Effects of small mammals and vertebrate predators on vegetation in the Chilean semiarid zone

Abstract

We monitored the cover and seed bank response of shrubs, perennial herbs, and ephemeral plants to experimental exclusion of both the principal rodent herbivore, Octodon degus, and its vertebrate predators from 1989 to 1994 in a semiarid Chilean mediterranean site. Although both richness and species composition of the plant community at the study site were largely determined by abiotic factors (mainly rainfall and soil nutrients), predator and herbivore exclusion had significant effects on the relative abundance of several plant species. Experimental exclusion of herbivores was associated with increased cover of some shrubs and a perennial grass, and decreased cover and seed densities of several ephemerals, especially those exotic or restricted to areas underneath shrubs. Herbivores apparently reduced shrubs through browsing and indirectly affected herb cover and seed densities by opening up areas under shrubs and/or modifying physical and chemical conditions of the soil. Plant responses to predator exclusion were less clear. Nevertheless, higher cover of some shrubs and ephemerals in the presence of predators suggests tritrophic effects through changes in small mammal densities and/or foraging behavior.

Density and biomass responses of ephemeral plants to experimental exclusions of small mammals and their vertebrate predators in the Chilean semiarid zone

“…Higher climate variability in the west coast of South America with uncertain seed production by ephemeral plants may have precluded the development of small mammal granivore guilds (Kerley & Whitford, 1994). In fact, the degu in semiarid north-central Chile is a herbivore which depends more on predictable resources such as leaves and twigs of perennial plants than on ephemerals (Meserve et al, 1984;GutieH rrez et al, 1997). Delayed reproductive response of degu to high herbage production in north-central Chile (Meserve et al, 1995) may also have ameliorating effects on ephemerals due to herbivory.…”

Effect of large and small herbivores on seed and seedling survival of Beilschmiedia miersii in central Chile

“…Although there is some evidence of herbivory from native mammals (Simonetti and Fuentes 1983), introduced mammals such as cows, goats, the European rabbit, and rodents have been considered as the most important herbivores limiting the recruitment of woody species in central Chile (Simonetti and Fuentes 1983, Gutiérrez et al 1997, 2007, Henríquez and Simonetti 2001, Holmgren 2002, Becerra and Bustamante 2008. Therefore, herbivory by exotic mammals can be a major constraint on the conservation and restoration of Chilean native plant species.…”

Nurse effect and herbivory exclusion facilitate plant colonization in abandoned mine tailings storage facilities in north-central Chile

“…Herbivory is one of the main negative biotic interactions that can hinder plant regeneration in any kind of environment (Gutiérrez et al 1997, Padilla & Pugnaire 2006. The ef fect can be slight, or even benefi cial for plants, as occurs in some grazing systems (Hodgson 1990, Briske 1996.…”