Effect of Temperature on Potassium and Sodium Exchange in a Sierra Nevada Riparian Soil
In the course of investigating nutrient availability in a montane meadow ecosystem of the Sierra Nevada range, it was determined that resin availability of Na+ and K+ was significantly affected by season (winter vs. summer and fall). The underlying mechanism(s) controlling this seasonal effect was investigated in the laboratory. Four replicate A horizon samples of a Typic Humaquept (silty clay texture, kaolinitic mineralogy, 3% organic C, pH 5.10) were saturated with Mg2+ Using 5-g subsamples from each replicate, soil was equilibrated for a period of 30 min with 30 mL of a 5.00 mmol solution of Na+ and K+ at 1, 15, 30, and 45°C. After centrifugation, the supernatant was analyzed for K+, Na+, and Mg2+ Exchanger sorption characteristics varied significantly with temperature. Overall, K+ was preferentially sorbed over Na+, but the proportional sorption of K+ decreased significantly at a temperature of 1°C. The temperature dependence of K+ and Na+ sorption partially explains seasonal differences in availability. Net sorption (K+ + Na+ − Mg2+) was statistically similar to 0 at temperatures of 15, 30, and 50°C, but significantly increased at 1°C. This increase in cation exchange capacity at low temperature may have special relevance to ecosystems during snowmelt when increased retention of certain cations could occur.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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