Soil Chemical Responses to Fire Seasonality and Frequency in a Texas Grassland

Abstract

On a clay-loam mixed grassland dominated by honey mesquite (Prosopis glandulosa Torr.) in northern Texas, we quantified soil pH, soil organic carbon (OC), electrical conductivity (EC), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), zinc (Zn), iron (Fe), manganese (Mn) and copper (Cu) in response to various effects of summer and winter fire treatments from 1991–1996. We conducted summer fire between August and September, and winter fire between January and March. Treatments that included summer fires increased soil pH, EC, Na, and Cu and temporarily decreased soil OC and Mn (P ≤ 0.05). The winter fire treatment had a long-term effect of increasing Fe and decreasing Mn. Changes in soil pH were positively correlated with EC, Ca, P and Na, and negatively correlated with K, Fe, Mn, and Zn (P ≤ 0.05). With the exception of the increases in EC and Na, and temporary loss of OC and Mn, fire treatment regimes that included summer fires did not appear to deplete soil nutrients and may be an acceptable strategy for managing mesquite-dominated grasslands