Solute-specific scaling of inorganic nitrogen and phosphorus uptake in streams

[摘要] Stream ecosystem processes such as nutrient cycling may vary with streamposition in the network. Using a scaling approach, we examined therelationship between stream size and nutrient uptake length, which representsthe mean distance that a dissolved solute travels prior to removal from thewater column. Ammonium (NH₄⁺) uptake length increased proportionallywith stream size measured as specific discharge (discharge/stream width) witha scaling exponent = 1.01. In contrast, uptake lengths for nitrate(NO₃⁻) and soluble reactive phosphorus (SRP) increased more rapidlythan increases in specific discharge (scaling exponents = 1.19 forNO₃⁻ and 1.35 for SRP). Additionally, the ratio of inorganic nitrogen(N) uptake length to SRP uptake length declined with stream size; there wasrelatively lower demand for SRP compared to N as stream size increased.Finally, we related the scaling of uptake length with specific discharge tothat of stream length using Hack's law and downstream hydraulic geometry.Ammonium uptake length increased less than proportionally with distance fromthe headwaters, suggesting a strong role for larger streams and rivers inregulating nutrient transport.

[学科分类] 地球化学与岩石