT_measurement_US-WCR_S001_010_001.csv” [29] “KSAT_measurement_US-WCR_S001_010_002.csv” [30] “KSAT_measurement_US-WCR_S001_010_003.csv” [31] “KSAT_measurement_US-WCR_S001_050_001.csv” [32] “KSAT_measurement_US-WCR_W001_000_001.csv” [33] “KSAT_measurement_US-WCR_W001_000_002.csv” [34] “KSAT_measurement_US-WCR_W001_000_003.csv” [35] “KSAT_measurement_US-WCR_W001_000_004.csv” [36] “KSAT_measurement_US-WCR_W001_000_005.csv” [37] “KSAT_measurement_US-WCR_W001_000_006.csv” [38] “KSAT_measurement_US-WCR_W001_010_001.csv” [39] “KSAT_measurement_US-WCR_W001_010_002.csv” [40] “KSAT_measurement_US-WCR_W001_050_001.csv” [41] “KSAT_measurement_US-WCR_W001_050_002.csv”

Questions or assistance accessing data please contact:

Daniel Beverly