Interrelations of vegetal cover, silicophytolith content and pedogenesis of Typical Argiudolls of the Pampean Plain, Argentina.

NATALIA BORRELLI; MARGARITA OSTERRIETH; JORGE MARCOVECCHIO

CATENA

Elsevier

Lugar: Amsterdam (Holanda); Año: 2008 vol. 75 p. 146 - 153

0341-8162

Knowledge of the origin, evolution and weathering of Pampean soils is still limited. There are few priorstudies of silicophytoliths, even though they could be important pedogenetic indicators that provideinformation about the role of amorphous silica in the reestablishment of soil structure. The aim of this workis to determine the silicophytolith content in Typical Argiudolls of the Pampean Plain, Argentina, its relationwith vegetal cover and its effect on pedogenesis. We worked in three plots with different vegetal cover:grasses and shelter-belt plantations of Acacia melanoxylon – Celtis tala and Eucalyptus globulus – Celtis tala. Inthe study area, morphological characterization and particle size distribution analysis of soils were completed,and pH and organic matter content were determined. The heavy liquid separation was realized with sodiumpolytungstate (δ=2.3 g/cm3) and an average of around 500 mineral grains were counted under opticalmicroscope for the quali-quantitative analysis. There were no differences between profiles with respect totheir morphological properties, organic matter content and particle size distribution, except for the higherorganic horizon development of the forest plots as compared with the grass plot. The silicophytolith contentwas higher in the forest plots than in the grass one; within each profile, this fraction content decreased fromthe surface (63–40%) to the subsurface levels (23–5%) of soils. This decrease parallels the pieces of amorphoussilica (b7.5 μm) distribution in all plots analyzed. Afforestation over the past 50 years does not affect eitherthe morphological or the physico-chemical properties of soils. These forest species, through the organichorizons, preserve soil conditions, which insures a higher representativity of silicophytoliths in comparisonwith the grass plot.