INVESTIGADORES
FARJI-BRENER Alejandro Gustavo
artículos
Título:
Discriminating direct and indirect effects of exotics grazers on native plant cover in the Monte desert of Argentina
Autor/es:
TADEY, MARIANA; FARJI-BRENER, ALEJANDRO GUSTAVO
Revista:
JOURNAL OF ARID ENVIRONMENTS
Editorial:
ACADEMIC PRESS LTD-ELSEVIER SCIENCE LTD
Referencias:
Año: 2007 vol. 69 p. 526 - 536
ISSN:
0140-1963
Resumen:
The relationship between exotic mammalian herbivores (EMH) and the native vegetation has often been focused on direct effects and viewed it as binary interactions. However, in arid environments indirect effects and the community context may also influence the effect of EMH on plants. We sampled the flora and soil nutrients in seven paddocks that differed in stocking rates, and used structural equation modeling (SEM) to partition the net effect of EMH into direct and indirect effects on the most abundant plant species of the Monte desert of Argentina. We proposed two indirect effects by which EMH can modify the cover of a focal plant species: the modification of the assemblage plant cover (APC) and alteration of soil nutrients (SN). Indirect effects appear to be as important as direct ones. EMH did not affect the status of soil nutrients; thus indirect effects through this pathway were irrelevant. Conversely, EMH always affected the APC negatively, but the effect of APC on a focal plant varied according to their identity. Therefore, indirect effects through the APC were positive or negative depending on plant species. Several possible mechanisms explaining how changes in the cover of nearby plants can alter the cover of a focal plant species are discussed. These results emphasize the importance of indirect interactions to explain the complex relationship between EMH and native plant cover in arid ecosystems.