| Effects of age and type of conversion from cropland to forest land and grassland on stability and organic carbon in soil aggregates |
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| DOI：10.7606/j.issn.1000-7601.2017.03.37 |
| Key Words: conversion from cropland to forest land and grassland plantation age plantation type aggregate stability soil organic carbon Loess Plateau |
| Author Name | Affiliation | | LI Bai-qiao | Institute of Soil and Water Conservation, Northwest A&F University ,Yangling 712100, China | | FU Yu | Institute of Soil and Water Conservation, Northwest A&F University ,Yangling 712100, China | | LI Guang-lu | Institute of Soil and Water Conservation, Northwest A&F University ,Yangling 712100, China；College of Resource and Environment, Northwest A & F University, Yangling 712100, China | | ZHANG Teng | College of Resource and Environment, Northwest A & F University, Yangling 712100, China | | ZHENG Teng-hui | Institute of Soil and Water Conservation, Northwest A&F University ,Yangling 712100, China |
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| Abstract: |
| The purpose of this study was to elucidate the effect of plantation type and age on aggregate stability and aggregate-associated organic carbon content. Soil samples were collected from five types of land in the southern part of the Loess Plateau including: artificial pure locust forest land converted from slope cropland with plantation ages of 6 years (FL06) and 15 years (FL15), artificial alfalfa grassland converted from slope cropland with plantation ages of 6 years (GL06) and 15 years (GL15) and the neighboring conventional slop cropland (CK). The results revealed that：in 0～20 cm soil layer, land use conversion from cropland to forest land and grassland could significantly increase the fractions for >2 mm and 1～2 mm aggregate but decrease for <0.25 mm compared with the cropland. The fractions for >2 mm and 1～2 mm aggregate under different plantation type and age was in the order of GL15>GL06>FL06>FL15>CK and GL15>FL06>GL06>FL15>CK, respectively. Land use conversion increased aggregate stability in the two soil layers. GL15 had the maximum mean weight diameter (MWD) and geometric mean diameter (GMD) values, followed by GL06. Soil organic carbon in >2 mm aggregate under forest land and grassland, and that in 1～2 mm aggregate under grassland all increased with plantation age. In 20～40 cm soil layer, the mean of aggregate content increased with aggregate size decreasing, both the MWD and GMD value of this layer were less than those of 0～20 cm soil layer. There was an trend that all aggregate fractions under forest land and grassland had the less organic carbon content than that of cropland. The findings suggested that land use conversion from cropland to forest land and grassland improved soil structure, and its effect on organic carbon content in every aggregate fractions change along with plantation type and age. GL15 had better aggregate stability and more aggregate-associated organic carbon. |
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