Effects of Exotic Deer on Forest Regeneration and Composition in Northern Patagonia

Abstract

SUMMARY (1) Exotic deer (mostly Cervus elaphus and Dama dama) are abundant in the Andean forests and adjacent Patagonian steppe in the Provinces of Neuquen and Rio Negro where two of Argentina's premier National Parks are located. (2) The effects of exotic deer on forest composition and regeneration were investigated by comparing the vegetation of Isla Victoria, a large island with an abundant deer population, with the nearby Peninsula Quetrihu6 which is free of deer and other large browsing animals. Understorey composition and tree age and size were sampled in the forests dominated by Nothofagus dombeyi and Austrocedrus chilensis in both areas. (3) Deer browsing has nearly eliminated the subcanopy tree, Aristotelia chilensis, which otherwise forms dense understoreys and has significantly reduced the abundance of numerous other woody and herbaceous species. (4) In the two areas studied, N. dombeyi and Austrocedrus occur mainly as post-fire evenaged populations with little or no regeneration. However, as stands age and treefall gaps are created, both canopy species sporadically regenerate. Where deer occur in high numbers they effectively impede this regeneration.