Nutrient fluxes in forests of the eastern Sierra Nevada: comparisons with humid forest systems

Abstract

Preliminary results of studies on nutrient fluxes in forests of the eastern Sierra Nevada were compared to those from more humid and polluted ecosystems. Snowmelt, soil solution, soil, and streamwater were collected from Jeffrey and lodgepole pine (Pinus jeffreyii [Grev. and Balf.] and Pinus contorta Dougl.) stands in Little Valley, Nevada, and from California red fir (Abies magnifica A. murr.) and Jeffrey pine/white fir (Pinus jeffreyii/Abies concolor [Gord and Glend.] Lindl.) stands at Sagehen, California. Snowmelt, soil solutions, and streamwaters from both sites were circumneutral and dominated by base cations and bicarbonate. The red fir stand at Sagehen had high NO₃^- concentrations (approximately 30-100 μmol/L) in both snowmelt and soil solution during the relatively dry 1993-4 water year. The Little Valley sites had substantially lower NO₃^- concentrations in both snowmelt (5-20 μmol/L) and soil solution (0.5-3 μmol/L) in both wet and dry years. At both sites, a pulse of streamwater NO₃^- (from 0.5 to 20-40 μmol/L) was detected during dry years but not wet years. The Andic soils at the Sagehen site have trace levels of available P in soils, whereas the Entisols and Inceptisols in Little Valley have 10 to 100 times greater levels. The results suggest a hypothesis that the greater mobility of NO₃^- in the Sagehen red fir site was caused by the amount and timing of NO₃^- release from snowmelt (e.g., too concentrated and early for dormant biota to respond to), and that P may also be limiting at Sagehen. Compared to other forest ecosystems in more humid and polluted environments, N, S and H+ deposition and fluxes at the Little Valley site are extremely low, but HCO₃^- and base cation fluxes are high. This reveals that the Little Valley site is relatively pristine, and that ionic fluxes at this site are dominated by natural carbonic acid leaching and weathering reactions.

Parent Publication

• Proceedings of the International Symposium on Air Pollution and Climate Change Effects on Forest Ecosystems

Citation

Johnson, Dale W.; Susfalk, Richard B.; Dahlgreen, Randy A.; Boucher, Virginia; Bytnerowicz, Andrzej. 1998. Nutrient fluxes in forests of the eastern Sierra Nevada: comparisons with humid forest systems. In: Bytnerowicz, Andrzej; Arbaugh, Michael J.; Schilling, Susan L., tech. coords. Proceedings of the international symposium on air pollution and climate change effects on forest ecosystems. Gen. Tech. Rep. PSW-GTR-166. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: 95-104