Nitrogen inputs, fluxes, internal generation and consumption, and outputs were monitored in a subalpine spruce-fir forest at approximately 1000-m elevation on Whiteface Mountain in the Adirondacks of New York, USA. Nitrogen in precipitation, cloudwater and dry deposition was collected on an event basis and quantified as an input. Throughfall, stemflow, litterfall and soil water were measured to determine fluxes within the forest. Nitrogen mineralization in the forest floor was estimated to determine internal sources of available N. Lower mineral horizon soil water was used to estimate output from the ecosystem. Vegetation and soil N pools were determined.During four years of continuous monitoring, an average of 16 kg N ha-' yr-' was delivered to the forest canopy as precipitation, cloudwater and dry deposition from the atmosphere. Approximately 30% of the input was retained by the canopy. Canopy retention is likely the result of both foliar uptake and immobilization by bark, foliage and microorganisms. Approximately 40 kg of N was made available within the forest floor from mineralization of organic matter. Virtually all the available ammonium (mineralized plus input from throughfall) is utilized in the forest floor, either by microorganisms or through uptake by vegetation. The most abundant N component of soil water solutions leaving the system was nitrate. Net ecosystem fluxes indicate accumulation of both ammonium and nitrate. There is a small net loss of organic N from the ecosystem. Some nitrate leaves the bottom of the B horizon throughout the year. Comparisons with other temperate coniferous sites and examination of the ecosystem N mass balance indicate that N use efficiency is less at our site, which suggests that the site is not severely limited by N. * One error in the original equation was corrected (T. G. Siccama, Yale Univ., pers. comm.).

Akstract. Successional changes in available soil nitrogen may be a key to understanding the dynamtcs of secondary succession. Nitrification potentials of forest floors from an old-field chronose-que~ce in Ca~pton, ~ew Hampshire, were measured in the laboratory for 9 mo. Total nitrate pro-ductiOn per umt orgamc matter decreased with increasing stand age. Lag time before the initiation of nitrate production was longer with increasing stand age. Although nitrate production decreased in o.ld~r fores.t floors of the ~hronosequence, total nitrogen removals during the incubation were relatively srmdar. Nrtrate production was strongly correlated with initial forest floor pH (r 2 = 0.96, P < .001), but was not correlated with any of five different measures of litter and forest floor tannin content. It appears that decreases in nitrification potential during this secondary succession could have resulted from changing forest floor pH and its effects on microorganisms.

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Biogeochemical cycles of Ca, Mg, K, and Na were studied in a small forested watershed on relatively base‐rich terrain at the Sleepers River Research Watersheds (SRRW) in northeastern Vermont and on base‐poor terrain at the Hubbard Brook Experimental Forest (HBEF) in central New Hampshire. The two watersheds are comparable except that shallower soils at the SRRW are weathered from calcareous and quartz mica schist till, whereas the deeper soils at the HBEF are weathered from schist, gneiss, and quartz monzonite till. Inputs of the four cations in precipitation were similar except for Ca; Ca inputs were an order of magnitude greater at the SRRW. Total annual cation outputs were more strongly related to total stream flow and parent material geochemistry than to cation inputs in precipitation. Analysis of the variation in cation output in stream water with respect to flow suggests strong geochemical control of cation output at the SRRW. Similar analysis of data from the HBEF suggests a more complex pattern of cation output related to biological cycling of cations. Inputs of acidity may serve to flush the soil at the HBEF of cations.

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