Sequestration of atmospheric CO2 in the Yatir Mediterranean semi-arid Aleppo Pine Forest (Pinus halepensis) close to the border of the semi-arid timberline was characterized and quantified under field conditions. Measurements of organic and inorganic CO2 sequestration with gas exchange, stock counting approach, and remote sensing were made in both rainfed control (~12% average annual Soil Moisture) and long-term experiment of irrigation (~10 years with ~24% annual average SM) plots, providing the opportunity to separate the effects of atmospheric water demand from soil water stress on the atmospheric CO2 sequestration responses. Measurements yield an organic carbon sequestration (OCS) rate of ~550 g CO2 m−2 yr−1, 60% in soil and 40% in biomass (standing and removed). In addition, measurements yield an inorganic carbon sequestration (ICS) rate of ~65 g CO2 m−2 yr−1 (for half meter soil depth) via calcite (CaCO3) precipitation in the soil due to root exhalation of CO2 (25%) and microbial activity (75%). The drip-irrigated plot showed approximately 3 times higher organic CO2 sequestration than the control plot, divided equally between the soil and the biomass. For the irrigated plot, the inorganic CO2 sequestration rate was ~1.8 times higher than that of the control plot. These measured values demonstrate the relatively high potential for carbon sequestration in Mediterranean drylands forests under irrigated and non-irrigated conditions.
Qubaja et al. (Fri,) studied this question.