Table of Content

20 March 2025, Volume 34 Issue 3

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Research into the spatial and temporal changes in patterns of animal husbandry-related CO₂ emission intensities and the factors influencing those emissions in Qinghai Province

Jun-hao LI, Guo-jing YANG, Xiao-dong PEI, Gui SHI, Ya WANG, Li-hua ZHOU

2025, 34(3):  1-16.  DOI: 10.11686/cyxb2024167

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Livestock CO₂ emissions constitute a significant source of greenhouse gases. This study analyzed the spatial and temporal distribution patterns of livestock CO₂ emissions intensity in Qinghai Province from 2008 to 2018. In this study， a geographical model was utilized to explore the intensity of the impact and the interactions of various factors on the spatial and temporal changes in livestock CO₂ emission intensities. The study found that： 1） With the implementation of ecological protection measures and the formulation of ecological animal husbandry practices in Qinghai Province， the intensity of animal husbandry CO₂ emissions decreased by 48.05% from 2008 to 2018， and the animal husbandry industry showed a trend towards development of a low-carbon status； 2） Between 2008 and 2018， the center of gravity of CO₂ emission intensity of animal husbandry migrated westward and southward by 17.99 km， and as of 2018， the CO₂ emission footprint of the livestock industry showed an obvious pattern of stronger intensity in the south and weaker intensity in the north. This indicates that the southern region of Qinghai Province still has a large potential for livestock CO₂ emission reduction， and there is an urgent need to accelerate agricultural industrial structure adjustment and promote the upgrading of livestock farming technology； 3） The factors influencing the change in livestock CO₂ emission intensity have shifted from combined factors such as the natural resource endowment， economy， and market demand to economic development indicators such as livestock output value and urbanization； 4） The interaction between the economic level of livestock and product structure factors has gradually replaced the interaction between natural resource endowment and similar factors， and the former is now becoming the key factor affecting the spatial distribution of livestock CO₂ emission intensity. The results of the study indicate that Qinghai Province， through the development of ecologically improved livestock farming practices， has gradually moved away from the traditional extensive mode of livestock development relying on natural endowments， has improved production efficiency， and has achieved carbon emission reduction in the livestock industry. However， there still exists considerable space for reducing carbon emissions in the livestock industry， requiring continued promotion of ecologically improved livestock farming practices and rural industrial structure adjustment， together with acceleration of industrial transformation and upgrading， to ensure the development of a low-carbon livestock industry. This study provides scientific analysis to assist the formulation of livestock emission reduction policies as part of the development of a sustainable， low-carbon livestock industry in Qinghai Province and in China.

Analysis of spatial characteristics of soil nutrients in grasslands in the Fenhe River upper reaches using GIS technology and cluster analysis

Jia-xin LI, Ya-hong JING, Jun ZHANG, Si-pu JING, Yu-xing YANG, Bo-yang FAN, Wen-jie LU

2025, 34(3):  17-28.  DOI: 10.11686/cyxb2024175

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Protecting and managing the soil environment plays a key role in ensuring the sustainable development of grasslands. This study employed geographic information system technology to investigate the soil nutrient status at 81 sites in grasslands in the upper reaches of Fenhe River. Cluster analysis with soil chemical properties as the primary criteria was used to group the surface soil of the 81 sites into three categories. The study evaluated spatial characteristics of soil nutrients for three soil horizons： 0-10 cm， 10-20 cm， and 20-30 cm. It was found that the overall level of grassland soil health in the study area was suboptimal， with low natural moisture content， relatively scarce total phosphorus and alkaline nitrogen content， and a weakly alkaline soil pH. There are significant differences in the spatial distribution characteristics of various nutrient related indicators. The best fitting models of these different indicators varied between soil horizons， and the spatial autocorrelation of most indicators was weak， which indicates that the spatial variation of soil nutrients is primarily impacted by both structural and random factors. In the horizontal direction， a distinct spatial pattern was observed for each indicator. Sites with high soil nutrient concentrations surrounded by sites also with high soil nutrients， known as high-high concentration aggregation zones， were predominantly found in the headwaters of the Fenhe River， while sites with low soil nutrient concentrations also surrounded by sites with low soil nutrients， known as low-low concentration aggregation zones， occurred mainly in the eastern part of the Fenhe River basin. Low-high clustering areas were scattered， and high-low clustering areas were less frequent and mostly located in the southern part of the upper reaches. Vertically， across the three soil horizons at sampling sites， no significant spatial variation was observed for total potassium and the content of other related soil chemical properties decreased with soil depth. The clustering characteristics of each soil property did not show a clear change with depth. The results provide scientific and reasonable guidance for the restoration of degraded grasslands.

