Temperature effects on the ash properties of pine and maple leaf litter

Abstract

The dominant litter samples Pinus sylvestris L. needle litter and Acer platanoides L. leaf litter were collected in the coniferous mixed forest located at 54 degrees 43 ' N 25 degrees 19 ' E (Vilnius, Lithuania) in April 2010. Different heating temperatures (150, 250, 350, 450 and 550 degrees C) and 2 hour heating duration were used to produce ashes. The selected heating temperatures affected mass loss, colour, pH, electrical conductivity (EC), C/N ratio, nutrient concentrations of the ash. The darkness of Munsell chroma values was visible at 250 degrees C and 350 degrees C in both types of litter and additionally at 450 degrees C in the needle litter ash. In contrast, the chroma values increased in brightness mainly between 450 and 550 degrees C. The general tendency of pH (p=0.01) increase was ranging at the 150-550 degrees C interval and the results did not include acid and extremely alkaline features but over the temperature of 350 degrees C were alkaline. Values of EC (p=0.01) showed similar differences in the same litters. EC reached the maximum value at 450 degrees C in Acer platanoides L. leaf litter. Likewise, heating temperatures affected litter ash nutrient composition. K, S, and P concentrations particularly depended on heating temperature and litter type. Nutrient concentrations were in the order Ca>K>Na>S>Mg>P>Zn>Fe for needle litter and Ca>K>S>Mg>P>Na>Fe>Zn for leaf litter samples. Significant differences in C/N ratio between the litters were observed as temperatures increased.