An experiment was conducted to investigate the effect of seasonally asymmetric warming on ecosystem respiration (Re), CH₄ uptake, and N₂O emissions in alpine grassland of the Tianshan of central Asia, from October 2016 to September 2019. The annual means of Re, CH₄, and N₂O fluxes in growing season were 42.83 mg C m⁻² h⁻¹, −41.57 µg C m⁻² h⁻¹, and 4.98 µg N m⁻² h⁻¹, respectively. Furthermore, warming during the non-growing season increased Re and CH₄ uptake by 7.9 % and 10.6 % in the growing season and 10.5 % and 9.2 % in the non-growing season, respectively. However, the increase in N₂O emission in the growing season was mainly caused by the warming during the growing season (by 29.7 %). The warming throughout the year and warming during the non-growing season increased N₂O emissions by 101.9 % and 192.3 % in the non-growing season, respectively. The Re, CH₄ uptake, and N₂O emissions were positively correlated with soil temperature. Our results suggested that Re, CH₄ uptake, and N₂O emissions were regulated by soil temperature, rather than soil moisture, in the case of seasonally asymmetric warming. In addition, the response rate was defined by the changes in greenhouse gas fluxes driven by warming. In our field experiment, we observed the stimulatory effect of warming during the non-growing season on Re and CH₄ uptake. In contrast, the response rates of Re and N₂O emissions were gradually attenuated by long-term annual warming, and the response rate of Re was also weakened by warming over the growing season. These findings highlight the importance of warming in the non-growing season in regulating greenhouse gas fluxes, a finding which is crucial for improving our understanding of C and N cycles under the scenarios of global warming.

The semiparasitic weed Pedicularis kansuensis Maxim. has rapidly spread in the alpine grasslands of northern China over the past twenty years and has caused serious ecological problems. In order to effectively halt the spread of this weed, a thorough understanding of the dormancy type and the seed-germination ecology of P. kansuensis is required. We have conducted a series of experiments to investigate the effects of plant growth regulators (gibberellin (GA₃) and strigolactone synthesis (GR24)), as well as different abiotic (temperature, light, cold stratification, and drought) and biotic (aqueous extracts of three native dominant plants) factors on the seed-germination characteristics of P. kansuensis. The seed-germination percentages ranged from 2% to 62% at all of the temperatures that were examined, with the highest occurring at 25/10 °C. The light conditions did not significantly affect the germination percentage. The seed germination was greatly improved after two to eight weeks of cold stratification. The seed germination decreased dramatically with an increasing polyethylene glycol (PEG-6000) concentration, from 55% to 0%, under 10% and 20% PEG-6000. The seed germination was improved at a proper concentration of GA₃, GR24, and the aqueous extracts of Festuca ovina L., Stipa purpurea L., and Leymus secalinus (Georgi) Tzvel. Furthermore, in the pot experiment, the seedling emergence of P. kansuensis was also improved by the cultivation of these three dominant grasses. These findings indicate that the dormancy type of P. kansuensis seeds is non-deep physiological dormancy, and such findings will help in paving the way for the creation of effective weed management strategies, based on a thorough knowledge of germination ecology.

Aboveground biomass (AGB) is a sensitive indicator of grassland resource quality and ecological degradation. However, accurately estimating AGB at large scales to reveal long-term trends remains challenging. Here, single-factor parametric models, multi-factor parametric models, and multi-factor non-parametric models (Random Forest) were developed for three grassland types (alpine meadow, alpine grassland, and swampy meadow) in the Bayanbuluk Grassland using MODIS satellite data and environmental factors, including climate and topography. A 10-fold cross-validation method was employed to assess the accuracy and stability of these models, and an AGB remote sensing inversion model was established to estimate the AGB of the Bayanbuluk Grassland from 2005 to 2024. Moreover, the BEAST mutation test, Theil–Sen median trend analysis, and Mann–Kendall test were used to analyse the temporal trends of AGB, identify the years of mutation points, and explore the changes in AGB across the entire study period (2005–2024) and at 5-year intervals, considering the influence of climatic factors. The results indicated that the machine learning (RF) model outperformed both multi-factor parametric and single-factor parametric models, with specific improvements in R² and RMSE across all grassland types. For instance, the RF model achieved an R² of 0.802 in alpine grasslands, outperforming the multi-factor parametric model with an R² of 0.531. The overall spatial distribution of AGB exhibited heterogeneity, with a gradual increase from northwest to southeast over the study period. Interannual AGB changes fluctuated significantly, with an overall increasing trend. Notably, from 2015 to 2019, 78% of the Bayanbuluk Grassland area showed a nonsignificant increase in AGB. Specifically, 46.7% of the alpine meadow AGB, 23% of the alpine grassland AGB, and 8.3% of the swampy meadow AGB showed non-significant increases. Further, temperature was found to be the dominant driver of AGB, with a stronger effect on alpine meadows and alpine grasslands than on swampy meadows. This is likely due to the relatively constant moisture levels in the swampy meadows, where precipitation plays a more prominent role. This study provides a comprehensive assessment of AGB trends, including both spatial and temporal analyses, which will inform future grassland resource management.

