Installation: (1) Drive down metal rod to desired depth (for 2010/2011 project it was between 70 and 90 cm) at 53 degrees. This angle allows for easy calculation for a 3;4;5 triangle to obtain desired depth (this angle was estimated for 2010/2011) project. (2) Attach lysimeter to nylon tubing at about 1 meter longer than depth of hole to allow slack when sampling. (3) Drop down lysimeter to end of bored hole. Make sure lysimeter reaches the end of the hole or water will pool up beneath the lysimeter and equipment will likely fail to collect water samples. (4) Mix up silica powder at a ratio of about 1:2 with water. Pour silica slurry into hole making sure that entire hole fills up with slurry. If it does not initially fill, then wait a few minutes for silica to plug soil pores and then repeat until hole fills to top. If it does not fill at all, bore a new hole since this means there is a passageway for large quantities of fluid to go in the hole and therefore lysimeter will not be in contact with saturated soil for sampling. D (5) Pack soil over top of bored hole to plug up passageway to disallow water flowing directly to lysimeter (6) Place PVC housing directly above point where lysimeter tubing exits soil (7) Attach tubing from lysimeter to sample bottles and place inside PVC housing. It often helps to wrap the extra tubing around the sample bottle, spinning it while wrapping, this will take up the extra slack. (8) Place PVC caps on PVC housing to completely enclose sample bottles (9) Pack soil around PVC housing to prevent disturbance of sample bottles (10) Place plywood over all PVC housings to ensure that rain and runoff does not preferentially follow the bored hole to the lysimeter, increasing water volume collected and diluting samples.
Sampling: (1) Priming lysimeters to withdrawal water sample. Usually done at least 3 days before collection. (2) Remove plywood (3) Remove PVC caps (4) Put end of hand pump tube into nylon tube in the cap of the sample bottle. There are two nylon tubes in the sample bottle. One goes into the ground and into the lysimeter, the other has a clip on it and will extrude only about 3 inches from the bottle cap… this short tube is the one to apply the vacuum on. (5) Hand pump sample bottle to 15psi. Make sure to unclip the clip on the nylon tubing to allow air to move through the tube. (6) Re-clip the tube and remove the hand pump tube from sample bottle tube. Make sure the clip is fully in place so vacuum remains. (7) Place PVC cap back on (8)Place plywood back on.
Collecting samples (1) Remove plywood; (2) Remove PVC cap (3)Pull out sample bottle from PVC housing (4) Unscrew cap of sample bottle (if a hissing sound is heard, make note that the bottle is still under vacuum pressure. This will be important when determine functionality of equipment and installation) (5) Pour contents of sample bottle into separate bottles to be taken back to the lab for analysis.(6) Rinse out sample bottles with Deionized water: rinse 100 ml of DI water 3 times. Make sure all DI water is out of sample bottles before cap is replaced, otherwise following samples will be diluted (7) Screw sample bottle cap back on tight (8) Place sample bottle back in PVC housing, wrapping the nylon tubing around the sample bottle to take up slack (9) Re-apply vacuum to sample bottle (see Priming Lysimeters above) (10) Place PVC cap back on PVC housing (11) Place plywood back on
We collected litter from sixteen plots on WS1. These particular plots have been intensely subsampled for other analyses (Peterson et al.2012) intensely sampled plots were selected to represent the distribution of cover times height as measured by LiDAR reconnaissance in 2008. This metric was selected because it was believed to be a good proxy for biomass distribution. Litter collections were conducted for the years of 2009-2011, beginning with collection on 12 August 2009 and ending with collection on 11 August 2011. The litter traps were co-located just outside the perimeter of the plots in order to avoid interaction with the current vegetative studies on the plots. Each litter trap was square with edges of 43 cm by 43 cm (1.849 m2). The ground-truthed plot sizes are 250 m2; the aerial plot sizes range down to 125 m2 due to steep slopes. Five collections of the litter traps were made in the 1st year. In the second year, four collections were made.
Litter was collected wet. Trap status, as well as any anamolies in trap content (bark, logs, etc.) were recorded.
For most collection periods, fine and coarse litter were brought back to the lab and separated with a 12 inch hardware cloth with 12.5 cm openings. To sieve the materials in this manner, a sample was dumped onto the screen and gently shaken and lightly rubbed to pass the small pieces through the screen. After the separation, twigs which slipped through the screen were returned to the coarse fraction and the needles stuck to the coarse objects were rubbed free and placed in the fine fraction. After the separation wet weight is recorded, the sample was placed in a labeled paper bag and oven-dried. Upon reaching a stable weight in the oven, the dry weight is recorded. A paper bag stapled and labeled like the sample bags is used to tare the bag weight out of the gross weight. Some traps were damaged between collections, namely, traps on plots 419, 518, and 522. Litter mass accumulated for these plots was only recorded for non-damaged traps and a note was taken on the number and extent of damage.
To calculate dry mass of leaves (in Mg) per hectare per period (interval between collections), three conversion factors were created following the form of:
Mass per Hectare =1849cm2 x Number of Traps x Dried Mass of Leasves/1000000
(1) Where Mass represents the dried mass of leaves. The rationale for creating three conversion factors was to account for the set of plots on which only three or four trap samples were valid; on these plots the expansion factor must naturally be greater.
