Northern Prairie Wildlife Research Center
Assuming that these chemicals are effective fire-fighting tools, consequences of chemical application are most appropriately compared with the effect of additional area burned in a more slowly controlled wildfire when chemicals are not used. Since the introduction of invasive exotic plants such as Bromus tectorum and Taeniatherum caput-medusae, fires in the Great Basin can have devastating and long-lasting ecological results as the native Agropyron-Artemisia association is replaced by a virtual monoculture of quick-burning annual grasses (West 1988; Billings 1993). Not only do these grasses drastically reduce species diversity (Knapp 1996), they can increase fire frequencies from the pre-invasion intervals of 60-110 years to post-invasion intervals of less than 5 years (Whisenant 1990). Effects we observed in the current study were minor by comparison. If B. tectorum or T. caput-medusae are present in the vicinity of a wildfire, far less ecological damage is likely to be done by application of retardants or foams than by allowing the fire to burn unchecked.
Managers intending to use these chemicals to control prescribed burns may wish to consider effects on species richness or on individual species of interest. Most significant treatment effects on species richness occurred in the riparian zone; care should be exercised in riparian areas (see also Gaikowski et al. 1996, McDonald et al. 1996), especially if they harbor particular species of concern.
Finally, this study did not adequately address the interaction between burning and chemical application. Studies of longer duration, in which plots can be followed for several seasons after treatment, are essential in assessing these interactions.