Northern China's Grasslands Research Articles

The impact of grazing intensity on the allelopathic effect of Artemisia frigida in a temperate grassland in northern China

Allelopathy is an important factor affecting plant community structure. However, few studies have focused on the mechanisms of allelopathy in the process of community succession driven by different grazing intensities. Therefore, field sampling, indoor experiments and field control experiments were conducted in a temperate grassland in northern China. We aimed to detect the impact of different grazing intensities on the chemical components and allelopathic effect of aqueous extracts of Artemisia frigida. The seed germination rate, radicle length, plant height and biomass of the four tested plant species were used to quantify the allelopathic effect of A. frigida. Grazing intensity altered the composition and concentration of chemical components contained in aqueous extracts of A. frigida. The maximum relative contents of 1,8-cineole and β-terpineol both occurred under heavy grazing. The allelopathic effect of A. frigida varied significantly among different grazing intensities and tested species, and the interaction effects between grazing intensity and tested species were also significant. The allelopathic effects of A. frigida significantly influenced the seed germination rate and radicle length of all the test species except Medicago sativa. The aqueous extracts of A. frigida also significantly affected the aboveground, belowground and total biomass of M. sativa and Melilotus officinalis. The allelopathic effect of A. frigida significantly promoted its own plant biomass and inhibited the plant biomass of Stipa krylovii. Our results confirmed that the allelopathic effects of A. frigida partly regulated the process of species composition in degraded rangelands.

Effects of precipitation regime on the structure of soil micro-food web in the grassland of northern China

Effects of precipitation regime on the structure of soil micro-food web in the grassland of northern China

Seasonal and interannual variations in energy balance closure over arid and semi-arid grasslands in northern China

Seasonal and interannual variations in energy balance closure over arid and semi-arid grasslands in northern China

Rare earth element geochemistry in soils along arid and semiarid grasslands in northern China

Rare earth element geochemistry in soils along arid and semiarid grasslands in northern China

Seasonal Precipitation Regulates the Magnitude and Direction of the Effect of Nitrogen Addition on Net Ecosystem Co 2 Exchange In A Saline-Alkaline Grassland of Northern China

Seasonal Precipitation Regulates the Magnitude and Direction of the Effect of Nitrogen Addition on Net Ecosystem Co 2 Exchange In A Saline-Alkaline Grassland of Northern China

Grassland management strategies influence soil C, N, and P sequestration through shifting plant community composition in a semi-arid grasslands of northern China

Current studies regarding the effects of grassland management strategies on the soil nutrient cycle have mostly focused on soil organic carbon (SOC). Less is known about the responses of SOC, total nitrogen (TN), and total phosphorous (TP) stocks to grassland management strategies at different soil depths. We therefore quantified vertical variations in SOC, TN, and TP stocks as well as controlling factors under three grassland management strategies (i.e., enclosure control, grazing twice a year, grazing combined with mowing) in 2014 and 2017 in a semi-arid grassland of northern China. We found that grazing twice a year and grazing combined with mowing led to an increase in plant production as well as soil C and N sequestration during 2014 to 2017. Changes in plant aboveground biomass (AGB), belowground biomass (BGB), and root-to-shoot ratio (R:S) all exerted significant positive effects on changes in soil C and N sequestration in the surface soil layer (0–30 cm), while changes in AGB and plant community composition played a more important role in mediating soil C, N, and P sequestration in response to grassland management strategies in the subsoil layer (30–100 cm). Specifically, grassland management strategies influence soil C, N, and P sequestration capacity by altering plant community composition. The results of this study provide new insights into the response mechanisms of plants and soils to grassland management practices and offer a range of new possible strategies that might be applied to the effective management of semi-arid grasslands.

