Search

Soil water repellency (SWR) is a physical phenomenon whereby water cannot penetrate or has difficulty penetrating the soil surface. There are many factors involved in its occurrence, but the main factors controlling its emergence in loess remain unclear. In this work, we have studied numerous physicochemical and biological factors functioning in different dominant vegetations ( Pinus tabulaeformis Carr., Robinia pseudoacacia L., and Hippophae rhamnoides L.) in a loess hilly region by gas chromatography-mass spectrometry (GC-MS) and high-throughput sequencing techniques. We observed that more than 75% of the soils under Robinia and Hippophae are categorized as slightly or strongly water repellent, while nearly 50% of the soils under Pinus are categorized as severely to extremely water repellent. The relative concentrations of total free lipids in the soil in the same water-repellency class were Pinus > Robinia > Hippophae , where fatty acids, alkanols, and sterols were positively correlated with SWR, whereas alkanes were not. For the abundance and diversity index of bacterial and fungal communities, the three species ranked in the following order: Robinia ≈ Hippophae > Pinus . Thus, solvent-extractable polar waxes were indicated to be better preserved in water-repellent soils under Pinus due to lower microbial diversity than Robinia and Hippophae . Here, we demonstrate polar waxes to be the principal factor controlling SWR. Moreover, the dominant phyla of fungi varied greatly than those of bacteria under three vegetation types. Correlation analysis showed that the abundance of Actinobacteria in dominant bacteria increased with SWR. Nonmetric multidimensional scaling suggested the fungal community in different water-repellent soils under Pinus to vary more than those under Robinia and Hippophae . The indicator species mainly belonged to Actinobacteria in bacteria and Basidiomycota in fungi at the phylum level; this finding was further supported by the linear discriminant analysis (LDA) effect size (LEfSe). Additionally, GC-MS identified a small amount of ergosterol, a specific biomarker of fungi under Pinus . These pieces of evidence collectively reveal that severe to extreme SWR occurs under Pinus and appears to be the most influenced by fungi and actinomycetes when the topsoil is close to air drying. However, there is a need for further testing on different plant species or land use., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The reviewer YT declared a shared affiliation with the author XC, XX, WW, SL, PG, YQ, QZ, XR, YX, and ML to the handling editor at the time of review, (Copyright © 2022 Chai, Xu, Li, Wang, Li, Geming, Qu, Zhang, Ren, Xu and Li.)

Chlorine treatment increases the surface hydrophobicity of starch granules of soft wheat flour and reduces its gluten network forming capacity and apparent content of the flour lipids, the latter presumably by forming chlorinated derivatives. It also increases its solvent holding capacity as shown by proton nuclear magnetic resonance ( 1 H NMR) experiments in presence of sucrose. The exchanging protons in the extra-granular space are present in an environment with restricted mobility, indicating strong interactions between chlorinated soft wheat flour (CSWF) components and solvent. Chlorination reduced the capability of free flour lipids to shield starch granules during rapid visco analysis (RVA). The higher viscosity reached in RVA with CSWF was attributed to not only its lipids having different properties but also its protein, resulting in improved starch swelling and amylose leaching. Finally, 1 H NMR indicated that starch and protein networks in CSWF-sucrose gels were better structured than in gels prepared from non-chlorinated flour., (Copyright © 2018 Elsevier Ltd. All rights reserved.)