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Do grazers alter nitrogen dynamics on grazing lawns in a South African savannah?

2010; Wiley; Volume: 49; Issue: 1 Linguagem: Inglês

10.1111/j.1365-2028.2010.01236.x

1365-2028

Corli Coetsee, William D. Stock, Joseph M. Craine,

Horticultural and Viticultural Research

African Journal of EcologyVolume 49, Issue 1 p. 62-69 Do grazers alter nitrogen dynamics on grazing lawns in a South African savannah? Corli Coetsee, Corresponding Author Corli Coetsee Department of Botany, University of Cape Town, Rondebosch 7701, South Africa School of Natural Resource Management, Nelson Mandela Metropolitan University, George 6530, South Africa*Correspondence: E-mail: [email protected]; [email protected]Search for more papers by this authorWilliam D. Stock, William D. Stock Department of Botany, University of Cape Town, Rondebosch 7701, South Africa Centre for Ecosystem Management, Edith Cowan University, 270 Joondalup Drive, Joondalup, WA 6027, AustraliaSearch for more papers by this authorJoseph M. Craine, Joseph M. Craine Division of Biology, Kansas State University, Manhattan, KS 66506, U.S.A.Search for more papers by this author Corli Coetsee, Corresponding Author Corli Coetsee Department of Botany, University of Cape Town, Rondebosch 7701, South Africa School of Natural Resource Management, Nelson Mandela Metropolitan University, George 6530, South Africa*Correspondence: E-mail: [email protected]; [email protected]Search for more papers by this authorWilliam D. Stock, William D. Stock Department of Botany, University of Cape Town, Rondebosch 7701, South Africa Centre for Ecosystem Management, Edith Cowan University, 270 Joondalup Drive, Joondalup, WA 6027, AustraliaSearch for more papers by this authorJoseph M. Craine, Joseph M. Craine Division of Biology, Kansas State University, Manhattan, KS 66506, U.S.A.Search for more papers by this author First published: 14 September 2010 https://doi.org/10.1111/j.1365-2028.2010.01236.xCitations: 37Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat Abstracten The presence of grazers on grazing lawns in East Africa and North America often alters nitrogen cycling and availability. Grazing lawns can be defined as areas where grasses are kept in a short, actively growing, palatable state by the action of grazers. Our aim was to test whether lawns have enhanced leaf nitrogen (N) concentrations, total soil N and δ15N when compared to tall grass areas in a South African savannah. Previous studies have used ecosystem δ15N as a proxy of N availability, and enriched δ15N values have been suggested to indicate higher N availability or higher N transformation rates. Across all sites, foliar N concentrations (but not soil N) were higher when compared to tall grass areas, and evidence of enriched foliar and soil δ15N values was found on the lawns. These results suggest that grazers may be involved in altering the rates of N transformations directly on grazing lawns. Regardless of whether these N transformations included increased net N mineralization, higher N concentrations in above-ground foliage attract grazers back to the lawns, encouraging their maintenance. Résuméfr La présence de brouteurs sur les pâturages « grazing lawns » d'Afrique de l'Est et d'Amérique du Nord modifie souvent le cycle et la disponibilité de l'azote. On peut définir ces grazing lawns comme des endroits où l'herbe est maintenue courte et nutritive, en croissance active, sous l'action du broutage. Notre but était de tester si ces lawns avaient des concentrations plus fortes en azote (N) dans les feuilles, et en azote total N et en δ15N dans le sol, par comparaison avec les zones de hautes herbes d'une savane d'Afrique du Sud. Des études antérieures ont utilisé le δ15N de l'écosystème comme proxy pour la disponibilité en azote, et on a suggéré que des valeurs supérieures de δ15N indiquaient une plus grande disponibilité en azote ou un taux plus élevé de transformation de l'azote. Dans tous les sites, la concentration foliaire en azote (mais pas l'azote du sol) était supérieure à celle des zones d'herbes hautes, et l'on a trouvé des preuves de valeurs de δ15N enrichies dans les feuilles et le sol de ces prairies. Ces résultats laissent penser que les herbivores peuvent être directement impliqués dans la modification du taux de la transformation de l'azote dans les grazing lawns. Que ces transformations incluent ou non une plus forte minéralisation nette en azote, de plus hautes concentrations d'azote dans les feuilles aériennes attirent les herbivores vers les lawns, ce qui favorise leur maintien. References Aranibar, J.N., Anderson, I.C., Epstein, H.E., Feral, C.J.W., Swap, R.J., Ramontsho, J. & Macko, S.A. (2008) Nitrogen isotope composition of soils, C3 and C4 plants along land use gradients in southern Africa. J. Arid Environ. 72, 326–337. Archibald, S. 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