Wildfire Prevention - Invasives as the Enemy

Steven O. Link, PhD (Botany) 

Native Plant Landscaping and Restoration LLC

4604 E. Robin Ct.

West Richland, WA 99353

509-948-0054

stevenlink@me.com 

 

Westside and Eastside - Invasives contribute to fuel loads. Learn ways to mitigate the impacts and have healthier

range and forest lands!

I will discuss two invasive species and a disease.

• Bromus tectorum – Cheatgrass

• Cytisus scoparius – Scotch Broom

• Phytophthora ramorum - Sudden oak death

Bromus tectorum – Cheatgrass

Acknowledgement

This work was funded by the Joint Fire Science Program. The work was done in cooperation with the Mid-Columbia River National Wildlife Refuge Complex. Special thanks are given to Randy Hill for help defining the questions and for continued technical support.

Bromus tectorum cover mapping and fire risk 

Effect of herbicide and herbicide concentration on Elymus wawawaiensis establishment in the shrub-steppe 

Management of fuel loading in the shrub-steppe: Responses six, seven, and eight years after treatments 

Fire risk in replanted bunchgrass communities

Bromus tectorum cover mapping and fire risk

Bromus tectorum infestation at the Saddle Mountain element of the Hanford Reach National Monument

High Bromus tectorum fuel load

Low Bromus tectorum fuel load

Lack of continuous fuel limits fire

Experimental DesignThe fire risk experiment was in plant communities that spanned the range of B. tectorum cover. Bromus tectorum cover was grouped into five classes. Each replicate is comprised of 8 to 18 plots in the three lowest B. tectorum cover classes and 2 to 6 plots at the two highest cover classes. A replicate is a collection of plots where the risk of fire was determined as the proportion of plots that burned. Each class has four replicates. We used 176 square plots, 10 m on a side.

Two hundred twenty six plots, 10 m on a side, were used to related B. tectorum cover to color band intensity.

Conclusions

• Bromus tectorum cover can be mapped using aerial color band reflectance photos taken in late summer.

• Based on the B. tectorum cover map and the relationship between B. tectorum cover and fire risk, fire risk can now

be mapped.

Maps showing risk areas in Washington

There are none.

Effect of herbicide and herbicide concentration on

Elymus wawawaiensis establishment in the

shrubsteppe

Field site at the Columbia National Wildlife Refuge

Prescribed Burn

Herbicide Application

Bunchgrass Drill SeedingElymus wawawaiensis (Snake River wheatgrass, Secar cultivar) was drill seeded at a rate of about 7 lb. acre-1 on Feb. 19, 2003. Drill rows were 0.3 m apart.

Roundup - 2 oz/acre

Plateau - 2 oz/acre

Plateau - 4 oz/acre

Plateau - 8 oz/acre

Management of fuel loading in the shrub-steppe: Responses six,

seven, and eight years after treatments

Our objective was to determine if our strategy to reduce Bromus tectorum cover and thus fire risk is sustainable after implementation. We tested three hypotheses reporting results for 2008, 2009, and 2010.

Hypothesis 1: Bunchgrasses established in 2003 will show an increasing degree of B. tectorum control over three years (2008, 2009, 2010).Hypothesis 2: Native species richness and cover in Plateau plots will not be different from controls 6, 7, and 8 years after treatment. Hypothesis 3: Alien species cover in Plateau plots will not be different from controls 6, 7, and 8 years after treatment.

We monitored populations, flowering, and size of established bunchgrasses. We documented new E. wawawaiensis arising from self-seeding.

Figure 1. Eighteen years after drill seeding, E. wawawaiensis, results in near elimination of B. tectorum.

Figure 4. Alien species cover from 2004 through 2010. The slope of the linear regression over time was significantly (p = 0.0005) greater than zero.

Figure 10. The relationship between E. wawawaiensis canopy volume and the interference distance with B. tectorum.

Figure 7. Elymus wawawaiensis 8 years after seeding showing senescence (gray tillers) with remaining green tillers mostly near the edge.

Figure 8. Mean and predicted % senescent plants (± 1 sem) in the imazapic seeded plots. 

