Aims

Abandoned grasslands may affect soil carbon and respiration components; however, it is unclear how microorganisms are involved in this process.

Methods

In this study, ten-year intervals of a 50-year sequence of restored abandoned grassland was selected on the Loess Plateau, with farmland used as a control. A total of 18 soil samples were collected. Soil samples were performed to indoor experiments and high-throughput sequencing to determine soil physicochemical properties, carbon components, enzyme activity, respiration components, and microbial community composition and diversity.

Results

The results showed that the vegetation structure and species diversity of abandoned grassland changed over time, which led to changes in soil physicochemical properties. Soil inorganic carbon (from 9.71 to 18.60 g/kg), organic carbon (from 2.05 to 9.36 g/kg), resistant organic carbon (from 0.92 to 7.22 g/kg), labile organic carbon (from 1.03 to 2.14 g/kg) and autotrophic respiration (from 0.57 to 1.93 μmol·m⁻²·s⁻¹) increased with the prolonged abandonment period, but heterotrophic respiration declined in 40–50 years (reduce from 4.92 to 4.63 μmol·m⁻²·s⁻¹). Meanwhile, we found a significant correlation between carbon and respiration components. As well, the composition and diversity of microorganisms are also greatly impacted. The main bacterial phyla were Actinobacteriota, Proteobacteria, Acidobacteria, and Chloroflexota. The main fungal phyla were Ascomycota, Mortierellomycota, and Basidiomycota, and the fungal diversity index increased with the prolonged abandonment period. Redundancy analyses showed that soil carbon components, enzyme activity, and respiration components were positively correlated with Acidobacteria, Mortierellomycota, fungal diversity (Ace, and Chao 1) and negatively correlated with Cyanobacteria and Glomeromycota.

Conclusions

The process of vegetation restoration on the Loess Plateau has increased soil carbon content and enzyme activities, thereby increasing soil microbial activity and diversity. Enhanced soil microbial activity promoted soil respiration, but fungi had a greater impact on soil respiration compared to bacteria. This suggests that we should pay more attention to the role of soil fungi in the future management of soil carbon pools in grassland ecosystems.

中文翻译：

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黄土高原废弃草地土壤细菌和真菌对碳和呼吸成分的差异响应

目标

废弃草地可能会影响土壤碳和呼吸成分；然而，目前尚不清楚微生物如何参与这一过程。

方法

本研究以黄土高原地区50年的废弃草地恢复序列为10年间隔，以农田作为对照。共采集土壤样品18个。对土壤样品进行室内实验和高通量测序，以确定土壤理化性质、碳成分、酶活性、呼吸成分以及微生物群落组成和多样性。

结果

结果表明，废弃草地的植被结构和物种多样性随着时间的推移而发生变化，从而导致土壤理化性质的变化。土壤无机碳（9.71至18.60克/公斤）、有机碳（2.05至9.36克/公斤）、抗性有机碳（0.92至7.22克/公斤）、不稳定有机碳（1.03至2.14克/公斤）随着废弃时间的延长，自养呼吸（从0.57μmol·m ^-2 ·s ^-1增加到1.93 μmol·m -2 ·s -1 ）增加，但异养呼吸在40-50年间下降（从4.92减少到4.63 μmol·m ^-2 ·s ^-1） 。同时，我们发现碳和呼吸成分之间存在显着的相关性。此外，微生物的组成和多样性也受到很大影响。主要细菌门为放线菌门、变形菌门、酸杆菌门和绿屈菌门。主要真菌门为子囊菌门、被孢霉门和担子菌门，真菌多样性指数随着废弃时间的延长而增加。冗余分析表明，土壤碳成分、酶活性和呼吸成分与酸杆菌、被孢霉、真菌多样性（Ace和Chao 1）呈正相关，与蓝藻和球囊菌呈负相关。

结论

黄土高原植被恢复过程增加了土壤碳含量和酶活性，从而增加了土壤微生物活性和多样性。土壤微生物活性的增强促进了土壤呼吸，但与细菌相比，真菌对土壤呼吸的影响更大。这表明我们在未来草地生态系统土壤碳库管理中应更加重视土壤真菌的作用。