Plant responses to grazing: A global synthesis.

Herbivory by domestic and wild ungulates is a major driver of global vegetation dynamics. However, grazing is not considered in dynamic global vegetation models, or more generally in studies of the effects of environmental change on ecosystems at regional to global scale. An obstacle to this is a lack of empirical tests of several hypotheses linking plant traits with grazing. We, therefore, set out to test whether some widely recognized trait responses to grazing are consistent at the global level. We conducted a meta-analysis of plant trait responses to grazing, based on 197 studies from all major regions of the world, and using six major conceptual models of trait response to grazing as a framework. Data were available for seven plant traits: life history, canopy height, habit, architecture, growth form (forb, graminoid, herbaceous legume, woody), palatability, and geographic origin. Covariates were precipitation and evolutionary history of herbivory. Overall, grazing favoured annual over perennial plants, short plants over tall plants, prostrate over erect plants, and stoloniferous and rosette architecture over tussock architecture. There was no consistent effect of grazing on growth form. Some response patterns were modified by particular combinations of precipitation and history of herbivory. Climatic and historical contexts are therefore essential for understanding plant trait responses to grazing. Our study identifies some key traits to be incorporated into plant functional classifications for the explicit consideration of grazing into global vegetation models used in global change research. Importantly, our results suggest that plant functional type classifications and response rules need to be specific to regions with different climate and herbivory history.

Fil: Díaz, Sandra Myrna. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina

Fil: Lavorel, Sandra. Universite Joseph Fourier; Francia

Fil: McIntayre, Sue. CSIRO Sustainable Ecosystems; Nueva Zelanda

Fil: Falczuk, Valeria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina

Fil: Casanoves, Fernando. Universidad Nacional de Córdoba. Facultad de Ciencias Agropecuarias; Argentina

Fil: Milchunas, Daniel G.. CSIRO Sustainable Ecosystems; Nueva Zelanda. State University of Colorado - Fort Collins; Estados Unidos

Fil: Skarpe, Christina. Norwegian Institute for Nature Research; Noruega

Fil: Rusch, Graciela. Norwegian Institute for Nature Research; Noruega

Fil: Sternberg, Marcelo. CSIRO Sustainable Ecosystems; Nueva Zelanda. Tel Aviv University; Israel

Fil: Noy-meir, Imanuel. The Hebrew University of Jerusalem; Israel

Fil: Landsberg, Jill. CSIRO Sustainable Ecosystems; Nueva Zelanda

Fil: Zhang, Wei. University of British Columbia; Canadá

Fil: Clark, Harry. Grasslands Research Centre; Nueva Zelanda

Fil: Campbell, Bruce D.. Hort Research Mt Albert; Nueva Zelanda