Purpose

In recent decades, riparian floodplains have undergone intensive reclamation worldwide, which has potential to influence soil carbon (C) accumulation. Such influence generally varies based on reclamation duration. Therefore, a study on changes in soil C stock along the reclamation chronosequence can help reveal the impact of reclamation on terrestrial C cycling.

Materials and methods

We chose natural floodplains (as the control) and croplands reclaimed for 13, 24, and 33 years in the lower reaches of the Yellow River and determined soil organic C (SOC) and soil inorganic C (SIC) contents at different depths and the stocks in 0–100 cm profiles.

Results and discussion

The SOC and SIC stocks generally increased at average rates of 2.73 and 5.54 Mg C ha⁻¹ yr⁻¹, respectively, and the SIC stock was closely related with the SOC stock across the reclamation chronosequence. The SOC content increased more at 0–20 cm depth in the profile along the reclamation chronosequence, but the SIC content often had a higher rate of increase in the deep soil layers. Significantly, the contents of SOC and SIC were both positively correlated with the proportion of silt fractions.

Conclusions

Our findings suggest that reclaimed croplands from riparian floodplain play an important role in C accumulation, highlighting the importance of soil inorganic C in C budget. Moreover, soil C accumulation relates closely to soil texture, which changes continuously along the reclamation chronosequence and often varies due to spatial heterogeneity.

中文翻译：

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开垦大大增加了河岸漫滩的土壤有机碳和无机碳储量

目的

在最近几十年中，河岸泛滥平原在世界范围内进行了大规模的开垦，这有可能影响土壤碳（C）的积累。这种影响通常根据开垦持续时间而变化。因此，对土壤碳储量沿开垦时间顺序变化的研究有助于揭示开垦对陆地碳循环的影响。

材料和方法

我们选择了天然洪泛区（作为对照）和黄河下游开垦了13、24和33年的农田，并确定了不同深度和储量下的土壤有机碳（SOC）和土壤无机碳（SIC）含量在0–100厘米的轮廓中。

结果和讨论

SOC和SIC储量通常分别以2.73和5.54 Mg C ha ^-1  yr ^-1的平均速率增加，并且在整个开垦时间序列中，SIC储量与SOC储量密切相关。沿填海时间序列，剖面中SOC含量在0–20 cm深度处增加更多，但SIC含量通常在深层土壤中具有较高的增加率。值得注意的是，SOC和SIC的含量均与淤泥成分的比例呈正相关。

结论

我们的发现表明，沿河泛滥平原开垦的农田在碳积累中起着重要作用，突显了土壤无机碳在碳预算中的重要性。此外，土壤碳的积累与土壤质地密切相关，土壤质地沿着开垦时间顺序连续变化，并且经常由于空间异质性而变化。