INVESTIGADORES
GRAU Hector Ricardo
congresos y reuniones científicas
Título:
Environmental History and forest regeneration dynamics in a degraded valley of NW Argentina cloud forests
Autor/es:
GRAU, HR; GIL-MONTERO, R; VILLALBA, R; CARILLA, J; ARAOZ, E; MASSE, G; MEMBIELA, M
Lugar:
Waimea, Hawaii
Reunión:
Simposio; Forests in the Mist: Ecology and Conservation of Tropical Montane Cloud Forests; 2004
Institución organizadora:
University of Hawaii
Resumen:
Extensive areas of
cloud forests have been transformed into degraded grasslands due to intense land
use in the past. As a consequence of economic modernization and rural to urban
migration, land use intensity is decreasing in many of these areas. We combined historical analysis of land use
and dendrochronological estimates 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. During the 20th century population
increased and became concentrated in the local capital townships. State and services employment increased while
density of domestic grazers decreased in the second half of the 20th
century. Rainfall increased; the period
post 1970 was the moister of the past 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 that facilitate Podocarpus
dispersal. Only in particular years
following periods of intense fire activity, Alnus acuminata, a very
light-demanding tree species, recruits.
Our study suggests that feedbacks between fire, land use, climate, and
vegetation may promote resilient degraded states that will not recover even when
land use intensity decrease and climatic conditions become favorable for tree
establishment.