FIRE AND INVASIVE PLANTS in the Northeastern United States Research Sponsored by the Joint Fire Science Program, Boise, ID http://jfsp.nifc.gov/

Three studies are in their third year --

1. The Effect of Growing Season Treatments on Invasive Woody Plant Species

2. Survey of Fuel Loads in Invaded and Uninvaded Forest Stands

3. Combustibility of Invasive and Native Fuels

Coastal island in Massachusetts. April 5, 2002 prescribed burn of Scotch broom plot.

J. A. Richburg & W. A. Patterson III, University of Massachusetts, Amherst

During 2001, we began a study to evaluate two key topics regarding fire and invasive species in the Northeast: how cutting and prescribed fire treatments, timed to the phenology of carbohydrate depletion and recovery, affect the survival of several woody invasive species; and how treatments alter fuel beds and affect fire behavior in invaded and uninvaded landscapes. We have applied dormant and growing season cut and burn treatments to seven different woody invasive species: multiflora rose - Rosa multiflora, common buckthorn - Rhamnus cathartica, gray dogwood - Cornus racemosa, Asian honeysuckles - Lonicera spp., Japanese barberry - Berberis thunbergii, Scotch broom - Cytisus scoparius, and catbrier - Smilax rotundifolia . Of these, catbrier and gray dogwood are native to the Northeast, but are undesirable in certain habitats. To determine which treatments have been most effective, we are comparing root carbohydrate levels through time and across treatments.

We have completed two years of treatments and have preliminary total non-structural carbohydrate (TNC) data for some species. Results indicate that all of our treatments impact root TNC levels, but growing season treatments have the greatest multiple-year impact. Droege (1996) found that TNC in huckleberry roots reacted similarly to cutting and burning treatments, but that a single growing-season treatment did not have a lasting impact on rhizome TNC levels. We followed up on her results by treating our growing season plots twice in our first growing season, followed with at least one treatment in the second year. These multiple treatments appear to prevent recovery of TNC to pre-treatment levels for at least two years. We will continue to follow recovery of TNC for a third year without additional treatments. The implications for management are that the timing of treatments may be even more important than the type of activity (cutting versus burning) when evaluating the success of the treatments in controlling invasive species. To have the greatest success at reducing woody stems, a treatment should be conducted during periods of low below-ground carbohydrate storage (such as immediately after spring flushing and growth) and should be followed with a second growing season treatment before TNC levels are replenished. We hope to demonstrate the longer-term effectiveness of this protocol by our continued sampling in 2003. We will be returning to all sites during 2003 to collect vegetative cover and fuel load estimates following the two years of treatments.

April 5, 2002 prescribed burn of a catbrier plot