Grazing response groups among understorey plants in arid rangelands

Authors

  • Jill Landsberg,

    Corresponding author
    1. CSIRO Division of Wildlife and Ecology, PO Box 84, Lyneham, ACT 2602, Australia;
      Corresponding author: Tel. +61 7 4042 1443; Fax +61 7 4042 1283; E-mail jill.landsberg@dwe.csiro.au
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  • Sandra Lavorel,

    1. Centre d'Ecologie Fonctionnelle et Evolutive, CNRS UPR 9056, 34293 Montpellier Cedex 5, France & Research School of Biological Sciences, Australian National University, Canberra, ACT 0200, Australia
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  • Jacqui Stol

    1. CSIRO Division of Wildlife and Ecology, PO Box 84, Lyneham, ACT 2602, Australia;
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Corresponding author: Tel. +61 7 4042 1443; Fax +61 7 4042 1283; E-mail jill.landsberg@dwe.csiro.au

Abstract

Abstract. We analysed attributes of the understorey flora in different plant communities along two grazing gradients in arid Australian rangelands. We aimed to determine if there were patterns among species in response to grazing, and easily recognizable ‘indicator response types’ for monitoring grazing-induced change in community composition. Measurements were stratified by vegetation patch type, in woody groves and open patches. Trait selection and analyses followed a hierarchical approach which searched for patterns within major plant life forms. Patch type exerted a dominant influence on both life forms and species attributes, but interacted with grazing. Grazing was associated with loss in differentiation of species composition between patch types, rather than loss in numbers of species overall. Heavy grazing was variously associated with small size, prostrate habit, low meristems, small leaves, coated leaves, high regrowth potential, plasticity in response to grazing, and high fecundity; and light grazing with opposing attributes. Many attributes tended to vary independently of each other and grazing-related attribute syndromes were recognisable only among grasses. This could be because the environmental filters acting on the communities have given rise to many different species with different natural attribute combinations, few of which are closely associated with grazing resistance. For grassy communities ‘large, erect tussocks branching above-ground’ and ‘small, sprawling basal tussocks’ may have potential as response types indicative of light and heavy grazing respectively, but no response types could be identified for herbaceous communities.

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