Distribution characteristics of grassland plant diversity along the altitudinal gradient and its driving factors： A case study of the eastern section of the northern slope of the Tianshan Mountains

An-jing JIANG, Yi-qiang DONG, Shi-jie ZHOU, Ting-ting NIE, Yue WU, Ze-yu LIU, Xing-yun SHAN, Ya-xin LEI, Kai WU, Sha-zhou AN

2025, 34(3):  29-40.  DOI: 10.11686/cyxb2024173

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Exploring the distribution pattern of species diversity， and its driving factors， in mountain grassland ecosystems along altitude gradients is of great importance to understanding of the environmental adaptability of regional plants， and requirements for the conservation of regional diversity and vegetation restoration and management. In this study， the quantitative characteristics and species diversity of plant communities in Qitai County， on the eastern section of the northern slopes of the Tianshan Mountains， were measured and analysed at 15 sites along altitudinal gradients spanning from 1250-3150 m. We also used the random forest model and the partial least squares path modeling （PLS-PM） to analyse the relationship between altitude， temperature， precipitation， and quantitative characteristics of the plants and plant diversity. The results showed that： 1） With increasing altitude， the grassland plant community cover and density showed a highly significant increasing trend， while the plant height showed a highly significant decreasing trend， and the biomass showed an initially decreasing trend and then an increasing trend （P<0.01）； 2） The α-diversity of plants was maximized （P<0.05） at mid-altitude along the altitudinal gradient， and the Sorenson index between neighboring altitudes showed an overall pattern of initial decrease and then increase with increasing altitude， while the Cody index of species substitution rate showed a tendency of increasing and then decreasing； 3） Plant cover， biomass， and Patrick’s index were all significantly correlated with climate （P<0.05）， with plant diversity mainly directly affected by cover， and elevation indirectly affecting plant density by significantly affecting temperature and precipitation， plant density also significantly positively affects plant coverage （P<0.01）. In summary， altitude indirectly affects the characteristics of plant communities by influencing climate， giving the plant communities a distinct vertical distribution along the altitudinal gradient.

Effects of short-term nitrogen addition， watering， and mowing on plant community characteristics and soil physicochemical properties in Sophora alopecuroides degraded grassland

Shu-qi LIU, Dong CUI, Wen-xin LIU, Hai-jun YANG, Yan-cheng YANG, Zhi-cheng JIANG, Jiang-chao YAN, Jiang-hui LIU

2025, 34(3):  41-55.  DOI: 10.11686/cyxb2024178

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In the context of global climate change and intensified human activities affecting grassland ecosystems， the increasing area of invasion by poisonous weeds in the arid and semi-arid regions of Xinjiang is threatening the health of grassland ecosystems through rapid loss of biodiversity and serious grassland degradation. The study of the effects of nitrogen deposition， precipitation change， and mowing on plant community characteristics and soil physicochemical properties of Sophora alopecuroides degraded grassland has theoretical and practical significance for sustainable management of this grassland ecosystem in the future. This study conducted a controlled experiment on degraded grasslands with S. alopecuroides as a single dominant species. We set up a total of eight treatments. The eight treatments were： CK （no nitrogen， no water， no mowing）， nitrogen addition （N treatment）， water addition （W treatment）， mowing （M treatment）， nitrogen-water interaction （NW treatment）， nitrogen-mowing interaction （NM treatment）， water-mowing interaction （WM treatment）， nitrogen-water-mowing interaction （NWM treatment）. We analyzed the variation in plant species diversity， primary productivity， plant height， vegetation cover， soil physicochemical properties， and the relationship between vegetation characteristics of S. alopecuroides and soil physicochemical factors. The results indicated that： nitrogen addition significantly increased the biomass of S. alopecuroides， while mowing significantly decreased the biomass and height of S. alopecuroides. Nitrogen addition in the N， NW， NM and NWM treatments significantly increased soil nitrate nitrogen content， and the NWM treatment significantly increased soil ammonium nitrogen content. Redundancy analysis and regression analysis showed that soil organic matter， total nitrogen， total phosphorus， Ca²⁺ and HCO₃^- significantly affected the density of S. alopecuroides. Nitrogen addition increased the content of inorganic nitrogen in soil. Mowing inhibited the growth of S. alopecuroides to some extent. The interaction effect of water addition and other factors was more significant than that of water addition alone on plants and soil. The results provide new insight for the management and restoration of S. alopecuroides degraded grassland.

