Nitrification plays an important role in nitrogen (N) turnover and N cycling. To date, there have been many studies on the net N turnover in grassland. However, few studies have specifically focused on the gross N turnover, which is mainly due to methodological limitations. Here, we set up an enclosed plot in a desert steppe and determined the gross nitrification (GN) rate of the soil by using the barometric process separation method. We found the seasonal dynamics of the GN in the desert steppe soil, such that the GN in the summer (117.65 ± 24.86 μg N kg⁻¹ h⁻¹) was significantly greater than in the spring and autumn (65.17 ± 7.33 μg N kg⁻¹ h⁻¹), and it peaked in July (213.75 ± 44.66 μg N kg⁻¹ h⁻¹). Additionally, the GN was lowest in the spring, with a means of 50.52 ± 3.95 μg N kg⁻¹ h⁻¹. The seasonal variation in the GN was different than the seasonal variation in the net nitrification rate, and the GN was generally much higher than the net nitrification rate. We further demonstrated that the soil moisture, temperature, bulk density and NH₄⁺-N were the main factors that influenced the seasonal variations in the GN, and that the soil moisture had the greatest impact on the GN among all the factors measured.

The stable carbon (C) isotope of soil CO₂ efflux (δ¹³CO_2e) is closely associated with soil C dynamics, which have a complex feedback relationship with climate. Three levels of warming (T0: ambient temperature (15.7 °C); T1: T0 + 2 °C; T2: T0 + 4 °C) were combined with three levels of increased precipitation (W0: ambient precipitation (245.2 mm); W1: W0 + 25%; W2: W0 + 50%) in order to quantify soil CO₂ flux and its δ¹³CO_2e values under nine treatment conditions (T0W0, T0W1, T0W2, T1W0, T1W1, T1W2, T2W0, T2W1, and T2W2) in desert steppe in an experimental beginning in 2015. A non-steady state chamber system relying on Keeling plots was used to estimate δ¹³CO_2e. The temperature (ST) and moisture (SM) of soil as well as soil organic carbon content (SOC) and δ¹³C values (δ¹³C_soil) were tested in order to interpret variations in soil CO₂ efflux and δ¹³CO_2e. Sampling was carried out during the growing season in 2018 and 2019. During the experiment, the ST and SM correspondingly increased due to warming and increased precipitation. CO₂ flux ranged from 37 to 1103 mg m⁻²·h⁻¹, and emissions peaked in early August in the desert steppe. Warming of 2 °C to 4 °C stimulated a 14% to 30.9% increase in soil CO₂ efflux and a 0.4‰ to 1.8‰ enrichment in δ¹³CO_2e, respectively. Increased precipitation raised soil CO₂ efflux by 14% to 19.3%, and decreased δ¹³CO_2e by 0.5‰ to 0.9‰. There was a positive correlation between soil CO₂ efflux and ST and SOC indicating that ST affected soil CO₂ efflux by changing SOC content. Although the δ¹³CO_2e was positively correlated with ST, it was negatively correlated to SM. The decline of δ¹³CO_2e with soil moisture was predominantly due to intensified and increased diffusive fractionation. The mean δ¹³CO_2e value (−20.2‰) was higher than that of the soil carbon isotope signature at 0–20 cm (δ¹³C_soil = −22.7‰). The difference between δ¹³CO_2e and δ¹³C_soil (Δ_e-s) could be used to evaluate the likelihood of substrate utilization. ¹³C enriched stable C pools were more likely to be utilized below 20 cm under warming of 2 °C in the desert steppe. Moreover, the interaction of T × W neither altered the CO₂ emitted by soil nor the δ¹³CO_2e or Δ_e-s, indicating that warming combined with precipitation may alleviate the SOC oxidation of soil enriched in ¹³C in the desert steppe.

The aim of this study was to investigate the effects of grazing on soil gross nitrification (GN) and denitrification (DN) rates and soil environmental factors on GN and DN in the desert grassland of northern China. Soil samples were collected from July to November in 2017 and March to June in 2018, with 5-5 soil samples taken from three enclosures (CK) vs. three heavy-grazing (G) randomized treatment blocks. We determined: (1) the soil moisture (SM), pH, bulk density (BD), total nitrogen (TN), soil organic carbon (SOC), and inorganic nitrogen (IN, NH₄⁺-N, and NO₃⁻-N) content, and (2) GN and DN. The relationship between the changes in GN, DN, and the soil environment was analyzed using stepwise multiple-regression analysis. Gross nitrification, DN, pH, BD, C/N, SM, IN, and NO₃⁻-N varied significantly by month. Grazing induced significant increases in SM and NO₃⁻ only. GN in the CK treatment was related to NH₄⁺-N and NO₃⁻-N, while GN in the G treatment was related to NH₄⁺-N and SM. DN in the CK treatment was related to NH₄⁺-N, while DN in the G treatment was related to C/N. Additionally, GN and DN had obvious seasonal variations and reached a maximum in July. This highlights the different underlying mechanisms that affect soil GN and DN and the dynamics, particularly in the desert grassland system.

