Invasive species infestations have a high economic and ecological cost, and are difficult to manage once established. Fire can be an effective tool to manage invasives during a vulnerable periods during their life-cycle (e.g. during seed set), especially in fire-adapted ecosystems such as tallgrass prairie. The purpose of this study is to determine how fire season and secondary management treatments affect fuel loads and fuel moisture, and how these changes then affect fire intensity and management of sericea lespedeza (Lespedeza cuneata). Land managers in eastern Kansas typically burn in early spring every 1-3 years, but spring prescribed fire increases sericea lespedeza cover. Sericea lespedeza seeds do not mature until October when many tallgrass plant species are entering dormancy. We conducted a large scale plot study to evaluate the effect of fire season both independently, and in conjunction with other common management strategies such as mowing and herbicide applications. Prescribed fire treatments were applied annually in either spring or fall beginning in October 2014 through April 2017. We measured fuel load, fuel moisture, litter depth, and grass/sericea height in an ecosystem infested by sericea to determine their influence on fire intensity and sericea seed viability.
Results/Conclusions
In fall, sericea lespedeza seed viability dropped from 80% pre-fire to 15% post-fire, showing that fall prescribed fire significantly reduces viability in sericea lespedeza. Maximum temperatures observed ranged from the 0-50 cm, which is within the height range to affect sericea lespedeza. Preliminary results showed spring burns had a positive relationship showing that fire temperature is dependent on fuel load. This indicates increasing fuel load will have a direct result in increasing fire temperatures. Preliminary results also showed fall burns showed a negative relationship showing that fire temperature is not dependent on fuel load. This indicates, in fall burns, increasing fuel loads will not increase fire temperatures. This relationship shows that secondary treatments, like mowing and herbicide applications, may have a more important role in intensity of fires than previously thought. Secondary treatments in conjunction with fall burns can have a reduction in sericea seed viability. Consequently, spring burns have been shown to increase sericea lespedeza populations.