Mechanisms of grazing management impact on preferential water flow and infiltration patterns in a semi-arid grassland in northern China

Grazing management is widely used to control grassland degradation in Inner Mongolia. However, the correlation between the soil physical properties, root traits, and infiltration patterns of different types of grazing management has seldom been studied. To reveal the effect of grazing management on water infiltration and preferential flow behavior, we first investigated the soil and plant properties in a grazing exclusion (19 years, GE), cold-season grazing (19 years, CG), and free-grazing grassland (19 years, FG) in a semi-arid grassland in Inner Mongolia. Dye tracer infiltration was adopted to obtain the water infiltration patterns from different types of grazing management. Finally, root biomass and root morphological traits were measured in a field experiment. The results showed that the plant height, vegetation coverage, richness index, Shannon-Wiener index, soil water content, total porosity, and mean weight diameter were higher at the GE site than at the FG site, whereas soil bulk density and sand content were lower at the GE site than at the FG site (P < 0.05). In addition, the root mean diameter, specific root length, and root mass density were higher at the GE site than at the FG site. As a result, differences in these root traits and soil and vegetation properties affected the preferential water flow behavior in the three types of grassland. The preferential flow evaluation index (PFI) of the GE, CG, and FG sites was 0.89, 0.30, and 0.15, respectively, which indicated that more obvious preferential flow occurred at the GE site than at the CG and FG sites. These findings highlight that the long-term GE enhanced plant density and root biomass, which could potentially promote the natural restoration of soil pores and preferential water infiltration. Therefore, local governments and herders should implement GE rather than other grazing management practices to prevent grassland degradation.

Dry Eye Disease Among Mongolian and Han Older Adults in Grasslands of Northern China: Prevalence, Associated Factors, and Vision-Related Quality of Life.

Purpose: Dry eye disease (DED) is projected to have increasing public health burden in China with the aging population. No published studies on the epidemiology of DED have been found in grasslands. We estimated DED prevalence among older adults living in grasslands of northern China and investigated its associated factors and impact on vision-related quality of life (VR-QoL).Methods: A multistage cluster random sampling technique was used to select Mongolian and Han participants aged over 40 from November 2020 to May 2021 in this area. An assessment of DED was performed with Ocular Surface Disease Index (OSDI) questionnaire, Schirmer's I test (ST), and Tear film break up time (TBUT). All the participants completed the Chinese version of National Eye Institute Visual Function Questionnaire (NEI-VFQ-25) assessing VR-QoL.Results: Of the 1,400 enumerated residents, 1,287 were examined. The overall age and gender standardized prevalence of DED was 34.5%, of which, 32.6% of Mongolian and 35.4% of Han had DED. In a multivariate model, statistically significant associations were found with advancing age [odds ratio (OR) 1.03, 95% confidence interval (CI) 1.02–1.04], female gender (OR 1.32, 95% CI 1.04–1.68), smoking (OR 0.7, 95% CI 0.5–0.98), anti-fatigue eye-drop use (OR 0.56, 95% CI 0.41–0.77), milk product intake (OR 0.55, 95% CI 0.39–0.77), number of household members (OR 0.8, 95% CI 0.72–0.88). DED was associated with lower scores on VR-QoL (β= −0.14, P < 0.01). Similar results were observed when analyses were stratified by ethnicity.Conclusions: The novelty-associated factors for DED in the grasslands area were anti-fatigue eye drop use, milk product intake, and number of household members. DED and its components were associated with VR-QoL. Further prospective studies are needed to confirm these findings.

Grassland restoration measures alter soil methane uptake by changing community phylogenetic structure and soil properties

Grassland restoration can play a critical role in regulating ecosystem carbon cycling, especially for changes in methane (CH4) flux. However, how grassland restoration measures affect soil CH4 flux remains poorly understood. Here, we investigated the relationships between soil CH4 flux and properties of both plant communities and soil under different grassland restoration measures (shallow ploughing, harrowing and natural recovery) in a field experiment conducted during the growing season in a semiarid grassland in northern China using the static chamber method. Soil was a CH4 sink across all three restoration measures. Compared to natural recovery, shallow ploughing significantly enhanced and harrowing significantly decreased soil CH4 uptake. The rates of soil CH4 uptake were positively associated with litter production and belowground biomass and negatively associated with plant taxonomic and phylogenetic diversity. Soil temperature, NH4+-N concentration, and soil organic matter quality had positive effects on CH4 uptake rate, but soil moisture and NO3−-N concentration had negative effects on CH4 uptake rate. Our results elucidate the pathway through which shallow ploughing facilitates soil CH4 uptake in a semiarid grassland and thus highlights its role in sustaining ecosystem multifunctionality as a measure for grassland restoration.

