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Fall River Long-Term Site Productivity Study:
Soil Water Metadata
Data and Metadata Archived by
Warren D. Devine on 5 April 2006
Olympia Forestry Sciences Laboratory
3625 93 rd Ave SW
Olympia, WA 98512
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(HydroSense).
1. Summary
CONTENTS
Section I. Soil Water Data Collected with CS620 Water Content Reflectometer
3
2. Data collection
A. Instruments
B. Data collection
3
3
3
4 C. Instrument calibration
3. Data files
Section II. Soil Water Data Collected with Profile Probe type PR1.
1. Summary
2. Data collection
A. Instruments
B. Access tube installation
C. Data collection
4
5
5
5
5
6
D. Instrument calibration
3. Data files
A. Calibrated data
B. Raw data
References
Appendix
7
8
8
8
10
11
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Section I. Soil Water Data Collected with CS620 Water Content Reflectometer.
1. Summary
The CS620 Water Content Reflectometer with Hydrosense Display Unit (Campbell
Scientific Inc., Logan, UT) was used to assess the effects of organic matter retention treatments, vegetation control, and microsite condition on growing-season soil water content. Soil water content in the soil depth interval from 0 to 20 cm was measured between 27 June 2000 and 21 August 2003. Measurements were made in three treatments (bole-only harvest without vegetation control, bole-only harvest with vegetation control, and total-tree harvest “plus” with vegetation control), on three of the four blocks, in a range of forest floor condition classes. Soil water was measured six times in 2000, six times 2001, ten times in 2002, and twice in 2003.
2. Data collection
A.
Instruments
Data were collected using the CS620 Water Content Reflectometer with
Hydrosense Display Unit. The 20-cm-long rods available from Campbell
Scientific were used with the Reflectometer.
B.
Data collection
Data were collected on six dates each during the year one and year two growing seasons (2000 and 2001), on ten dates during the year three growing season
(2002), and on two dates during the year four growing season (2003).
1
Sample dates appear in Appendix 1, and the full field procedure for data collection using the CS620 is shown in Appendix 2. On each sampling date, 324 to 432 soil water content readings were taken, distributed as follows:
Blocks sampled 3
Plots sampled per block
Forest floor conditions per plot
Sample point per condition
Readings per sample point
3
4
3
3-4
Total readings per sampling date 324-432
Block 2, 3, and 4 were sampled. Within each block, three plots were sampled
(one per treatment described above). Within each plot, four forest floor conditions were sampled: 1) shaded, 2) accumulated slash, 3) decay (red rot), and
4) intact forest floor. The exception was the total tree plus treatment, where the
1 On many occasions, all readings were not completed in a single day. When this occurred, readings were collected on multiple site visits over a period of several days. This is noted in
Appendix 1.
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- 4 - bare soil condition replaced the accumulated slash condition. Within each condition, the organic matter of the forest floor was temporarily removed and three to four readings (≥20 cm apart) were taken with the CS620, each time inserting the rods vertically into the soil so that they penetrated to a depth of 20 cm.
C.
Instrument calibration
2
The CS620 output is a period of time measured in milliseconds. This output is the period of a square wave signal that varies with volumetric soil water content.
Prior to analyzing the data from this study, the period values must be converted to volumetric soil water content (VSWC; m
3
m
-3
) using a soil-specific calibration.
The soil-specific calibration for the Fall River site was performed by Bryan
Wender (formerly of Olympia Forestry Sciences Laboratory). The procedure involved measuring soil water content using the CS620, sampling the soil from the measurement location using a 7.2-cm diameter corer, and subsequently determining true VSWC of the core samples using the oven drying method. By applying this procedure to soil with a range of water contents, the measurement period ( P ) was related to VSWC (m
3
m
-3
) to create a soil-specific calibration equation for the 20-cm probes:
VSWC = -3.46 + 6.85
P - 3.01
P
2
The equation differed from the manufacturer’s standard calibration for 20-cm probes which is:
VSWC = -0.364 + 0.084
P + 0.481
P
2
3. Data files
All of the data collected with the CS620 appear in the spreadsheet
“CS620hydrosenseData.xls.” There are two columns of sensor output data in this spreadsheet: percent and period. The percent column is VSWC according to the manufacturer’s standard calibration, and the period column is the raw sensor output
(milliseconds). The data in the spreadsheet’s percent column should NOT be used in analysis or reported because they are much different than data derived from a soilspecific calibration. They are included on the spreadsheet because, in some instances in
2000, percent but not period data were recorded. In these cases, the manufacturer’s standard equation was inverted to transform VSWC values (percent column) to period values. Thus, period values are available for all readings. For data analysis and
2 For more information on the calibration procedure see the document titled “Calibrating the
HydroSense Soil Water Sensor to Five Soil Types in Western Washington” by Bryan Wender, 28
January 2003. Report on file at Olympia Forestry Sciences Laboratory.
