Abstract
Land use change could significantly affect soil organic carbon (SOC) and other soil chemical properties. However, the responses of soil labile C fractions at different soil depths to land-use change are not still clear. The aim of this study was to investigate the effect of paddy field conversion on woodlands or corn fields on total soil organic C (TOC) and its labile C fractions including particulate organic C (POC), microbial biomass C (MBC), and potassium permanganate-oxidizable C (KMnO4–C) along a 0–100 cm soil profile. Our results indicate that soil TOC concentrations increased by 3.88 g kg−1 and 3.47 g kg−1 in the 0–5 cm soil layer and 5.33 g kg−1 and 4.68 g kg−1 in the 5–20 cm soil layer during 13 years after the conversion from paddy fields to woodlands and corn fields, respectively. In the 20–40 cm soil layer, the woodlands had the highest TOC concentration (12.3 g kg−1), which was 5.13 g kg−1 and 3.5 g kg−1 higher than that of the paddy and corn fields, respectively. The increase in TOC was probably due to the absence of soil disturbance and greater root residue input into the woodland soil. In corn fields, pig manure addition contributed to the increase in soil organic C concentrations. In addition, the proportion of soil KMnO4–C increased after conversion from paddy fields to woodlands or corn fields in the 0–40 cm soil layer, ranging from 39.9–56.6% for the woodlands and 24.6–32.9% for the corn fields. The soil POC content was significantly higher in woodland and corn field soils than in paddy field soils at lower soil depths (5–40 cm). However, there were no differences in MBC contents in the whole soil profile between the woodlands and paddy fields. The KMnO4–C and MBC was the most important factor affecting the CMI values through the whole 0–100 cm soil profile. Overall, converting paddy fields to woodlands or corn fields increased the TOC and labile C fractions in the 0–40 cm soil layer. Future studies should focus on the response of the deeper soil C pool to land-use change.
Highlights
Rice (Oryza sativa L.) is one of the most important food crops in the world
Our results suggest that land-use change significantly affected total soil organic C (TOC) and its labile C fractions in the 0–40 cm soil layer as well as the TN in the 0–20 cm soil layer
At lower soil depths (20–40 cm), the TOC contents were significantly higher in woodland soils than in paddy field soils, possibly because of the root exudates with deeper roots, thereby further increasing the C input in deep soil
Summary
Rice (Oryza sativa L.) is one of the most important food crops in the world. It is cultivated in areas covering 31 million ha in China [1]. The area used for rice cultivation in the Zhejiang province has gradually declined over the past two decades [2]. This is attributed to the development of urbanization and large numbers of farmers choosing to work in cities instead of working in rural areas. Land-use conversion is accompanied by changes in management practices (e.g., tillage or fertilization) that will directly affect the soil quality [4,5]
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