Figure 9. Gray colored senescing E. wawawaiensis seeded in 1986 near the study area in 2009.

Figure 11. Relation between planted bunchgrass density and B. tectorum cover.

Fire risk in replanted bunchgrass communities

Management Implications and Conclusion 

We conclude that B. tectorum cover can be significantly and sustainably reduced by burning and applying Plateau herbicide at 4 or 8 oz acre-1 in the fall and then drill seeding E. wawawaiensis in the late winter.

Seven years after treatment application the density of drill seeded E. wawawaiensis was 1.23 ± 0.24 plants m-2. Doubling the seeding rate may increase density enough to further reduce B. tectorum cover to be closer to the minimal value of 2.8% achieved with E. wawawaiensis density of 2.77 plants m-2.

Research Questions

Examine viability of bunchgrass cultivars that arose from small initial populations leading to population bottlenecks that may reduce viability. Are locally sourced native plants more likely to sustain themselves.

Examine the fire risk of more restored plant communities. What combination of species leads to significant reductions of fuel cover and increases in bare soil and soil cryptogams. Can Poa secunda provide sufficient interference to reduce Bromus tectorum cover?

Cytisus scoparius – Scotch Broom

Zouhar, Kris. 2005. Cytisus scoparius, C. striatus. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/ [2013, June 16].

Fire Risk and Effects on Native Species

Scotch broom invasions are also said to increase fire intensity and frequency in invaded Oregon white oak communities. Scotch broom's frequent location on steep slopes adds to its fire hazard potential.

Where Scotch broom has invaded prairie and Oregon white oak woodlands on Fort Lewis, it forms dense stands and increases fire hazard by creating extensive areas with large amounts of dead wood.

Mature Oregon white oaks appear to have been killed by severe fire that was fueled by Scotch broom at Fort Lewis.

Dense stands of Scotch broom negatively affect native plant communities. At Fort Lewis study plots indicate that no native prairie species remained after 12 years of closed Scotch broom cover.

In Oregon and Washington, there have been complete stand failures of Douglas-fir regeneration because of Scotch broom infestations

Scotch broom control

Fall burning is recommended to remove Douglas-fir and Scotch broom from heavily infested areas, along with follow-up fires to kill dense Scotch broom postfire seedling establishment.

When prescribed fire is used to stimulate Scotch broom germination from the seed bank, follow-up treatments such as subsequent controlled burns, spot burning, revegetation with fast growing native species, herbicide treatments, grazing, and hand-pulling can be used to kill seedlings and thus reduce the seed bank.

Scotch broom is best controlled by an integrated vegetation management program including monitoring, prevention, biological control, uprooting, cutting, controlled burns, competitive planting, and spot treatments with herbicides as a last resort.

Sowing native plant species may be a preventive method of weed control. Later successional plants may be encouraged to take root among the unwanted vegetation. Broom stands provide a good environment for establishment of some native broadleaved shrubs and trees. These native seedlings should be encouraged. Seeds of taller growing plants should be sown among the broom, as they may eventually shade out the broom.

Phytophthora ramorum - Sudden oak death

http://extension.oregonstate.edu/catalog/pdf/em/em8877.pdf

http://puyallup.wsu.edu/ppo/sod/

Sudden Oak Death is the common name for a disease caused by Phytophthora ramorum, a previously unknown and recently introduced non-native pathogen.

Extensive areas of mortality have led to concerns about increased fire hazard.

First recognized in oaks, this pathogen can infect many woody species.

Symptoms include bleeding cankers on the tree's trunk and dieback of the foliage, in many cases eventually leading to the death of the tree.

Very few control mechanisms exist for the disease, and they rely upon early detection and proper disposal of infected plant material.

Phytophthora ramorum has been detected in western Washington nursery sites, but eradication efforts have prevented its spread. The recent detection of P. ramorum in a stream associated with an infested nursery illustrates the risk of spread to Washington's natural and urban landscapes.

A phosphonate fungicide (Agri-fos. Phosphonate) works by stimulating various of kinds of immune responses on the part of the tree.