Nitrogen Content of Letharia vulpina Tissue from Forests of the Sierra Nevada, California: Geographic Patterns and Relationships to Ammonia Estimates and Climate |
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Authors: | Sarah Jovan Tom Carlberg |
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Institution: | (1) Department of Botany and Plant Pathology, Oregon State University, 2082 Cordley Hall, Corvallis, OR 97331-2902, USA;(2) USDA Forest Service, Six Rivers National Forest, Eureka, CA 95501, USA |
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Abstract: | Nitrogen (N) pollution is a growing concern in forests of the greater Sierra Nevada, which lie downwind of the highly populated
and agricultural Central Valley. Nitrogen content of Letharia vulpina tissue was analyzed from 38 sites using total Kjeldahl analysis to provide a preliminary assessment of N deposition patterns.
Collections were co-located with plots where epiphytic macrolichen communities are used for estimating ammonia (NH3) deposition. Tissue N ranged from 0.6% to 2.11% with the highest values occurring in the southwestern Sierra Nevada (range:
1.38 to 2.11). Tissue N at 17 plots was elevated, as defined by a threshold concentration of 1.03%. Stepwise regression was
used to determine the best predictors of tissue N from among a variety of environmental variables. The best model consisted
only of longitude (r
2 = 0.64), which was reflected in the geographic distribution of tissue values: the southwestern Sierra Nevada, the high Sierras
near the Tahoe Basin, and the Modoc Plateau, are three apparent N hotspots arranged along the tilted north–south axis of the
study area. Withholding longitude and latitude, the best regression model suggested that NH3 estimates and annual number of wetdays interactively affect N accumulation (r
2 = 0.61; % N ∼ NH3 + wetdays + (NH3 × wetdays)). We did not expect perfect correspondence between tissue values and NH3 estimates since other N pollutants also accumulate in the lichen thallus. Additionally, other factors potentially affecting
N content, such as growth rate and leaching, were not given full account. |
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Keywords: | Air pollution Ammonia Agriculture Bioindication California Forest health Letharia vulpina Lichens National Parks Nitrogen Nitrophytes Sierra Nevada |
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