The main factors influencing the variability of nitrification and denitrification enzyme activity (DEA), in soil of a Mediterranean shrubland, were investigated in an undisturbed area and in plots treated with experimental fires of two different intensities. Soil was sampled 4 times during 1 year after burning, in periods characterised by different environmental conditions. In the control, net nitrification ranged from 0.95 to 1.32 μg NO3--N g-1 day-1 and did not show significant average differences among sampling events, probably because water content and NH4+-N availability were both limiting the process at any time. Overall, nitrification seemed associated with microsites where NH4+-N production was higher. This pattern was not evident in the burned plots, where, moreover, a partial reduction of activity immediately after burning was observed. DEA showed higher variability among sampling events, as compared with nitrification, with a peak in winter. It also presented a close spatial relationship with microsites of nitrification activity. In the burned sites, water content, organic C and NO3--N content concurred to explain DEA variability together with NH4+-N availability and nitrification activity. Plots treated with intense fire showed the lowest values of DEA, especially in the period more favourable to this activity.
Factors influencing nitrification and denitrification variability in a natural and fire-disturbed Mediterranean shrubland
CASTALDI, Simona;
2002
Abstract
The main factors influencing the variability of nitrification and denitrification enzyme activity (DEA), in soil of a Mediterranean shrubland, were investigated in an undisturbed area and in plots treated with experimental fires of two different intensities. Soil was sampled 4 times during 1 year after burning, in periods characterised by different environmental conditions. In the control, net nitrification ranged from 0.95 to 1.32 μg NO3--N g-1 day-1 and did not show significant average differences among sampling events, probably because water content and NH4+-N availability were both limiting the process at any time. Overall, nitrification seemed associated with microsites where NH4+-N production was higher. This pattern was not evident in the burned plots, where, moreover, a partial reduction of activity immediately after burning was observed. DEA showed higher variability among sampling events, as compared with nitrification, with a peak in winter. It also presented a close spatial relationship with microsites of nitrification activity. In the burned sites, water content, organic C and NO3--N content concurred to explain DEA variability together with NH4+-N availability and nitrification activity. Plots treated with intense fire showed the lowest values of DEA, especially in the period more favourable to this activity.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
