As nitrous oxide (N₂O) is one of the most important greenhouse gases, N₂O emission pathways and regulation techniques in soils with different vegetation types have become a research focus. Currently, a diverse array of research exists on the N₂O emissions from soils of different vegetation types, e.g., forest, grassland, and agriculture. Few studies have investigated the microbial processes of N₂O emissions from lawn soils. Fertilization levels in lawn soils are often similar to or much higher than those in agricultural ecosystems, thus fertilized lawn is an important source of atmospheric N₂O. In the study, we employed the ¹⁵N-nitrate labelling method combined with the nitrification inhibition technique to distinguish microbial processes and their contribution to N₂O emissions in long-term nitrogen fertilised lawns. We found that the N₂O emission rate from the control treatment was 1.0 nmol g⁻¹ h⁻¹ over the incubation, with autotrophic nitrification contributing 60%. The N₂O emission rate increased to 1.4 nmol g⁻¹ h⁻¹ from the soil treated with long-term N fertilization, and the contribution of autotrophic nitrification increased to 69%. N fertilization did not significantly increase the contribution of denitrification (24–26%) in the total N₂O emissions. However, N fertilization substantially decreased the contribution of heterotrophic nitrification from 13 to 0.4% in the total N₂O emissions. Co-denitrification to N₂O was detected but the overall contribution was of minor importance (3–5%). The correlation analysis revealed that soil NO₃⁻ levels were the main influencing factors in the N₂O producing microbial processes. Our results suggest that N fertilization altered both N₂O production rates and the contribution pattern of microbial processes, and indicate the autotrophic nitrification and heterotrophic nitrification are more sensitive to N fertilization than denitrification and co-denitrification.

Atmospheric nitrogen(N) deposition increased soil active N, and excessive N content led to the increase of the ratio of nitrogen to phosphorus (N: P), which changed plant growth from N limitation to phosphorus(P) limitation. Potentilla is not only an important native greening material, but also a common diversity component in various grasslands in China. Its population fluctuation in the process of N deposition will affect the species diversity and productivity of grassland ecosystem. Potting experiment was conducted for 2 years with Potentilla tanacetifolia, a common species in the northern warm steppe, as the material. Through the interactive treatment of different N addition (0, 10, 20, 40 kg N ha yr⁻¹) and P addition (4, 6, 8 kg P ha yr⁻¹) gradients, to analysis the feedback effect between leaf N and P content and net photosynthetic rate (Pn). We explored the N: P threshold of N and P limitation from the perspective of Pn. The results showed that: 1) Under low soil N concentration, P addition can promote N absorption of P.tanacetifolia, while the high soil N concentration can reduce the N: P by increasing the leaf P content to weaken the limiting effect caused by nutrient imbalance of plants. 2) In N addition environment, proper P addition increased Pn by increasing stomatal conductance (Gs), while excessive P addition decreased Gs and inhibited Pn. 3) The Pn showed a single peak normal distribution characteristic with the enhancement of the N: P of leaves, and the Pn was at a high level between 14.5–17.0. It was preliminarily believed that the threshold value of N: P in leaves of P.tanacetifolia was 14.5–17.0. Plant photosynthesis is very sensitive to the environment and easy to be affected by the external environment. The results of N and P addition showed that Pn of broad-leaf forbs was easily affected by N and P restriction, and P addition increased Pn of broad-leaf forbs under N restriction. There was a certain relationship between N:P and Pn. It was preliminarily believed that the N: P of P.tanacetifolia leaves is not limited by nitrogen and phosphorus in the range of 14.5-17.0.

