Old fields are spreading in the world because of agriculture abandonment, and they show a persistence of exotic plant species with little recovery towards the original vegetation composition. Soil biota may also differ between old fields and native grasslands, but were comparatively less studied than plant communities, despite their importance in biogeochemical processes. Here we compared soil bacterial communities of exotic-dominated old fields with those of remnants of native grasslands in the Inland Pampa, Argentina, using the 16S rRNA gene amplicon sequencing approach. We also characterized plant communities, soil physico-chemical properties, and soil respiration. We expected more diverse soil bacterial communities, with higher heterogeneity, in remnant grasslands than in old fields because of a more diverse and more heterogeneous plant community. However, our results showed that soil bacterial communities had higher Shannon diversity in old fields than in remnant grasslands, but richness was not significantly different. Also we found different bacterial community compositions between grasslands even at a low taxonomic level. On the other hand, old fields harbored less heterogeneous bacterial communities than remnants, and bacteria and plant beta diversity were correlated. Despite contrasting plant and bacterial composition between old fields and remnant grasslands, soil physico-chemical properties were quite similar between grasslands. Overall, our results showed that bacterial communities in grassland soils were associated with changes in plant communities after agricultural abandonment. Plant-microbial feedbacks might regulate plant and soil bacterial community assemblage in old fields, yet further research is needed to demonstrate this potential feedback mechanism.

由于农业的遗弃，旧田地在世界范围内扩散，它们显示了外来植物物种的持久性，几乎无法恢复到原始植被组成。在老田和天然草地之间，土壤生物区系也可能有所不同，但是尽管它们在生物地球化学过程中的重要性，但与植物群落相比，研究较少。在这里，我们使用16S rRNA基因扩增子测序方法，比较了异国情调占主导地位的旧田的土壤细菌群落与阿根廷内陆潘帕州的天然草原残余土壤群落。我们还描述了植物群落，土壤理化性质和土壤呼吸的特征。我们期望有更多的土壤细菌群落，具有更高的异质性，残留草地上的土地比旧土地上的土地更丰富，因为植物群落更加多样化和多样化。然而，我们的研究结果表明，旧田地的土壤细菌群落具有较高的香农多样性，而剩余草地的香农多样性却没有显着差异。我们还发现，即使在低分类学水平下，草原之间的细菌群落组成也不同。另一方面，旧田地的异质细菌群落比残留物少，细菌与植物的β多样性相关。尽管旧田地和残存草地之间的植物和细菌组成存在差异，但草地之间的土壤理化性质非常相似。总体，我们的研究结果表明，弃耕后草地土壤中的细菌群落与植物群落的变化有关。植物微生物的反馈可能调节旧田中植物和土壤细菌群落的聚集，但是还需要进一步的研究来证明这种潜在的反馈机制。