Afforestation and natural succession on former croplands are typical measures used for revegetation in ecologically fragile areas worldwide. However, there are few studies regarding the differences between natural grasslands and artificial plantations in terms of soil aggregate dynamics, organic carbon (OC), and total nitrogen (TN) accumulation. We sampled soils from farmland (FL) and from two vegetation restoration patterns [Robinia pseudoacacia plantations (RP) and natural grasslands (NG)] of two age classes (18 and 42 years) on the Loess Plateau of China. The size-distribution and stability of soil aggregates, as well as OC and TN stocks in bulk soil and aggregates were measured. Revegetation of FL resulted in considerable increases in bulk soil OC and TN stocks at depths of 0–40 cm: OC increased by 101.3% in NG and 75.5% in RP, and TN by 77.5% in NG and 106.1% in RP. Bulk soil OC stocks in 18- and 42-year-old NG at depths of 0–40 cm were 9.0% and 17.4% higher, respectively, than those in RP of the same age. Conversely, the 18- and 42-year-old RP had 18.6% and 16.4% higher TN stocks than those in NG of the same age. Microaggregates dominated aggregate-size distribution in all land uses and had the highest OC and TN stocks. NG soils had higher proportions of macroaggregates and mesoaggregates and greater aggregate stability than RP soils of the same restoration age. However, there was no significant difference in macroaggregate- and mesoaggregate-associated OC and TN stocks between NG soils and RP soils of the same age. Furthermore, bulk soil OC and TN stocks were strongly associated with aggregate stability. Bulk soil OC stocks were positively correlated with mesoaggregate-associated OC stocks, whereas TN stocks in bulk soil were closely related to macroaggregate-associated TN stocks. Overall, the results of this study suggest that restoration with RP favors soil N accumulation, whereas NG may be optimal for increasing C sequestration and stabilizing soil aggregates in the Loess Plateau.

在以前的农田上造林和自然演替是在全球生态脆弱地区进行植被恢复的典型措施。但是，关于天然草地和人工林之间在土壤聚集动力学，有机碳（OC）和总氮（TN）积累方面的差异的研究很少。我们从农田（FL）和两种植被恢复模式中取样土壤[ Robinia pseudoacacia黄土高原两个年龄段（18岁和42岁）的人工林（RP）和天然草地（NG）]。测量了土壤团聚体的大小分布和稳定性，以及散装土壤和团聚体中的OC和TN库。FL的重新植被导致0-40 cm深度的大量土壤OC和TN蓄积量增加：NG中OC增加101.3％，RP中75.5％； TN NG中增加77.5％，RP中106.1％。在18岁和42岁的NG中，0至40 cm深度的大量土壤OC储量分别比相同年龄的RP高9.0％和17.4％。相反，18岁和42岁的RP的TN存量比相同年龄的NG分别高18.6％和16.4％。在所有土地利用中，微骨料占总大小分布的主导地位，OC和TN存量最高。与相同恢复年龄的RP土壤相比，NG土壤的大骨料和中骨料所占比例更高，且骨料稳定性更高。但是，在相同年龄的NG土壤和RP土壤之间，大型聚集体和中聚集体相关的OC和TN储量没有显着差异。此外，大量土壤的OC和TN存量与骨料的稳定性密切相关。散装土壤中的有机碳储量与中骨料相关的OC储量呈正相关，而散装土壤中的总氮储量与宏观聚集的总氮储量密切相关。总体而言，这项研究的结果表明，用RP进行恢复有利于土壤氮的积累，而NG可能是提高黄土中碳固存和稳定土壤团聚体的最佳选择。但是，在相同年龄的NG土壤和RP土壤之间，大型聚集体和中聚集体相关的OC和TN储量没有显着差异。此外，大量土壤的OC和TN存量与骨料的稳定性密切相关。散装土壤中的有机碳储量与中骨料相关的OC储量呈正相关，而散装土壤中的总氮储量与宏观聚集的总氮储量密切相关。总体而言，这项研究的结果表明，用RP进行恢复有利于土壤氮的积累，而NG可能是提高黄土中碳固存和稳定土壤团聚体的最佳选择。但是，在相同年龄的NG土壤和RP土壤之间，大型聚集体和中聚集体相关的OC和TN储量没有显着差异。此外，大量土壤的OC和TN存量与骨料的稳定性密切相关。散装土壤中的有机碳储量与中骨料相关的OC储量呈正相关，而散装土壤中的总氮储量与宏观聚集的总氮储量密切相关。总体而言，这项研究的结果表明，用RP进行恢复有利于土壤氮的积累，而NG可能是提高黄土中碳固存和稳定土壤团聚体的最佳选择。大量土壤的OC和TN存量与团聚体稳定性密切相关。散装土壤中的有机碳储量与中骨料相关的OC储量呈正相关，而散装土壤中的总氮储量与宏观聚集的总氮储量密切相关。总体而言，这项研究的结果表明，用RP进行恢复有利于土壤氮的积累，而NG可能是提高黄土中固碳和稳定土壤团聚体的最佳选择。大量土壤的OC和TN存量与团聚体稳定性密切相关。散装土壤中的有机碳储量与中骨料相关的OC储量呈正相关，而散装土壤中的总氮储量与宏观聚集的总氮储量密切相关。总体而言，这项研究的结果表明，用RP进行恢复有利于土壤氮的积累，而NG可能是提高黄土中固碳和稳定土壤团聚体的最佳选择。