Zhang, Y. 1989. Throughfall and stemflow chemistry in a northern hardwood forest in the Adirondack region of New York. M.S. Thesis. SUNY ESF, Syracuse, 95 pp.

Abstract: Concentrations and fluxes of throughfall and stemflow were characterized for solutions under two tree species at the Huntington Forest, Adirondack Mountains. Forty-three throughfall and 34 stemflow events were sampled during the growing season from June 1986 to September 1986 and May 1987 to September 1987. Thirty-six throughfall events were sampled during the dormant season from October 1986 to April 1987 and October 1987 to April 1988. Chemical composition of precipitation from an adjacent open site was compared with that of throughfall and stemflow collected beneath an American beech canopy and a sugar maple canopy. The temporal changes in elemental inputs to the forest floor under beech and maple canopies were investigated. Analysis of water flux showed that maple throughfall was greater than that of beech during the growing season, but did not differ significantly during the dormant season. Beech stemflow was greater than maple stemflow during the growing season. Ion concentrations in throughfall and stem flow were usually substantially greater during the growing seasons than those in precipitation, except concentration of H+ which were greatly reduced. Among all elements studied, enrichment of K+, Ca2+, and Mg2+ was most marked. Both beech and maple canopies substantially reduced concentration of H+, possibly through ion exchange. Concentrations of No3-, and NH4+ in maple stemflow were lower than that in precipitation, maybe due to absorption by leaf and bark surface tissues, or consumption by canopy and bark dwelling organisms. Elemental enrichment in throughfall and stemflow comes from two sources: washoff by dry deposition from leaf surfaces as precipitation passes through the canopy and leaching from tree tissues. Dry deposition contributed more to H+, NO3-, SO42-, and NH4+ than in the case of other elements, while foliar leaching contributed more to the net enrichment of K+, Ca2+, and Mg2+. Vapors were more important sources of H+, NO3-, and SO42-. Coarse particles were most important for NH4+ and Ca2+. The leaching rates of Ca2+ and Mg2+ differed between beech and maple canopies. Dry deposition and leaching contributed about evenly to the net enrichment of Ca2+ flux under beech canopy. Foliar leaching was more important than dry deposition input to the net flux of Ca2+ under maple canopy. for Mg2+, foliar leaching contributed more to net flux than dry deposition for both beech and maple canopies. American beech and sugar maple have similar influences in altering elemental inputs via wet deposition, but the contribution of different ions varies with tree species. Throughfall elemental flux is larger under the maple canopy than that under beech, while stemflow elemental flux contributed more under beech than under maple. This indicates that changes in the composition of tree species may influence elemental fluxes in the forest.