Grazing effects on biological soil crusts and their interaction with shrubs and grasses in an arid rangeland.

MARÍA S. TABENI; IRENE GARIBOTTI; CLARA PISSOLITO; JULIETA N. ARANIBAR

JOURNAL OF VEGETATION SCIENCE

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2014 vol. 25 p. 1417 - 1425

1100-9233

Question: Biological soil crust (BSC) communities can be used in the identifica-tion and monitoring of degradation. A key question is how landscape-scale live-stock disturbance and other local-scale factors influence BSC communities. Wehypothesize that at the landscape scale, increased grazing pressure would lead todecreasing cover of BSC, but at the local scale biotic interactions between BSCand vascular plants would modulate the influence of grazing on BSC.Methods: Spatially explicit sampling of vegetation composition and cover wasconducted using point-sampling methods in digital images along two distur-bance gradients in the central Monte Desert in Argentina.Results: The grazing gradient is the major determinant of changes in the struc-ture of plant communities at the landscape scale. Approximately 1500 to2000 m from a watering point, there is a threshold in vegetation structure asso-ciated with a nonlinear trend of the BSC, herb, grass and shrub cover. Bivariatespatial patterns show attraction between BSC and shrubs in the vicinity of settle-ments, and repulsion between BSC and both grasses and litter in less disturbedsites.Conclusion: Grazing affects BSC directly through trampling and indirectly byaltering vascular plant communities that interact with the BSC communities.Both these effects vary according to the spatial scale being considered. Theresults evidence that understanding of livestock impact in structuring arid eco-systems requires an integrated analysis of BSC and vascular plant communitiesat different spatial scales.