IMPACTS OF INTRODUCED LARGE HERBIVORES ON AUSTROCEDRUS-CHILENSIS FORESTS IN NORTHERN PATAGONIA, ARGENTINA

Austrocedrus chilensis (D. Don) et Boutleje (Cupressaceae) is an endem ic conifer of northern Patagonia, Argentina and south-central Chile, w hich has been affected by browsing by livestock and introduced deer (e specially red deer). In northern Patagonia, we studied the effects of livestock and deer on the densities and heights of Austrocedrus saplin gs and on the structure and floristic composition of the vegetation in which this species occurs under a variety of different browsing regim es. Twenty-seven stands were sampled within the 'Compact' forest type (i.e., dense and pure) of Austrocedrus in both national reserves and o n unprotected properties. Principal components analysis (PCA) indicate s that greater abundance of Austrocedrus saplings is associated with l ower stand basal areas as expected for this relatively shade-intoleran t species. Although browsing does not directly reduce the abundance of saplings, it has an important influence in terms of reducing height g rowth and producing deformed stems. Multiple correspondence analysis ( MCA) indicates that saplings between 0.5 and 1 m in height were more f requently browsed than other height classes; saplings shorter than 0.3 m in height were not greatly influenced by browsing. Saplings of inte rmediate heights (0.5-1 m) were scarce at sites lacking any current br owsing, but this may reflect release of saplings from earlier browsing and subsequent inhibition of continued recruitment into intermediate height classes. High browsing indexes occur beneath canopy gaps, which are also sites of higher sapling densities. In the present study, sit es characterized by heavy browsing also have a high cover of spiny shr ubs (Berberis spp.) and other unpalatable woody species (e.g., Lomatia hirsuta). Where the preferred browse species, Schinus patagonicus, is abundant, Austrocedrus is less influenced by browsing. However, as br owsing reduces the abundance of S. patagonicus, Austrocedrus becomes a preferred species. Austrocedrus stands that are in a phase of fine-sc ale gap-phase regeneration are the most susceptible to inhibition of t ree regeneration by livestock and deer browsing. In such stands, long- term persistence of a forest cover requires protection from large brow sing animals. (C) 1998 Elsevier Science B.V. All rights reserved.