CO₂ fixation by autotrophic microbes has a significant effect on the carbon cycle in temperate grasslands. Nitrogen (N) deposition in soil has been steadily increasing for decades, which has consequences for soil microorganisms. However, the impact of this deposition on the diversity and abundance of CO₂-fixing soil microorganisms remains unclear in temperate grasslands. In the present study, the cbbL gene, a key gene in the Calvin–Benson–Bassham cycle that encodes the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase, was used to study CO₂-fixing microbes under different rates of N addition (0, 15, 30, 50, 100, and 150 kg N ha^–1 yr^–1) in a 9-year field experiment in a temperate grassland. The results showed that N addition led to significant reductions in cbbL gene abundance and genetic diversity and altered cbbL gene community composition. High N addition enhanced the relative abundances of Acidiferrobacterales and Rhizobiales but reduced those of Burkholderiales and Rhodobacterales. Structural equation modeling further revealed that N addition primarily reduced cbbL genetic diversity by increasing the soil NO₃-N content and decreasing the soil pH. N addition indirectly reduced cbbL gene abundance, possibly by increasing the soil N/phosphorus (P) ratio and decreasing the soil pH. These findings suggest that N addition increases the soil available N and causes soil acidification, which may inhibit growth of CO₂-fixing microbes to some extent.

Grassland soil organic carbon (SOC) accounts for 15.5% of the SOC in reservoirs of terrestrial carbon (C) and is a major component of the global C cycle. Current and future reactive N deposited on grassland soils may alter biogeochemical processes and soil microbes. Microorganisms perform most of the decomposition on Earth and shift SOC accumulation. However, how variation in the identity and composition of the bacterial community influences SOC is far from clear. The objective of this study is to investigate the responses of SOC concentration to multiple rates of N addition as well as the roles of bacteria in SOC accumulation. We studied SOC storage and bacterial community composition under N addition treatments (0, 1.5, 3.0, 5.0, 10.0, 15.0, 20.0, and 30.0 g N·m⁻² yr⁻¹) in a 6-yr field experiment in a temperate grassland. We determined the soil inorganic nitrogen concentration and pH in a 0–10 cm soil layer. We used high-throughput genetic sequencing to detect bacteria. N addition led to significant increases in the concentrations of SOC. N addition reduced the soil pH but increased the NO₃-N and NH₄-N levels. The bacterial diversity was highest under low nitrogen addition. N addition increased the relative abundance of Proteobacteria, and Proteobacteria became the second dominant phylum under high N addition. Structural equation modeling further revealed that soil pH and bacterial community structure have an impact on SOC under N deposition. Nitrogen-regulated SOC is associated with Proteobacteria and Planctomycetes. These findings suggest that N deposition may alter the SOC content, highlighting the importance of understanding changes in the bacterial community for soil nutrients under N deposition.

Ecological restoration has a positive impact on global climate change. How plant-soil stores carbon in degraded grassland ecological restoration requires long-term monitoring and support. To reveal the dynamics of plant-soil carbon storage in the succession process of ecological restoration, compare the effects of artificial interference and natural restoration, and determine the impact of climate change and biodiversity on vegetation soil carbon storage, we conducted a study in National Grassland Natural Park, which is located on the southern foot of the Yinshan Mountains in Hohhot, Inner Mongolia, China. Based on long restoration chronosequences (2012–2022), using a space-for-time substitution approach and one-way ANOVA tests, Pearson correlation and structural equation modeling were used to investigate the interactions among these various factors. The results indicated that the carbon storage of aboveground vegetation first increased, and then, decreased with time. The underground root carbon storage and soil carbon storage at 0–10 cm and 20–30 cm first increased, then decreased, and finally, stabilized. The highest soil carbon storage (0–30 cm) was 102.11 t/ha in 2013, which accounted for 96.61% of the total organic carbon storage. The Shannon–Wiener index, individual number of species, and surface root carbon storage (0–10 cm) significantly increased the carbon storage of surface soil (0–10 cm) (p < 0.05). Compared to natural restoration, artificial restoration over seven years decreased soil carbon storage at 0–30 cm and underground root carbon storage at 0–10 cm (p < 0.05). Consequently, combining artificial restoration with natural restoration can help in establishing a more stable ecosystem faster and in increasing the carbon storage of the ecosystem. It is an effective management measure to promote grassland restoration in arid areas. Also, climate (MAT, MAP) change was closely correlated with plant-soil carbon storage.

Pseudomonas sp. ZS001 is a bacterium potentially degrading soluble starch isolated from peanut plantation soil sprayed with starch-based material in Dasi Town, Tianjin. Reporting the genome sequence of strain ZS001 can help us understand the genome composition, potential functional characteristics, and application value of Pseudomonas members at the genetic level.