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Short-term changes in chemical properties of topsoil (0–10 cm) after low-intensity fires caused by landings of first stages of space rockets Proton-M in Central Kazakhstan

Surface fires affect the species composition and the dynamic development of continental semi-arid ecosystems. We analyzed short-term post-pyrogenic changes in soil properties including pH, concentrations of nitrates, nitrites, ammonium, exchangeable calcium and magnesium and hydrolytic acidity in three key areas affected by low-intensity fires in comparison with background (control) ecosystems in Central Kazakhstan. There, only above-ground vegetation burned, but regeneration shoot buds survived. In all key areas, low-intensity fires were caused by regular landings of fragments of jettisoned first stages of Proton-M rockets launched from the Baikonur Cosmodrome. Low intensities and short periods (1–2 days) of pyrogenic impacts on vegetation predetermined only small changes in soil properties. There were significant (p-value < 0.05) decreases in exchangeable calcium and magnesium concentrations and pH and an increase in hydrolytic acidity in some samples. But changes in concentrations of nitrogen compounds were generally insignificant.