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The grazing fingerprint : modelling species responses and trait patterns along grazing gradients in semi-arid African savannas

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Wesuls, Dirk ; Pellowski, Magdalena ; Suchrow, Sigrid ; Oldeland, Jens ; Jansen, Florian ; Dengler, Jürgen:
The grazing fingerprint : modelling species responses and trait patterns along grazing gradients in semi-arid African savannas.
In: Ecological Indicators. Bd. 27 (2013) . - S. 61-70.
ISSN 1470-160x
DOI: https://doi.org/10.1016/j.ecolind.2012.11.008

Abstract

Persistence or disappearance of plants under grazing pressure has led to their categorisation as grazingincreasers or decreasers. We aimed to extend this classical indicator concept in rangeland ecologyby interpreting the shape of species responses and trait patterns modelled along continuous grazinggradients at different spatial scales.Taking transects of two different lengths, we recorded the cover of vascular plant species along grazinggradients in central Namibian rangelands. We used a hierarchical set of ecologically meaningful modelswith increasing complexity – the HOF (Huisman–Olff–Fresco) approach – to investigate species’ grazingresponses, diversity parameters and pooled cover values for two traits: growth form and life cycle.Based on our modelling results, we classified species responses into eight types: no response, monotonicincreasers/decreasers, threshold increasers/decreasers, symmetric unimodal responses, left skewedand right skewed unimodal responses.The most common category was that of no response (42% of the short and 79% of the long transectresponses). At both scales, decreaser responses with higher grazing pressure were more frequent thanincreaser responses. Monotonic and threshold responses were more frequent along the short transects.Diversity parameters showed a slight but continuous decline towards higher grazing intensities.Responses of growth form and life cycle categories were mostly consistent at both scales. Trees, shrubs,dwarf shrubs, and perennials declined continuously. Woody forbs tended to show a symmetric unimodaldistribution along the gradients, while herbaceous forbs and annuals showed skewed unimodal responsestowards lower grazing intensities.The different grazing response types proposed in this study allow for a differentiated picture of nichepatterns along grazing gradients and provide a basis to use species as indicators for a continuum ofvegetation states altered by livestock impact. The general decline of plant diversity with increasing grazingintensities highlights the importance of reserves that are less impacted by grazing to support theresilience of the studied system.

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Publikationsform: Artikel in einer Zeitschrift
Begutachteter Beitrag: Ja
Zusätzliche Informationen: BAYCEER119327
Institutionen der Universität: Fakultäten > Fakultät für Biologie, Chemie und Geowissenschaften > Fachgruppe Geowissenschaften > Professur Störungsökologie
Fakultäten > Fakultät für Biologie, Chemie und Geowissenschaften > Fachgruppe Geowissenschaften > Professur Störungsökologie > Professur Störungsökologie - Univ.-Prof. Dr. Anke Jentsch
Fakultäten
Fakultäten > Fakultät für Biologie, Chemie und Geowissenschaften
Fakultäten > Fakultät für Biologie, Chemie und Geowissenschaften > Fachgruppe Geowissenschaften
Titel an der UBT entstanden: Ja
Themengebiete aus DDC: 500 Naturwissenschaften und Mathematik
Eingestellt am: 18 Jun 2015 06:35
Letzte Änderung: 18 Jun 2015 06:35
URI: https://eref.uni-bayreuth.de/id/eprint/15139