For the first year, leaf collections were precise to 365 days for almost all plots. Thus, the sum of the collected masses per hectare over the course of that year represented the annual collection. For a few plots, one additional day was included in the final collection period, and the influence of that period on the sum was weighted by a conversion factor of 0.9696.
For the second year, leaf collections were only calculated through 5 May 2011. Thus, the most recent time period was weighted by a conversion factor (1:4631) to extend its influence on the sum through the summer for a full two-year interval. When the most recent collections have been completed, this factor will be removed or recalculated.
For one plot (518) this years data was damaged for two collection periods, one in the late summer and one in the fall. Mean values from the other two collection periods (early summer and winter) were weighted to the appropriate amount of days and used as a proxy for the missing measurements. We acknowledge that this greatly decreases the accuracy of this plot. For another plot (419), large chunks of bark and rotted log were found in the sample during one remeasurement.
Custom regression equation used to convert soil moisture output from milliVolts to water content. Calibrations were developed for a capacitance instrument (ECH2O), a time domain reflectometry cable tester (CT), and a water content reflectometer (WCR) in soils collected from the Wind River and H.J. Andrews Experimental Forests.d the standard equations predicted soil moisture content 0%–11.5% lower (p < 0.0001) than new calibrations. Each new calibration equation adequately predicted soil moisture from the output for each instrument regardless of location or soil type. Prediction intervals varied, with errors of 4.5%, 3.5%, and 7.1% for the ECH2O, CT, and WCR, respectively. Only the ECH2O system was significantly influenced by temperature for the range sampled: as temperature increased by 1°C, the soil moisture estimate decreased by 0.1%. Overall, the ECH2O performed nearly as well as the CT, and thanks to its lower cost, small differences in performance might be offset by deployment of a greater number of probes in field sampling. Despite its higher cost, the WCR did not perform as well as the other two systems.
The instruments that use the capacitance technique or TDR to determine ? rely on the high dielectric constant of water (80) relative to mineral soil (3–5) and air (1), because water in the soil will influence the propagation of an electric signal through the soil medium. Both these techniques use empirical relationships between the soil water content and the change Can. J. For. Res. 35: 1867–1876 (2005) doi: 10.1139/X05-121 © 2005 NRC Canada 1867 Received 2 December 2004. Accepted 29 May 2005. Published on the NRC Research Press Web site at http://cjfr.nrc.ca on 3 September 2005.
N.M. Czarnomski, T.G. Pypker, J.Licata, and B.J. Bond. Department of Forest Science, 321 Richardson Hall, Oregon State University, Corvallis, OR 97331, USA. G.W. Moore. Department of Rangeland Ecology and Management, Rm. 325 Animal Industries Building, 2126 TAMU, Texas A&M University, College Station, TX 77843-2126, USA. Corresponding author (e-mail: Nicole.Czarnomski@oregonstate.edu).in an electrical signal to estimate ?. Three common instruments available for the measurement of ? are the ECH2O soil moisture probe (hereafter referred to as “ECH2O”; Decagon Devices, Pullman, Washington, USA), the TDR cable tester (hereafter referred to as “CT”; we used model 1502C, Tektronix, Inc., Beaverton, Oregon, USA), and the water content reflectometer (hereafter referred to as “WCR”; we used the CS615 from Campbell Scientific, Logan, Utah, USA; since our measurements Campbell Scientific has introduced a new model).
The ECH2O calculates the apparent soil dielectric constant (Ka) of a soil by measuring the charge time of a capacitor in the soil. If the applied voltage is known, the time required to charge the capacitor is related to the output voltage of the instruments.The CT uses TDR to estimate ?. TDR determines Ka by measuring the time required for an electromagnetic pulse to travel up and down a pair of metal transmission lines of a fixed length (e.g., Topp et al. 1980). The high dielectric constant of water relative to soil and air will delay the propagation of the electromagnetic pulse. The WCR also propagates a signal along two parallel rods, but instead of measuring the propagation time of an electromagnetic pulse, the WCR uses the capacitance of the soil to predict Ka.
ECH2O: A Decagon Devices Inc. model EC-20 probe with a 20-cm plate. Signal output ranges between 250 and 1000 mV at 2500-mV excitation. The manufacturer provides an equation that is reported accurate within 3% ? if the soil does not have “high” sand content, clay content, or electrical conductivity. The manufacturer has determined that the instrument is weakly sensitive to changes in temperature and therefore does not suggest the need for a temperature correction (Campbell 2001).
CT: A Tektronix model 1502C cable tester with two parallel 33 cm long × 4 mm diameter stainless steel rods that were set 5 cm apart. A commonly used method for interpreting the nanosecond signal was created by Topp et al. (1980); however, we used a slightly different method created by Gray and Spies (1995) because it was calibrated for soils in the Pacific Northwest. Each has a different calibration equation to relate ? to Ka.
WCR: A Campbell Scientific, Inc. model CS615 with 30-cm rods (3.2 mm diameter and 3.2-cm spacing) connected to a circuit board. The circuit board is enclosed in epoxy and acts as a bistable multivibrator. Past research indicates that WCR is sensitive to temperature (Seyfried and Murdock 2001).