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- 5 - summarization, the period values should be converted to VSWC using a soil-specific calibration such as the equation presented above.
Section II. Soil Water Data Collected with Profile Probe type PR1
1. Summary
To understand the influences of organic matter retention and vegetation control on the soil water profile over the course of the growing season, we initiated a sampling procedure in April 2002 using the Profile Probe type PR1 soil water probe (Delta-T
Devices Ltd., Cambridge, UK). This instrument is one of the few available that measures soil water content simultaneously at multiple soil depths. Because it is portable (i.e., does not need to be permanently installed in one location), the PR1 can by used to measure soil water at numerous sample points over a relatively short period in time (i.e., hours).
The PR1 measures volumetric soil water content (VSWC) at six soil depths between 10 and 100 cm. The probe requires access tubes that are installed in the soil prior to use.
The probe is then inserted into these tubes to take soil water content readings. In early
2002, 30 access tubes were installed at the Fall River site, and during the following three years 42 additional tubes were installed. Volumetric soil water content was measured at an approximate three- to four-week interval during the 2002-2004 growing seasons using the PR1 probe.
2. Data collection
A. Instruments
The instruments used were the Profile Probe type PR1 and the Moisture Meter type HH2, both from Delta-T Devices Ltd. During the course of the study we used two Profile Probe units, the first with serial number 7-024 and the second with serial number 3-38. Details on the operation of the PR1 are given in the user manual (Delta-T Devices Ltd., 2001).
B. Access tube installation
Fiberglass access tubes (100-cm long) from Delta-T Devices Inc. were installed on 24 plots to monitor soil water content (plot numbers listed in the file
“FallRiverPR1.xls”). The distribution of plots was: two plots from each of three treatments (bole-only harvest without vegetation control, bole-only harvest with vegetation control, and total-tree plus harvest with vegetation control) in each of four blocks. Tubes were installed three meters east of the metal fence post marking the center of the vegetation survey subplot in each plot. However, if the location was not suitable (e.g., presence of a stump, log, or an atypical microsite) it was relocated by at least 0.5 m. The access tube locations are recorded in the
“PR1AccessTubeList.xls” file.
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Access tubes were installed using a soil auger specifically designed for the purpose and sold by Delta-T Devices, Inc. as part of their access tube installation kit. First a hole was augered at the desired location, then the tube was inserted into the hole and pounded in using the technique described in the installation kit.
Tubes were installed so that the sensor locations on the probe (10-100 cm) would be equivalent to the same distance beneath surface of the mineral soil.
The initial set of 24 access tubes was installed 8-11 April 2002. After PR1 data collected from those tube locations revealed that six of the tubes likely had poor tube-soil contact (evidenced by extremely low readings indicating an air pocket near the tube at one or more of the six sensor locations), a second tube was installed on the same plot. The six additional tubes were installed 25 June 2002.
On 2 December 2002, four tubes were installed in the 50-year-old stands adjacent to the Fall River LTSP experiment. Two of these were installed in the stand to the west, and two were installed in the stand to the south. Between 17 November and 8 December 2003, 30 additional tubes were installed so that there were at least two tubes with good soil contact on all of the 24 plots that had been selected for monitoring with the PR1. On 9 February 2005 eight more tubes were installed in the older stands near the LTSP experiment (four in the south stand and four in the west stand).
C.
Data collection.
Using the procedure described in the user manual (Delta-T Devices Ltd., 2001), readings were taken at all tubes, usually on a single day, at an approximate onemonth interval during the growing season. At each tube three readings were taken, with the probe rotated 120 degrees between readings (Appendix 3). The
HH2 meter identifies the access tube at which each reading is collected with a letter (beginning with A). During data collection, the technician recorded this letter on a field sheet containing a current list of the access tubes. After downloading the HH2 meter to a PC, the technician then added the tube ID (e.g.,
33b) to the data file.
Influence of precipitation on data
Because we did not want to measure soil water content when soil was saturated following a rain event, we took readings only after there had been 48 or more hours with less than 6 mm cumulative precipitation.
