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| Study on compositions of soil humus and their combining forms of Pinus koraiensis plantations |
| Chen Lixin,Song Zhitao,Ji Xuan |
| School of Forestry,Northeast Forestry University,150040,Harbin,China |
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Abstract Field investigation combined with quantitative analysis was used to study the carbon content of organic matter,compositions of soil humus and their combining forms in rhizosphere and non-rhizosphere soil in Pinus koraiensis plantations(25,45,58,68 years old) and the Pinus koraiensis-Tilia amurensis mixed forest(60 years old).The results showed that the carbon content of soil organic matter and each composition of soil humus in both Pinus koraiensis plantations and the Pinus koraiensis-Tilia amurensis mixed forest decreased with the increase of soil depth,and these in rhizophere soil were higher than those in non-rhizosphere soil.For compositions of soil humus,the carbon content of humic acid was higher than that of fulvic acid in all forest types except for the rhizophere soil in 58-year old plantation and the non-rhizophere soil in 45-year old plantation.The humic acid to fulvic acid ratio(HA/FA) ranged from 1.00 to 2.45.The carbon content of heavy fraction humus,loosely combined humus and stable combined humus was ordered as this 58-year old's>68-year old's >25-year old's>45-year old's.Carbon contents of other fractions of soil humus in the Pinus koraiensis-Tilia mixed forest were higher than that of Pinus koraiensis plantations except tightly combined humus.
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Received: 30 October 2006
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