Wollastonite application showed negligible potential to enhance carbon sequestration in a subtropical fir plantation

Enhanced rock weathering (ERW) involving the modification of soils with crushed silicate rocks has increasingly been considered for application to mitigate atmospheric CO2. However, the potential of ERW as a CO2 sequestration technology is still unclear, because silicate effect on ecosystem productivity was inadequately quantified before. In this study, ERW was deployed by adding 5 t ha-1 of wollastonite rock powder to a young Cunninghamia lanceolata plantation. The C uptake by the ecosystem was estimated by integrating the inorganic C sequestration via rock weathering and the net ecosystem productivity (NEP). Results showed that 15.72 % of the cation (Ca2+ and Mg2+) delivered by weathering was charge-balanced by HCO3-, representing an CO2 removal (CDR) of 0.32 t CO2 ha-1 year-1 from ERW based on the charge-balance theory. The NEP, calculated as the difference between net primary production and cumulative heterotrophic respiration, averaged 162.91 and 137.38 g C m-2 in control and wollastonite rock amended stands, respectively, with no significant difference observed between treatments. After integrating the CDR and NEP, we found that the C sequestration responded to WA with no change. We highlighted a minor potential for ERW to draw down atmospheric CO2 in this forest.