Nutrient cycling in Huntington Forest and Turkey Lakes deciduous stands: nitrogen and sulfur

Abstract

Biogeochemical cycling of S and N was quantified at two hardwood sites (Turkey Lakes watershed (TLW) and Huntington Forest (HF)) that have sugar maple (Acersaccharum Marsh.) as the major overstory component and are underlain by Spodosols (Podzols). TLW and HF are located in central Ontario (Canada) and the Adirondack Mountains of New York (U.S.A), respectively. Major differences between the TLW and HF sites included stand age (300 and 100 years for TLW and HF, respectively), age of dominant trees (150–300 and 100 years for TLW and HF, respectively), and the presence of American beech (Fagusgrandifolia Ehrh.) at HF as well as lower inputs of SO42− and NO3− (differences of 99 and 31 mol ion charge (molc)•ha−1•year−1, respectively) at TLW. There was an increase in concentration of SO42− and NO3− after passage through the canopy at both sites. A major difference in the anion chemistry of the soil solution between the sites was the much greater leaching of NO3− at TLW compared with HF (1300 versus 18 molc•ha−1•year−1, respectively). At HF, but not TLW, there was a marked increase in SO42− flux (217 molc•ha−1•year−1) when water leached from the forest floor through the mineral soil. The mineral soil was the largest pool (>80%) of N and S for both sites. The mineral soil of TLW had a C:N ratio of 16:1, which is much narrower than the 34:1 ratio at HF. This former ratio should favor accumulation of NH44+ and NO3− and subsequent NO3− leaching. Laboratory measurements suggest that the forest floor of TLW may have higher N mineralization rates than HF. Fluxes of N and S within the vegetation were generally similar at both sites, except that net requirement of N at TLW was substantially lower (difference of 9.4 kg N•ha−1•year−1). The higher NO3− leaching from TLW compared with HF may be attributed mostly to stand maturity coupled with tree mortality, but the absence of slow decomposing beech leaf litter and lower C:N ratio in the soil of the former site may also be contributing factors.

Seasonal and spatial variations in soil nitrogen and phosphorus supply rates in a boreal aspen forest

“…The amounts of NO 3 --N accumulated on the resin in the Ae horizons increased as the amounts increased in the forest-floor horizon, suggesting that nitrate released in the organic layers is leached down to the Ae horizon. Mitchell et al (1992b) have reported that the dominant form of inorganic N leached through forest soils is NO 3 --N in hardwood forests. Rates of NH 4 + -N accumulation on the resin varied from 0.5 to 6 µg 10 cm -2 2 wk -1 for the Ae horizon and from 0.4 to 12 µg 10 cm -2 2 wk -1 for the forest-floor horizons.…”

A hierarchical approach for simulating northern forest dynamics

“…An area in central Ontario, Canada not far from the study region has been reported to receive around 7 kg/ha per year through this flux (Mitchell et al, 1992). While this is lower than that reported for areas in New England (USA) (Bormann et al, 1977;Mitchell et al, 1992;Bormann and Likens, 1994), this is not surprising as the upper Lake States are more isolated from the industrial and automotive sources of N. Currently, NORTHWDS assumes atmospheric deposition of N is assumed to be a constant 7 kg/ha per year.…”

The application of an integrated biogeochemical model (PnET‐BGC) to five forested watersheds in the Adirondack and Catskill regions of New York

“…However, the model-predicted root litter was greater than the measured values. At a hardwood plot adjacent to the Arbutus watershed, Mitchell et al (1991) estimated nitrogen litter fall (foliar plus woody) and net uptake (increment in bole and wood plus litter fall) to be 44Ð8 kg ha 1 year 1 and 44Ð7 kg ha 1 year 1 respectively. The estimates by Mitchell et al (1991) did not include the root litter, whereas the modelled litter fall and uptake fluxes of nitrogen (77Ð3 kg ha 1 year 1 and 81Ð9 kg ha 1 year 1 respectively) included the root litter and thus were higher than values reported by Mitchell et al (1991).…”

“…At a hardwood plot adjacent to the Arbutus watershed, Mitchell et al (1991) estimated nitrogen litter fall (foliar plus woody) and net uptake (increment in bole and wood plus litter fall) to be 44Ð8 kg ha 1 year 1 and 44Ð7 kg ha 1 year 1 respectively. The estimates by Mitchell et al (1991) did not include the root litter, whereas the modelled litter fall and uptake fluxes of nitrogen (77Ð3 kg ha 1 year 1 and 81Ð9 kg ha 1 year 1 respectively) included the root litter and thus were higher than values reported by Mitchell et al (1991). For the same reason, the modelled litter fall and uptake fluxes of sulphur (9Ð6 kg ha 1 year 1 and 7Ð2 kg ha 1 year 1 respectively) were greater than the values of 4Ð0 kg ha 1 year 1 and 5Ð3 kg ha 1 year 1 respectively obtained by Mitchell et al (1991).…”