Can novel combinations of prescribed extreme fire and herbicide be used to overcome resprouting woody plant resilience and restore degraded rangelands in the southern Great Plains?

Background/Question/Methods

Ecosystems with diminished environmental services require innovative resource management strategies. Conventional restoration and conservation practices have been historically ineffective and/or economically cost prohibitive at repairing degraded rangelands in the southern Great Plains. Landowners throughout this region are confronted with multiple difficult decisions regarding the need to pursue economically profitable objectives pertaining to wildlife and livestock while concurrently avoiding ecosystem alterations that negatively affect the ecological integrity of their land. Despite extensive management efforts, woody plants and cacti continue to invade and degrade these rangeland ecosystems. We established two identical experiments in different shrub-dominated ecoregions of Texas to assess whether novel interventionist approaches were capable of overcoming the resilience of the dominant woody plant community.  Using different combinations of prescribed extreme fire (high intensity fires conducted during severe droughts) and herbicide applications, our objective was to alter the ecological trajectory of the system beyond the effects observed with conventional management techniques.

Results/Conclusions

At both study sites, prescribed extreme fire significantly reduced resprouting shrub densities compared to plots that were not burned.  These findings differ from other studies that report fire changing the structure of shrubs but not their densities.  A potential reason for these differences is that fire treatments in this study were conducted during severe drought conditions (Palmer Drought Severity Index was < -3) and we produced maximum fireline intensities (up to 68,000 kJ/m/s) that were well above values recorded for other fire experiments in these ecoregions.  The second intervention approach using extreme fire and herbicide treatment combinations was not supported.  Interactions between prescribed extreme fire and herbicide did not significantly reduce shrub densities more than using herbicide alone at either site.  Our findings demonstrate that novel intervention approaches, like extreme prescribed fire, can trigger unexpected, high levels of mortality in resprouting shrubs and begin to restore degraded rangeland ecosystems, but we acknowledge that widespread application of this management strategy hinges on our ability to shift social perceptions influencing the application of fire on the landscape.