Herbivores regulate native–alien plants dynamics in sub‐Antarctic beech ( Nothofagus antarctica ) forests of Tierra del Fuego, Argentina

SOLER, ROSINA; BUSTAMANTE, GIMENA; CRUZ-ALONSO, VERÓNICA; LENZNER, BERND; ESSL, FRANZ

APPLIED VEGETATION SCIENCE

WILEY-BLACKWELL PUBLISHING, INC

Año: 2023 vol. 26

1402-2001

Questions: What is the role of native and domestic herbivores in native–alienvegetationchanges in sub-Antarcticforests? Does herbivory suppression increase nativewhile reducing alien species diversity?Location: Central–easternTierra del Fuego Island, Argentina.Methods: In four sites, we set up three different treatments: excluded grazing by livestock(cattle), by livestock and native (guanaco) herbivores, and grazed control plotsin Nothofagus antarctica forests. We then monitored the dynamics of understoreynative and alien plants (species richness, abundance) of dicots, monocots, and fernsover 6 years. Generalized Linear Mixed Models were used to determine the effectsof herbivore exclusion and time on species richness and abundance. In addition, wecalculated the abundance rate of change to quantify temporal dynamics.Results: Overall species richness did not change in the exclusion plots, but native andalien abundances were affected by herbivory and time since exclusion. The abundanceof native monocots changed after herbivore exclusion, increasing its dominance significantlyinside exclusion plots. However, the cessation of herbivory did not reducealien species in general. Only alien dicots significantly declined in the livestock exclusiontreatment. Further, we found that the two dominant alien grass species (Holcuslanatus and Poa pratensis) respond differently to grazing exclusion, and their responsewas modulated by forest basal area.Conclusions: Our results indicate that cattle and guanaco grazing had variable effectson native and alien plants, and that herbivore exclusion has a substantially positiveeffect on native grasses. However, the magnitude of temporal changes was more significantfor vegetation richness and abundance than the effect of exclusion treatments.Herbivore exclusions can initiate a rapid recovery of compositional attributesof native vegetation in N. antarctica forests grazed by livestock.