To investigate the effects of restoration measures on degraded grasslands in the typical steppe of Inner Mongolia, two restoration treatments—enclosure (EN) and enclosure with additional bio-organic fertilizer application (EF)—were established with moderately grazed degraded grassland as the control (MG). The impacts of these measures on vegetation community characteristics and soil physicochemical properties were systematically analyzed, and the post-restoration ecological benefits were quantitatively evaluated using an assessment system. The results showed that (1) over the two experimental years, both EN and EF treatments improved vegetation community characteristics and soil physicochemical properties, with the overall restoration effect ranking as EF > EN > MG; (2) compared with the first experimental year, the restoration of plant and soil characteristics was more significant in the second year; (3) ecological benefit analysis showed that the Soil Quality Index (SQI) decreases with soil depth. Compared to MG, the EF treatment increased topsoil SQI by 38.89–65.71% in the first and second years of restoration, respectively. Comparative evaluation indicated that EF led to more significant increases in vegetation community characteristics than MG. Thus, the EF treatment can significantly enhance the ecological benefits of typical degraded grasslands.

Biogas slurry is rich in nitrogen, phosphorus and bioactive substances, making it an effective material for restoring degraded grasslands. Against this background, we conducted a field experiment in Zhenglan Banner, Xilingol League, Inner Mongolia Autonomous Region, China, from 2024 to 2025, to study the short-term effects of biogas slurry fertilizer on vegetation characteristics and above- and belowground plant traits. The experiment comprised three treatments: a water control (CK), 50% diluted biogas slurry (BS_50%), and full-strength biogas slurry (BS_100%). All treatments were applied at a rate of 300 m³·ha⁻¹, with CK receiving an equivalent volume of water. The biogas slurry contained 0.11% nitrogen (N), 0.07% phosphorus (P₂O₅), and 0.09% potassium (K₂O). Results showed that, compared with the control, biogas slurry application increased plant height, coverage, and biomass by 8.04–54.00%, 5.48–17.76%, and 18.40–96.01% in the first year, respectively. Plant crude protein and crude fat also increased by 7.33–31.17% and 21.54–30.00%. In the second year, the increases were 26.41–50.22%, 6.16–20.55%, and 13.91–52.42% for plant height, coverage, and biomass and 4.46–28.27% and 14.24–19.89% for crude protein and crude fat, respectively. The carbon, nitrogen and isotope indices of leaves and roots also increased simultaneously. Biogas slurry application altered plant community composition, BS_50% transiently increased plant family richness, BS_100% exerted persistent inhibitory effects, and species diversity across all fertilization treatments showed a recovery trend in the second year. Principal component analysis and redundancy analysis showed that treatment groups were clearly separated in 2024 but overlapped substantially in 2025. Root δ¹³C and root δ¹⁵N were key indicators distinguishing vegetation community characteristics. The results of this study confirmed that the application of biogas slurry fertilizer could actively improve the vegetation recovery of degraded grasslands. It provided reference support for the resource utilization of biogas slurry fertilizer and the sustainable management of grassland ecosystems.

Organic carbon in grassland mainly exists in the soil, and root production and turnover play important roles in carbon input into the soil. However, the effects of climate change on plant root dynamics in desert steppe are unknown. We conducted an experiment in a desert steppe, which included ambient temperature (T0); temperature increased by 2 °C (T1); temperature increased by 4 °C (T2); natural precipitation (P0); precipitation increased by 25% (P1); precipitation increased by 50% (P2); and the interaction between warming and increased precipitation. Plant community aboveground characteristics; root production; and root turnover were measured. We found that the root length production of the T0P2; T1P1; T2P0; and T2P1 treatments were significantly higher than that of the T0P0 treatment, with an increment of 98.70%, 11.72%, 163.03%, and 85.14%, respectively. Three treatments with temperature increased by 2 °C (T1P0; T1P1; and T1P2) and significantly increased root turnover rate compared to the T0P0 treatment, with increases of 62.53%, 42.57%, and 35.55%, respectively. The interaction between warming and increased precipitation significantly affected the root production of the community (p < 0.01), but this interaction was non-additive. Future climate warming will benefit the accumulation of root-derived carbon in desert steppe communities.