Fast carbon turnover after logging in the Semi-Arid Chaco forest (Argentina)

ESTEBAN KOWALJOW; GEORGINA CONTI; NATALIA PÉREZ HARGUINDEGUY; SANDRA DÍAZ

Sacramento

Congreso; Soil's role in restoring ecosystem services; 2014

Soil Science Society of America (SSSA)

Although the effect of forest logging on soil organic C (SOC) has been studied across different ecosystems, there is no consensus on the general resulting pattern, showing increases, decreases or not net changes in comparison with the former forest. A reduction on SOC content is expected as a result of disturbance activities promoting C loss or removal from the surface organic matter. Increased litter inputs resulting from a higher net primary productivity of young stands relative to mature stands could also being expected, increasing the SOC content of the logged sites, coupled with the deeper effect of an increased decomposition of dead roots from the removed woody biomass. A balance between these factors could also be resulting in no net C change on soils after logging. We aim to test the change on SOC up to 2 m depth in the semiarid Chaco of Central Argentina where an increased selective logging as result of extended silvopastoral activities is increasingly common. Using a paired sampling design we aim to compare the effect of selective logging of four different ages (3, 7, 9 & 22 years after logged, n=4) over the SOC content through the soil profile up to 2 m depth. SOC between forests have shown no significant differences indicating the homogeneity in climatic and soil variables under the study area. SOC under selective logging showed significant differences between them and with the correspondent former forest not only at surface but also at depth. SOC content had significantly increased after 22 years of forest logging showing a similar pattern that the model proposed by Covington and others, although the results showed on this study need to be replicated including selective logging on a broader range of times since logging has taken place. Our results seems to indicate a net decrease in SOC during the first years after disturbance (1.64 kg m-2 to a 2 m depth) followed by an increase during the following 22 years in the SOC content reaching a maximum of a net increase of 4.65 kg m-2 to a 2 m depth after 22 years of disturbance. A better understanding of the direction and magnitude of these changes is important for predicting the effect of land use change on soil fertility at regional level as well as its consequences for the global C cycle.