Empirical and simulated critical loads for nitrogen deposition in California mixed conifer forests

Empirical critical loads (CL) for N deposition were determined from changes in epiphytic lichen communities, elevated NO 3 − leaching in streamwater, and reduced fine root biomass in ponderosa pine ( Pinus ponderosa Dougl. ex Laws.) at sites with varying N deposition. The CL for lichen community imp...

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Bibliographic Details
Published in:Environmental pollution (1987) 2008-10, Vol.155 (3), p.492-511
Main Authors: Fenn, M.E., Jovan, S., Yuan, F., Geiser, L., Meixner, T., Gimeno, B.S.
Format: Article
Language:English
Subjects:
Air Pollutants - analysis
Air Pollutants - toxicity
Atmospheric deposition
Biomass
Biomonitoring
botanical composition
California
carbon nitrogen ratio
Coniferophyta
critical loads
Ecosystem
Ecosystem protection
environmental impact
environmental monitoring
Environmental Monitoring - methods
epiphytes
Epiphytic lichens
forest litter
forest trees
Forestry
Harmful effects
indicator species
leaching
Letharia vulpina
lichens
Lichens - growth & development
nitrate nitrogen
nitrogen
Nitrogen - analysis
Nitrogen - toxicity
nitrogen content
Nitrogen saturation
Pinus ponderosa
Plant Roots - growth & development
pollution load
root systems
streams
temperate forests
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Summary:Empirical critical loads (CL) for N deposition were determined from changes in epiphytic lichen communities, elevated NO 3 − leaching in streamwater, and reduced fine root biomass in ponderosa pine ( Pinus ponderosa Dougl. ex Laws.) at sites with varying N deposition. The CL for lichen community impacts of 3.1 kg ha −1 year −1 is expected to protect all components of the forest ecosystem from the adverse effects of N deposition. Much of the western Sierra Nevada is above the lichen-based CL, showing significant changes in lichen indicator groups. The empirical N deposition threshold and that simulated by the DayCent model for enhanced NO 3 −leaching were 17 kg N ha −1 year −1. DayCent estimated that elevated NO 3 − leaching in the San Bernardino Mountains began in the late 1950s. Critical values for litter C:N (34.1), ponderosa pine foliar N (1.1%), and N concentrations (1.0%) in the lichen Letharia vulpina ((L.) Hue) are indicative of CL exceedance. Critical loads for N deposition effects on lichens, trees and nitrate leaching provide benchmarks for protecting California forests.
ISSN:0269-7491
1873-6424
DOI:10.1016/j.envpol.2008.03.019