INVESTIGADORES
GRAU Hector Ricardo
artículos
Título:
Fire-Mediated Forest Encroachment in Response to Climatic and Land-Use Change in Subtropical Andean Treelines
Autor/es:
ARAOZ, E; GRAU, HR
Revista:
ECOSYSTEMS (NEW YORK. PRINT)
Editorial:
SPRINGER
Referencias:
Año: 2010 vol. 13 p. 992 - 1005
ISSN:
1432-9840
Resumen:
We used dendroecological techniques to analyze
the effects of rainfall and grazing on fire regime and
its implications for tree regeneration in subtropical
mountains of northwestern Argentina during the
20th century, a period characterized by increasing
rainfall and decreasing land-use intensity. We
dated fire scars and establishment of Alnus acuminata
(the dominant tree species) in six watersheds
along a 600 km latitudinal range. We correlated
fire frequency with rainfall records and performed
Superposed Epoch Analyses to assess the relationship
between rainfall and fire events during the
century, and in two sub-periods: 19301965 (low
rainfall, high grazing) and 19662001 (high rainfall,
low grazing). We performed permutation
analyses to assess the association between fire
events and tree establishment, and to describe the
spatial distribution of fires and forests in relation to
hillslope aspect. Rainfall was associated with
regional fires at interannual and decadal scales: fire
probability increased after growing seasons with
above-average rainfall and through the century, in
concurrence with rainfall increase. The climatic
control of fire was stronger under lower land-use
intensity. Tree establishment was temporally associated
with fire events, which occurred mainly in
north facing slopes, where grassland cover is more
extensive and forest colonization more likely.
These results suggest that fire is limited by the
availability of fine fuels, which is enhanced by high
rainfall and reduced grazing; and tree establishment
is limited by the competition with grasses.
Consequently, increasing rainfall and decreasing
grazing favored higher fire frequency, thus promoting
forest encroachment during 20th century.