Vegetation Type Affects the Relationship Between Soil Carbon to Nitrogen Ratio and Nitrogen Leaching

• Published in: Water, air, and soil pollution Vol. 177; no. 1-4; pp. 335 - 347
• Main Authors: Rowe, E.C, Evans, C.D, Emmett, B.A, Reynolds, B, Helliwell, R.C, Coull, M.C, Curtis, C.J
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer 01.11.2006; Springer Nature B.V
• Subjects: ammonium nitrogen; Applied sciences; atmospheric deposition; Biological and physicochemical phenomena; Carbon; Carbon/nitrogen ratio; Catchment scale; Catchments; coniferous forests; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Environmental monitoring; eutrophication; Exact sciences and technology; forest plantations; grassland soils; Grasslands; heathland soils; Immobilization; immobilization in soil; Leaching; least squares; Natural water pollution; Nitrates; Nitrogen; Pollution; Pollution, environment geology; prediction; simulation models; soil horizons; soil organic carbon; soil pollution; soil surveys; Soils; uptake mechanisms; Vegetation; Vegetation type; vegetation types; water pollution; Water treatment and pollution; watersheds; woodland soils; Woodlands; United Kingdom; Deciduous forest; Heathland and moor; Atmospheric fallout; Plant community; Saturation; Property of soil; deposition; Environmental factor; Nitrates; Forest soil; Nitrogen; pollution; grassland; Eutrophication; Carbon nitrogen ratio; Watershed; Lixiviation; Nutrient; Water pollution; forestry; heathland; retention; Coniferous forest; Grassland soil
• ISSN: 0049-6979; 1573-2932
• DOI: 10.1007/s11270-006-9177-z

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 super(-1) N for deciduous woodland and acid grassland and 50 mol C mol super(-1) N for coniferous woodland and heathland. Upper thresholds were similar, at 24 and 51 mol C mol super(-1) N, respectively, for total inorganic N (NH sub(4) + NO sub(3)) 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.