Controlling Mature Ash Juniper in Texas with Crown Fires

Abstract

Dozed plots and windrow plots were evaluated during 1979 and 1980 with respect to their effectiveness in igniting a crown fire in an adjacent live juniper stand. Dozed plots were ineffective in igniting a crown fire. However, if herbaceous fuel is less than 500 kg/ha, windspeed is less than 10 km/hr, humidity is above 45% and air temperature is less than 30 degrees C, recently chained or dozed juniper (<100 days since treatment) can be burned with minimal risks. Windrowed plots produced the best results for igniting the adjacent crowns. Correlation coefficients and coefficients of determination indicated that air temperature, maximum windspeed, and leaf moisture would best predict the area the fire would burn per 6 m of windrow length. Crown fires usually stopped where distance between trees exceeded 7 to 10 m. For optimum results, average windspeed should exceed 16 km/hr, canopy cover should exceed 35%, relative humidity should be between 20 and 40%, air temperature should be between 2 and 32 degrees C, and leaf moisture should be below 60%. Although potential for broad application is limited, this technique could reduce the total cost of juniper control or could be used in wildlife habitat management.