Soil-atmosphere greenhouse gases (CO2, CH4 and N2O) exchange in evergreen oak woodland in southern Portugal
Shvaleva, A.,New University of Lisbon, Oeiras (Portugal). Inst. of Technological Chemistry and Biology | Lobo-do-Vale, R.,Technical Univ. of Lisbon (Portugal). Inst. of Agronomy | Cruz, C.,University of Lisbon (Portugal). Faculty of Sciences | Castaldi, S.,Second Univ., Caserta (Italy) | Rosa, A.P.,University of Lisbon (Portugal). Faculty of Sciences | Chaves, M.M.,New University of Lisbon, Oeiras (Portugal). Inst. of Technological Chemistry and Biology | Pereira, J.S.,Technical Univ. of Lisbon (Portugal). Inst. of Agronomy
A 10-20% decrease in annual precipitation is predicted in the Mediterranean basin, in particular to the Iberian Peninsula, with foreseen effects on the exchange of soil-atmosphere greenhouse gases (GHGs; CO2, CH4, and N2O). To simulate this scenario, we setup an experimental design in the particularly dry period of 2008-2009 using rainfall exclusion and irrigation, to obtain plots receiving 110% (538 mm), 100% (493 mm) and 74% (365 mm) of the natural precipitation. Soil CO2 fluxes showed a strong increase from summer to autumn as a consequence of increasing soil heterotrophic respiration that resulted from rewetting. Fluxes of N2O were negligible. According to our data, soil was a permanent CH4 sink independently of the soil water content (6-26% of water-filled pore space) and of soil temperature (7-28 deg C), supporting the concept that seasonally dry ecosystems (Mediterranean) may represent a significant sink of atmospheric CH4. The study provides evidence that the 26% decrease or 10% increase in the ambient rainfall from annual precipitation of ca 500 mm did not significantly affect soil functionality and had a limited impact on soil-atmosphere net GHGs exchange in evergreen oak woodlands in southern Portugal.
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