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Inorganic nitrogen and phosphorus in Sierran forest O horizon leachate
T M Loupe1, W W Miller, D W Johnson
1Hydrologic Sciences Program, College of Agriculture, Biotechnology, and Natural Resources, University of Nevada, Reno, NV 89512, USA.
Journal of Environmental Quality
|March 3, 2007
Summary
Forest floor O horizons release nitrogen (N) and phosphorus (P) during simulated precipitation. The O(i) horizon, specifically, yielded higher nutrient concentrations, potentially impacting Lake Tahoe
Area of Science:
- Forest Ecology
- Environmental Chemistry
- Limnology
Background:
- Elevated inorganic nitrogen (N) and phosphorus (P) in Sierran forest runoff suggest forest floor O horizons as a source.
- Lake Tahoe's water quality is deteriorating, necessitating investigation into nutrient sources.
Purpose of the Study:
- To test the hypothesis that forest floor O horizons are the source of nutrients in overland/litter interflow.
- To quantify nutrient release from different forest floor layers (O(e) and O(i) horizons) under simulated precipitation.
Main Methods:
- Collected forest floor monoliths (O(e) and O(i) horizons) from Lake Tahoe basin.
- Established three treatments: combined O(e)+O(i), O(e) only, and O(i) only.
- Simulated precipitation using misting and snow application, collecting and analyzing leachate for N and P.
Main Results:
- Overall net release of inorganic nitrogen and phosphorus observed.
- While combined horizons released more total nutrients, the O(i) horizon showed significantly higher concentrations of nitrate-N and phosphate-P per unit mass.
- Ammonium-N was retained, but nitrate-N and phosphate-P were released.
Conclusions:
- Forest floor leachate, particularly from the O(i) horizon, is a significant source of bioavailable N and P.
- Nutrient transport from terrestrial forest floors to aquatic systems in the Lake Tahoe basin may contribute to declining water clarity.
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