Effects of straw and milk vetch mulching on the ecological stoichiometric characteristics of soil-microbe-sweet potato plants

Shao-xing LI, Wen-feng SONG, Yu-ling ZHOU, Li-xia SONG, Ke REN, Qun MA, Long-chang WANG

2025, 34(3):  56-70.  DOI: 10.11686/cyxb2024165

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There is an urgent need to explore sustainable agricultural cultivation measures and alleviate nutrient limitations as a response to the problems of soil erosion and low quality of cultivated land in the dry-farming areas of southwest China. This study focused on sweet potato plantings within a “fava bean （Vicia faba）/corn （Zea mays）/sweet potato （Ipomoea batatas）” rain-fed three-crop rotation pattern in southwest China. Four treatments were set up： no mulching （CK）， straw mulching （S）， straw and milk vetch （Astragalus sinicus） mulching （S+M） and milk vetch mulching （M）. By studying the content of carbon， nitrogen and phosphorus， ecological stoichiometric characteristics and the homeostasis index of the soil-microbe-sweet potato plant stoichiometric data， the effects of straw and milk vetch mulching cover on soil nutrient restriction and ecological stoichiometric characteristics were explored. It was found that： 1） The straw and milk vetch mulching treatments significantly increased soil organic carbon and total nitrogen content， and from changes in the soil stoichiometric ratio， it was deduced that the mulching treatments effectively alleviated soil nutrient restriction. 2） The straw and milk vetch mulching treatments significantly increased the content of soil microbial biomass carbon， nitrogen and phosphorus， and showed differences in the C-N-P stoichiometric ratios of microorganisms at different crop growth stages， with large fluctuations in the early growth period， and relatively stable values in the middle and late growth period. In terms of homoeostasis characteristics， except for the CK treatment， the microbial and soil stoichiometric ratios showed strong homoeostasis. 3） The nitrogen content of sweet potato organs was significantly increased by straw and milk vetch mulching treatments， and the best effect was achieved in the S+M mulching treatment. The yields of sweet potato were ranked S+M>S>M>CK. In terms of stoichiometric ratio， S+M treatment was superior. This treatment prolonged the growth time of sweet potato， and effectively alleviated the nutrient restriction. The stoichiometric ratio of various organs of sweet potato plants showed strong homoeostasis during the whole crop growth period. In summary， in the dry-farming areas of southwest China， crop mulching with straw and milk vetch improved the yield of sweet potato， regulated soil nutrient limitations and resulted in a stable homoeostasis in the stoichiometric ratios of soil and microorganisms.

Effect of particle size ratio， fertilizer application amount， and seeding rate combinations coal gangue matrix properties in restoration of a mining area

Li-li MA, Fu-zhen JIANG, Yu-shou MA, Kai-bin QI, Shun-bin JIA, Zheng-peng LI

2025, 34(3):  71-84.  DOI: 10.11686/cyxb2024195

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Coal gangue， a solid waste produced from mining activities， has a poor physical structure， making the nutrients it contains inaccessible to plants. Therefore， improving the matrix properties of coal gangue is crucial in the ecological restoration of mining areas. This study utilized an L₉（3⁴） orthogonal design to investigate the combined effects of： （A） coal gangue particle size ratio<7 mm （0%， 25% or 50%）， （B） organic fertilizer application amount （15+7.5， 30+15 or 45 m³·ha^-1+22.5 t·ha^-1 sheep manure+commercial organic fertilizer）， （C） slow-release urea application amount （30， 60 or 90 kg·ha^-1）， and （D） seeding rate （60， 120， or 180 kg·ha^-1）， on above-ground vegetation and soil nutrients. The optimal improvement model was selected using TOPSIS multivariate analysis. The findings revealed that over time， the above-ground biomass and soil nutrient levels decreased across different treatments. Specifically， soil organic matter， total nitrogen， total phosphorus， available nitrogen， available phosphorus， and available potassium decreased significantly， while total potassium showed a notable increase. Range analysis indicated that the application rate of slow-release urea and seeding rate were critical for above-ground biomass， whereas the particle size ratio<7 mm and organic fertilizer amount were key factors for soil nutrient content. A comprehensive TOPSIS analysis based on above-ground biomass and soil fertility indicators identified the T₂ （A₁B₂C₂D₂） treatment as the most effective， comprising 0% of coal gangue with a particle size ratio<7 mm， 30 m³·ha^-1 of sheep manure+15 t·ha^-1 of commercial organic fertilizer， 60 kg·ha^-1 of sustained-release urea， and a seeding rate of 120 kg·ha^-1. The results of this study offer valuable insights for ecological restoration in the Muli mining area.

