Ignition and fire behaviour of Juniperus virginiana in response to live fuel moisture and fire temperature in the southern Great Plains

Abstract

Fire is the most effective tool for managing Juniperus virginiana encroachment and associated fire risk, but its application has been limited. In a laboratory experiment we assessed a critical knowledge gap: how fire temperature and live fuel moisture (LFM) influences ignitability, sustainability, combustibility and consumability of J. virginiana. Percentage occurrence of ignition rose as fire temperature increased. The time to ignition increased while the occurrence of ignition decreased with increasing LFM. LFM and fire temperature each had a significant effect on all measured dependent variables (P≤0.05) as was their interaction, except in the case of sustainability. As expected, time to flaming was shortest and flame lengths were the highest under the hottest fire and lowest LFM scenarios. Flame heights increased quadratically as LFM decreased with a critical threshold at 60% LFM. Land managers can select burning prescriptions based on the interaction between fire temperature and LFM to either increase J. virginiana ignition or reduce hazards. In this study, the low and moderate fire temperatures were similar to those of prescribed fires at low and high fuel loads and the high temperature level mimics conditions found in extreme wildfires. Thus, higher fuel loads and hotter fires are required to maximise efficacy of fires targeting J. virginiana control.