Soil carbon stocks in stable tropical landforms are dominated by geochemical controls and not by land use

Summary

This field study demonstrates that in deeply weathered tropical soils on stable plateau landforms, soil carbon stocks and turnover patterns are controlled primarily by soil mineralogy and geochemistry rather than land use type (forest versus cropland). The authors attribute this to mineral limitation: the investigated soils have already exceeded their maximum capacity for mineral-stabilised organic carbon, limiting further accumulation even under high-input forest systems. The implication is that reforestation efforts in such deeply weathered soils would produce only minor, shallow carbon gains without substantial subsurface storage.

UK applicability

UK soils are generally less deeply weathered and retain greater mineral reactivity than tropical soils studied here, suggesting mineral-related carbon stabilisation capacity remains functional in UK arable and grassland systems. However, the finding that geochemical constraints can override land-use effects may inform interpretation of UK soil carbon responses in low-activity clay regions.

Key measures

Soil organic carbon stocks (SOC); radiocarbon (Δ14C) turnover time; physicochemical soil properties; organo-mineral associations; exchangeable base cations

Outcomes reported

The study quantified soil organic carbon stocks and radiocarbon-derived turnover times across soil profiles in tropical forest and cropland on geochemically distinct parent materials. Soil physicochemical properties, particularly labile organo-mineral associations and exchangeable base cations, were identified as dominant controls over carbon dynamics, independent of land use.

Topic tags