Forest streams may discharge one tenth of the annual total global forest carbon sink through dissolved organic carbon
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GRAPHICAL ABSTRACT
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PUBLIC SUMMARY
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Forest streams discharge 0.20 Pg C yr-1 of dissolved organic carbon (DOC), 10% of the forest carbon sink.
DOC-to-GPP ratios differ across climate zones, ranging from <0.01% to a maximum of 1.63%.
Catchment area and surface runoff are the drivers of DOC efflux (66.2%, 13.7%) with positive effects.
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ABSTRACT
The efflux of dissolved organic carbon (DOC) from aquatic networks in forest ecosystems is an important component of the global C cycle. Utilizing the machine learning method Random Forest model (high predictability and stability, R2=0.75, RMSE = 4.10 mg L-1), we projected global forest streams DOC concentration, based on estimated relations to mean annual temperature, soil organic carbon, land surface runoff, silt content, aridity index and annual average discharge, using over 3,000 observations worldwide. By integrating these projections with a database of annual average stream discharge, we quantified the annual efflux of DOC from global forest streams. We found that (1) approximately 0.20 Pg of DOC (ranging from 0.06 to 0.39 Pg) is exported annually from forest ecosystems via stream discharge, accounting for around 10% of the total global forest C sink; (2) the ratio of DOC exported from forest streams to the gross primary productivity of forested landscapes varied across climatic zones, ranging from negligible levels (≤0.01) to 1.63%; and (3) catchment area and land surface runoff were the dominant predictors (accounting for 66.2 and 13.7% of the total variation) of global forest streams DOC efflux, and both showed positive relationships with DOC efflux. Overall, our findings highlight the important role of streams in forest C efflux, and improve our understanding of hydrological processes associated with C cycling under global change scenarios. -
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REFERENCES
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Tan S., Yue K., Peñuelas J., et al. (2025). Forest streams may discharge one tenth of the annual total global forest carbon sink through dissolved organic carbon. The Innovation Geoscience 3:100148. https://doi.org/10.59717/j.xinn-geo.2025.100148
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Tan S., Yue K., Peñuelas J., et al. (2025). Forest streams may discharge one tenth of the annual total global forest carbon sink through dissolved organic carbon. The Innovation Geoscience 3:100148. https://doi.org/10.59717/j.xinn-geo.2025.100148
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Figure 1.
Global distribution and probability density of dissolved organic carbon (DOC) concentrations in forest streams
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Figure 2.
Predictive performance and controlling factors of dissolved organic carbon (DOC) concentration in forest streams
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Figure 3.
Predicted average dissolved organic carbon (DOC) concentration in global forest streams at 0.5 × 0.5° resolution.
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Figure 4.
Partial dependence plots showing the marginal effects of six key predictor variables on dissolved organic carbon (DOC) concentration (mg L−1) in the Random Forest model.
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Figure 5.
Global map of dissolved organic carbon (DOC) efflux from forest streams at 0.5 × 0.5° resolution.
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Figure 6.
Relative importance of environmental drivers of global dissolved organic carbon (DOC) efflux in forest streams.
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Figure 7.
Global map of the ratio of dissolved organic carbon (DOC) yield to gross primary productivity (GPP) in forest streams at 0.5 × 0.5° resolution.
