Abstract
Empirical critical loads (CL) for N deposition were determined from changes in epiphytic lichen communities, elevated NO3- 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 NO3-leaching were 17 kg N ha-1 year-1. DayCent estimated that elevated NO3- 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.
Original language | English (US) |
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Pages (from-to) | 492-511 |
Number of pages | 20 |
Journal | Environmental Pollution |
Volume | 155 |
Issue number | 3 |
DOIs | |
State | Published - Oct 2008 |
Keywords
- Atmospheric deposition
- Biomonitoring
- Ecosystem protection
- Epiphytic lichens
- Harmful effects
- Nitrogen saturation
ASJC Scopus subject areas
- Toxicology
- Pollution
- Health, Toxicology and Mutagenesis