THROUGHFALL AND CANOPY BUFFERING IN 3 SITKA SURFACE STANDS IN DENMARK

Throughfall was studied in three even-aged sitka spruce stands in Denm ark during the years 1989 to 1994. Deposition of sea salts dominated t he fluxes of substances in varying degrees between years and sites. Du ring the study period, non-marine S deposition did not change substant ially. At the site most affected by animal husbandry, fluxes of NH4+ a nd NO3- increased over the years. Elevated fluxes of TOC, K+, and PO43 - occurred in the growing season due to canopy leaching caused by atta cks by the green spruce aphid. Fluxes of Cl-, SO42-, Na+, Ca2+, and Mg 2+ were highest in the dormant season. Buffering of pH was affected by the nitrogen dynamics in the canopy, and also, at least during the su mmer, by elevated levels of organic compounds.