Analysis of genetic variation in agronomic of half-sib families of Medicago sativa

Peng-fei HU, Yu-nong YE, Tong-rui WANG, Jing WANG, Xing WANG, Bing-zhe FU, Xue-qin GAO

2025, 34(3):  85-96.  DOI: 10.11686/cyxb2024149

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Through the investigation of agronomic traits of 35 half-sibling families of Medicago sativa， the genetic variation of agronomic traits among families was analyzed， in order to make informed decisions on likely gain in the breeding of alfalfa varieties. It was found that there was very significant variation in traits among the different families. The coefficient of variation among different traits ranged from 5.24%-33.18%. Generalized heritability， family heritability and genetic progress were， respectively， 0.05%-69.04%， 1.07%-72.90% and 0-20.08. Plant height， stem diameter and branch number were significantly correlated with fresh herbage yield； the number of branches was significantly correlated with hay yield and seed yield； there was a significant correlation between different stubble measures， except for the ratio of fresh∶dry and the ratio of stem∶leaf. Using membership function multivariate analysis， four elite families， （designated FM₂₂， FM₇， FM₁₅ and FM₁）， were identified， and the average genetic gains for plant height， stem diameter， branch number， fresh grass yield， hay yield， fresh-to-dry ratio， stem-leaf ratio and seed yield of the selected families were， respectively， 3.78%， 0.43%， 10.21%， 1.08%， 4.82%， -0.16%， -0.27% and 9.36%， respectively. There was a large genetic variation among the traits of the 35 half-sibling families， and there was a large potential for improvement. The elite families initially identified provide a germplasm resource for ongoing breeding improvement of alfalfa.

Selection of intercropping combinations suitable for alfalfa and Poaceae forages in semi-arid areas of the Loess Plateau

Ya-jiao ZHAO, Xiao-jing LIU, Fang LIN

2025, 34(3):  97-110.  DOI: 10.11686/cyxb2024057

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The research aimed to screen suitable intercropping combinations of forage in semi-arid areas of the Loess Plateau. From 2016 to 2019， a field experiment was conducted in Lanzhou， Gansu province， involving intercropping alfalfa （Medicago sativa） with maize （Zea mays）， sorghum （Sorghum bicolor）， oat （Avena sativa） and triticale （Triticale）. The experiment explored the production characteristics and land use characteristics of forage intercropping. It was found that the hay yield from alfalfa/maize intercropping and alfalfa/sorghum intercropping was significantly higher than that of monoculture alfalfa. In 2018 and 2019， hay yield and crude protein yield of alfalfa/oat intercropping and alfalfa/triticale intercropping were significantly higher than those of corresponding monocultures of gramineous forages. Also， group dry forage yield and crude protein yield of alfalfa/sorghum （maize） was higher than other planting patterns， and the crude protein yields of maize， oat （except the second year of planting） and triticale was significantly increased in intercropping systems compared with their monoculture； alfalfa exhibited the opposite pattern. In the four intercropping combinations， the land equivalent ratio， regional time equivalence rate and land utilization efficiency were all greater than 1； the aggressivity of the four gramineous forages was greater than 0， and the competition ratio was greater than 1 in each case. Among the studied intercropping combinations， the land equivalent ratio， regional time equivalence ratio and land utilization efficiency were the highest in alfalfa/triticale intercropping systems. In summary， to optimize yield， it is recommended to adopt alfalfa/maize and alfalfa/sorghum intercroppings； to optimize land use， it is recommended to adopt alfalfa/triticale intercropping.

Interspecific relationship and forage productivity effects in mixed sowings of Sorghum bicolor and Dolichos lablab

