Evidence for differential effects of reduced and oxidised nitrogen deposition on vegetation independent of nitrogen load. (January 2016)

• Record Type: Journal Article
• Authors: van den Berg, Leon J.L.; Jones, Laurence; Sheppard, Lucy J.; Smart, Simon M.; Bobbink, Roland; Dise, Nancy B.; Ashmore, Mike R.
• Is Part Of: Environmental pollution. Volume 208:Part B(2016)
• Page Start: 890
• Page End: 897
• Publication Date: 2016-01
• Subjects: NHx:NOy ratio -- N deposition -- Countryside survey -- Acidification -- Grassland -- Heathland -- Bogs; Pollution -- Periodicals; Pollution -- Environmental aspects -- Periodicals; Environmental Pollution -- Periodicals; Pollution -- Périodiques; Pollution -- Aspect de l'environnement -- Périodiques; Pollution -- Effets physiologiques -- Périodiques; Pollution; Pollution -- Environmental aspects; Periodicals; Electronic journals; 363.73
• DOI: 10.1016/j.envpol.2015.09.017
• Languages: English
• ISSNs: 0269-7491

Abstract

Abstract: Nitrogen (N) deposition impacts natural and semi-natural ecosystems globally. The responses of vegetation to N deposition may, however, differ strongly between habitats and may be mediated by the form of N. Although much attention has been focused on the impact of total N deposition, the effects of reduced and oxidised N, independent of the total N deposition, have received less attention. In this paper, we present new analyses of national monitoring data in the UK to provide an extensive evaluation of whether there are differences in the effects of reduced and oxidised N deposition across eight habitat types (acid, calcareous and mesotrophic grasslands, upland and lowland heaths, bogs and mires, base-rich mires, woodlands). We analysed data from 6860 plots in the British Countryside Survey 2007 for effects of total N deposition and N form on species richness, Ellenberg N values and grass:forb ratio. Our results provide clear evidence that N deposition affects species richness in all habitats except base-rich mires, after factoring out correlated explanatory variables (climate and sulphur deposition). In addition, the form of N in deposition appears important for the biodiversity of grasslands and woodlands but not mires and heaths. Ellenberg N increased more in relation to NHx deposition than NOy deposition in all but one habitat type. Relationships between species richness and N form were habitat-specific: acid and mesotrophic grasslands appear more sensitive to NHx deposition while calcareous grasslands and woodlands appeared more responsive to NOy deposition. These relationships are likely driven by the preferences of the component plant species for oxidised or reduced forms of N, rather than by soil acidification. Highlights: N deposition was significantly related to species richness in all habitats except base-rich mires. Form of N in deposition was related to biodiversity in grasslands and woodlands. Reduced N deposition was related to higher Ellenberg N values in all but one habitat type. Reduced N was negatively related to species richness in acid and mesotrophic grasslands. Abstract : Effects of total N deposition and reduced and oxidised N deposition were studied across eight habitat types in the UK using data from the British Countryside Survey.