Grazing Intensity Rather than Host Plant's Palatability Shapes the Community of Arbuscular Mycorrhizal Fungi in a Steppe Grassland.

Arbuscular mycorrhizal fungi (AMF) are the predominant type of mycorrhizal fungi in roots and rhizosphere soil of grass species worldwide. Grasslands are currently experiencing increasing grazing pressure, but it is not yet clear how grazing intensity and host plant grazing preference by large herbivores interact with soil- and root-associated AMF communities. Here, we tested whether the diversity and community composition of AMF in the roots and rhizosphere soil of two dominant perennial grasses, grazed differently by livestock, change in response to grazing intensity. We conducted a study in a long-term field experiment in which seven levels of field-manipulated grazing intensities were maintained for 13 years in a typical steppe grassland in northern China. We extracted DNA from the roots and rhizosphere soil of two dominant grasses, Leymus chinense (Trin.) Tzvel. and Stipa grandis P. Smirn, with contrasting grazing preference by sheep. AMF DNA from root and soil samples was then subjected to molecular analysis. Our results showed that AMF α-diversity (richness) at the virtual taxa (VT) level varied as a function of grazing intensity. Different VT showed completely different responses along the gradient, one increasing, one decreasing, and others showing no response. Glomeraceae was the most abundant AMF family along the grazing gradient, which fits well with the theory of disturbance tolerance of this group. In addition, sheep-grazing preference for host plants did not explain much of the variation in AMF α-diversity. However, the two grass species exhibited different AMF community composition in their roots and rhizosphere soils. Roots exhibited a lower α-diversity and higher β-diversity within the AMF community than soils. Overall, our results suggest that long-term grazing intensity might have changed the abundance of functionally diverse AMF taxa in favor of those with disturbance-tolerant traits. We suggest our results would be useful in informing the choice of mycorrhizal fungi indicator variables when assessing the impacts of grassland management choices on grassland ecosystem functioning.

Species-specific herbivore grazing of type-specific grassland can assist with promotion of shallow layer of soil carbon sequestration

Grassland soils represent a significant potential pool for the sequestering of atmospheric CO2; however, the magnitude of this pool depends to a certain extent on the grazing management of the grassland. Whether different herbivore species and combinations (herbivore assemblage) influence the soil organic carbon (SOC) in various grasslands remains unclear. Here we have investigated the impacts of herbivore assemblages (NG, no grazing; SG, sheep grazing; CG, cattle grazing; and MG, mixed grazing of sheep and cattle) under moderate grazing intensity on a shallow layer of SOC storage across the three different grassland types (meadow steppe, typical steppe, and desert steppe) in the temperate steppes of Eastern Eurasia. We found that herbivore-species-specific effects on SOC storage depended on the grassland type. In mesic grasslands (i.e. meadow steppe and typical steppe), CG enhanced SOC storage, but there were no effects from SG. In contrast, SG in the xeric grassland (i.e. desert steppe) dramatically increased SOC storage while no effects were observed for CG. Importantly, MG of sheep and cattle consistently increased SOC storage across all grassland types. We suggest that adopting herbivore-type-specific stewardship in different grasslands could assist with the enhancement of ecosystem C functionality and services; large herbivores and small herbivores are suitable for grazing in mesic grasslands and xeric grasslands, respectively. Moreover, MG with diverse herbivores may be the optimal moderate grazing mode for soil C sequestration in most grasslands of northern China.

Edge effects and spatial degradation process in highly fragmented grassland – impact on soil microbial community

Patchy degradation is a typical characteristic of grassland degradation. However, little is known about the responses of soil microbial community composition and richness to patchy degradation process, although soil microbes play important roles in the functioning of terrestrial ecosystems. Further, there is always a transitional area of vegetation between non-degraded and degraded patches (i.e. ecotone), but the characteristics of soil microbial communities at ecotone are not well understood. Here, we investigated spatial patterns of soil microbial composition and richness from non-degraded to degraded patch in a patchy degraded grassland of Northern China. The results showed that bacterial and fungal richness had contrast patterns during patchy degradation process. Bacterial richness increased while fungal richness decreased from non-degraded to degraded patch. Notably, soil bacteria had significant edge effects, characterized by more abundant bacterial taxa at ecotone compared with non-degraded and degraded patches, which was attributable to the release of competition from the lower dominant phylum-Actinobacteria abundance. Moreover, the relative abundance of rare taxa for bacteria and fungi consistently decreased during patchy degradation process, indicating a reduction of ecosystem function. Relative abundance of soil microbial rare taxa could be a good ecological indicator in responding to grassland degradation. Overall, our study revealed the spatial patterns of soil microbial community during patchy degradation process and the microbial characteristics at ecotone, which is crucial for mechanistic understanding of grassland degradation process, and also providing a theoretical basis for the development of grassland restoration strategy.

