Geoindicators of recovery threshold in highly degraded landscape of Northwestern Argentina
by
José M. Sayago
Instituto de Geociencias y Medio Ambiente , Universidad Nacional de Tucumán. Miguel Lillo 205, 4000 - San Miguel de Tucumán, Argentina
Coauthors: Adriana Niz (Facultad de Ciencias Ecastas y Tecnología, Universidad Nacional de Catamarca, Argentina). Mario A. Toledo (Instituto de Geociencias y Medio Ambiente, Universidad Nacional de Tucumán, Argentina)

The Northwest of Argentina was affected during centuries by deforestation of native forest, exhaustive overgrazing and irrestric cultivation resulting in strong modification of the primitive ecosystems and high land degradation. In order to asses the response to climatic change modifications in natural vegetation, rainfal erosion, sediment transport to river and soil degradation were monitoring in the arid, semi-arid and dry/wet sub-tropical ecosystem during the 1970-90 period of rainfall increase.

In the western Catamarca province under very dry climatic conditions, the rainfall increase influenced gully erosion and sediment transport but the recovery of natural vegetation was poor. In the western Chaco plain under dry/wet sub-tropical climate, the rainfall increase also influenced in water erosion, mass movement and sediment transport to river and the recovery of natural vegetation was poor in the piedmont of pre-andean ridges and Chaco plain but with a clear recovery in the easterly slope still covered by rainforest. In summary, the landscape under arid and semi-arid conditions (“espinal”) denoted a clear increase in soil erosion and sediment transport to river but poor vegetation recovery during the period of high rainfall. In the dry sub-tropical region lands formerly covered by the Chaco forest present high soil degradation and fluvial metamorpohosis after few year of intensive cropping. In the upper basin still covered by the Yunga wet sub-tropical, a decrease in erosion and sediment transport was denoted with the progress of the rainy period, probably by means of the natural vegetation recovery. Following the ideas of Schumm (1977) and Verstappen (1983) we propose for the sub-tropical region of north-west Argentina the concept of recovery threshold for highly degraded landscape.

Date received: November 19, 2004