Woody plant encroachment mitigated differentially by fire and herbicide

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This study aimed to quantify a direct treatment to reduce or slow down woodland expansion in an experimental rangeland in central Oklahoma, United States under three treatments: 1) herbicide, 2) fire with herbicide, and 3) control (no fire, no herbicide) within areas classified as “open grassland” in 1979. Encroachment was greatest in the control treatments, followed by herbicide-only treatment application and lowest in the fire and herbicide treatment with minor differences in mean plant height (4.11 m ± 0.28). Encroached areas were mostly dominated by tall individuals (45 ± 3.5%), followed by the intermediate-height class (31.53 ± 1.10%) and the least recorded in the smallest-height class (23.46 ± 2.29%), suggesting expansion occurred during the initial phases of treatment application. The costly practice of herbicide application did not provide a feasible solution to control further woodland expansion. However, when using herbicide with fire, woodland expansion was reduced, highlighting the effectiveness of early intervention by fire in reducing encroachment. This further supports landscape-scale studies highlighting the effect of fire to reduce woodland expansion.