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Abstract Long‐term river monitoring of the Kuparuk River (North Slope, Alaska, USA) confirms significant increases in solutes that are indicative of active layer thickening due to thawing permafrost. However, there is no evidence of an increase in total dissolved phosphorus (TDP) or soluble reactive phosphorus (SRP), the nutrient that limits primary production in this and similar rivers in the region. Here, we show that Mehlich‐3 extractable iron (Fe) and aluminum (Al) in active layer soils impart high P geochemical sorption capacities across a range of landscape features that we would expect to promote lateral movement of water and solutes to headwater streams in our study watershed. Reanalysis of a recently published pan‐Arctic soils database that includes active layer and permafrost soil samples suggests that this high P sorption capacity could be common in other parts of the Arctic region. We conclude that soil minerals enhance P retention on hillslopes and propose pedogenic secondary Fe and Al minerals may continue to retain P in these soils and limit biological productivity in the adjacent river even as active layer thickening increases potential P mobility in the watershed. We suggest that similar interactions may occur in other areas of the Arctic where comparable geochemical conditions prevail.
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This content will become publicly available on June 1, 2027
Fractionation and environmental assessment of legacy phosphorus from acidic, organic, and calcareous soils
Phosphorus (P) is essential for plant growth, but excessive and continuous application of P fertilizers and animal manure has led to the accumulation of legacy phosphorus (legacy-P) in soils. While legacy-P presents a potential resource to support future agricultural demands, limited understanding of its chemical forms across different soil types hinders its sustainable management. This study aimed to characterize the chemical nature and storage potential of legacy-P in three contrasting soil types: acidic, organic, and calcareous. Key soil properties—including pH, organic matter, total P, Mehlich-3 P, and concentrations of aluminum (Al), calcium (Ca), iron (Fe), and magnesium (Mg)—were evaluated alongside P fractionation using a modified Hedley method. Furthermore, the soil P saturation ratio (PSR) was calculated to evaluate the relative saturation of soil sorption sites with P. Results showed considerable variability in Mehlich-3 P across soil types, ranging from 7–62% of total P in acidic soils, 1–8% in organic soils, and 3–47% in calcareous soils. Acidic soils were dominated by humic/fulvic-bound P (> 42%), organic soils by recalcitrant residual P (> 62%), and calcareous soils by Ca/Mg-bound P (> 69%), highlighting the influence of soil chemistry on P stability. Despite considerable variation among soil types in P fractionations, PSR results suggested that Ca/Mg-associated minerals play a greater role in retaining legacy P in organic and calcareous soils than Al- and Fe-associated minerals. In acidic soils, both mineral groups contributed similarly to P retention.
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- Award ID(s):
- 2019435
- PAR ID:
- 10692174
- Publisher / Repository:
- Springer
- Date Published:
- Journal Name:
- Biogeochemistry
- Volume:
- 169
- Issue:
- 3
- ISSN:
- 1573-515X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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