Assessment of soil and tree carbon concentrations under varying levels of Chinese privet invasion

Invasive plant species are increasingly recognized for their capacity to alter ecosystem structure and function, yet their impact on carbon storage remains underexplored. This study investigates how Chinese privet (Ligustrum sinense), a widespread invasive shrub in the southeastern United States, may be influencing above- and belowground carbon in a secondary forest recovering from past agricultural use. We compared soil organic carbon (SOC) across three vegetation types (heavily invaded and uninvaded deciduous forest, and an adjacent loblolly pine stand) and tree biomass carbon at varying amounts of Chinese privet within a historic landscape in central Georgia. SOC was assessed at three depths (0-5, 5-10, and 10-15 cm) while tree carbon was estimated using structural measurements and species-specific allometric equations. Results showed that SOC was lowest in the invaded site, despite having similar soil texture and bulk density to uninvaded sites. The pine stand SOC was significantly lower than the uninvaded site, likely due to differences in litter inputs and disturbance history. Tree density and biomass carbon were significantly lower in privet-invaded areas compared to uninvaded sites. Overall, soil and tree carbon density were over 40% lower in the presence of Chinese privet. These findings suggest that Chinese privet may contribute to long-term reductions in both biomass and soil carbon pools by suppressing native woody regeneration and altering belowground processes. As forests play a critical role in carbon sequestration, understanding the indirect impacts of invasive species on carbon dynamics is vital for informing management and restoration strategies in disturbed landscapes.