Topsoil development along a litho-climatic sequence of deposited aeolian sediments in the semiarid Pampas (Argentina)

Abstract

The remaining Caldenal forests patches in the semiarid Pampas are a sink for aeolian sediments originating from the neighboring agricultural lands. The A horizon inside these patches has developed above a volcanic ash layer deposited in 1932. This particularity allows quantifying the thickening rate and soil development in a relatively short period (since 1932 to present). To evaluate the possible soil development in a semiarid environment under variable texture and climatic conditions, the A horizons of six SW to NE ordered sites were analyzed. Results showed that A horizons thickness increased from SW to NE, in agreement with the direction of the prevailing winds. Soil texture was finer in the same direction, with means of 130.4 µm (fine sand, SW extreme) and 82.4 µm (very fine sand, NE extreme). The size and the rounded shape of the particles composing the A horizons agree with an aeolian origin of the sediments. Higher soil development, expressed by darker colors, better structure (granular and subangular aggregate types of moderate to strong degree) and higher organic C concentrations (4.5 %), was detected to the NE, which coincided with finer texture and higher mean annual precipitation and temperature. Results showed that forest patches are not only sinks for C enriched wind-blown sediments in semiarid environments, but also promote topsoil development even in a short period. Outcomes may be useful to couple to studies on dust and C distribution in the agroecosystem, with the aim off achieving the land neutrality at landscape scale.