Tree mortality
Valor T. 1
1 Department of Agri-Food Engineering and Biotechnology, Universitat Politècnica de Catalunya-BarcelonaTech
Last updated: 28/09/2026
Recommended citation:
Valor, T. 2026. Tree mortality. In: Pere Casals, Davide Ascoli, Lena Vilà-Vilardell, Imma Oliveras, Madoka Krick (eds.) 2026. Methods handbook for characterizing fire use behavior, assessing fire effects, and monitoring soil and vegetation responses at the stand level. FIRE-ADAPT project (number 101086416), deliverable D1.1
Indicator
Fire Severity: Severity on Soil
Brief introduction
This method is designed to monitor tree mortality in conifer species following prescribed burning. Mortality is assessed through the absence of green needles, with evaluations made both one month (optional) and a minimum of three years post-burn. Additionally, tree severity attributes such as crown and cambium injury can be recorded, if desired.
This method assesses delayed tree mortality, a critical aspect often overlooked since long-term assessments of tree mortality are less commonly performed. This information is crucial for evaluating whether burning management objectives have been achieved and for guiding future prescribed burning treatments.
Method specifications
Method type
Soft
Hard
Method timing
Before
fire
During
fire
After fire
(short-term)
After fire
(mid-term)
After fire
(long-term)
Field skills
Low
Medium
Hard
Lab skills
Low
Medium
Hard
Material cost
Low
Medium
Hard
Time cost
Low
Medium
Hard
Calculation expertise
Low
Medium
Hard
Equipment
- Numbered metal tags for tree identification
- Binoculars for assessing tree mortality (if necessary)
- Sub-metric GPS for recording tree locations
- Diameter tape for measuring DBH
- Field notebook or electronic device for recording data
Experimental design
Establish a randomly located plot1 within prescribed burning units before the burn. In each plot, tag all trees greater than 2.5 cm in DBH, record whether they are alive or dead, and identify the species. After burning, assess tree mortality, defined as the absence of green needles, a minimum of 3 years after burning. If the objective is to analyze temporal trends in tree mortality, initial mortality can be assessed within a month after burning by the absence of green foliage in the crowns if buds are killed. Delayed mortality typically occurs in girdled trees, where death becomes evident 2 to 3 years post-burning, or in severely fire-damaged trees where additional factors, such as drought, insects, or wind events, contribute to gradual decline.
Methodology
- Before the burn, establish a 30 x 30 m plot1 at a random location within the burn units.
- Tag all trees with a DBH greater than 2.5 cm with numbered metal tags.
- Record the location of each tagged tree using a sub-metric GPS.
- Record the status of each tree (alive or dead) before and after burning. Dead is defined as the absence of green needles.
- Optional: record tree severity attributes, levels of crown and cambium injury, if desired, to analyze their relationship with tree mortality.
- Optional: a month after burning, initial tree mortality can be evaluated by checking for the absence of green needles in the crowns if buds were killed, using binoculars if necessary.
- Three years after burning, evaluate tree mortality by checking for the absence of green needles on each tree, using binoculars if necessary.
1 Plot size depends on the area burned and the density of trees with a diameter susceptible to death. 30 x 30 m or 30 x 50 m are commonly used.
Calculations
For each prescribed burning unit, calculate tree mortality per hectare as the number of dead trees in the plot multiplied by 10.000 m2 and divided by the plot area in m2
Data templates
NA
Further information
Hood, S. M., Varner, J. M., Van Mantgem, P., & Cansler, C. A. (2018). Fire and tree death: understanding and improving modeling of fire-induced tree mortality. Environmental Research Letters, 13(11), 113004.
Valor, T., González-Olabarria, J. R., Piqué, M., & Casals, P. (2017). The effects of burning season and severity on the mortality over time of Pinus nigra spp. salzmannii (Dunal) Franco and P. sylvestris L. Forest Ecology and Management, 406, 172-183.