Can prescribed fire be used to manage a C(4) invasive grass in a C(4) grassland?

Background/Question/Methods

Targeted invasive species control is difficult when the invasive and native species belong to the same plant functional type due to their overlap in resource use and seasonal growth periods.  In addition, management attempting to target an invasive species that has a higher rate of increase than native components can inadvertently favor the further spread of the invasive species.  However, if the difference in the rate of increase between invasive and native species is offset by an even greater and opposite difference in susceptibility, a carefully planned disturbance regime could help restore native communities. We evaluated the effects of prescribed burning at different times of the year on the post-fire tiller recruitment of the non-native C₄ grass KR bluestem (Bothriochloa ischaemum) and the native C₄ grass little bluestem (Schizachyrium scoparium). To control fire, we burned individual grass patches inside a steel barrel of 46cm diameter.  Post-fire recruitment was estimated by counting live tillers after the burn. We recorded water potential, phenological stage and the fire temperatures of species at burn time to determine their potential effects on post-fire tiller recruitment.  A total of six burns will be completed by March 2012.  

Results/Conclusions

Results for the first three burns of this study conducted in 2011 indicate that apparent post-fire tiller recruitment was consistently greater for little bluestem than for KR bluestem.  The greatest difference in post-fire tiller recruitment (8 vs. 80%) was observed in June.  We discuss the possibility that the policy of summer burn bans limits our capacity to control non-native invasive grasses not adapted to the historical summer fire regime of central Texas.