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Abstract
Nitrogenous (N) air pollutant concentrations and surface deposition of nitrate (NO
3-) and ammonium (NH
4+) to branches of ponderosa pine (
Pinus ponderosa Dougl. ex. Laws.) seedlings were measured on a vertical transect in a mature ponderosa/Jeffrey (
Pinus jeffreyi Grev. & Balf.) pine canopy in the mixed conifer forest stand in the San Bernardino Mountains of southern California during the 1992 to 1994 summer seasons (mid-May to mid-October periods). In general, concentrations of nitric acid vapor (HNO
3), nitrous acid vapor (HNO
2), ammonia (NH
3), particulate NO
3- and NH
4+ were elevated and not affected by the position within the canopy. In contrast, surface deposition of NO
3- and NH
4+ to ponderosa pine seedling branches strongly depended on position in the canopy. The highest deposition of the two ions occurred at the canopy top, while at the canopy bottom deposition was often three to four times lower. The range of deposition fluxes of NO
3- and NH
4+ were similar in each of the three seasons. A comparison of the results of this study with other sites in California indicated that deposition fluxes of the studied ions were elevated. In addition to the deposition of NO
3- and NH
4+, conductance (K
1) of total NO
3-, HNO
3 vapor, and particulate NH
4+ to pine branch surfaces depended on the position in the canopy. The highest values were always measured at the canopy top.
Parent Publication
Citation
Bytnerowicz, Andrzej; Fenn, Mark E.; Arbaugh, Michael J. 1998. Concentrations and deposition of nitrogenous air pollutants in a ponderosa/Jeffrey pine canopy. In: Bytnerowicz, Andrzej; Arbaugh, Michael J.; Schilling, Susan L., tech. coords. Proceedings of the international symposium on air pollution and climate change effects on forest ecosystems. Gen. Tech. Rep. PSW-GTR-166. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: 105-113
