Early spring prescribed burning in mixed Pinus halepensisMill. and Pinus pinaster Ait. stands reduced biological soilfunctionality in the short term

Abstract

This study evaluates the effects of prescribed burnings on soil physico-chemical andbiological properties in the short term. This practice is still in the process of evalua-tion and its effect on Mediterranean pine forests is not understood completely. Pre-scribed burning was carried out in three plots of mixed Pinus halepensis and Pinuspinaster stands in Castilla-La Mancha (Spain) while monitoring soil temperature. Veg-etation coverage was measured and soil samples were taken before, immediatelyafter and 1 year after burning. Texture, pH, soil electrical conductivity, cationexchange capacity, soil organic carbon, total nitrogen, available phosphorus, magne-sium, calcium, potassium, basal soil respiration, microbial biomass carbon content andenzymatic activities of urease, dehydrogenase, phosphatase, and β-glucosidase wereevaluated by generalized linear models, and a principal component analysis was usedto reveal the relations between variables. The vegetation cover was reduced by 85%after fire. Soil organic carbon increased immediately after burning to return to theprevious values one year later. Phosphorous and cationic exchange capacityincreased immediately after burning and remained high one year later, while electricalconductivity and sodium were significantly lower after a year. Basal soil respirationand glucosidase were not affected by prescribed burning. Microbial biomass carbon,urease, phosphatase, and dehydrogenase had significantly lowered one year afterburning. Our results show that prescribed burning managed to decrease the vegeta-tion cover of the understory while it also reduced soil biological functions in areaswith poorly developed soil and a dry climate, where recovery periods can be longerthan expected.