1. Wildfire and Invasive Species
A vicious circle!

2. Lesson Outcomes Define Invasive Species
List common invasive species in the range ecosystem,
List reasons why invasive species are successful following wildfire
Describe the effects of wildfire interval due to invasive species

3. Compare the Plants in the Photos

4. What is an invasive species?
Invasive plants are those that exhibit “weedy” or aggressive growth characteristics
Invasive species will out-compete native species and often spread and dominate wildlands
Plant shown is yellow star thistle, currently invading Idaho rangelands.

5. Common Invasive Species in Rangelands
Downy Brome
Also known as cheatgrass
Short lived annual that will burn readily
Fire Adaptive - often first plant in following disturbance
Major invasive plant in the West; disturbance can include fire, roads, or anything that takes out the native plants. Catches fire easily, burns quickly and fast to reestablish in an area.

6. Leafy Spurge Highly invasive in a wide variety of ecosystems
Extensive root systems allow them to survive fire
Poisonous to some livestock and humans
Leafy spurge can reduce grass production by 75% in infested fields. The perennial plant spreads by seeds and roots. The deep and extensive root system makes the plant resistant to grazing, cultivation, and herbicides. Roots can be up to 25 feet long.
Burning has little effect on established plants with deep root systems. Fire may increase leafy spurge density by promoting sprouting of previously dormant buds along the extensive rhizome and root system.  
Leafy spurge also establishes through seed after fire, although fire may reduce germination.

7. Spotted Knapweed Most common of the knapweeds
Can displace natives even if the area is undisturbed
Large taproot allows survival following fire

8. Fire Intervals
Plant community will affect how often a fire will burn an area
Invasives tend to decrease fire intervals – that is the time between fires in an ecosystem
Fire intervals are affected by how ‘hot’ a plant burns. Many invasives burn very hot, damaging existing native plants. This leaves bare ground, and invasives are sometimes better adapted to reseed in bare ground.

9. a different fire interval.
Each color represents
a different fire interval.
The pink areas are less
than 5 years between
fire.
A normal interval prior to
Cheatgrass invasions were years.
A fire return interval map shows fire frequency in the JFO since 1958.  Lands within the green perimeter burned in the 2005 Clover Fire.  Those outlined in yellow were burned in the Sailor Cap Fire in 2006, and lands within the brown perimeters were part of the Murphy Complex Fires of 2007. 

10. Fire and Soil Characteristics
Short term nutrient spike because of burned organic matter.
Very hot fires may sterilize the soil or create hydrophobic conditions.
Fire changes the soil to create conditions that are ripe for invasive species. It has a short term increase in available nutrients, such as Nitrogen. If the fire is really hot it may sterilize the soil, or create hydrophobic (water repelling) conditions. This may eliminate all native plants, and make it very easy for aggressive invasive plants to establish in the area.

11. Why is it a vicious circle?
Invasives often have more burn potential
Invasives push out natives that have fire resistance because fire is too hot or too often
Fire comes, burns too hot; kills natives; adds N to soil to better prepare for more invasive seed germination!