The Monkey Puzzle tree in Southern Chile

BEKESSY, S.A., A.C. NEWTON, J.C. FOX, A. LARA, A.C.PREMOLI, M. CORTES, M. GONZÁLEZ, B. BURNS, F. IZQUIERDO & M.A. BURGMAN

Species conservation and management. Case studies using RAMAS GIS

Oxford University Press Inc.

Año: 2004; p. 48 - 63

Commonly known as the Monkey Puzzle tree or Pehuén, Araucaria araucana (Molina) K. Koch (Araucariaceae) is an impressively large and long-lived conifer, attaining 50 m in height, 2.5 m in girth and reaching ages of at least 1300 years (Montaldo 1974).  Its current distribution spans only three degrees of latitude and is divided between a main area straddling both sides of the Andean divide in Chile and Argentina, and two disjunct populations on the Coastal Range, Chile (Figure 1).  The present distribution is a remnant of a more extensive former distribution, which has been severely diminished by logging, human-set fires and land clearance since European colonisation (Veblen 1982). Monkey Puzzle is a socially significant species, producing high-quality timber and providing a unique resource for tourism and recreation.  The tree figures importantly in the religion of the native Pehuenche people and is also valued for its large, edible seeds which are extensively collected for local markets (Aagesen 1998a; Tacón 1999).  Monkey Puzzle has been classified under IUCN guidelines as vulnerable (Farjon & Page 1999) and is currently officially protected in both Chile and Argentina as well as internationally through listing in Appendix I of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).  Despite its protected status and exceptional ecological, economic and cultural significance, this species continues to experience intense human-induced pressures, such as grazing, burning and harvesting, both for seeds and occasionally timber (Aagesen 1998b). The ecology of Monkey Puzzle is disturbance-driven, principally by volcanism, fire, landslides and wind, and it has developed effective adaptations, such as thick bark and epicormic buds, to withstand such disturbances (Burns 1993).  Monkey Puzzle is generally dioecious, but may occasionally be monoecious with predominantly gravity dispersed seed and wind dispersed pollen.  Both seed and pollen are relatively heavy and may not disperse over large distances (Muñoz 1984; Heusser et al. 1988).  Asexual reproduction by root suckering has been reported (Schilling & Donoso 1976), but it is unknown how important this process is to population maintenance and expansion (Veblen et al. 1995). Creating a population model for the Monkey Puzzle tree posed several interesting challenges.  Firstly, the demographic dynamics of Monkey Puzzle operate on time scales that are much longer than those of most other species; adult trees are effectively immortal and growth was not detectable over the three-year measurement period of this study.  This leads to problems with creating a model that is meaningful in the time frame of typical conservation management.  Secondly, as with most tree species, modelling density dependence is a critical aspect to population dynamics, yet complex to incorporate, as the influence of a dominant tree will be far greater than that of a seedling.  Finally, the model needed to include the effect of unpredictable catastrophes (fire and volcanic eruptions), as the distribution of Monkey Puzzle is interspersed with active volcanoes.  Although challenging, a PVA model can be extremely useful in cases such as this, where it is otherwise difficult to predict the consequences of current management practices on the future condition of the species.