Effects of nitrogen addition and precipitation alteration on soil respiration and its components in a saline-alkaline grassland

The responses of soil total respiration (Rs) and its components (soil autotrophic respiration (Ra) and heterotrophic respiration (Rh)) to nitrogen (N) deposition have been widely evaluated in non-saline-alkaline grasslands. However, their responses to N addition under drought and wet conditions, especially in saline-alkaline grasslands, remain unclear. A two-factorial experiment involving N addition and precipitation changes (decreased or increased 50% precipitation relative to ambient) was conducted in a saline-alkaline grassland of Northern China, while soil respiration was measured in different treatment plots during two growing seasons (2018, 2019). Results showed that the addition of N or changes in precipitation alone had no significant effect on Rs, Ra or Rh in both years because root productivity and soil microbial biomass were not affected. However, N addition with increased precipitation synergistically augmented seasonal mean Rs and Ra by 25.7% and 46.8% in 2018, and by 42.4% and 89.3% in 2019, respectively, owing to the increase in plant productivity. The variation in Ra primarily contributed to variation in Rs, and the effect size of N addition on Rs and Ra were increased with precipitation. In addition, a structural equation model showed that the response of soil respiration to N addition and precipitation changes was regulated by soil salinization, in which the Ra was regulated by soil based cations while Rh was controlled by soil pH values. Our study highlights that N addition with increased precipitation preferentially affects plants rather than microorganisms, and that Rh was not sensitive to N addition and precipitation changes in saline-alkaline grassland.

An Intelligent Question Answering System of the Liao Dynasty Based on Knowledge Graph

The Liao Dynasty was a minority regime established by the Khitan on the grasslands of northern China. To promote and spread the cultural knowledge of the Liao Dynasty, an intelligent question-and-answer system is constructed based on the knowledge graph in the historical and cultural field of the Liao Dynasty. In the traditional question answering system, the quality of answers was not high due to incomplete data and distinctive vocabulary. To solve this problem, a combination method of Liao Dynasty question-and-answer database and KB is proposed to realize knowledge graph question answering, and a joint model of Siamese LSTM and fusion MatchPyramid is proposed for semantic matching between questions in the question-and-answer database. With the joint model, it is easy to perform semantic matching by fusing sentence-level and word-level interactive features through LSTM and MatchPyramid. Furthermore, the question sentence with the same semantics as the user input question sentence is retrieved in the question-and-answer database, and the answer corresponding to the question sentence is returned as the result. The experimental results show that our proposed method has achieved relatively good performance in the historical domain of the Liao Dynasty and the open-domain knowledge graph, and improved the accuracy of question and answer.

Relative Importance of Deterministic and Stochastic Processes on Soil Microbial Community Assembly in Temperate Grasslands.

Changes in species composition across communities, i.e., β-diversity, is a central focus of ecology. Compared to macroorganisms, the β-diversity of soil microbes and its drivers are less studied. Whether the determinants of soil microbial β-diversity are consistent between soil depths and between abundant and rare microorganisms remains controversial. Here, using the 16S-rRNA of soil bacteria and archaea sampled at different soil depths (0–10 and 30–50 cm) from 32 sites along an aridity gradient of 1500 km in the temperate grasslands in northern China, we compared the effects of deterministic and stochastic processes on the taxonomic and phylogenetic β-diversity of soil microbes. Using variation partitioning and null models, we found that the taxonomic β-diversity of the overall bacterial communities was more strongly determined by deterministic processes in both soil layers (the explanatory power of environmental distance in topsoil: 25.4%; subsoil: 47.4%), while their phylogenetic counterpart was more strongly determined by stochastic processes (the explanatory power of spatial distance in topsoil: 42.1; subsoil 24.7%). However, in terms of abundance, both the taxonomic and phylogenetic β-diversity of the abundant bacteria in both soil layers was more strongly determined by deterministic processes, while those of rare bacteria were more strongly determined by stochastic processes. In comparison with bacteria, both the taxonomic and phylogenetic β-diversity of the overall abundant and rare archaea were strongly determined by deterministic processes. Among the variables representing deterministic processes, contemporary and historical climate and aboveground vegetation dominated the microbial β-diversity of the overall and abundant microbes of both domains in topsoils, but soil geochemistry dominated in subsoils. This study presents a comprehensive understanding on the β-diversity of soil microbial communities in the temperate grasslands in northern China. Our findings highlight the importance of soil depth, phylogenetic turnover, and species abundance in the assembly processes of soil microbial communities.

