Enhanced silicate weathering accelerates forest carbon sequestration by stimulating the soil mineral carbon pump

Summary

This 2-year field experiment in tropical rubber plantations demonstrates that enhanced silicate rock weathering (ERW) via wollastonite application significantly increases soil organic carbon sequestration, with gains four to eight times larger than inorganic carbon increases. The primary mechanism operates through the soil mineral carbon pump—the release of calcium, silicon, and iron stimulates stabilisation of organic carbon in mineral-associated organic matter—with secondary contributions from root growth and microbial carbon inputs. The authors argue that organic carbon responses must be explicitly accounted for in climate mitigation assessments of ERW, as these may exceed the direct inorganic carbon dioxide removal effect.

UK applicability

UK conditions differ substantially from tropical rubber plantations in climate, soil type, and plantation structure, limiting direct applicability. However, the mechanistic insights regarding silicate weathering, mineral carbon stabilisation, and the interplay between geochemical and biological carbon pathways may inform UK soil health and carbon sequestration research, particularly if ERW is considered for temperate arable or grassland systems.

Key measures

Soil organic carbon concentration; bicarbonate (HCO3−) concentration; carbon partitioning in MAOM, macroaggregates, and particulate organic matter; calcium, silicon, and iron release; root biomass; microbial-derived carbon inputs

Outcomes reported

The study measured soil organic carbon (SOC) and inorganic carbon (HCO3−) concentrations, and the distribution of carbon across mineral-associated organic matter (MAOM), macroaggregate, and particulate organic matter fractions following wollastonite powder applications. Path analysis identified the mechanistic drivers of carbon sequestration, comparing the magnitude of organic versus inorganic carbon gains.

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