Fast Carbon Turnover after Logging in the Semi-Arid Chaco Forest (Argentina).

Although the effect of forest logging on soil organic carbon (SOC) has been studied across different ecosystems, there is no consensus on the general resulting pattern. Logging activities could promote both direct SOC loss through soil and litter removal as well as SOC gains through litter inputs from regrowing vegetation and woody roots decomposition. We test the change on SOC in the semi-arid Chaco of Argentina where selective logging as result of silvopastoral activities is increasingly common. Using a paired sampling design we compared the effect of selective logging at four different ages (3, 7, 9 and 22 years after logged) over the SOC content up to 2 m. SOC between unmanaged forests have shown no significant differences indicating fairly homogeneous conditions across the study area. SOC under logging sites showed significant differences between them and with the former forest not only at surface but also at depth. Our results indicate a net decrease in SOC during the first years followed by an increase during the following years, reaching a maximum net increase of 4.65 kg m-2 to a 2 m soil depth after 22 years. Although these results need to be replicated including sites on a broader range of times after logging, the actual rates of C change found after disturbance were surprisingly fast, affecting not only surface SOC but also C stored at depth. A change of this magnitude could have deep consequences on regional soil fertility and the global C cycle.