Perennial grasses traits as functional markers of grazing intensity in basaltic grasslands of Uruguay

Martín Jaurena1*, Felipe Lezama2, Pablo Cruz3

Natural grasslands in the basaltic region of Uruguay are threatened by an increase in stocking rates and changes in land use. To assess the effect of grazing intensification, plant functional types are proposed as simple tools to aid the monitoring and management of vegetation. In the present study we evaluated the effect of stocking rate increase at community level taking into account plant traits of 23 dominant perennial grass species. In order to identify plant functional types, we determined the grazing response in an experiment with two wethers stocking rates (0.78 and 1.56 livestock units ha-1) quantifying species cover and traits values. Leaf dry matter content (LDMC) and specific leaf area (SLA) were the traits that best described the perennial grasses response to the stocking rate increase and therefore are suggested to be used as functional markers. Three functional types were identified. Low stocking rates were related to functional type A (tall, warm season species with low SLA and high LDMC and functional type B (tall, cool-season species, with intermediate levels of leaf traits). On the other hand, high stocking rate encouraged functional type C (prostrate, warm season species, with high SLA and low LDMC). The classification of a highly diverse community into three functional types and the selection of traits as functional markers candidates is an innovative approach to develop simple and general methods to diagnosis the state of basaltic grasslands in Uruguay and to advise on its management.

Keywords: Natural grasslands, diagnosis, management, stocking rate
1Instituto Nacional de Investigación Agropecuaria INIA, Estación Experimental del Norte, Ruta 5 km 386, Tacuarembó, Uruguay. *Corresponding author (mjaurena@tb.inia.org.uy).
2Universidad de la República, Facultad de Agronomía, Avenida Eugenio Garzón 780, Montevideo, Uruguay. Institut National de la Recherche Agronomique INRA UMR 1428 AGIR, BP 52627, 31326 Castanet-Tolosan, France.