PURPOSE:
To monitor spatial and temporal patterns of soil moisture in the Konza Prairie LTER watersheds.
LOCATION OF SAMPLING STATIONS:
Access tubes are located in Tully soils. Two tubes are in N04D, 020B, 004B, 001C, and 001D each; four tubes are located in N20B. All tubes are near species composition transects and are marked with conduit (see data set PVC02 maps): N04D ( Fig.27 ), 020B ( Fig. 24 ), 004B ( Fig. 28 ), 001C ( Fig. 23 ), 001D ( Fig. 26 ), N20B ( Fig. 25 ).
FREQUENCY OF SAMPLING:
Soil moisture is taken every two weeks from April 1 through November 1. From November through March, readings are taken monthly when the temperature is above 20(F) and there is no snow cover.
METHODS:
* Two neutron probes are stored in Bushnell Rm 202.
* Charge battery in the unit if necessary (a full charge will last about 70 operating hours).
* Turn power switch to "SLOW" for ten minutes so the unit can warm up.
* Take Standard count: Switch display to "STD COUNT" and power switch to "SLOW;" Press start button. After the count stabilizes (about four minutes), record the count and the time.
* Measure for standing water in the tube with the meter stick.
* Adjust the depth measurements accordingly so the probe will not be inserted into water.
* Set the unit onto the aluminum access tube.
* Set display to kg/m3 and power switch to "NORM." * Pull release pin and lower the probe to the first stop (25 cm); press start button.
* At the beep, the display will quit blinking; record the reading; lower the probe another 25 cm and press start button.
* After the lowest depth raise the probe into the unit and latch in place with the release pin.
* Remove unit from the access tube and replace rubber stopper and can.
* After the last watershed tube has been measured, set display back to "STD COUNT" and the power switch to "SLOW." Press start button. When the count stabilizes, record ending count and time. Turn power switch to "OFF."
* If all sites cannot be measured the same day, record a new beginning and ending standard count on the field form.
PRECAUTIONS:
If recommended procedures are followed and the unit is not abused, operating the neutron probe is not hazardous. Carry the unit away from the body to minimize any possible radiation exposure. Make sure the probe is firmly latched in the unit before removing from the access tube. Do not immerse the probe into water.
SUMMARY OF ALL CHANGES UP TO 1993:
* Tubes in 001C were added in 1984.
* A measuring stick was dropped into 020B tube #1 in 1989, restricting depth reading to 75 cm.
* Tube #1 in 004B was damaged by a truck in July, 1989; a replacement tube was installed approximately 2 m away in December, 1991.
* The new tube #1 in 004B extended 23 cm above the ground instead of the normal 8 cm; in January, 1993, the tube was cut to a 8 cm protruding height to conform with heights of the other tubes. Thus, readings from December 1991 to December 1992 were actually 15 cm above their indicated depth (i.e., 10, 35, and 60 cm depth instead of 25, 50, and 75 cm).
* Measurements from four tubes in N01B were taken from 1983 until April 1992, but were then abandoned because of potential problems with bison.
