Anomalous water retention capacity of alpine meadow soil with eolian dust accretion on the Tibetan Plateau

Abstract

Under high altitude or cold climatic conditions, the characteristics and factors controlling the water retention capacity of alpine meadow soils are poorly known. Here, we focus on alpine meadow soils, with eolian dust accretion, in the Tibetan Plateau and measured basic soil physiochemical properties and soil water retention curves (SWRCs). The results indicate that the competition between eolian processes (dust transport, eolian sorting, and dust accretion) and pedogenesis have led to significant changes of the physicochemical properties and soil water capacity of the alpine meadow soils in both spatial and with depth in the studied area. The most significant features of the alpine meadow soils are the strong accumulation of soil organic matter (SOM), soil acidification, and carbonate leaching. The studied alpine meadow soils have an unusually high saturated water content (SWC), field capacity (FC), and permanent wilting point (PWP). However, the plant available water content (AWC) does not always increase with increasing SOM, because of the rate of increase of the FC does not exceed that of the PWP. We conclude that the negative effects of carbonate leaching on soil aggregate formation and soil structural stability are likely responsible for the observed variations in FC and the resulting AWC. Finally, based on direct measurements of SWRCs and the corresponding alpine meadow soil physicochemical parameters, we developed and validated several pedotransfer functions (PTFs) for these alpine meadow soils which can be used to predict water retention from basic soil data.