Abstract

ARTURI, M.F; GRAU, H.R.; ACENOLAZA, P. G.  and  BROWN, A.D.. Estructura y sucesión en bosques montanos del Noroeste de Argentina. Rev. biol. trop [online]. 1998, vol.46, n.3, pp.525-532. ISSN 0034-7744.

Floristic composition and tree size distribution of different forest patches were studied between 1600 and 1800 m altitude in the Subtropical Montane Forests of Parque Biológico Sierra de San Javier, Argentina. Quadrats (20 x 20 m) were sampled in 12 sites. Sites were ordered using correspondence analysis. The first ordination axis was clearly associated to a gradient in complexity and diversity. The less complex forests were dominated by Alnus acuminata, Podocarpus parlatorei, and Crinodendron tucumanum. Richest and most complex forests were dominated by Myrtaceae species such as Blepharocalyx salicifolius, Myrcianthes mato and Myrcianthes pseudomato, accompanied by Cedrela lilloi, Ilex argentina, Prunus tucumanensis, and others. Intermediate values of diversity and complexity were found in mature forests of A. acuminata and P. parlatorei, and in forests dominated by the treelets Dunalia lorentzii, Sambucus peruviana and Solanum grossum. Sites were grouped using the Twinspan software package. Within each cluster, diameter distribution of the most important species was used to describe regeneration trends. Myrtaceae species showed an "inverted-J" distribution of diameter, suggesting a continous regeneration mode. On the other hand, species which dominate simple forests such as A. acuminata, P. parlatorei, and C. tucumanum showed bell-shaped diameter distribution, suggesting lack of regeneration under the canopy. These conclusions were also supported by seedling and sapling densities. The results suggest that A. acuminata, P. parlatorei, and C. tucumanum are pioneer species, and that the forests dominated by such species were originated in grasslands or shrublands. These species seems to be gradually replaced by shade tolerant taxa originating patchy heterogeneity and landcape diversity as a result of discrete events of recruitment followed by forest succession.

Keywords : Montane forests; cloud forests; forest structure; succesion; disturbance; Yungas; Argentina.