Tendencias sucesionales de los bosques montanos subtropicales del noroeste argentino

Abstract

SUMMARYSubtropical montane forests from NW Argentina are characterized by a mosaic of different forest unities originated after grazing pressure reduction in different successional stages. This study analyzed successional trajectory of four forest situations, in terms of composition, structure and demography; including three secondary forest situations dominated by Alnus acuminata, Crinodendron tucumanum and Podocarpus parlatorei, and one old grow forests situation dominated by Myrtaceae family species. Ten permanent plots established at 1,700 m asl in Sierra San Javier, Tucumán, were permanently monitored in 1991 and re-measured in 1996, 2001 and 2007. Alnus acuminata and C. tucumanum secondary forests presented a fast accumulation of biomass, reaching 181 t/ha in few decades. P. parlatorei forests reached high values of biomass (393 t/ha), similar to those reached by Myrtaceae forest (418 t/ha). However, in both situations, forest biomass decreased due to the mortality of pioneer species that accumulated great amount of basal area and to the low recruitment of old growth forest species. We conclude that despite variability in change rates, secondary forest tended to converge in composition towards more diverse Myrtaceae forest with slow replacement of old growth species and high understory treelet recruitment, as Solanum grossum. These long term studies are useful to understand montane forest dynamic and their ecosystems services, such as their effect in carbon sequestration, watershed protection and regional biodiversity conservation.Key words: biomass, permanent plots, Podocarpus parlatorei, secondary succession, demographic rates. RESUMENLos bosques montanos subtropicales del noroeste argentino forman un mosaico de diferentes unidades boscosas originadas por la reducción de la presión ganadera en distintas etapas sucesionales. Este estudio analizó la trayectoria sucesional de cuatro situaciones boscosas con diferente composición, estructura y demografía, incluyendo tres situaciones de bosques secundarios dominados por Alnus acuminata, Crinodendron tucumanum y Podocarpus parlatorei, y una de bosques maduros dominados por mirtáceas. Se monitorearon 10 parcelas permanentes establecidas en 1991 en la sierra de San Javier, Tucumán a 1.700 m s.n.m., y remedidas en 1996, 2001 y 2007. Los bosques secundarios de A. acuminata y C. tucumanum acumularon biomasa rápidamente, alcanzando 181 t/ha en pocas décadas. Los bosques de P. parlatorei alcanzaron valores elevados de biomasa (393 t/ha), similar a los bosques maduros de mirtáceas (418 t/ha). En ambas situaciones disminuyó la biomasa debido a la muerte de especies pioneras que acumularon gran cantidad de área basal y al reducido reclutamiento de especies arbóreas sucesionalmente tardías. Se concluyó que, a pesar de la variabilidad en las tasas de cambio, los bosques secundarios tendieron a converger composicionalmente hacia bosques de mirtáceas, con un lento reemplazo de especies de bosque maduro y un abundante reclutamiento de especies de sotobosque, destacándose So...

Widespread but heterogeneous responses of Andean forests to climate change

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Niche squeeze induced by climate change of the cold-tolerant subtropical montanePodocarpus parlatorei

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Pathways of megaherbivore rewilding transitions: typologies from an Andean gradient

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