Immobilization of ash in soil aggregates.

SIX, J.; ENRIQUEZ, A.S.

Bariloche

Workshop; WIND-REMOBILISATION PROCESSES OF VOLCANIC ASH; 2019

Universidad de Ginebra, Suiza. NSF of Suiza.

Volcanism can be negatively perceived for human population and natural systems; however, it can derive in very rich soils and replenish particles in areas under strong wind erosion. After the Puyehue?Cordón Caulle Volcanic Complex event in 2011, we studied processes of soil aggregates formation at an early stage of the succession. Areas with concave topography, as meadow are, tend to accumulate ash (erodible material) relocated from convex areas (deflation), as surrounded steppes are. Five and half years after the eruption, we sampled topsoil (0-5 cm) in meadows of the East semiarid region, and examined the distribution of different size fractions of water-stable soil aggregates and their associated carbon (C) and total nitrogen (N) contents. While the free ash is still moving in the steppe, soil neoformation processes were detected in meadows through the presence of large (LM= 4%) and small (SM=21%) macroaggregates, although microaggregates (m= ~45%) and silt + clay (s+c= ~29%) - ash size - dominated the soil fractions. The C and N contents decreased in a sequence: LM > SM > m > s+c, highlighting the importance of soil organic matter in the formation of larger-size aggregates and theirquality. The incorporation of the ash into the soil aggregates suggests dynamism in the immobilization-stabilization processes in meadows, despite the semiarid context.