Influence of simulated burning of soil-litter from low sagebrush, squirreltail, cheatgrass, and medusahead on water-soluble anions and cations

We evaluated the influence of temperature and heating time on water-soluble anions and cations of soil-litters of low sagebrush (Artemisia arbuscula ssp. longicaulis), squirreltail (Elymus elymoides), cheatgrass (Bromus tectorum), and medusahead (Taeniatherum caputmeduase ssp. asperum). Soil-litters were collected from volcanic tablelands north of Honey Lake, California. These high clay, montmorillonitic, soils have rarely experienced wildfires. Soil-litter samples, in a 50 mt crucible, were placed in a preheated muffle furnace using a time-temperature matrix of 150, 250, 350, and 450 degrees C at 1, 5,and 15 min. High performance ion-exchange chromatography was used to quantify water-soluble cations and anions. For most measured solutes, there was either a significant (P less than or equal to 0.05) burn time x temperature or a significant burn time x temperature x soil-litter type interaction. As compared to pre-burn values, heating of soil generally increased the concentration of the water-soluble solutes measured; nitrate was the exception. Maximum solute values were generally obtained at a temperature of 350 degrees C at 5 and 15 min heating time. A temperature of 450 degrees C at 15 min heating time resulted in the significant reduction of solute concentration below the maximum values. Nitrate was significantly higher in squirreltail soil-litter than the other soil-litters when the burn time was 1 min. Heating, in general, fostered an increase in water-soluble ammonium. For most solutes, heat-induced increases were greatest for the low sagebrush soil-litter.