黄土丘陵区露天煤矿复垦土壤熟化过程中团聚体碳氮演变特征. (Chinese)

Reclaimed Mine Soil (RMS) is the type of high compacted and nutrient exhausted soil, due to the mining and reclamation operations. The soil aggregate associated carbon (C), nitrogen (N), and isotope can be a platform to understand the pedogenic process of reclaimed mine soil. This study aims to monitor the soil aggregate recovery and Soil Organic Matter (SOM) formation. Different sorts of age chronosequence soil (0, 3, 12, 14, 17, 25, 28, and 32 a) were collected from the Robinia pseudoacacia L. forests in the Pingshuo opencast coal mine in China. Moreover, the soil was selected from adjacent and undisturbed Populus simonii forest as a reference (CK) as well. The wet-sieving method was used to separate the fractions of soil aggregate, and the aggregate-associated C, N, 13C, and 15N isotopes. The results showed that: 1) The proportion of >250-2 000 μm aggregate in the 32 a soil was 737.02% higher than that in the 0a soil, whereas, the proportion of 53-250 μm in the 32 a soil was 19.25% lower than that in the 0a soil, indicating that the reclamation operations destroyed the structure and stability of water-stable aggregate. Moreover, the mean weight diameter of soil aggregate in the 32 a soil was 133% higher than that the in 0a soil, indicating the excellent recovery of the structure and stability with the ages. 2) Soil aggregate associated C and N increased with the reclamation time. The >2 000 μm and >250-2 000 μm associated C and N were dominated in the total C and N. In addition, the aggregate-associated C, N, and C/N ratio increased with the time. Specifically, the large-size aggregate (>250 μm) associated C/N was significantly higher than that of the microaggregate (P<0.05). 3) The δ13C values were differed from -15.14‰--26.40‰, while the δ15N values were ranged from 1.13‰-10.87‰. More importantly, the δ13C values decreased with the time in the soil aggregate >2 000 μm, >250-2 000 μm, and lower than 53 μm, the δ15N values decreased in the >2 000 μm as well. The 13C isotopes were significantly enriched in the soil aggregate 53-250 μm and lower than 53 μm fractions, compared with the large-size aggregates (P<0.05). It infers that the soil C was incorporated into the RMS from the large-size to small-size aggregate fractions during the pedogenic process. 4) The proportion of the new C was accounted for over 80% of the total C in the soil aggregate >2 000 and >250-2 000 μm, without the significant temporal variation (P>0.05). However, the proportion of the new C increased significantly in the lower than 53 μm fraction over 17 years after reclamation, whereas the proportion remained stable after that, indicating the nearly saturated recalcitrance pool (<53 μm C) after 17-year reclamation. Overall, the reclamation operations significantly increased the proportions of small-size soil aggregates. However, the vegetation restoration can be expected to facilitate the recovery of aggregate structure, stability and aggregate associated C and N. [ABSTRACT FROM AUTHOR]

矿区土地复垦中，由于机械碾压导致复垦土壤呈现高压实状态，复垦土壤的有机质则因机械扰动而矿化。探究复垦土壤团聚体与有机质恢复机理，可为深入理解露天煤矿高压实复垦土壤质量演替规律提供依据。以平朔露天煤矿典型植被恢复模式--刺槐纯林不同复垦年限（0、3、12、14、17、25、28、32 a）土壤及周边未扰动土壤（CK）为研究对象，采集0～20 cm表层土壤样品，分析土壤水稳性团聚体（>2 000 μm、>250～2 000 μm、53～250 μm、<53 μm）及团聚体碳（C）、氮（N）以及13C和15N同位素特征。结果表明：1）土地复垦中机械碾压破坏了土壤水稳性团聚体结构与稳定性，但随着复垦时间增加，32 a样地>250～2 000 μm团聚体的比例较0 a提高737.02%，而53～250 μm团聚体比例则降低19.25%；团聚体稳定性随着复垦时间而增加，表现为32 a样地土壤团聚体平均重量直径（Mean Weight Diameter，MWD）较0 a提高133%。2）各粒径团聚体C、N及C/N均随着复垦时间增加而增加，>2 000和>250～2 000 μm团聚体C和N在土壤总C和N中占主导地位。>2 000和>250～2 000 μm团聚体C/N整体上高于53～250 μm团聚体。3）各样地土壤δ13C变化范围为?15.14‰～?26.40‰；δ15N的变化范围为1.13‰～10.87‰。>2 000、>250～2 000和<53 μm团聚体的δ13C值及>2 000 μm团聚体的δ15N值随复垦年限增加呈现降低趋势。与>2000 μm和>250～2 000 μm团聚体相比，53～250和<53 μm团聚体中13C显著富集（P<0.05），这表明复垦土壤熟化过程中，土壤C从大粒径团聚体向小粒径周转。4）>2 000与>250～2 000 μm团聚体中，新C占土壤总C的比例为>80%，且各样地间差异不显著（P>0.05），而在<53 μm团聚体中，新C的比例在复垦14～17 a间显著增加，此后则变化不显著。上述结果表明，土地复垦中机械碾压增加了小粒径团聚体的比例，降低了团聚体稳定性，而随着复垦时间增加，植被恢复促进了土壤团聚体结构、稳定性及C、N的恢复。 [ABSTRACT FROM AUTHOR]

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