IMASL   20939
INSTITUTO DE MATEMATICA APLICADA DE SAN LUIS "PROF. EZIO MARCHI"
Unidad Ejecutora - UE
artículos
Título:
Changes in hydrology and salinity accompanying a century of agricultural conversion in Argentina
Autor/es:
JAYAWICKREME D; SANTONI CS; KIM J; JOBBAGY EG; JACKSON RB
Revista:
ECOLOGICAL APPLICATIONS
Editorial:
ECOLOGICAL SOC AMER
Referencias:
Lugar: Washington DC; Año: 2011 vol. 21 p. 2367 - 2379
ISSN:
1051-0761
Resumen:
Conversions of natural woodlands to agriculture can alter the hydrologic
balance, aquifer recharge, and salinity of soils and groundwater in ways that influence
productivity and sustainable land use. Using a land-use change chronosequence in semiarid
woodlands of Argentinas Espinal province, we examined the distribution of moisture and
solutes and estimated recharge rates on adjacent plots of native woodlands and rain-fed
agriculture converted 690 years previously. Soil coring and geoelectrical profiling confirmed
the presence of spatially extensive salt accumulations in dry woodlands and pervasive salt
losses in areas converted to agriculture. A 1.1-km-long electrical resistivity transect traversing
woodland, 70-year-old agriculture, and woodland, for instance, revealed a low-resistivity
(high-salinity) horizon between ;3 m and 13 m depth in the woodlands that was virtually
absent in the agricultural site because of leaching. Nine-meter-deep soil profiles indicated a
53% increase in soil water storage after 30 or more years of cultivation. Conservative
groundwater-recharge estimates based on chloride tracer methods in agricultural plots ranged
from ;12 to 45 mm/yr, a substantial increase from the ,1 mm/yr recharge in dry woodlands.
The onset of deep soil moisture drainage and increased recharge led to .95% loss of sulfate
and chloride ions from the shallow vadose zone in most agriculture plots. These losses
correspond to over 100 Mg of sulfate and chloride salts potentially released to the regions
groundwater aquifers through time with each hectare of deforestation, including a capacity to
increase groundwater salinity to .4000 mg/L from these ions alone. Similarities between our
findings and those of the dryland salinity problems of deforested woodlands in Australia
suggest an important warning about the potential ecohydrological risks brought by the current
wave of deforestation in the Espinal and other regions of South America and the world