Effect of vegetation introduction versus natural recovery on topsoil properties in the dried Aral Sea bed

Abstract

Desiccation of the Aral Sea has resulted in the emergence of vast saline and flat terrains, jeopardizing human health and agricultural activities because of sand and dust storms. Vegetation, mainly indigenous Haloxylon species, has been introduced to ameliorate the soil. As a critical indicator of rehabilitation, the physicochemical properties of soil after the introduction of vegetation remain poorly understood. This study examined (1) the changes in topsoil properties after vegetation establishment based on a 30‐year chronosequence and employed (2) site comparisons of topsoil properties between two cases of natural versus introduced vegetation on a dried Aral Sea bed. Twelve paired areas that were naturally or artificially vegetated during 1990, 2000, 2005, 2008, 2013, and 2017 were selected for examination. Irrespective of vegetation type, increases in organic matter and nutrients (TOC >90%, TN >143%, and P2O5 >23%) were detected in the surface soil (0–10 cm) along the 30‐year chronosequence. In addition, decreases in ECe (92% and 69%), CEC (41% and 11%), Ca2+ (38% and 12%), and TIC (81% and 11%) were observed in both natural and introduced vegetation, respectively. The introduced vegetation was associated with a slightly greater accumulation of soil K+ and TN than the natural vegetation. Our results indicate vegetation‐derived nutrient and organic matter accumulation as well as the possible removal of salts by root exudates in the surface soil. Overall, vegetation contributed to soil amelioration, with similar effects observed at naturally and artificially vegetated sites.