Question: Do low or high intensity fires affect micro-organism activity in the upper soil layer of Mediterranean maquis?

Location: 600 m from the sea in the Nature Reserve of Castel Volturno (Campania, southern Italy, 40°57′ N; 13°55′ E).

Methods: Soil respiration was measured in situ on intact soil; enzyme activity (cellulase, xylanase, invertase, trehalase and protease) and ATP content were measured on soil samples collected under three species of maquis vegetation: Phillyrea angustifolia L., Myrtus communis L. and Cistus incanus L.

Results: Soil microbial respiration showed no significant differences in CO2 flux in treated and untreated plots, but the ATP content in the soil under C. incanus and M. communis was lower in the treated plots for most of the study period. In the soil under Ph. angustifolia, ATP content was low only for one week after fire. The reduction was more marked in the samples from ‘high fire intensity’ than from ‘low fire intensity’ plots. Soil respiration and ATP content exhibited seasonal variations linked to soil water content. Among the enzyme activity measured in the soil under the three plant covers, only invertase declined in burned plots throughout the study period, particularly in the ‘high fire intensity’ plots. Activity of the enzymes cellulase, xylanase, trehalase and protease had a different sensitivity depending on the respective shrub cover.

Conclusions: Impact of fire on soil microbial activity is largely dependent on vegetation mosaic and species identity.

Abbreviations: EA = Enzyme activity; HIF = High intensity fire; LIF = Low intensity fire; UNB = Unburned area.