Title: Soil and ecosystem carbon fluxes in a Mediterranean forest during and after drought
Citation: AGROCHIMICA vol. LVIII p. 91-115
Publication Year: 2014
JRC N°: JRC90822
ISSN: 0002-1857
URI: http://www.pisauniversitypress.it/scheda-libro/autori-vari/the-hot-summer-of-2012some-effects-on-agriculture-forestry-and-related-issue-9788867413904-230112.html
Type: Articles in periodicals and books
Abstract: Mediterranean climate is characterized by long, hot and dry summer periods, and by a highly variable inter-annual and seasonal rainfall distribution which is expected to increase in the next century. Understanding how Mediterranean ecosystems respond to the different climatic drivers (i.e. soil and air temperature, photosynthetic active radiation, soil moisture, rain amount) is of extreme importance to predict how carbon balance will be affected by future climate change scenarios. From this point of view, climatic anomalies such as heat waves, droughts and anomalous precipitation patterns provide a unique opportunity to gain insights from field studies in order to better model ecosystem response and feedbacks at larger temporal and spatial scales. In this paper we present and discuss eddy covariance and soil respiration measurements performed in a maritime pine (Pinus pinaster) forest in central Italy during an extremely prolonged drought and the subsequent rewetting phase. While during the drought carbon fluxes were limited by soil water content, we measured large emissions of carbon directly after rain events. The emission increase was particularly intense for soil respiration fluxes when water pulses occurred on dry soil. These wet-days warm-soil respiration peaks contributed to 50-70% of total ecosystem respiration and released an amount of carbon to the atmosphere that was double the amount emitted during the whole preceding dry season. Thus, this release accounted for a large fraction of the ecosystem annual carbon balance. The fast temporal response to suddenly available superficial soil water suggests that these emissions originated from heterotrophic respiration in the litter and in the first few centimeters of the soil profile. The combined analysis of eddy covariance and soil respiration data allowed us to partition total ecosystem respiration into soil and above-ground respiration and to show that carbon releases of autotrophic origin were not affected, on the short timescale, by the temporal distribution of rainfall occurring during the warm season. Since the capability of an ecosystem to be a net sink of CO2 depends on its ability to fix and retain more carbon than that is respired back to the atmosphere, carbon losses associated to an increased variability of rainfall events could dramatically impact the ecosystem carbon balance and determine the fate of this forest of being a net carbon sink or source.
JRC Directorate:Sustainable Resources

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