Long-term leaf C:N ratio change under elevated CO2 and nitrogen deposition in China: Evidence from observations and process-based modeling

Climate change, elevating atmosphere CO2 (eCO2) and increased nitrogen deposition (iNDEP) are altering the biogeochemical interactions between plants, microbes and soils, which further modify plant leaf carbon‑nitrogen (C:N) stoichiometry and their carbon assimilation capability. Many field experiments have observed large sensitivity of leaf C:N ratio to eCO2 and iNDEP. However, the large-scale pattern of this sensitivity is still unclear, because eCO2 and iNDEP drive leaf C:N ratio toward opposite directions, which are further compounded by the complex processes of nitrogen acquisition and plant-and-microbial nitrogen competition. Here, we attempt to map the leaf C:N ratio spatial variation in the past 5 decades in China with a combination of data-driven model and process-based modeling. These two approaches showed consistent results. Over different regions, we found that leaf C:N ratio had significant but uneven changes between 2 time periods (1960-1989 and 1990-2015): a 5% ± 8% increase for temperate grasslands in northern China, a 3% ± 6% increase for boreal grasslands in western China, and by contrast, a 7% ± 6% decrease for temperate forests in southern China, and a 3% ± 5% decrease for boreal forests in northeastern China. Additionally, the structural equation models indicated that the leaf C:N change was sensitive to ΔNDEP, ΔCO2 and ΔMAT rather than ΔMAP and ecosystem types. Process-based modeling suggested that iNDEP was the main source of soil mineral nitrogen change, dominating leaf C:N ratio change in most areas in China, while eCO2 led to leaf C:N ratio increase in low iNDEP area. This study also indicates that the long-term leaf C:N ratio acclimation was dominated by climate constraint, especially temperature, but was constrained by soil N availability over decade scale.

Grazing exclusion enhances plant and topsoil carbon stocks in arid and semiarid grasslands

Grazing exclusion (GE) is widely considered to be an important strategy for restoring overgrazed grasslands and promoting carbon (C) storage. However, the changes in the components of ecosystem C with GE and their related drivers remain largely unexplored. Here, we investigated the effects of GE on the ecosystem C components (plant and soil C stocks) and their key driving factors through sampling inside and outside 15 grazing exclosures across the Inner Mongolia arid and semiarid grasslands in northern China. Our results showed that, except for dead root C, GE significantly promoted plant C stocks. The increase of C stocks in AGB and litter resulted from the increases of both biomass and C concentration, while the increase in live root C stock was mainly attributed to biomass accumulation. GE also promoted the topsoil (0–10 cm) C stocks but had little effect on the subsoil (10–30 cm) C stocks. Overall, GE had no significant effect on total ecosystem C stocks. Our results further indicated that across the grasslands, GE likely enhanced C accumulation in AGB, litter and live root in more humid and/or fertile sites. We also found that the increases of C stocks in AGB and litter were driven by the direct effects of GE and its indirect effects mediated by soil water content. The increases of C stocks in live root and topsoil with GE were linked to only high soil water contents. The generalizability of the soil water effect was confirmed by a meta-analysis which further revealed that across the grasslands of China, the responses of ecosystem C components to GE were associated with changes in soil water conditions. Therefore, our study highlighted the important role of soil water in regulating ecosystem C dynamics with GE at the national scale. Overall, our results showed that across arid and semiarid grasslands, GE is generally beneficial for plant and topsoil C accumulation. However, GE effects mediated by soil water on ecosystem C components may change to some extent due to altered soil water conditions under climate change.

