Standard Operating Procedures - Arid lands soil carbon monitoring

KEY DETAILS

Principal Investigator
Dr. Lucy Smyth
Date
8 April 2025
Version
1.0.2
Programme
Arid Biodiversity Programme
Key partners
ORKCA Contact email
lsmyth@naturalstate.org

1. PREAMBLE

Natural State’s research methods and activities are detailed by a set of accepted Standard Operating Procedures (SOPs). These documents describe the steps involved in all Natural State research methodologies, from data collection to data processing and storage. Each SOP documents key methodological details for a specific data type. The objectives and background of the projects or surveys these methods are used for, features of the study area where these methods are applied, and details on survey and sampling designs for these methods may be found in survey Design Documents (DDs), which are available in the Related Documents section below or may be perused in the main NS Design Documents documentation page.

2. GLOSSARY

Natural State Glossary

3. METHODS OVERVIEW

The arid lands carbon monitoring protocol is used to soil carbon across the landscape so that spatial and temporal changes in soil carbon can be documented. Sampling requires collecting soil carbon and bulk density samples separately.

3.1 METHOD AIMS

The arid lands carbon monitoring methods are designed to:

  1. Document soil carbon stocks across the landscape.
  2. Investigate the proportion of labile versus mineral associated soil carbon across the landscape.

3.2 METHODOLOGICAL BACKGROUND

These methods for monitoring soil carbon in arid lands require the establishment 40 m X 40 m plots. In most cases these will be vegetation plots already established in the landscape. Each plot will be divided info four subplots, and soil carbon and bulk density sampling will take place in each subplot.

4. SAMPLING PREPARATION

The equipment mentioned in the list below needs to be gathered, checked and packed before sampling begins. If any sensors need to be configured prior to commencing sampling this will be documented below the equipment list.

4.1 EQUIPMENT LIST

  • 7 X 50 m measuring tapes
  • 1 m measuring stick
  • a large bucket (~20 L)
  • a small trowel
  • soil auger
  • bulk density measuring kit
  • 12 X 2 L ziploc bags per plot for storing samples
  • handheld GPS
  • tablet with S123 loaded and a functional camera

4.2 DEVICE CONFIGURATION

  • The S123 app needs to be loaded onto the tablet and the ABP Soil Carbon Survey needs to be loaded.
  • Station locations need to be loaded onto the handheld GPS.

5. SAMPLING PROCEDURES

These methods for monitoring soil carbon in arid lands require the establishment 40 m X 40 m plots. Each of these plots will be divided into four subplots, and soil carbon and bulk density sampling will occur in each subplot. One bulk density sample should be taken in the middle of each subplot, and each sample should be placed into a ziploc bag and labelled with a QR code. Then four soil carbon samples should be taken per subplot at two depths: 0 - 20 cm and 20 - 40 cm. The four soil carbon sampling locations per subplot should be located in a square oriented in the same direction as the plot, with each corner 1 m radially out from the centroid of the subplot. First, the four samples from the depth of 0 - 20 cm should be taken and mixed together in the large bucket. A subsample of the mixed samples (1/4 of the total volume) should then be placed into a ziploc bag and labelled with a QR code. Then the same procedure should be repeated for the samples from the 20 - 40 cm depth. Sampling at both depths must be repeated in all four subplots. Six plots will be sampled per property, paired to existing sampling sites from the camera trap and acoustic survey. These six plots will be the same for the vegetation survey.

5.1 ORKCA PILOT STUDY

  1. Navigate to the sampling location. This should be at the midpoint of the two camera traps deployed during the Arid Biocredit Pilot.
  2. Establish the extent of the 40 m X 40 m plot by running a 50 m measuring tape 20 m north and 20 m south and by running a second one 20 m east and 20 m west, intersecting at the sampling location, as shown above.
  3. Use another four 50 m measuring tapes to demarcate the 40 m edges of the plot.
  4. Run the last measuring tape diagonally from the centroid of the plot to the northeast corner.
  5. Locate the centroid of this subplot which will be located at 17.68m along the diagonal measuring tape.
  6. Open S123 and collect all metadata required by the Arid Soil Carbon Survey.
  7. Take a bulk density sample using the bulk density kit at the centroid of Subplot 1.
  8. Place the bulk density sample into a ziploc bag, label the bag with a QR code and scan the QR code into S123.
  9. Use the 1 m measuring stick facing radially outwards towards the north east from the bulk density sampling location to locate the first soil carbon sampling location.
  10. Use the soil auger to take a soil carbon sample from a depth of 0 - 20 cm.
  11. Put the soil carbon sample into the bucket.
  12. Move the 1 m measuring stick 90 degrees clockwise and take the second soil carbon sample.
  13. Put the soil carbon sample into the bucket.
  14. Repeat steps 11-12 for soil carbon samples 3 and 4.
  15. Use the trowel to meticulously mix the soil contained in the bucket.
  16. Use the trowel to place 1/4 of the soil from the bucket into a ziploc bag, label with a QR code and scan into S123.
  17. Repeat steps 8-15 at a depth of 20 - 40cm.
  18. Repeat steps 3-16 for the remaining 3 subplots.

6. POST PROCESSING

No post processing is required.

6.1 SAMPLE PROCESSING AND STORAGE

Soil samples should be stored in a cool and dark location (out of direct sunlight) and transported to the lab at the University of Cape Town as soon as possible.

6.2 DATA ENTRY AND UPLOADS

S123 forms need to be sent to the cloud upon return to internet or cell phone reception.

7.1 DESIGN DOCUMENTS

7.2 OTHER RELEVANT SOPS

7.3 DATA ELEMENTS

Survey Design

Data Collection

Dashboard

8. REVISION AND VERSION HISTORY AND DESCRIPTION

v1.0.0 Initial SOP created in March 2025. v1.0.1 Updates following field visit, incuding selection of the six sites per property. v1.0.2 Updates to the figure of sampling layout.