Effects of freezing and thawing on soil water stable aggregates in Yili grassland
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DOI:10.7606/j.issn.1000-7601.2017.06.35
Key Words: water stable aggregate  grassland soil  freezing and thawing  wet sieving method  freeze-thaw cycles  freezing temperature
Author NameAffiliation
XU Qiao Key Laboratory of Pollutant Chemistry and Environmental Treatment, College of Chemistry & Environmental Sciences, YiLi Normal University, Yining, Xinjiang, 835000, China
College of Geography Science and Tourism, Xinjiang Normal University, Urumqi, Xinjiang 830054, China 
CUI Dong Key Laboratory of Pollutant Chemistry and Environmental Treatment, College of Chemistry & Environmental Sciences, YiLi Normal University, Yining, Xinjiang, 835000, China
College of Biology and Geography, Yili Normal University, Yining, Xinjiang 835000, China 
WANG Xing-lei Key Laboratory of Pollutant Chemistry and Environmental Treatment, College of Chemistry & Environmental Sciences, YiLi Normal University, Yining, Xinjiang, 835000, China 
ZHU Zhen-hua Key Laboratory of Pollutant Chemistry and Environmental Treatment, College of Chemistry & Environmental Sciences, YiLi Normal University, Yining, Xinjiang, 835000, China 
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Abstract:
      This study mainly took the soil of grassland in Yili as the research object. We sampled the 0~20 cm surface soil of Tuohulasu grassland in Yining County and obtained soil aggregates in different particle fraction via dry sieving method. After simulating water rate of soil aggregates and conducting freeze-thaw tests at laboratory, the weight of different size fraction water-stable aggregates were measured via wet sieving method. The results showed that: (1) Initial moisture content is the key factor affecting soil water stable aggregates. With the increase of soil initial moisture content, four size fraction water-stable aggregates, including>5 mm, 5~4 mm, 4~2 mm and 2~1 mm, gradually declined, or declined after an increase; water stable aggregates of 1~0.5 mm and 0.5~0.25 mm size fraction showed the changing trend of increasing first and then decreasing, or increase first, then decline and then increase again. (2) The frequency of freeze-thaw cycles is an important factor affecting soil water-stable aggregates. With an increasing frequency of freeze-thaw cycles, each size fraction of water stable aggregates showed different patterns. Water stable aggregates in>1 mm size fraction had overall decreasing trend, while other two size fractions of the aggregates including 1~0.5 mm and 0.5~0.25 mm showed an increasing trend. (3) Freezing temperature is another important factor affecting soil water stability. While the temperature decreased, the water stable aggregates of >5 mm and 5~4 mm size fraction also decreased, however, water stable aggregates of 1~0.5 mm and 0.5~0.25 mm size fractions increased significantly, and water-stable aggregates of 4~2 mm and 2~1 mm size fractions had no significant changes.