CONICET | Buscador de Institutos y Recursos Humanos

Many areas of cloud forests have been transformed into degraded grasslands due to intense land use in the past. This trend is being reverted in many areas, as a consequence of economic modernization and rural to urban migration. We combined historical analysis of land use and dendrochronological reconstructions of climate, fire and tree establishment to explore the interactions between climate, socioeconomic changes and vegetation dynamics in a degraded valley in the cloud forest life zone of NW Argentina. Historical records indicate that although population increased, it become concentrated in the local capital townships. State and services employment increased as density of domestic grazers decreased dramatically in the second half of the 20th century. Following a regional pattern, rainfall increased and the period post 1970 was the moister of the last 250 years. Despite these trends, the most abundant secondary species are not colonizing degraded grasslands. The increase in rainfall and decrease in grazing intensity is negatively associated to tree recruitment, particularly in the case of Podocarpus parlatorei, the dominant tree species in secondary forests. We interpret that decreasing grazing and increasing rainfall favored grasslands over shrublands. Grasslands are maintained with frequent fires, which eliminate Podocarpus seedlings and unpalatable shrubs which favour Podocarpus dispersal. On in particular years following fire intense periods, Alnus acuminata a highly pioneer tree species, recruits. Our study suggest that feedbacks between fire, land use, climate, and vegetation may promote resilient degraded states that will not recover even in conditions of decreasing land use intensity.

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