During winter months, tubes often accumulated water, due either to condensation or leaks. Because this water could affect readings, tubes were swabbed out to remove all moisture prior to inserting the probe. The swab consisted of a strip
(approximately 10- x 20-cm) of shammy material securely tied to a screw-eye in the end of a dowel. This swab was a necessity for drying the tubes for fall, winter, and spring readings, as many accumulated water.
Data format
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All data collected prior to 20 February 2004 were collected only as percent
VSWC (determined by the factory standard mineral soil calibration given above).
Data collected on this date and thereafter were collected as mV and VSWC
(based on same factory standard mineral soil calibration). Because we learned that the standard calibration was inaccurate for Fall River soil, beginning 20
February 2004, we converted mV readings to VSWC with our soil-specific calibration and ignored the VSWC data from the factory standard calibration. For all data collected prior to 20 February 2004, which were not recorded in mV, we used the inverse of the standard factory equation to convert these data back to volts. We then used the soil-specific calibration to convert the data from volts to
VSWC. Thus, despite differences in initial format, all data were converted from volts to VSWC using our soil-specific equation.
D. Instrument calibration.
The output of the PR1 is millivolts (mV), which is then converted to VSWC using a factory standard or a soil-specific calibration equation. The PR1 requires soilspecific calibration for maximum accuracy (Delta-T Devices Ltd., 2001).
Beginning in 2003, Douglas Waldren and Warren Devine began testing various calibration procedures to determine the best method for creating a soil-specific calibration. The factory standard mineral soil calibration, as given in the user manual,
VSWC = -0.113 + (1.62
V ) – (3.56
V
2
) + (8.63
V
3
) where VSWC is equivalent to theta (m
3
m
-3
), and V is volts, was giving readings that were much too low, particularly for low soil water contents. This was determined through comparisons with calibrated output from the CS620 probe and from soil samples for which water content was assessed using the ovendrying method. After several attempts at calibration using the protocol suggested by the factory (Dynamax Inc., 2002), it was determined that the calibration procedure (which included drying and sieving the soil sample) altered soil structure significantly, and that an accurate calibration could not be achieved using this procedure. We did learn, however, that calibration equations were similar for soils from the A, AB, Bw1, and Bw2 horizons.
We then took an approach that involved as little disturbance of the soil as possible. We took field readings at six locations across the study site (two to six soil depths per location from 10 to 100 cm) using the Profile Probe. Five of these locations (depths of 10-30 cm) were access tubes installed one to two years earlier that had poor soil contact at lower depths (>30 cm). The sixth location (depths to
100 cm) was close to the face of the soil pit located near the site’s weather station.
Our goal in taking these readings was to measure soils across a wide range of soil water content values. We collected two 348-cm
3
samples from the soil immediately surrounding the probe sensor where each of the readings were taken.
We dried the samples to constant weight at 105° C to determine gravimetric and
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- 8 - volumetric water content. The relationship between the probe readings and the sample VSWC (mean of the two soil samples per reading) was the calibration equation that we used to convert volts ( V ) to VSWC (m 3 m -3 ):
VSWC = (0.574
V ) + 0.217
Our soil-specific calibration produced VSWC values that were typically greater than those produced by the generalized mineral soil calibration provided with the probe, particularly in dry soil. When our calibrated equation yielded VSWC values of 0.27, 0.35, and 0.40 m
3
m
-3
, the factory mineral soil equation yielded
VSWC values of 0.02, 0.18, and 0.32 m
3
m
-3
, respectively. The values produced by our calibrated equation were consistently within 0.05 m
3
m
-3
of calibrated values produced by frequency- and time-domain reflectometry sensors at the site
[CS616, CS620, and TDR100 (Campbell Scientific, Inc., Logan, Utah, USA)].
During the course of the study we tested the six probe sensors on each probe on reference soil samples of known VSWC to verify that all six sensors were functioning similarly. Twice between April 2002 and January 2006 we sent the
PR1 back to the factory for recalibration of the six sensors.
3. Data Files
A.
Calibrated data
The file “CalibratedPR1data.xls” contains the Profile Probe data collected at Fall
River from 15 May 2002 through 3 November 2004 (a total of 25 dates)
3
. Data are in the form of percent VSWC: raw PR1 data (volts) were converted to VSWC
(m
3
m
-3
) using our soil-specific calibration and then multiplied by 100. Empty cells are due to either: 1) no access tube was yet installed at that location, 2) readings were too low to register (below factory standard calibration range; i.e., below 89 mV) due most likely to poor contact between the access tube and the adjacent soil, or 3) readings were too high to register (above 474 mV) and thus recorded an error message rather than a value.
