Effects of afforestation by aerial sowing on topsoil physicochemical properties in the sandy desert, NW China

Abstract

Purpose: Nowadays, the afforestation by tree planting is one of the most effective measures to combat desertification and restore the degraded land in the global. However, the effects of large-scale afforestation by aerial sowing in desert on soil physicochemical properties has rarely been reported. Methods: We assessed the variation of topsoil physicochemical properties and their interaction along the nearly 40 years succession and quantified the relatively contribute of soil texture and salinity to nutrients using random forest. Structural equation modeling was applied to obtain a mechanistic understanding of variation of soil nutrients. Results: The results showed that afforestation by aerial sowing had less effects on increase of topsoil clay (< 2 μm) and silt (2–50 μm), but significant on very fine sand (VFS, 50–100 μm). Soil electrical conductivity (EC) and alkaline cations K+, Ca2+, and Mg2+, except Na+ were significantly increased along vegetation restoration stages. However, the total carbon (TC), nitrogen (TN), and phosphorus (TP) also exhibited a significant improvement in the first 5 years7 and subsequently stabilized for TC and TN but decreased for TP. Random forest and structural equation model show that soil texture and salinity had differentiated effects on soil nutrients. Variance partitioning analysis indicated that soil salinity and texture could explain 43.78% and 31.24% variations of soil nutrients, respectively. Conclusion: Afforestation by aerial sowing in desert is beneficial to improve topsoil texture and nutrients; however, it was notable that soil phosphorus becoming an increasingly scarce resource along vegetation restoration. Therefore, considering phosphorus supplementation into the further afforestation management is an essential subject.