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Abstract
The air in California’s forests spans a broad range of purity, from virtually no locally generated pollutants to highly elevated levels of pollutants in forests downwind of urban and agricultural source areas. Ten-year remeasurement data from Forest Inventory and Analysis (FIA) plots in California were used in combination with modelled atmospheric nitrogen (N) deposition to evaluate tree diameter growth and mortality responses across the state. After controlling for tree size, site productivity, climate attributes, stand density, and competition experienced by each tallied tree, we found significant N deposition effects on tree bole growth when N deposition exceeded a threshold of approximately 15 kg/ha/yr. Increased tree mortality for all 14 species combined appears to increase when N deposition exceeds 10 kg/ha/yr, although the confidence intervals on the response curve are large. Preliminary analyses suggest ozone modifies the growth response, particularly at lower N deposition levels.
Parent Publication
Citation
Fenn, Mark E.; Fried, Jeremy S.; Preisler, Haiganoush K.; Bytnerowicz, Andrzej; Schilling, Susan; Jovan, Sarah; Kuegler, Olaf. 2015. Remeasured FIA plots reveal tree-level diameter growth and tree mortality impacts of nitrogen deposition on California’s forests. In: Stanton, Sharon M.; Christensen, Glenn A., comps. 2015. Pushing boundaries: new directions in inventory techniques and applications: Forest Inventory and Analysis (FIA) symposium 2015. 2015 December 8–10; Portland, Oregon. Gen. Tech. Rep. PNW-GTR-931. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station: 185-188.
