Standard Operating Procedures - Large and Small Tree Field Surveys

KEY DETAILS

Principal Investigator

Dr. Lucia Nadal, Dr. Nicola Stevens
Date

June 2025
Version

1.0.0
Programme

Rangelands Carbon Programme
Key partners

University of Oxford, University of Liverpool
Contact email

lnadal@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

3.1 METHOD AIMS

The Large and Small Tree survey methods are designed to:

1. Survey large trees within quarter hectare plots to determine species, status, and biomass.
2. Survey small trees within five 25 sq. m plots within each quarter hectare large tree plot.

3.2 METHODOLOGICAL BACKGROUND

These methods for surveying trees are adapted from the SEOSAW Field Manual. They are intended to record tree diversity, biomass, structure, mortality and damage. The method can be applied for long-term monitoring or as snapshot inventories. The protocol was developed specifically for African woodlands and savannas without sacrificing compatibility with global standards. The protocols stipulated here are specifically for square, quarter hectare plots but can be seemlessly adapted for other plot configurations.

The most important distinction between this protocol and the SEOSAW protocol is that this protocol uses the Diameter at Knee Height (50 cm) as the primary point of measurement for basal area rather than the Diameter at Breast Height (130 cm). This change was made because of a high rate of branching below breast height.

4. SAMPLING PREPARATION

The equipment mentioned in the list below needs to be gathered, checked and packed before sampling begins.

4.1 EQUIPMENT LIST

• A smart phone or tables with the S123 large tree and small tree surveys loaded.
• Six 50+ m tape measures or ropes measured to 50 m.
• Twenty-five stakes
• colored tape
• A differential GPS and base station.
• Handheld GPS (a smart phone or )
• DBH tape
• Digital calipers (optional)
• Hypsometer
• POM stick
• Surveyor’s pole
• Spray paint/chalk
• Tree tags (optional)

4.2 DEVICE CONFIGURATION

The S123 app needs to be loaded on the tablet and the CPP or GEM large tree and small tree surveys need to be loaded. The handlend GPS must be loaded with the coordinates of all plot centroids and the RTK rover must be loaded with a shapefile containing the corners of all subplots and small-tree plots.

5. SAMPLING PROCEDURES

All sampling procedures begin with proper setup. Plots are subdivided into four subplots and five small-tree plots.

5.1 GENERAL SETUP

1. Navigate to the plot centroid using the handheld GPS.
2. Follow the (RTK User Manual)[INSERT LINK] to properly setup the RTK base station and rover, ensuring the base station is located in an open area.
3. Using the RTK rover, navigate to the corners of all subplots and small tree plots and insert stakes to mark the location of the corners. Wrap colored tape around the stakes to designate each stakes purpose for denoting corners, midpoints, or small-tree plots.
4. Lay tape measures or ropes along all four outer edges of the plot and run two tape measures north-south and east-west through the plot centroid.

[INSERT FIGURE OF PLOT]

5.2 LARGE TREE SURVEY

1. Open the S123 App and collect all survey metadata required by the CPP/GEM Large Tree Survey.
2. Begin in Subplot 1, the southwest quarter of the plot. Record if any trees present in the subplot have a dkh of 5 cm or greater. Use the digital calipers/DBH tape to measure trees for which you are not sure if the DKH is greater than 5 cm.
3. If no trees in the subplot meet the criterion for large trees, record this information in S123 and proceed to the next subplot (SE), repeating step 2.
4. If large trees are present in a subplot, begin with the most southwestern tree and record tree details. Record the species, whether the tree is alive or dead, and whether it is single-stemmed or multistemmed. If multistemmed, record the number of stems with a DKH of 5 cm or greater.
5. Use the hypsometer or surveyor’s pole to measure the maximum height of the tree.
6. For each stem, use a POM stick to identify a point 50 cm above ground level and use either DBH tape or digital calipers to measure the DKH. [WHEN WOULD WE NOT MEASURE AT 50 CM?]
7. Record the stem mode [I USE THIS TERM BECAUSE IT’S WHAT’S IN S123 BUT IS IT THE BEST TERM? ALSO ADDED TO GLOSSARY] (condition, anchor, presence of parasites, etc.) and any damage on the tree and the average height of the damage. Also record the suspected cause of the damage.
8. Repeat steps 6-7 for all other stems on the tree.
9. Use the chalk or spray paint to mark the bottom of the tree to indicate that the tree has been fully sampled.
10. [IS THERE A PARTICULAR ORDER TO HOW TREES ARE SAMPLED].
11. Repeat steps 4-8 for all other trees in the subplot with a DKH of 5 cm or greater.
12. Repeat steps 2-9 for the other three subplots rotating in counter clockwise order (SE, NE, NW).

