ecological assessment of the influence of grazing on plant community structure

• Published in: The Journal of ecology 1972-07, Vol.60 (2), p.333-342
• Main Authors: Ares, J.O, Leon, R.J.C
• Format: Article
• Language: English
• Subjects: Biomass; Biotopes; Community structure; Grasses; Grazing; Grazing intensity; Plant communities; plant ecology; Plants; Range management; Vegetation structure
• ISSN: 0022-0477; 1365-2745
• DOI: 10.2307/2258350

Spatial biotope heterogeneity may constitute an obstacle to the understanding of successional changes in plant communities. Selection, by means of the criteria of the Zürich-Montpellier phytosociological school, of relatively homogeneous units from the total biotope or mosaic of an area helps to overcome this difficulty. Nevertheless the application of this methodology is restricted by the particular scale of biotope heterogeneity and, on account of this, vegetational units are defined in the present study also in terms of similarity indices of the different stands from each community. An equitability index has proved useful to characterize structural successional changes in a grassland community submitted to artificial mowing. A similar analysis applied to relatively homogeneous units of a grassland biotope may help to evaluate successional processes in that ecosystem. In accordance with these considerations, two plant communities from a grassland area were analysed, and equitability indices of several stands subject to different grazing pressures were calculated, for two fields in Verόnica, Buenos Aires province, Argentina. The changes of slope of the regression between the equitability index of stands showing different range conditions and the relative grazing pressure upon them, as estimated by faeces distribution in the field, suggest that relative species biomass distribution may be used to construct synoptic indicators of grazing impact on plant communities submitted to range conditions, regardless of particular species composition.