B.
Raw data
The raw data collected by the PR1 is saved separately for each date of collection
(39 dates). Format of the file name is: “ProfileprobeYYYY_MM_DD.extension” where Y is year, M is month, and D is day. Extensions are either “.txt” (text files)
3 These are the data that were used in the formal analysis of soil water content during years three through five. Data from the other dates were not included for one of the following reasons: 1) equipment failure or weather resulted in an incomplete data set for that date, 2) data collected in winter months, prior to 20 February 2004, contained numerous missing values because the factory standard calibration returned an error rather than a reading for values greater than 474 mV
(which were common at 60- and 100-cm depths in winter), or 3) the sampling dates were outside of the time interval of interest (spring 2002 through fall 2004).
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- 9 - or “.csv” (comma separated variable files which is the original file format).
Within each file, a variety of header information is given (see user manual: Delta-
T Devices Ltd., 2005), and the data lines begin on row 39. As noted in section 2, part D, the format of these data varies inasmuch as some files have two data columns (“% Vol” and “mV”; volumetric water content based on standard factory calibration and millivolt output, respectively) per reading per depth, while others one have one column (“% Vol”). Because the factory standard calibration had a limited millivolt range, errors are listed in the data files for “% Vol” when a reading is outside of this range. These errors are shown as either “L” (below calibration range) or “I” (above calibration range). When either of these errors is listed, no “% Vol” value is given, resulting in a missing data point. For some dates, data are missing for some of the tubes. Explanations of these missing data appear in Appendix 4.
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References
Campbell Scientific, Inc. 2001. Hydrosense instruction manual. Campbell Scientific, Inc.,
Logan, UT.
Delta-T Devices Ltd., 2001. User manual for the profile probe type PR1, version PR1-
UM-01-2. Delta-T Devices, Cambridge, UK.
Delta-T Devices Ltd., 2005. User manual for the moisture meter type HH2 version 4.0.
Delta-T Devices, Cambridge, UK.
Dynamax Inc., 2002. PR1 performance and calibration in high salinity – and high clay content soils. Delta-T Devices Data Sheet PR1 Profile Probe Application Note, revised Dec. 2002. Dynamax Inc., Houston, TX.
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Appendix 1. Dates of data collection using the CS620 Hydrosense.
Date
6/27/2000
Comment
7/13/2000, 7/17/2000
7/24/2000, 7/25/2000,
7/26/2000, 7/27/2000
Data collected over two days.
Data collected over four days.
8/9/2000, 8/10/2000
8/25/2000, 8/31/2000
9/22/2000, 9/27/2000
5/22/2001, 5/23/2001
6/6/2001
7/3/2001
8/9/2001
9/7/2001
9/24/2001
5/14/2002, 5/15/2002
6/3/2002, 6/6/2002,
6/11/2002
6/25/2002, 6/27/2002
7/10/2002
7/23/2002
Data collected over two days.
Data collected over two days.
Data collected over two days.
Data collected over two days.
Data collected over two days.
Data collected over three days.
8/8/2002
8/21/2002
9/5/2002
9/20/2002
10/7/2002
7/31/2003
8/21/2003
Data collected over two days.
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Appendix 2. Field procedure for measuring soil water content at Fall River using the CS620 Hydrosense probe (written by Christel Kern, 14 May 2002).
I.
Prepare for field: a.
Hydrosense with 20 cm probes b.
Spare AA batteries c.
Data sheets & clipboard (hard copy in project folder in fireproof cabinets at main office and digital copy on oak c:/adatafolder/fallriver/soil moisture/smoisture dsht.xls) d.
Rag e.
Site map f.
Fall River Safety: fax, caulks, hardhat (in cab), gate key, CB, radio…
II.
Collect HYDROSENSE moisture readings: a.
Plots 14 (TT+_VC), 20 (BO_VC), 21 (BO), 31 (BO), 33 (BO_VC), 34 (TT+_VC),
43 (TT+_VC), 45 (BO_VC), 47 (BO); (“sapflow plots”) b.
4 Conditions per plot i.
In BO and BO_VC plots, sample Shaded, Accumulated Slash,
Decay (i.e., red rot), and Forest Floor. ii.
