Spatiotemporal variation of aluminium and micro- and macronutrients in the soil solution of a coniferous forest after low-intensity prescribed surface fires

Abstract

Even though the functioning of nutrient-poor forest ecosystems strongly depends on the cycling of various elements, rather little is known about the effects of fires on the fluxes of Al, Ca, Fe, K, Mg, Mn, Na, P and S. Solution fluxes at three different soil depths (organic (O) layer, upper mineral soil (A) and lower mineral soil (B) horizon) were measured every 2 weeks with free-draining lysimeters before and after low-intensity prescribed surface fires in a Scots pine forest in Germany. Measurements of element content in pre-fire litterfall and soil were also conducted. Linear mixed-effect modelling revealed that low-intensity fires caused a short-term (<3 months) increase of element fluxes from the O layer and a medium-term (3–8 months) increase from the A horizon. This solute flush was followed by retention processes in the B horizon, except for S, Ca and Mg, which were removed from the soil system, probably because anion exchange sites favoured dissolved organic carbon over SO42−, and because Ca2+ and Mg2+ partially maintained the charge balance. Our findings indicated that fires affected nutrient-poor soil systems by causing a short-and medium-term element translocation from the O layer into the B horizon, which functioned as a retaining soil horizon by reducing the losses of important elements.