INVESTIGADORES
CARILLA Julieta
artículos
Título:
150 years of tree establishment, land use and climate changes in neotropical degraded montane grasslands, NW Argentina
Autor/es:
CARILLA, JULIETA; GRAU, HECTOR RICARDO
Revista:
BIOTROPICA
Editorial:
Wiley - Blackwell
Referencias:
Lugar: Zurich; Año: 2010 vol. 42 p. 49 - 58
ISSN:
0006-3606
Resumen:
Degraded grasslands resulting from intensive land use appear to be
highly resistant to tree invasion due to interactions between land use,
climate, grazing and fire. We describe long-term patterns of tropical
montane forest regeneration into degraded grasslands and analyze their
relationships with historical changes in rainfall, grazing and fire in
Los Toldos valley (Northwest Argentina), cloud forest life zone
(1600masl). We used dendrochronological techniques to reconstruct
spatial and temporal patterns of Podocarpus parlatorei establishment
(the dominant tree species in secondary forests) and grassland fires
for the last 150 yr. We assessed current livestock spatial distribution
along the valley through feces sampling. Inferred tree establishment
patterns (i.e., considering age structure and mortality) were analyzed
in relation to temporal and spatial patterns of grazing and fire
derived from our own analyses and from government statistics, and to
rainfall patterns derived from previous dendrochronological
reconstructions. Current grazing intensity was higher close to the
local township. Fire occurrence increased with periods of above-average
rainfall (higher fuel productivity), and tended to increase with
distance to township (less grazing). Tree establishment in grasslands
was spatially associated with high grazing intensity and low fire
frequency, and temporally associated with periods of high grazing
intensity and below-average rainfall. Despite climatic and land-use
changes leading to conditions potentially favorable for trees (i.e.,
more rainfall, less grazing), grasslands persist in this study area,
likely due to the direct (saplings burning) and indirect (soil
degradation and desiccation) effects of recurrent fires, enhanced by
decreasing grazing and increasing rainfall.