Quantifying pH buffering capacity in acidic, organic-rich Arctic soils: Measurable proxies and implications for soil carbon degradation

• Published in: Geoderma 2022-10, Vol.424 (1), p.116003, Article 116003
• Main Authors: Zheng, Jianqiu, Berns-Herrboldt, Erin C., Gu, Baohua, Wullschleger, Stan D., Graham, David E.
• Format: Article
• Language: English
• Subjects: Acid-base; Biogeochemistry; Buffering capacity; INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Organic matter; pH; Water potential
• ISSN: 0016-7061; 1872-6259
• DOI: 10.1016/j.geoderma.2022.116003

[Display omitted] •Arctic soil pH buffering capacity (β) varies with depth and microtopography.•Soil water retention is an important proxy for β in organic-rich Arctic soils.•Variations in β modulate pH-sensitive biogeochemical transformations.•Earth system models neglecting β may yield CO2 and CH4 prediction uncertainty. Dynamic pH change promoted by biogeochemical reactions in Arctic tundra soils can be a major control on the production and release of CO2 and CH4, which contribute to rising global temperatures. Large quantities of soil organic matter (SOM) in these soils are susceptible to microbial decomposition, leading to pH changes during permafrost thaw. Soil pH buffering capacity (β) modulates the extent of pH change but has not been thoroughly studied and represented in predictive ecosystem scale biogeochemical models in Arctic tundra soils. In this study, we generated titration curves for 21 acidic tundra soils from three Arctic sites across northern Alaska, United States of America. Geochemical and hydrological soil properties were evaluated, and correlations with β were developed. Strong correlations between β and both gravimetric water content (Θg) (R2 = 0.847, p