Application of Le Bissonnais Method to Study Soil Aggregate Stability in Red Soils under Different Types of Vegetation
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The National Natural Science Foundation of China (41671273)

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    Abstract:

    【Objective】Revegetation can improve stability of soil aggregates, whih are one of the key factors affecting soil quality and soil erosion resistance. In order to explore differences in aggregate stability in soils under different types of revegetation, and main mechanisms of aggregate destruction in red soil, a field experiment was carried out in the red soil region of South China. 【Method】Based on a long-term field experiment, which consisted of four plots under different typs of vegetation (Zoysia matrella, Vetiveria zizanioides, Indigofera amblyantha, and Amorpha fruticosa ) planted 5 years ago for revegetation, this experiment was oriented to explore soil aggregate stability in different soil layers (0~10 cm, 10~20 cm and 20~30 cm), with the Le Bissonnais (LB) method, including three treatments, i.e. fast wetting (FW), wet stirring (WS), and slow wetting (SW), and mechanisms of soil aggregate decomposition (dispersing, mechanical disturbing and clay swelling). 【Result】Results show: 1) the plots under Zoysia matrella and Vetiveria zizanioides were higher in organic matter content, porosity, owing to their better developed root systems, than the other two in different soil layers compared with Indigofera amblyantha and Amorpha fruticosa. The difference between the four platns was especially significant in the section of fine roots (diameter less than 2 mm), which made up the majority of the root system, accounting for 99.53%~99.81%, 98.83%~99.39%, 95.56%~98.99%, and 86.26%~94.85% in the plots under Zoysia matrella, Vetiveria zizanioides, Indigofera amblyantha, and Amorpha fruticosa, respectively; 2) in terms of mean weighted diameter (MWD) and percentage of >0.25 mm aggregates in the soils after three aggregate destructive tests, the four plots exhibited an order of Zoysia matrella > Vetiveria zizanioides > Indigofera amblyantha > Amorpha fruticosa, which suggests that the soil aggregates in the plots under herbs (Zoysia matrella and Vetiveria zizanioides) were higher in stability than the plots under shrubs (Indigofera amblyantha and Amorpha fruticosa ). It is therefore assumed that type of vegetation has a significant impact on soil aggregate stability; 3) organic matter, bulk density, sand content and root parameters all had significant influences on soil aggregate stability, especially fine roots with diameter ranging from 0.5 to 2 mm, which is key to soil aggregate stability; and 4) in terms of percentage of >0.25 mm aggregates in the plots subjected to destructive tests, an order of FW < WS < SW was observed in the plots of Zoysia matrella and Amorpha fruticosa, and one of FW < SW < WS in the plots of Vetiveria zizanioides and Indigofera amblyantha. The percentages of >0.25 mm aggregates varied in the range of 50.45%~79.59% in the four plots subjected to FW test, lower than that in the plots subjected to WS or SW tests. The MWD of soil aggregates ranged from 1.21 mm to 1.83 mm in the soils subjected to WS test and from 1.81 mm to 2.36 mm in the soils subjected to SW test, indicating the aggregates in the soils were stable ones, while it ranged from 0.39 mm to 1.21 mm in the soil subjected to FW test, much lower than that in the former two, indicating that the aggregates were unstable ones. Therefore it could be assumed that FW is the most destructive to soil aggregates and that dispersion is the primary mechanism of soil aggregate decomposition. 【Conclusion】Herbs are more effective than shrubs in improving soil structure stability, and FW test is a better method to evaluate soil aggregate stability in this region. All the findings in this experiment may serve as reference for researches on soil aggregate stability and choices of plant species selection for revegetation in this region.

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CHENG Liang, QIN Jiahui, ZHANG Lichao, CAO Danni, HAO Haoxin, GUO Zhonglu. Application of Le Bissonnais Method to Study Soil Aggregate Stability in Red Soils under Different Types of Vegetation[J]. Acta Pedologica Sinica,2020,57(4):855-866.

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History
  • Received:February 25,2019
  • Revised:July 22,2019
  • Adopted:August 19,2019
  • Online: May 06,2020
  • Published: