Effects of Biocrusts on Dustfall Retention and Soil Fixation and Their Influencing Factors in the Chinese Loess Plateau

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The National Natural Science Foundation of China (No.42077010), the “Light of West China” Program of the Chinese Academy of Sciences (No.2019), and the 2115 Talent Development Program of China Agricultural University (No.1191-00109011).

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    【Objective】 Wind activity and aeolian dust transportation are key terrestrial processes in dryland ecosystems. Biocrusts are photoautotrophic communities that consist of cyanobacteria, actinomycetes, mosses, green algae, fungi, and other organisms. As an important living skin and pioneer communities developing on surface soil in drylands, biocrusts strongly influence most soil processes (hydrological, ecological, biological, and chemical processes) and have a variety of essential ecological functions. Although biocrusts are usually relatively thin (a few millimeters or centimeters at most), these organisms have unique micro-structures which could positively influence the formation of aeolian soil parent material. In order to further explore the aeolian sedimentary effects of biocrusts on soil parent material, we conducted this study to understand the effects of biocrusts on dustfall retention and soil fixation, as well as their influencing factors.【Method】 In the north of Chinese Loess Plateau, the biocrusts developed on aeolian and loessal soils were sampled, and the analyses and simulated experiments were carried out in the laboratory. The amount of dustfall retention and soil fixation of biocrusts at different developmental stages (cyano crust, mixed crust, and moss crust) were measured. The variations of dustfall retention amount under different wind speeds, dustfall grain sizes, and dustfall amount were explored. We also explored the key influencing factors.【Result】 The dustfall retention amount of biocrusts was 1.1~4.8 times higher than that without biocrusts, and it increased with the developmental stages of biocrusts from cyano crust to moss crust. On average, the erosion reduction of biocrusts was 19.5~4892 t·km-2·a-1under 1~8 m·s-1 wind speeds. Moreover, the dustfall retention amount increased with increasing soil water content, and these increases were positively correlated with wind speed. It was found that the dustfall retention amount was increased by 4.9%, 53.1%, 59.6%, and 72.3%, respectively, under 5~8 m·s-1 wind speeds when relative water content increased from 0 to 80%. Additionally, the dustfall retention amount was also significantly and positively correlated with the surface roughness of biocrusts. Similarly, the soil fixation amount of biocrusts also increased along with their developmental stages from cyano crust to moss crust. The soil fixation amount of moss crust was 1.4 times higher than that of cyano crust. At the same developmental stage, the soil fixation amount of biocrusts on aeolian sandy soil was significantly (F=30.74, P<0.003) higher than that on loessal soil. Furthermore, the soil fixation amount was positively correlated with the thickness of biocrusts and negatively correlated with the surface roughness. It firstly increased and then decreased with increasing soil water content.【Conclusion】 These findings show that biocrusts can significantly retain dustfall and fix soil due to their root, mycelium, exudates, and pore structures, and these biocrust functions are of great significance for the aeolian sedimentary process of soil parent material, the pedogenic process of primitive soil, and the primary succession of dryland ecosystem in the Chinese Loess Plateau. Additionally, this study demonstrates the important effects of biocrusts on the formation of aeolian soil parent material, and their key influencing factors are surface roughness, developmental stages, and water content of biocrusts. Therefore, it is essential to pay attention to the biocrust effects on dust retention and soil fixation in arid and semiarid climate regions.

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CAO Yousong, XIAO Bo, LI Shenglong, WANG Yanfeng, YU Xingxing. Effects of Biocrusts on Dustfall Retention and Soil Fixation and Their Influencing Factors in the Chinese Loess Plateau[J]. Acta Pedologica Sinica,2023,60(6):1610-1625.

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  • Received:December 15,2021
  • Revised:July 15,2022
  • Adopted:August 23,2022
  • Online: September 08,2022
  • Published: November 28,2023