i DRY DEPOSITION OF NITROGEN AND SULFUR TO PONDEROSA AND JEFFREY PINE IN THE

Little is known about the concentrations, deposition rates, and efects of nitrogenous and sulfurous compounds in photochemical smog in the San Bernardino National Forest (SBNF) in southern Calfirnia. Dry deposition of NO, and NH: to foliage of ponderosa pine (Pinus ponderosa Laws.) and Jeflrey pine (Pinus jeffreyi Grev. & B a y) was correlated (R = 0.83-0-88) with historical average hourly 0, concentrations at 10 sites across an O, gradient in the SBNF. Mean deposition Jluxes of NO5 to ponderosa and Jefrey pine branches were 0.82 nmol m-'s ' at Camp Paivika (CP) , a high-pollu-tion site, and 0.19 nmol m-2 s- ' at Camp Osceola ( C A 0) , a low- pollution site. Deposition fluxes of NH,' were 0.32 nmol m- ' s ' at CP and 0-17 nmol m s ' at CA 0, while mean values for SO, ' were 0.03 at CP and 0.02 nmo l m-2 s at CA 0. Deposition JEuxes to paper and nylon filters were higher in most cases than fluxes to pine branches at the same site. jrhe results of this study suggest that an atmospheric concentration and deposition gradient of N and S compounds occurs along with the west-east 0, gradient in the SBILTF- Annual stand-level dry deposition rates for S and N at CP and CAO were estimated. Further studies are needed to determine if high N deposition loads in the SBNF signiJicantly afect plantisoil nutrient relations, tree lzealth, and the response ofponderosa pine to ozone