Fire impact on water and carbon fluxes in a wild olive-based ecosystem

Fire, harvesting and beetles attacks are important disturbances for the forested ecosystems. The aim of this study is to examine the impact of the disturbances on water and carbon fluxes using a eddy‐covariance (EC) – based tower in a wild-olive forest.

The study has been performed at the Orroli site, Sardinia (Italy), which is an experimental site for the FLUXMED project of the Water Joint Programming Initiative. From 2003, a 10 m micrometeorological tower equipped with eddy-covariance system has been used to measuring water, carbon and energy surface fluxes, as well as key state variables (e.g. leaf and soil skin temperature, radiations, air humidity and wind velocity).

The landscape is covered by patchy vegetation: wild olives trees in clumps and herbaceous species, drying to bare soil in late spring. The climate is Mediterranean maritime with long droughts from May to October, and rainy period is concentrated in the autumn and winter months. In this ecosystem water uptake by olive’s roots, from underlying substrate to the shallow soil layer, allow woody vegetation and grass to remain physiologically active during dry conditions.

In summer 2017, which was a very dry season, an extended fire affected the forested area, impacting the north – west footprint of the tower, with consequences also to the close trees due to beetle attack, probably related to the sensitive conditions of the trees after the drought.

We compared pre-disturbance with post-disturbance land surface fluxes. Both fire and beetle attack, altered the partitioning of available energy to lE and H, evapotranspiration (ET) and carbon assimilation. Results show a reduction of evapotranspiration and carbon assimilation during the growing season. Differently, in autumn and winter the difference between pre-disturbance and post-disturbance was negligible due to low physiological activities of vegetation.