Three Dimensional Changes of Soil Organic Carbon Content and Its’ Key Factors in Cultivated soils of Henan Province During the Recent 30 Years
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S159;P934

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Supported by the National Key Research and Development Program (No.2021YFD1700900) and Technical System of Maize Industry in Henan Province(No.S2010-02-G07).

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    Abstract:

    【Objective】 The information of temporal-spatial variation of soil organic carbon content (SOC) with high resolution and high precision is the base for assessing the capability of soil in sequestrating carbon. Though there had been much research on the changes in topsoil SOC, research on SOC of deeper soil layers is still rare. To reduce the gaps in understanding of the ability of deep soil to sequestrate carbon, our research sought to investigate the sensitive area where SOC had changed significantly, the depth where SOC had changed significantly, and the factors that drive SOC change. Thus, research on the temporal-spatial changes of SOC of 0~15 cm, 15~30 cm, 30~60 cm and 60~100 cm of cultivated land in Henan, China from 1982-2010 was conducted and the SOC accumulation rate in this area was compared with that of the COP21 target . 【Method】The legacy soil data that was collected from the second national soil survey carried out in 1982 and the recent topsoil data and soil profile data that were sampled in 2010 were used in this research. Digital soil mapping technology with the aid of a quantile random forest algorithm (QRF) and 26 environmental covariates was used to produce SOC maps. For every soil layer in both 1982 and 2010, 500 SOC distributions with equal probability were produced by QRF, and then the SOC map pools for both 1982 and 2010 were derived. Then, stochastic sampling with replacement was repeated 1 000 times from both SOC map pools, respectively, and each time, a subtraction of the two SOC maps was performed to get a SOC change map. So, 1 000 SOC change maps with equal probability were got and based on that the uncertainties of SOC change were assessed. Only those SOC changes with a probability above 0.66 were received as significant results and were used to calculate SOC storage change in the next step. To better understand the mechanism of SOC change, SOC changes among soil types were compared, and the Pearson correlation coefficient between SOC change and primitive SOC content, some climate variables, crop yields, straw returning amount, soil texture, and soil pH were analyzed. 【Result】It was revealed that the significant increase of SOC in 0~15cm, with a magnitude of 2~4 g·kg-1, had taken place across the plain and basin regions of Henan province. Nevertheless, the increase of SOC in 15~30 cm soil layers with a magnitude of 0~2 g·kg-1 mainly took place in the Fluvo-aquic soils that were distributed alongside the Huang river and scattered to the Cinnamon soils and Paddy soils. The changes of SOC in soil layers below the 30 cm depth were low in probability. Overall, the total storage of SOC in 0~1 m depth of soils across the cultivated land of Henan province increased by 7.04% in the past 28 years with a mean annual rate of 2.43‰, which was far from the expected value of COP21 4‰. It was also found that the effects of bio-climate variables were more important than soil variables in SOC change. Except for single-cropping rice areas with a fallow period every year, SOC significantly or extremely significantly correlated with biomass input. The mean annual temperature range (the difference between the mean hottest month temperature and the mean coldest month temperature) was positively correlated with SOC accumulation, while climate warming had a negative effect on it. Probably due to the differences in the environment and soil properties, the relationships between SOC change and soil texture, between SOC change and soil pH in different soil types were high variable. The initial SOC values were negatively correlated with SOC change in 0~15cm in two of five soil categories, so was that in 15~30 cm in all the five soil categories, which may be implied a slowing rate for the SOC accumulation in the future. 【Conclusion】The SOC accumulating rate in Henan province will be difficult to meet the object of COP21 in the future. Thus, it is suggested not to overestimate the effects of agricultural soil on carbon sequestrating and much attention should be paid to reducing net carbon emission.

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ZHAO Yanfeng, LI Yixin, MA Panpan, CHEN Jie, LI Yuanyuan, YANG Qiong, CHENG Daoquan. Three Dimensional Changes of Soil Organic Carbon Content and Its’ Key Factors in Cultivated soils of Henan Province During the Recent 30 Years[J]. Acta Pedologica Sinica,2023,60(5):1409-1420.

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History
  • Received:January 29,2022
  • Revised:October 20,2022
  • Adopted:November 18,2022
  • Online: January 03,2023
  • Published: September 28,2023