5.3 SMALL TREE SURVEY

1. Open the S123 App and collect all survey metadata required by the CPP/GEM Small Tree Survey.
2. Begin in small-tree-plot 1, the southwest corner of the plot. Record if any trees are present in the small-tree-plot with a dkh between 2 and 5 cm. Use the digital calipers/DBH tape to measure trees for which you are not sure if the DKH is within that range.
3. If no trees in the small-tree-plot meet the criterion for small trees, record this information in S123 and proceed to the next small-tree-plot (SE corner of the plot), repeating step 2.
4. If small trees are present in a small-tree-plot, begin with the most southwestern tree and record the tree’s species.
5. Use the hypsometer or surveyor’s pole to measure the maximum height of the tree.
6. Measure the DKH using calipers or the DBH tape.
7. Record the stem mode [I USE THIS TERM BECAUSE IT’S WHAT’S IN S123 BUT IS IT THE BEST TERM? ALSO ADDED TO GLOSSARY] (condition, anchor, presence of parasites, etc.) and any damage on the tree and the average height of the damage. Also record the suspected cause of the damage.
8. Use the chalk or spray paint to mark the bottom of the tree to indicate that the tree has been fully sampled.
9. Repeat steps 3-8 for all other trees in the subplot with a DKH between 2 and 5 cm.
10. Repeat steps 2-9 for the other four small-tree-plots rotating in counter clockwise order (SE, NE, NW) and finishing in the central small-tree-plot.

5.4 METHODS FOR GEOREFERENCING INDIVIDUAL TREES

1. Follow steps 1-3 for large or small trees.
2. If trees meeting the criteria for large or small trees are present, proceed to the most southwestern tree in the subplot. Poisition the RTK rover on the side of the tree closest to the base station. In S123, record the RTK datetime and the RTK ID.
3. Proceed with remaining steps for large and small trees.

5.4 ADDITIONAL STEPS FOR LONG-TERM MONITORING

1. Follow steps 1-7 for large trees.
2. Nail an allo tag to the stem at a height of [INSERT HEIGHT HERE].
3. Carefully record the tag number in S123 and double check that it does not have a typo.
4. Repeat steps 6-7 above for large trees and steps 2-3 here for all remaining stems on the tree.
5. Repeat all steps for other large trees in the subplot.
6. Repeat all steps for the other subplots.

6. POST PROCESSING

If georeferencing individual trees, pull the records from the RTK and view the results in GIS software. Check that the number of RTK records matches the number of trees recorded in S123.

6.1 SAMPLE PROCESSING AND STORAGE

No sample processing or storage is necessary.

6.2 DATA ENTRY AND UPLOADS

When wifi access is available, upload the S123 survey to the cloud.

7. RELATED DOCUMENTS

7.1 DESIGN DOCUMENTS

DD - Carbon Pool Plots DD - Global Environmental Monitoring Plots

7.2 OTHER RELEVANT SOPS

RTK User Manual GCP Setup Manual

7.3 DATA ELEMENTS

Survey Design

See respective Design Documents linked above.

Data Collection

• S123 data collection form - CPP Large Trees
• S123 data collection form - CPP Small Trees
• S123 data collection form - GEM Large Trees
• S123 data collection form - GEM Small Trees

Dashboard

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8. REVISION AND VERSION HISTORY AND DESCRIPTION

v1.0.0 Initial SOP describing work conducted in 2024 and the Q1 2025.

9. BIBLIOGRAPHY

SEOSAW partnership. (2021). A network to understand the changing socio‐ecology of the southern African woodlands (SEOSAW): Challenges, benefits, and methods. Plants, People, Planet, 3(3), 249-267. doi: 10.1002/ppp3.10168.