Resumo

SUAREZ, Adriana; BROQUEN, Patricia; GIRARDIN, Jorge Luis  e  CHIODI, Fernando. Variabilidad Pedogenética y Productividad Forestal a Través De Una Toposecuencia (Región Extrandina - so Neuquén). Cienc. suelo [online]. 2014, vol.32, n.1, pp.129-137. ISSN 1850-2067.

The objective of this research was to study soil variability related to landscape changes through a typical toposequence, under grass shrub steppe (ESG) at the Extrandinian Region in order to evaluate forest soil quality for Ponderosa pine (PP) production and to acquireknowledge onvolcanic ash soils. Volcanic ash deposition was higher on the windward side of the slope (NE exposition) compared to the NW side of the slope, producing deeper solums in the former.. Soil features are remarkably different between both sides of the slope. On the leeward side, soil properties are determined by volcanic ash; they are deep (80 to 130 cm), with a horizon sequence A-Bw-2C, low bulk density (0.9 to 1.1 Mg m^-3) and andic properties with volcanic glass throughout the whole soil profile (H» 25%). On the winward side, soil properties were determined by the underlying material -tuff- which evolved to clay, they are shallow (30-50 cm), with a horizon sequence A-2Btss-2Cr, medium bulk density (1.2 to 1.3 Mg m^-3) and presence of swelling clays. The A horizon depth was higher under PP (NE hillside: PP 36 cm, ESG 30 cm; NW hillside: PP 15 cm, ESG: 11 cm). This difference between PP and ESG can be attributed to the protective effect of afforestation. Volumetric growth of PP was 50% higher on the leeward side of the slope than on the windward side. This was favoured by soil depth, the absence of limiting features for root development and the clayey textures at the bottom of the soil profile. PP growth on the windward side of the slope was limited by soil depth and seasonal changes affecting the Btss horizon structure that causes excessive root compression.

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