Intensive management modifies soil CO2 efflux in 6-year-old Pinus taeda L. stands
Intensive forestry may reduce net CO2 emission into atmosphere by storing carbon in living biomass, dead organic matter and soil, and durable wood products. Because quantification of belowground carbon dynamics is important for reliable estimation of the carbon sequestered by intensively managed plantations, we examined soil CO2 efflux (SCO2) in a 6-year-old loblolly pine (Pinus taeda L.) plantation in response to weed control (W), weed control plus irrigation (WI), weed control plus irrigation and fertigation (addition of fertilizer to the irrigation water) (WIF), and weed control plus irrigation, fertigation and pest control (WIFP) since plantation establishment. Average SCO2 ranged from 1.27 to 5.59 µmol m-2s-1, and linear models indicated that soil temperature explained up to 56% of the variation in SCO2. Plot position explained an additional 2–11% of the variation in SCO2. Soil moisture was only weakly correlated with SCO2 in the W treatment, and SCO2 was not significantly correlated to fine root mass. Predicted carbon loss from forest floor respiration ranged between 778 and 966 g C m-2 year -1 and was 20% lower in the WIF treatment relative to the W treatment. Annual soil carbon loss through soil respiration declined linearly with increasing carbon content in total root biomass (tap + coarse + fine) at age 6.