Land-use history and fire effects on soil fertility in eastern Spain

Changes in land use and fire directly affect the physico-chemical properties of the soil. In an eastern Spanish area, we analysed the effects of land-use history and fire frequency prior to fire on soil fertility 9 years after fire. The results showed that long-term cultivation caused decreases in soil organic matter, total nitrogen (N) and C/N. Between 20 and 40 years after cropping ceased, soil organic carbon (C) and total N had generally not recovered values similar to those found in soils that were never cropped. Total phosphorus and available phosphorus contents were larger in the latest abandoned plots than in the earliest abandoned plots and the uncropped ones, which was interpreted as a result of fertilization. Increasing fire frequency from one to two fires generally caused a decrease in soil organic C, total N, C/N, total phosphorus and available phosphorus. We observed that the losses of organic C in the soil caused by fire were larger among the uncropped plots and hypothesized that fuel loads and thus fire intensities were larger in these ecosystems. Our results also suggested that both long-term cultivation and fire would tend to separate C and P cycles.