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Nitrogen Retention Capacity of a Northern Hardwood Forest Soil Under Ammonium Sulfate Additions
To determine the N‐retaining capacity of a beech‐dominated stand in the Hubbard Brook Experimental Forest, we added (NH4)2SO4 at three levels (40, 160 and 520 kg N°ha‐1°yr‐1) to replicate plots in monthly increments for two years, and measured NH4+ and NO3‐ concentrations in monthly samples from zero‐tension lysimeters. The two lower treatment levels failed to increase N loss through the deepest soils horizon when compared to controls. Plots under the highest treatment level retained >95% of the added N; NH4+ accounted for 77% of the leaching loss. The treatments caused an accumulation of exchangeable NH4+ in the soil, but concentrations of exchangeable NO3‐ remained small, even after samples were incubated at room temperature. Leaching, uptake by plants, and the increase exchangeable NH4+ accounted for 3‐25% of the added N. Accumulation of available N without nitrification contradicts common expectations concerning N saturation. It was not clear why excess N was not nitrified.
Nitrogen Retention Capacity of a Northern Hardwood Forest Soil Under Ammonium Sulfate Additions
To determine the N‐retaining capacity of a beech‐dominated stand in the Hubbard Brook Experimental Forest, we added (NH4)2SO4 at three levels (40, 160 and 520 kg N°ha‐1°yr‐1) to replicate plots in monthly increments for two years, and measured NH4+ and NO3‐ concentrations in monthly samples from zero‐tension lysimeters. The two lower treatment levels failed to increase N loss through the deepest soils horizon when compared to controls. Plots under the highest treatment level retained >95% of the added N; NH4+ accounted for 77% of the leaching loss. The treatments caused an accumulation of exchangeable NH4+ in the soil, but concentrations of exchangeable NO3‐ remained small, even after samples were incubated at room temperature. Leaching, uptake by plants, and the increase exchangeable NH4+ accounted for 3‐25% of the added N. Accumulation of available N without nitrification contradicts common expectations concerning N saturation. It was not clear why excess N was not nitrified.
Nitrogen Retention Capacity of a Northern Hardwood Forest Soil Under Ammonium Sulfate Additions
Christ, Martin (author) / Zhang, Yimin (author) / Likens, Gene E. (author) / Driscoll, Charles T. (author)
Ecological Applications ; 5 ; 802-812
1995-08-01
11 pages
Article (Journal)
Electronic Resource
English