Successional rates in post-grazing secondary forests in NW Argentina Mountains

CARILLA, JULIETA; GRAU, HECTOR RICARDO; MALIZIA, AGUSTINA

Land use and Mountain Biodiversity

Taylor & Francis Group

Año: 2006; p. 261 - 271

Northwest Argentina’s upper-montane forests occur in a mosaic of different physiognomies, which, in part, reflect different stages of postgrazing forest succession. We analyzed 10 yr of changes in structure and composition of secondary forest permanent plots dominated by Podocarpus parlatorei, Alnus acuminata, and Crinodendron tucumanum, at 1600 to 1800 m elevation, in Sierra San Javier, Tucumán, Argentina. Plots were measured in 1991 and in 2001 and were compared with mature forests dominated by species of the Myrtaceae family. Myrtaceae forests showed the highest values of species richness, whereas early successional forests dominated by A. acuminata showed the lowest. Successional trends in species composition indicated convergence towards mature forests, but secondary forests differed in terms of demographic rates and patterns of succession. A. acuminata forests stored biomass faster, reaching 25 m2/ha of basal area in a few decades. However, due to the short lifespan of A. acuminata and the low recruitment rate of mature forest species, biomass started to decrease in a few decades, and composition tended to be dominated by understory trees, mainly Solanum grossum. Podocarpus parlatorei forests reached very high basal area values (more than 50 m2/ha) and showed recruitment of mature forests species. However, possibly due to the intense intraspecific competition of the dominant trees, these forests showed very small changes in structure and were characterized by slow growth rates. Forests dominated by C. tucumanum were similar to A. acuminata forests in terms of successional patterns, whereas mature forests showed intermediate characteristics between A. acuminata and P. parlatorei forests.