Tree Tagging for Restoration Monitoring
1 Purpose
This SOP describes standardized procedures for tagging trees during restoration field work at EA Program field sites. Tree tagging creates a permanent, individual record for each tree so that management decisions are consistent, repeatable, and transparent across field crews and over time. A future student or technician should be able to revisit a tagged tree and understand exactly why it was flagged and how its condition has changed.
Tree tagging is used to:
- Identify which trees will be retained, removed, or monitored
- Track individual tree condition over time
- Create a permanent record for future groups and project documentation
- Support consistent decision-making across crew members
Recording a consistent set of fields for each individual tree allows data to be combined, compared, and reused across projects and seasons (Handley et al., 2021).
2 Scope
- Applies to: All EA Program field sites with tree cover, including riparian forest, oak woodland, mixed conifer stands, and planted trees at restoration and campus sites
- Does not apply to: Shrubs with DBH below 2.5 cm (use SOP-F603 for shrub cover); diameter, height, and plot-based inventory measurement (use SOP-F604); timber cruising for commercial harvest; formal urban tree risk assessment, which requires a qualified arborist (International Society of Arboriculture, 2017)
- Location: All EA Program terrestrial field sites with woody vegetation
3 Definitions
- DBH (diameter at breast height): The diameter of a tree trunk measured at 1.37 m (4.5 ft) above ground on the uphill side of the tree. The standard dimension for comparing tree sizes. Measurement procedure is defined in SOP-F604 (Avery & Burkhart, 2002; USDA Forest Service, 2023).
- Tag: A numbered aluminum disk fastened to the tree. Each tag number is unique within the project.
- Flagging: Colored plastic tape tied loosely around a tree at eye level. Color communicates the management decision for that tree.
- Condition rating: A five-level score (Excellent, Good, Fair, Poor, Dead) describing tree health and structure.
- Crown: The upper part of a tree, including all branches and foliage.
- Crown spread: The average horizontal width of the crown, taken as the mean of the widest spread and a second spread measured at right angles to it (American Forests, 2014).
- Retain: Leave the tree in place. Do not remove or damage.
- Remove: Tree is scheduled for cutting or restoration thinning.
4 Responsibilities
| Role | Responsibility |
|---|---|
| PI / Field Lead | Approve flag color codes before the season starts; review completed field forms and photo logs weekly; ensure the project meets restoration goals |
| Trained Personnel | Tag trees per this SOP; complete all fields in the tree assessment record; take required photos; flag trees correctly the first time |
| New Students | Complete training before tagging independently |
Minimum crew size is two persons at all times (safety requirement; see SOP-F001 Field Safety).
5 Safety and Hazards
- Overhead: Dead branches and leaning or unstable trees (widow-makers) can fall without warning. Look up before approaching any tree. Do not work under or near hazard trees in high wind.
- Sharp tools: Hand saws, loppers, and pruners. Keep blades sheathed while walking, pass tools handle-first, and never carry open blades through brush.
- Terrain, biota, and weather: Uneven terrain, poison oak, ticks, snakes, stinging insects, and heat are common at EA field sites and are covered in SOP-F001 Field Safety.
5.1 Required PPE
5.2 Emergency Procedures
Refer to SOP-F001 Field Safety for stop-work conditions, biotic and weather hazards, emergency contacts, and incident response. Work in pairs at all times in forested areas.
6 Equipment and Materials
| Item | Notes |
|---|---|
| Numbered aluminum tags | Pre-numbered; one per tree |
| Aluminum or stainless nails | For attaching tags; see Section 8.2 on growth allowance |
| Flagging tape (color set) | Per the color codes in Section 7 |
| Diameter (DBH) tape | Reads diameter directly in cm (pi tape) |
| GPS unit or smartphone | Record coordinates per SOP-F006 |
| Camera or smartphone | Minimum three photos per tree |
| Field data sheets | Printed from Appendix A |
| Clipboard and pencils | Pencils work better than pens in wet conditions |
| Long measuring tape | For crown spread |
| Clinometer or laser rangefinder | For tree height (optional); see SOP-F604 |
| Lumber crayon or paint marker | For marking the DBH measurement point |
| Hand saw or loppers (optional) | For small branch clearance to access the trunk |
7 Flagging Color Codes
Confirm color codes with the crew and PI before working. Project-specific changes must be documented in the field log.
| Flag Color | Designation |
|---|---|
| ORANGE | Confirmed removal: invasive species (primary target) |
| YELLOW | Confirmed removal: dead, dying, or hazard tree |
| PINK | Confirmed removal: restoration thinning |
| GREEN | Retain: do not remove |
| WHITE | Under review: secondary evaluation required (do not remove yet) |
| RED | Monitoring tree: reassess next cycle |
| BLUE | Approved native for transplant or seed collection |
Rule: Tie flagging loosely at eye level. Do not wrap tightly; flagging can girdle the tree over time.
