Nitrogen Cycling and Mass Balance for a Forested Catchment in the Italian Alps – Assessment of Nitrogen Status

Document Type

Article

Journal/Book Title/Conference

Biogeochemistry

Volume

78

Issue

1

Publisher

Springer Verlag

Publication Date

2006

Keywords

nitrogen cycling, mass balance, forested catchment, Italian Alps, assessment, nitrogen status

First Page

97

Last Page

123

Abstract

During 1999–2001 the chemical composition and fluxes were measured in rainfall, throughfall, soil solution and stream water in a remote forested site in the Italian Alps. The analysis of temporal patterns revealed the differential behaviour of nitrogen and sulphur and suggested that different mechanisms controlled their flux. No important changes in sulphate concentration and fluxes emerged as the solution passed through the various components of the forest ecosystem, and temporal variations of SO4 in the soil solution and stream were likely driven by the physical process of dilution. The availability of nitrate and ammonia, by contrast, was drastically reduced as throughfall water entered the soil and passed through the mineral layers, irrespective of season. The calculated hydrochemical budget based on throughfall and soil solution N fluxes revealed that ~80% N retention in the forest soil, corresponding to 12 kg ha−1 yr−1, despite a relatively high N deposition loading (15 kg ha−1 yr−1). Most of the leached nitrogen (90%) was in the organic form. Indicators of the N status of this ecosystem, such as C/N ratio in solid and solution phase of the soil and N foliage content as well as land use history were examined. Despite the strong N retention in the forested part of the catchment, the stream water N–NO3 levels were consistently above 10 μg l−1 suggesting that the Val Masino catchment as a whole was less efficient in processing atmospheric N inputs. This contrasting N behaviour illustrates the role of landscape features, such as the soil cover and vegetation type, that is characteristic of an alpine catchment.

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Originally published by Springer Verlag. Publisher's PDF available through remote link.

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