EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Erosion and sediment enrichment ratio in volcanic soils

Ludmila La Manna1,2, César Mario Rostagno2,3, Manuela Tarabini1,2, Federico Gomez1,2,4, and Ana Navas5
Ludmila La Manna et al.
  • 1Centro de Estudios Ambientales Integrados (CEAI), Facultad de Ingeniería, Universidad Nacional de la Patagonia San Juan Bosco, Sede Esquel, Chubut, Argentina
  • 2Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina *Corresponding author:
  • 3Unidad de Investigación Ecología Terrestre, CENPAT-CONICET, Puerto Madryn, Chubut, Argentina
  • 4Instituto Nacional de Tecnología Agropecuaria (INTA), Estación Experimental Agroforestal Esquel, Chubut, Argentina
  • 5Estación Experimental de Aula Dei, Spanish National Research Council (EEAD-CSIC), Avda. Montañana 1005, Zaragoza, 50059, Spain.

Patagonian Andean region is widespread affected by soil degradation and erosion processes. The subhumid sector, which corresponds to the transition (ecotone) between the Andean forests and the Patagonian steppe, has suffered the highest human pressure and overgrazing, accelerating the soil erosion processes.

Near Esquel town (Subhumid sector of Chubut province, Argentina), where soils are mainly developed from volcanic ashes, erosion studies based on fallout radionuclides (Caesium-137) and simulated rainfalls were performed. Studies based on Caesium-137 showed that soil losses in the last 50 years were higher than 30 m3 ha-1 year-1 under different land uses.

Rainfall simulation experiments, carried out under the same conditions (Rain fall intensity: 100 mm h-1 for 30 minutes; Drop diameter: 2.5 mm; Drop velocity: 5.3 m s-1) showed that erosion rates are highly affected by land use. Potential erosion rates in degraded rangelands varied between 143 and 750 g m-2, depending on soil characteristics (such as texture and presence of non-crystalline materials), soil cover and slope. In mature exotic conifer afforestations, with soil completely covered by litter, soil erosion was negligible, varying between 0 and 10 g m-2. Erosion rates increased both in young afforestations with open canopies (8 a 44 g m-2), and in mature afforestations where fresh litter and duff layers were removed (35 a 200 g m-2).

In the different studied systems, soil losses involved not the detachment of individual particles, but of soil micro aggregates rich in organic matter. Sediments enrichment ratio was always higher than 1, varying between 1.2 and 1.8. These results show that the sediments were enriched with organic matter, as compared to the contributing soils, indicating its selective removal. The erosion studies performed evidence the high erodibility of volcanic soils when their cover is lost, and the close link between erosion and carbon losses in these systems.

How to cite: La Manna, L., Mario Rostagno, C., Tarabini, M., Gomez, F., and Navas, A.: Erosion and sediment enrichment ratio in volcanic soils, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10027,, 2020

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