Management options influence seasonal CO2 soil emissions in Mediterranean olive ecosystems.

Field trials were conducted at traditional Mediterranean olive agro-ecosystems grown at two locations (Italy –IT, Greece –GR). Groves were managed for many years using sustainable (S , cover crops, compost application, mulching of pruning biomass) or conventional (C) practices (e.g., soil tillage, burning of pruning residuals). The IT grove was rainfed (rain) while the GR was irrigated (IRR). This study examined the seasonal variation of soil CO 2 emission (R s) to explore the effect of the management options (C, S) on R s at both sites. The second aim was to test the hypothesis that the seasonal R s is differentially modulated by soil temperature and moisture, namely that (i) soil moisture limits R s when it is below the lower limit of the readily available water (RAW LLim) and (ii) soil temperature above a threshold (max_T) reduces R s even if soil moisture is non limiting. On the whole-season basis, the mean R s rate at the rainfed site was 2.17 ± 0.06 (SE) at C rain and 2.32 ± 0.06 μmol CO 2 m−2 s–1 at S rain plot, while at the irrigated site R s was about 3.64 ± 0.11 (C IRR) and 4.05 ± 0.15 μmol CO 2 m−2 s–1 (S IRR). The seasonal oscillation of R s was consistent across locations and partitionable in three periods according to DOY (Day of Year) interval: Phase I (DOY 20–103 –GR; 20–118 -IT), Phase II (DOY 141÷257, GR; 142–257, IT) and Phase III (DOY 291–357, GR; 286–350, -IT). Pooling all the R s data across sites and managements, max_T was ∼ 20 °C discriminating a differential response of R s when soil moisture was < or > RAW LLim. These differential modulations exerted by temperature and moisture were integrated into a conditional model developed with a repeated random subsampling cross-validation procedure to effectively (R 2 = 0.84) predict R s. This paper mechanistically describes the interaction of the environment (soil moisture and temperature) and the management options (S , C) under various moisture conditions on R s and would support carbon flux accounting procedures (e.g., regulating ecosystem services) tailored to the estimation of sink/source capability of traditional olive agro-ecosystem within environmental-friendly agricultural domains. • Management and water supply options influenced the CO 2 soil emissions (R s). • Seasonal R s was partitioned in 3 phases based on soil temperature and moisture. • Temperature and moisture differentially modulated R s based on threshold values. • Sustainable plots showed high R s on most sampling dates. • The R s model was effective (R 2 =0.84) in rainfed and irrigated European sites. [ABSTRACT FROM AUTHOR]