In TT+_VC, sample Shaded, Decay (i.e., red rot), Forest Floor and
Bare Soil. c.
3 Sample Points per condition i.
preferably, 2 sample points per condition near sapflow trees d.
4 moisture readings per sample point. i.
Clear organic matter from mineral soil; approx 40 x 40 cm spot ii.
Keep reading points at least 20 cm apart iii.
Replace organic matter when finished e.
Hit ‘ENTER’ button to turn hydrosense ON. f.
Make sure Hydrosense is setup for 20cm probes. i.
Hit ‘MENU’ until it reads ‘Probe 20 cm’ g.
Hit ‘ENTER’ to collect reading h.
Record Percent and Period numbers on datasheet. i.
NOTE: i.
Probes cannot be wet (eg., from rain) going into soil. Wipe with rag. Wait for 48 h after a rain event to take readings. ii.
Keep probes screwed in tight; keep parallel from each other; keep dirt out of probe sockets.
III.
Collect PROFILE PROBE moisture readings a.
Tubes are located in plots 1, 3, 5, 9, 10, 11, 14, 20-23, 26, 29, 31, 33, 34,
36, 41, 43, 45, 47, 49, & 50
IV.
Office Return: a.
Put Hydrosense datasheets in Fireproof cabinet/ “Data to be entered”/
“Fall River Soil Moisture” Folder. b.
Profile Probe data should be stored at \\Oak\datadrive\Fall
River\Microclimate\Soil Moisture\raw data\ c.
Record and Report Equipment problems. d.
Report problems or unfinished plots to LCB
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Appendix 3. Field procedure for measuring soil water content at Fall River using the PR1 Profile Probe (written by Christel Kern, 1 June 2002).
Equipment:
1.
Moisture Probe (PR1 and HH2)
2.
Swab to dry out wet tube
3.
Site Map with tube locations
4.
Data sheet with list of tubes
Preparation:
1.
<ESC> to wake the meter
2.
<SET>; scroll to “Device”; <SET> to verify “PR1”; <ESC> to return to
“Device”
3.
scroll to “Date and Time”; <SET> twice to verify date; <ESC> twice; scroll to
“set Time”, <SET> to verify time; <ESC> twice;
4.
scroll to “Soil Type”; <SET> twice to verify “Mineral”; <ESC> twice
Measurement Instructions:
1.
Make sure probe is in the tube all the way. Sometimes you have to give it a little nudge to fit over the lip of the tube.
2.
Line-up a screw on the probe head with the black vertical line on the tube.
3.
<ESC> to ‘wake’ the computer
4.
<SET> a.
Data <SET> b.
Plot ID <SET> c.
Use up/down arrows to choose letter to represent plot. d.
Note Plot ID letter and Plot number on data sheet. e.
<SET>, <ESC>, <ESC>
5.
<READ>
6.
Use <#> to check the readings. Take notes if reading is unusual.
7.
<STORE>
8.
Twist probe clockwise to next screw (120 degrees).
9.
Repeat steps 5-7 until 3 readings are stored per tube.
10.
Go to next tube and repeat steps 1-9.
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Appendix 4. Details on Profile Probe data files with missing data. Files not listed here are complete. Note that in 2002 and 2003, when there was only one tube per plot, no letter was assigned to the tube ID (“a” is assumed).
File Comment
Profileprobe2002_06_04 Partial data set. Some data was lost when battery was changed in HH2. Because there is only one tube per plot, no tube letter is given. All are the “a” tubes.
Profileprobe2003_01_09 Partial data set. Tubes were very damp inside and readings were affected by this.
Profileprobe2003_07_21 Some missing data points due to a poor connection in the cable between the probe and the meter. Data collected again one week later.
Profileprobe2003_11_17 Partial data set. The rest of the data were collected the following day.
Profileprobe2003_11_18 Partial data set. The rest of the data were collected the previous day.
Profileprobe2003_12_03 Partial data set, collected to assess tubes during installation.
Profileprobe2003_12_08 Partial data set, collected to assess tubes during installation.
Profileprobe2004_01_21 Partial data set. Block 1 and west stand not done. Many tubes had missing values for the 100-cm reading because the data were above the calibration range.
Profileprobe2004_07_06 Several tubes were not read due to problem with meter.
Profileprobe2005_02_09 Partial data set. Data collected when installing new tubes in older stand.
Profileprobe2005_10_11 Partial data set. Battery in HH2 was changed during data collection and some of the data were lost because of this.
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