Heterotrophic nitrification is a process of organic nitrogen degradation completed by the participation of heterotrophic nitrifying microorganisms, which can accelerate the nitrogen transformation process. However, the current research mainly focuses on heterotrophic nitrifying bacteria and their ammonium degradation capacities. And there is little accumulation of research on fungi, the main force of heterotrophic nitrification, and their capacities to transform organic nitrogen. In this study, novel heterotrophic nitrifying fungus (XTY1) and bacterium (GS2) were screened and isolated from upland soil, and the strains were identified and registered through GenBank comparison. After 24 h single nitrogen source tests and ¹⁵N labeling tests, we compared and preliminarily determined the heterotrophic nitrification capacities and pathways of the two strains. The results showed that XTY1 and GS2 had different transformation capacities to different nitrogen substrates and could efficiently transform organic nitrogen. However, the transformation capacity of XTY1 to ammonium was much lower than that of GS2. The two strains did not pass through NH₂OH and NO₂⁻ during the heterotrophic nitrification of organic nitrogen, and mainly generated intracellular nitrogen and low N₂O. Other novel organic nitrogen metabolism pathways may be existed, but they remain to be further validated.

Atmospheric nitrogen (N) deposition and climate warming significantly influence soil nitrogen transformation processes. Nitrification, a key step in the N cycle, is primarily driven by ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB). However, their responses to environmental changes in warm-temperate shrub tussock grasslands—a major grassland type in China—remain poorly understood. In this study, we examined the effects of N addition and warming on the community composition of ammonia oxidizers and soil nitrification potential (NP) through pot experiments simulating field conditions. Our results demonstrated that (1) the AOB community was more responsive to N addition and warming than AOA, with the genus Nitrosospira increasing by 6.30–21.75% under treatments; (2) soil pH increased significantly under warming (from 6.53 to 6.86) but remained unchanged under N addition; (3) NP increased significantly under all treatment conditions, most markedly under warming alone (2.83-fold increase compared to the control); and (4) NP was positively correlated with both soil pH and the relative abundance of Nitrosospira. These findings suggest that warming and N deposition enhance nitrification in shrub tussock soil by altering AOB community structure and increasing soil pH. This study provides new insights into the microbial mechanisms driving N cycling in warm-temperate grasslands under global change.

The establishment of native grassland species is widely implemented on abandoned land as a strategy to restore degraded soils. However, its effects on soil properties are highly species‐specific, as plant‐driven physicochemical changes subsequently reshape microbial community structure. The linkages between soil physicochemical properties and microbial communities following native grassland establishment remain poorly understood. To address this knowledge gap, we examined the effects of 11 native grassland species on soil physicochemical properties and fungal community structure. Using co‐occurrence network analysis, we elucidate how plants drive fungal community reorganisation through soil‐mediated trophic pathways. The results showed that soil aggregate stability, chemical properties, and fungal communities differed significantly among the 11 species. Soil chemical properties, such as pH and EC, correlated with symbiotic fungi dominated modules; both soil aggregate stability and chemical properties were linked to pathogenic fungi dominated modules, while saprophytic fungi dominated modules displayed no linkage to either soil aggregate stability or chemical properties. These findings establish that fungal trophic modes govern species‐dependent restoration outcomes via modular soil–microbe linkages, thereby offering predictive frameworks for species‐specific management of abandoned soils.

Invasive plants often alter biological soil conditions to increase their own competitiveness. Through indoor simulated nitrogen deposition culture experiments, we investigated the differences in growth indicators and nutrient content levels between the invasive plant Cenchrus spinifex Cav. and the native symbiotic plant Agropyron cristatum (L.) Gaertn. under diverse nitrogen application modes and planting-competition ratios. Furthermore, we examined the alterations in key microbial communities involved in soil nitrogen cycling of C. spinifex. The results indicated that the invasion of C. spinifex could inhibit the growth of native plants, and in fact altered the accumulation and transformation processes related to soil nitrogen, resulting in reduced rates of soil nitrogen transformation. The overarching aim of this research was to construct a theoretical foundation for the scientific comprehension of the invasion mechanisms of C. spinifex, in order to better prevent the further spread of this invasive plant and mitigate its pernicious impact on the current environment.