Effects of Fencing on Vegetation and Soil Nutrients of the Temperate Steppe Grasslands in Inner Mongolia

Grazing exclusion has been widely implemented in degraded grassland. However, the changes of plant communities and soil nutrients in response to fencing are still controversial. Thus, the effects of free grazing, 17 and 36 years of fencing on the plant biomass and litter biomass, carbon (C), nitrogen (N) and phosphorus (P) concentrations and stocks of plant, litter and soil were investigated in the temperate steppe grasslands of northern China. The results indicated that fencing increased the aboveground live biomass and litter biomass. In addition, fencing increased C, N and P stocks of aboveground live biomass, litter biomass and soil. Although root biomass and its nutrient stocks were also significantly increased by 17 years of fencing, they were decreased with fencing extending from 17 to 36 years. Moreover, there were no significant differences in aboveground live biomass and soil N and P stocks between 17 and 36 years of fencing. Litter biomass and its C, N and P stocks were positively correlated with soil C, N and P stocks. Our results demonstrated that 17 years of fencing is an effective way to restore vegetation and soil nutrients in the temperate steppe of Inner Mongolia, but a longer fencing duration has no further positive effects on biomass production and soil nutrients accumulation.

Vegetation resistance and resilience to a decade-long dry period in the temperate grasslands in China.

The duration of climate anomalies has been increasing across the globe, leading to ecosystem function loss. Thus, we need to understand the responses of the ecosystem to long‐term climate anomalies. It remains unclear how ecosystem resistance and resilience respond to long‐term climate anomalies, for example, continuous dry years at a regional scale. Taking the opportunity of a 13‐year dry period in the temperate grasslands in northern China, we quantified the resistance and resilience of the grassland in response to this periodic dry period. We found vegetation resistance to the dry period increased with mean annual precipitation (MAP), while resilience increased at first until at MAP of 250 mm and then decreased slightly. No trade‐off between resistance and resilience was detected when MAP < 250 mm. Our results highlight that xeric ecosystems are most vulnerable to the long‐term dry period. Given expected increases in drought severity and duration in the coming decades, our findings may be helpful to identify vulnerable ecosystems in the world for the purpose of adaptation.

Prevalence and risk factors of allergic rhinitis and asthma in the southern edge of the plateau grassland region of northern China: A cross-sectional study

BackgroundThe prevalence rates of allergic rhinitis (AR) and asthma in the border region of China may be different from those in the central region of plateau grasslands. A survey was performed to investigate the prevalence and risk factors for AR, asthma, and AR combined with asthma among adults (age ≥ 20 years) residing in the southern border of plateau grasslands in northern China. MethodsFrom May to August 2018, a cross-sectional survey was completed by subjects that were selected using a cluster random sampling method. The subjects completed a questionnaire and were administered skin prick tests (SPTs). Risk factors for AR, asthma, and AR combined with asthma were examined by multivariate logistic regression analyses. ResultsA total of 1815 adult subjects in the selected region completed study. The prevalence rates of physician-diagnosed AR, asthma, and AR combined with asthma were 13.9% (253), 9.8% (177), and 2.9% (52), respectively. Among the patients with AR, 20.6% were found to have concurrent asthma; among the patients with asthma, 29.4% were found to have concurrent AR. Artemisia and Humulus pollen were the most common sensitizing pollen types. Approximately 70% of subjects with AR and <30% of asthma patients were sensitized to Artemisia and Humulus pollen. Symptoms of AR and asthma mainly appeared during August. A multivariable logistic regression analysis identified sensitization pollen as an independent risk factor for both AR and AR combined with asthma (AR: OR = 16.23, 95% CI: 10.15–25.96; AR combined with asthma: OR = 6.16, 95% CI: 1.28–29.66). An age >40 years old, family history of asthma, moderate-to-severe AR, adverse food reactions, and mold allergies were independent risk factors for AR combined with asthma. ConclusionsThis study identified the prevalence rates of AR and asthma in the southern borders of the plateau grassland in northern China (>1500 m above sea level). Sensitization pollen is an independent risk factor for AR and AR combined with asthma.