To better understand the phenotypic plasticity of the highly invasive native weed, Pedicularis kansuensis, we investigated and compared phenotypes (morphology, biomass, and nutrient composition) at different levels of invasion (low: 0 < cover ≤ 30%; medium: 30% < cover ≤ 70%; and high: cover > 70%). With the increase in invasion level, the plasticity of inflorescence length, single-leaf thickness, and specific leaf area increased, while the plasticity of single-leaf area and crown width decreased. During the invasion process, we observed significant density-dependent effects, including changed morphological characteristics, increased total aboveground biomass, and decreased plant height, inflorescence length, root length, crown width, single-leaf area, structure biomass of structures (root, stem, inflorescence), and individual biomass (p < 0.05). During the reproductive period of P. kansuensis, the resource allocation (C, N, and P content, total biomass, biomass allocation) to inflorescence was significantly higher than to root and stem, while the elemental ratios (C:N, C:P, N:P) of inflorescences were significantly lower than those of roots and stems (p < 0.05). When the invasion level increased, the ratio of inflorescence C:N and biomass allocation to roots increased significantly; conversely, inflorescence N and biomass allocation to inflorescences and stems decreased significantly (p < 0.05). This led to a decrease in resource allocation to aboveground parts and more resources allocated to the roots, significantly increasing the root-to-shoot ratio (p < 0.05). Based on the phenotypic differences among different invasion levels, we suggest that P. kansuensis adapted to a competitive environment by regulating morphology, biomass, and nutrient allocation, thereby enhancing the potential of invasion and spread.

In order to study the changes in invasive plant population characteristics under different nutrient addition treatments, this study used the native invasive species Pedicularis kansuensis, which is spreading in the Bayabulak alpine grassland, as the research object and conducted two consecutive years of field studies in which nutrients were added to plots. Changes in the P. kansuensis population’s invasive characteristics were monitored in 2020 and 2021 in four different nutrient-addition treatments, namely no-nutrients (control), low-nitrogen, high-nitrogen, and phosphorus treatments. The result showed that (1) nutrient addition had significant effects on P. kansuensis height and root/shoot ratio (p < 0.05); the time effect had significant effects on P. kansuensis height, coverage, abundance, aboveground biomass, and belowground biomass (p < 0.01), and the interaction between nutrient addition and time had a significant effect on P. kansuensis height (p < 0.01). (2) Nitrogen addition effectively inhibited the growth and the development of P. kansuensis, especially under high-nitrogen conditions in the second growing season, where the effect of height (2.50 cm), coverage (0.13%), richness (3 strains), aboveground biomass (0.21 g m⁻²), and belowground biomass (0.03 g m⁻²) was significant, with the P. kansuensis population almost disappearing by the end of the trial. (3) Phosphorus addition had no significant effect on the P. kansuensis population’s invasive characteristics. These results indicate that higher nitrogen addition could effectively slow the invasion of the P. kansuensis population, and the findings of this study could provide certain baseline data and scientific guidance for the effective control of the P. kansuensis invasion of the Bayabulak alpine grassland in the future as well as identify certain theoretical bases for the effect of nutrient addition on invasive plants overall.

Plant invasion significantly disrupts plant community structure and ecosystem functioning, especially the stability of net primary productivity (NPP). However, evidence remains scarce regarding how invasion affects NPP stability at both community and ecosystem levels, particularly whether these effects are consistent between aboveground and belowground systems. Here, we investigated the responses of the stability of both aboveground and belowground NPP (ANPP and BNPP) to the invasion of the parasitic plant Pedicularis kansuensis , based on a two‐year manipulative experiment in an alpine grassland in northwest China. Invasion decreased ANPP resistance while increasing its recovery and conversely increased BNPP resistance but decreased its recovery. Notably, the asymmetric responses of ANPP and BNPP to invasion underscored the complexity of grassland ecosystems and highlighted the critical role of belowground processes in maintaining ecosystem recovery. Species asynchrony and richness were key factors for ANPP stability, whereas BNPP stability was more directly influenced by invasive species, contributing more significantly to overall NPP stability. Our findings provide crucial evidence that the stability of aboveground and belowground components responds asymmetrically to invasion, emphasizing the need for future comprehensive assessments of both dimensions in ecosystem studies. The insights gained underline the importance of belowground stability for sustaining ecosystem recovery and offer guidance for ecological management and conservation strategies.