1. REM 456 - Integrated Rangeland Management
Stave Bunting
Plant Response to Fire
REM Integrated Rangeland Management

2. Depends on fire history of ecosystem
Ecosystems with less frequent fire
Tundra
Deserts
Plant success depends on ability to compete or adapt to climate…. Not necessarily able to survive fire
Cold Desert
Jen Peterson
Hot Desert
K. Launchbaugh
Tundra
Photo by Daniel R. Rathrauff, USGS

3. Depends on fire history of ecosystem
Ecosystems evolves with frequent fire
Grasslands
Dry Forests
Plants adapted to avoid or tolerate fire.
Plants may even benefit fire:
Germination – seeds scarified by fire
Create Habitat – removing existing plants & releasing nutrients.
photogallery.nrcs.usda.gov
photogallery.nrcs.usda.gov

4. Fire characteristics Plant mortality
Severity = impacts of heat from fire
Fire that reaches 120 to 130F typically kills plant tissue.
Residency time = how long fire burns in area
Even low temperature fire can be damaging if it moves slowly across the landscape
Fire behavior and landscape patterns
Patchy fire can recover rapidly because seeds may be available in unburned areas
Widespread fires can foster erosion and reduce seeds available in area.
Season of fire and phenological stage of plants is important.
Buds and leaves are more sensitive to fire when they are metabolically active.

5. Plant Adaptation to Fire - Avoidance
Fuel characteristics affected by plant structure:
Fuel Load = amount of live and dead fuel (weight/unit area)
Fuel Size Class = Dead fuels divided into size classes based on diameter: (e.g., < 1/4-inch, 1/4 to 1-inch, 1 to 3 inches, and > 3 inches)
photogallery.nrcs.usda.gov

6. Plant Adaptation to Fire - Avoidance
Fuel Bed Depth = the depth of surface fuel layer i.e., the average height of surface fuels contained in the combustion zone of a spreading fire front
S. Bunting

7. Plant Adaptation to Fire - Avoidance
Packing Ratio = compactness of fuel bed

8. Plant Adaptation to Fire - Avoidance
Bulk Density = the actual fuel weight per unit.
WEIGHT per unit area ÷ fuel bed DEPTH

9. Plant Characteristics affect Fire Severity
Severity of fire affected by plant characteristics:
Morphological = Fire resistant bark
Chemical = chemicals that reduce probability of combustion
Waxy and stiff surfaces can reduce flammability
Volatile compounds can increase flammability
Jen Peterson
Sheri Hagwood. Bureau of Land Management
S. Bunting

10. Plant Characteristics affect Fire Severity
Growth form
Bunchgrasses vs Sodgrass Crested Wheatgrass vs Western Wheatgrass
Jen Peterson
K.Launchbaugh

11. Plant Characteristics affect Fire Severity
Growth form
Strong vs Dispersed Bunchgrass
Idaho Fescue vs Bluebunch Wheatgrass
Jen Peterson
Jen Peterson

12. Plant Adaptation to Fire - Tolerance
Growth after fire depend on:
Location of buds
Below ground buds – The upper 1 inch of soil typically only experiences a very brief increase in temperature during a fire on rangelands
photogallery.nrcs.usda.gov

13. Plant Adaptation to Fire - Tolerance
Basal sprouts (rabbitbrush or horsebrush)
Rhizomes and other adventitious sprouting (pinegrass)
Also affected by season – when are growing points elevated?

14. Plant Adaptation to Fire - Tolerance
Fire-adapted seeds
Hard seed coating that is scarified by fire
Serotinous cones i.e., logdepole pine
Seeds protected in canopy i.e., ponderosa pine

15. Plant Adaptation to Fire - Tolerance
Julie Hankins
Fire-adapted seeds (continued)
Seeds that are wind dispersed i.e., fire weed (Epilobium angustifolium)
Seed vulnerability is typically dependant on seed position and amount of moisture seeds contain

16. Plant Adaptation to Fire - Tolerance
Carbohydrate Allocation Patterns
Some plants can simply mobilize resources better than others.
Julie Hankins

17. Other Factors Affect Plant Response
Post-Fire Weather
Post-Fire Animal Use
Plant Competition

18. Summary Questions
What time of year is fire most damaging to grasses and why?
What time of year is fire most damaging shrubs and why?
Deferring livestock grazing for several seasons after fire is a practice employed by land managers intended to promote plant vigor and ecosystem recovery. The concept of extended rest periods to compensate for the cumulative effect of both grazing and fire seems intuitive. However, extended rest periods may not be ecologically important to plant recovery and altered grazing systems can impose unwarranted financial hardship on livestock producers. In addition delayed grazing after fire can create a subsequent fuel load of standing dead grass.
Removal of grazing after fire could also inadvertently promote weed establishment. Without grazing to suppress them, invasive or noxious weeds may take advantage of nutrient and water resources in the early spring when native species have not yet initiated growth.
The challenge to land managers is to determine when and how to begin grazing after fire to maintain productivity of native perennial herbaceous species. 18

19. How Fire differs from Grazing as a Plant Disturbance

20. Fire Grazing Not selective for specific plants
Selects palatable over unpalatable
Removes dead and live tissue
Live tissue preferentially removed
Produces heat
No heat produced
Recycles nutrients in inorganic form
Recycles nutrients in organic (feces)
and inorganic (urine) forms
Nutrients in a relatively even
layer across the landscape
Nutrient in patches
Patchiness on landscape scale
Patchiness on plant-scale
Most likely in dry-hot season
Occurs year round
Generally reduces seed viability,
though some seeds require fire
to be viable
Generally reduces seed viability
though some seeds require consumption

21. REM 456 - Integrated Rangeland Management
Stave Bunting
Plant Response to Fire
REM Integrated Rangeland Management