Influence of fire on the soil phosphorus status in sand plain lowland fynbos, south-western Cape

Changes in total and resin-extractable (available) phosphorus of the Clovelly soil as a result of an accidental fire in coastal fynbos at Pella were studied for 12 months. The fire caused an increase in pH from 4,6 – 5,3 and organic matter from 1,6 – 2% at the soil surface but these returned to pre-fire values within seven months. Total phosphorus levels did not change significantly immediately after the fire but a reduction occurred during the winter months (June – August). Resin-extractable phosphorus increased significantly but pre-fire levels were re-attained within four months after the fire. Soil temperatures of 200 – 400°C appear to stimulate physical mineralization of bound phosphorus and this resulted in a release of resin-extractable phosphorus in the soil. Veranderinge in totale en harsekstraheerbare (beskikbare) fosfor in die Clovelly-grondvorm as gevolg van ’n onverwagte brand van kusfynbos by Pella is vir 12 maande bestudeer. Die brand het ’n toename in pH van 4,6 – 5,3 en in organiese materiaal van 1,6 – 2% in die grondoppervlak veroorsaak, maar die waardes het binne sewe maande teruggekeer na dié voor die brand. Totale fosfor-konsentrasies het nie onmiddellik na die brand betekenisvol verander nie, maar het gedurende die wintermaande (Junie – Augustus) afgeneem. Harsekstraheerbare fosfor het betekenisvol toegeneem, maar die waardes voor die brand is weer binne vier maande na die brand bereik. Dit blyk dat grondtemperature van 200 – 400°C fisiese mineralisasie van gebonde fosfor stimuleer en dit het tot die vrystelling van harsekstraheerbare fosfor in die grond gelei.