Vegetation type affects the relationship between soil carbon to nitrogen ratio and nitrogen leaching

Rowe, E. C.; Evans, C. D.; Emmett, B. A.; Reynolds, B.; Helliwell, R. C.; Coull, M. C.; Curtis, C. J.. 2006 Vegetation type affects the relationship between soil carbon to nitrogen ratio and nitrogen leaching. Water Air and Soil Pollution, 177. 335-347. 10.1007/s11270-006-9177-z

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Abstract/Summary

Nitrate leaching occurs when the soil's nitrogen immobilisation and plant uptake capacity has been saturated. Several widely-used models of nitrogen saturation incorporate a breakthrough function in which N begins to be leached at C/N values below an upper threshold, and is completely leached at C/N values below a lower threshold. In a survey of deciduous and coniferous woodland, acid grassland and heathland sites for which both C/N and nitrate flux measurements were available, deciduous woodland and acid grassland typically had lower C/N ratios, and began leaching nitrate at a lower C/N ratio, than coniferous woodland and heathland. Least-square fits of nitrate breakthrough functions gave upper thresholds (no nitrate leaching) of 27 mol C mol−1 N for deciduous woodland and acid grassland and 50 mol C mol−1 N for coniferous woodland and heathland. Upper thresholds were similar, at 24 and 51 mol C mol−1 N, respectively, for total inorganic N (NH4 + NO3) leaching flux as a proportion of total inorganic N influx. In conifer plantations, stand maturity had a large effect, suggesting that a breakthrough function is unsuitable for modelling systems that are in disequilibrium. However, there was sufficient evidence to suggest that using different breakthrough C/N thresholds for different groups of vegetation would improve predictions of N saturation and leaching at both plot and catchment scales. The difference may be related to the reactivity of soil carbon; soils with a large proportion of recalcitrant carbon are likely to begin leaching nitrate at a higher C/N value than soils with more labile carbon.

Item Type:	Article
Identification Number/DOI:	10.1007/s11270-006-9177-z
Programmes:	CEH Programmes pre-2009 publications > Biogeochemistry
CEH Sections:	_ Biogeochemistry & Ecosystem Function
ISSN:	0049-6979
Additional Keywords:	deposition, eutrophication, forestry, grassland, heathland, pollution, retention
NORA Subject Terms:	Botany Agriculture and Soil Science
Date made live:	13 May 2008 11:01
URI:	http://nora.nerc.ac.uk/id/eprint/2915

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