Comparing turnover of soil organic phosphorus and bulk soil organic carbon in a 56-year oil palm chronosequence

Soil organic phosphorus (SOP) can represent a large fraction of the total soil phosphorus pool, and its mineralization plays a key role in plant P supply. Phosphorylated organic compounds generally exhibit stronger adsorption to soil minerals than non-phosphorylated organic carbon, suggesting that SOP may cycle more slowly than bulk soil organic carbon (SOC). However, direct comparisons of SOP and SOC turnover times remain largely unknown due to methodological limitations.

Here, we investigated SOP turnover using soils from a 56-year chronosequence documenting the conversion of C₄ pasture to C₃ oil palm, thereby exploiting the natural δ¹³C contrast between vegetation types as an in situ tracer of carbon turnover. To specifically assess SOP dynamics, we applied a recently developed method to isolate SOP compounds from other soil organic compounds and quantified the δ¹³C signature of this SOP pool (Tian and Spohn, 2025). Turnover times of isolated SOP were then compared with those of bulk SOC across the chronosequence.

This study provides empirical data on SOP dynamics that are currently poorly represented in soil biogeochemical assessments and offers a transferable approach for disentangling phosphorus and carbon turnover in soils across ecosystems.

 

Reference

Tian, Y., & Spohn, M. (2025). A method to isolate soil organic phosphorus from other soil organic matter to determine its carbon isotope ratio. Soil Biology and Biochemistry, 210, 109911.

 

Acknowledgement

This research was funded by the European Research Council (ERC) (grant number 101043387).