Introduced Species and Management of a Nothofagus/Austrocedrus Forest

Abstract

Isla Victoria (Nahuel Huapi National Park, Argentina), a large island dominated by native Nothofagus and Austrocedrus forest, has old plantations of many introduced tree species, some of which are famed invaders of native ecosystems elsewhere. There are also large populations of introduced deer and shrubs that may interact in a complex way with the introduced trees, as well as a recently arrived population of wild boar. Long-standing concern that the introduced trees will invade and transform native forest may be unwarranted, as there is little evidence of progressive invasion, even close to the plantations, despite over 50 years of opportunity. Introduced and native shrubs allow scattered introduced trees to achieve substantial size in abandoned pastures, but in almost all areas neither the trees nor the shrubs appear to be spreading beyond these sites. These shrub communities may be stable rather than successional, but the technology for restoring them to native forest is uncertain and probably currently impractical. Any attempt to remove the exotic tree seedlings and saplings from native forest would probably create the very conditions that would favor colonization by exotic plants rather than native trees, while simply clear-cutting the plantations would be unlikely to lead to regeneration of Nothofagus or Austrocedrus. The key to maintaining native forest is preventing catastrophic fire, as several introduced trees and shrubs would be favored over native dominant trees in recolonization. Deer undoubtedly interact with both native and introduced trees and shrubs, but their net effect on native forest is not yet clear, and specific management of deer beyond the current hunting by staff is unwarranted, at least if preventing tree invasion is the goal. The steep terrain and shallow soil make the recently arrived boar a grave threat to the native forest. Eradication is probably feasible and should be attempted quickly.

Propagule Pressure: A Null Model for Biological Invasions

“…For example, prescribed burnings designed to open space for native species may prove futile if propagules from nearby populations of NIS are not precluded from subsequent colonization (e.g. Simberloff et al 2003).…”

Predicaments of endangered huemul deer, Hippocamelus bisulcus, in Argentina: a review

“…Hence, Serret (2001) cautioned that NP may not contain viable subpopulations: according to Reed et al (2003), no group qualifies as viable. Settlers within NP raise livestock (Martin and Chehebar 2001), utilizing up to 56% of park areas (Simberloff et al 2003), but commonly run several fold more livestock than permitted (Serret et al 1994). Although parts of NP with huemul were declared 'Critical Areas', 90% of the area is still exclusively used by cattle and only 10% by huemul.…”

Cytisus scoparius (Fam. Fabaceae) in southern Brazil - first step of an invasion process?

“…The global distribution of Scotch broom is related to European colonization around the world, to land conversion into agricultural lands and exotic tree plantations of economic value (Pauchard and Alaback 2004). A globally pervasive species and a common garden escapee (Peterson andPrasad 1998, Mkhize et al 2013), Cytisus scoparius has been shown to cause signifi cant declines in native biodiversity around the world (Bossard 1996, Simberloff and Martín Nuñez 2003, Shaben and Myers 2010, Srinivasan 2012. The species has negative impacts on forestry in natural forests and tree plantations, modifi es the species composition at invaded sites, and hampers the establishment of rare endemic taxa, favoring generalist fauna, along with shade-tolerant and exotic fl ora (Zielke et al 1992, Zarri et al 2006, Shaben and Myers 2010, Srinivasan 2012.…”

“…also at risk but to a lesser extent (Potter et al 2009). However, until now Scotch broom has only been cited from scattered montane localities in the Valdivian temperate forests of Chile and Argentina RODRIGO LEÓN CORDERO, FÁBIO P. TORCHELSEN, GERHARD E. OVERBECK and MADHUR ANAND (Simberloff and Martín Nuñez 2003, Pauchard and Alaback 2004, INBIAR 2014.…”