RELVA Maria Andrea
congresos y reuniones científicas
Direct and indirect effects of introduced ungulates in temperate forests of southern Andes.
RELVA, M. A.
Workshop; Understanding Biodiversity loss: a workshop on forest fragmentation in South America; 2006
Cemagref y Universidad Nacional del Comahue
Abstract At the beginning of XX century several exotic species were introduced in the temperate forests of the southern Andes (Vazquez 2002), particularly due to commercial and sport reasons. Among them, red deer (Cervus elaphus), whose populations are increasing both in geographic range and in abundance (Flueck et al. 2003), and domestic cattle, which constitute the main economical activity of native people living within National Parks. Up to the moment, deer management has contributed more to the conservation of their populations than to their control (Ramilo 1984). In addition to this, the National Park eradication policy of domestic cattle, which occupies 56% of available land of Nahuel Huapi National Park, has failed due to social-economic reasons (Lauría Sorge and Romero 1999). This presentation shows the main results up to the date, about direct and indirect effects of introduced ungulates on natural regeneration of native Austrocedrus chilensis forests. The animal use patterns and some A. chilensis responses against herbivory, at individual and community level have been evaluated through experimental and non-experimental methods. Fieldwork in forests with different histories of animal use and browsing intensities, suggested that A. chilensis is not among preferred consumed species. However, when other more preferred species have been extinguished or have their abundance reduced they are subject to browsing. In these circumstances, and even at moderate levels of browsing, the main effect is to reduce height growth and to produce dwarf individuals. On the other hand, it seems that browsing promotes seedling establishment (Relva and Veblen 1998, Relva and Sancholuz 2000). At community level, through selective feeding, deer alter the competitive ability of the species, producing local extinction of palatable or susceptible species (e.g Ribes magellanicum, Aristotelia chilensis) and dominance of non- palatable or resistant species (e.g Berberis spp). Introduced deer interact synergically together with others disturbances, such as massive tree blowdowns, invasions of exotic plants (Simberloff et al. 2003) and clear-cutting, in modifying successional trajectories of native forests. Finally, future possible research lines are proposed and discussed in order to determine compatible herbivory levels with conservation of native forests.