8 Procedure
8.1 Before Entering the Field (Daily Pre-Work)
Complete this checklist before leaving the vehicles each day:
8.2 Tree Tagging Step-by-Step
| Step | Action | Why it matters |
|---|---|---|
| 1. Approach and evaluate | Assess tree form, lean, root zone, crown condition, and nearby hazards from more than one side before tagging | A tree that looks sound from one side may have rot, lean, or deadwood visible from another angle (International Society of Arboriculture, 2017) |
| 2. Identify species | Confirm common and scientific name; cross-check against the project Invasive Priority List and Retain Species List. Use SOP-F602 iNaturalist for ID support where needed | Tagging the wrong species leads to the wrong management decision |
| 3. Measure DBH | Measure at 1.37 m on the uphill side per SOP-F604 | DBH drives removal priority, allometric calculations, and monitoring frequency |
| 4. Assign flag color | Select the color per Section 7 and tie loosely at eye level | Color communicates the decision to every future crew member |
| 5. Install tag | Fasten the numbered tag on the uphill side at DBH height with a single aluminum or stainless nail. Leave the nail head protruding about 2 to 3 cm so the tree can grow without engulfing the tag | A consistent, accessible tag is easy to relocate and read in later seasons; leaving the nail proud accommodates radial growth and bark ingrowth (USDA Forest Service, 2023) |
| 6. Photograph | Take at least three photos: (a) full tree form, (b) tag number close-up, (c) notable defects or hazards | Photos resolve disputes and provide evidence if a tag is lost |
| 7. Record data | Complete all fields in the tree assessment record (Appendix A) before moving to the next tree | If it is not written down, it did not happen |
If crown spread is recorded, measure the widest spread across the crown, then measure a second spread at right angles to the first, and average the two: (A + B) / 2 (American Forests, 2014). Tree height, if recorded, is measured with a clinometer or laser rangefinder per SOP-F604.
8.3 Tree Condition Ratings
Use a consistent five-level scale. Note structural defects (lean, cracks, cavities, deadwood, included bark) that influence the rating and any hazard flag (International Society of Arboriculture, 2017).
| Condition | Field indicators |
|---|---|
| EXCELLENT | No significant defects; vigorous, full crown; normal growth |
| GOOD | Minor defects; healthy overall; normal growth |
| FAIR | Moderate defects; reduced vigor; some dieback |
| POOR | Major defects; significant dieback; structural risk |
| DEAD | No live tissue; standing snag or fallen log |
9 Quality Control
Perform these checks every tagging day:
- Tag uniqueness: Confirm no tag number was used twice. Reconcile the day’s tags against the assigned number ranges.
- Species cross-check: Verify each species identification against the Invasive Priority and Retain Species lists. Flag uncertain IDs for review rather than guessing.
- Data completeness: Confirm every tagged tree has a fully completed assessment record (Appendix A) with no blank required fields.
- Photo completeness (end of day): Before leaving the site, scroll through the day’s photos and confirm that every tag number has the three required photos (full form, tag close-up, defects). Re-photograph any tree that is missing photos before leaving.
- Second-observer check: On a subset of trees (for example, 10%), have a second crew member independently confirm species, condition rating, and flag color. Resolve any disagreements with the field lead.
10 References
12 Training Record
Before tagging trees independently, each student or new technician must:
- Read this SOP in full
- Read SOP-F001 Field Safety and pass a field safety check (PPE, stop-work conditions, emergency contacts)
- Know the correct flag color codes
- Demonstrate correct DBH measurement technique (per SOP-F604)
- Correctly tag and flag three practice trees with the crew lead observing
- Complete a tree assessment record without errors
- Take an acceptable three-photo set (full tree, tag close-up, defects)
- Be signed off by the PI or field lead
| Trainee | Date read SOP | Date practice trees | Signed off by | Date |
|---|---|---|---|---|
13 Appendix A: Individual Tree Assessment Record
Print one copy per tree (or one per plot) before going to the field. Circle the appropriate option where choices are given.
Tag number: _____________ GPS coordinates: _______________________
Species (common): ___________________________
Species (scientific): _________________________
DBH: _______ (circle: in / cm) Est. height (ft): _______ (clinometer or rangefinder; see SOP-F604)
Crown spread (ft): _______ (average of two perpendicular axes: (A + B) / 2)
Condition rating: EXCELLENT / GOOD / FAIR / POOR / DEAD (circle one)
Flag color: ORANGE / YELLOW / PINK / GREEN / WHITE / RED / BLUE (circle one)
Proximity hazards (e.g., lean toward trail, overhanging deadwood, near utility): _______________________________
Adjacent utilities? YES / NO (if yes, note type and distance): _______________________________
Removal rationale (e.g., invasive species, hazard, restoration thinning, dead): _____________________________
Photo file references (e.g., TAG042_full, TAG042_tag, TAG042_defect): _______________________________
Assessor initials: ________ Date and time: ___________
Additional notes / sketch (trunk abnormalities, lean direction, nearby landmarks):
_________________________________________
_________________________________________
14 Appendix B: Daily Photo Log
Minimum three photos per tree. Store photos with the tag number in the filename (for example, TAG042_full_form.jpg).
| Photo # | Tag # | Subject | Direction facing | Notes |
|---|---|---|---|---|
| 1 | Full tree form | |||
| 2 | Tag number close-up | |||
| 3 | Defects / hazards | |||
| 4 | ||||
| 5 |
15 Appendix C: Field Note
This SOP is a field guide. It does not replace project permits or crew lead direction. Review this SOP with your crew lead at the start of each project season.