Jiang-ping MA, Yi-yin ZHANG, Teng-fei WANG, Bin WANG, Jian LAN

2025, 34(3):  111-122.  DOI: 10.11686/cyxb2024139

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The seeding rate of Sorghum bicolor and Dolichos lablab in mixed sowings is a key factor affecting the yield and nutritional value of mixed sowings. It is of high relevance to evaluate the optimal seeding rates of D. lablab and S. bicolor in mixed sowings in the Ningxia Yellow River Irrigation Area， to alleviate the shortage of forage supply in this area. In this study， D. lablab was sown at four different seeding rates in mixtures （SL₁： 16.5 kg·ha^-1， SL₂： 33.0 kg·ha^-1， SL₃： 49.5 kg·ha^-1， SL₄： 66.0 kg·ha^-1）， sown together with S. bicolor at 18.0 kg·ha^-1 in each case. The experiment also included D. lablab and S. bicolor monocultures （L₀： 49.5 kg·ha^-1 and S₀： 18.0 kg·ha^-1）. The aim was to investigate the yield， interspecific competition indexes and economic benefits of the two monocultures and the mixed-sown combinations. The results for two years confirm that the total hay yield and crude protein yield from mixed sowings of S. bicolor and D. lablab were significantly higher than those of monocultures （P<0.05）， and were maximized in the SL₂ treatment. For yield and crude protein， respectively， values were 63.66% and 9.13% higher than those of D. lablab sown alone. The land equivalent ratio of all mixtures was greater than 1 and was highest for the SL₂ treatment （1.26）， making the yield increase of this treatment was obvious. The aggressivity of S. bicolor in the mixed sowings was greater than 0， and the competitive ratio was greater than that of D. lablab， indicating that the competitive strength of S. bicolor was stronger than that of D. lablab， and S. bicolor is a competitive advantage crop. The system productivity index increased progressively with increase in the seeding rate of D. lablab， and the net income over the two years under the SL₂ treatment was the highest （37469.45 and 38284.09 yuan·ha^-1） among the treatments. Based on the yield， land equivalent ratio， monetary advantage index and net income of the mixed swards， the performance of S. bicolor and D. lablab in SL₂ mixed seeding treatment was the best. Therefore， it is recommended that the optimum seeding rate of D. lablab and S. bicolor in the Yellow River Irrigation Area of Ningxia is 33.0 kg·ha^-1.

Effects of different lactic acid bacteria strains on fermentation quality and mycotoxin contents of whole-plant corn silage

Yu-cheng LIANG, Xiao-wen ZHANG, Tao SHAO, Wen-bo WANG, Xian-jun YUAN

2025, 34(3):  123-133.  DOI: 10.11686/cyxb2024179

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The study aimed to evaluate the effects of Lactobacillus paracasei LS2， Lactiplantibacillus plantarum S6-2， and Lactobacillus casei GD2-1 on the fermentation quality and mycotoxin concentrations in corn silage. Fungal infected （FI） or non-fungal infected （NFI） whole-plant corn was ensiled with： 1） no treatment （CON）， 2） L. paracasei （LS2）， 3） L. plantarum （S6-2）， or 4） L. casei （GD2-1） for 180 days. The results indicated that inoculation withGD2-1 significantly reduced the ammonia nitrogen contents， and all three lactic acid bacterial strains significantly increased the water-soluble carbohydrate contents in the NFI treatments （P<0.05）. Inoculation withS6-2 significantly reduced the ammonia nitrogen contents， and inoculation withLS2 andS6-2 increased the water-soluble carbohydrate content in the FI treatments （P<0.05）. The LS2 inoculated silages showed the highest acetic acid contents. Fungal infection significantly increased the concentrations of deoxynivalenol and zearalenone in fresh corn. The detoxification effects of lactic acid bacteria were mycotoxin-dose dependent. The inoculants did not affect the zearalenone concentration in FI and NFI silages and deoxynivalenol in NFI silages. Inoculating LS2，S6-2， and GD2-1 significantly （P<0.05） decreased the aflatoxin B₁ concentration in FI silages， andS6-2 significantly （P<0.05） decreased the deoxynivalenol concentration in FI silages. In summary， inoculating the three lactic acid bacteria reduced the ammonia-nitrogen concentration and increased the water-soluble carbohydrates and acetic acid contents during the ensiling， improving the fermentation quality of the whole-plant corn silage. The three strains did not significantly affect the zearalenone contents of FI and NFI silages， but reduced the concentration of aflatoxin B₁ in FI silages， and S6-2 reduced the deoxynivalenol concentration in the FI silages.

Screening and identification of symbiotically efficient and stress-resistant rhizobia of wild Medicago lupulina in Gannan

Xue-mei LI, Tuo YAO, Chang-ning LI, Xiao-lei YANG, Wan-xia WANG, Yi-xin ZHANG

2025, 34(3):  134-143.  DOI: 10.11686/cyxb2024163

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This research investigated the rhizobacterial resources of wild Medicago lupulina in alpine meadows， by screening for strains exhibiting efficient symbiosis with host plants. YMA Congo red medium was used to isolate rhizobacteria from wild M. lupulina， and strain identification was carried out through colony morphology observation and assessment of acid and alkali production， combined with 16S rRNA gene sequence analysis. Growth-promoting properties were verified by back-inoculation to the original host， and strain resilience was determined by evaluating in vitro acid， alkali and temperature tolerance. Four strains of interest were isolated from wild M. lupulina in this way， designated GNT1， GNT2， GNT4 and GNT6， and the colony morphology and acid and alkali production results were consistent with the characteristics of rhizobia. Strains GNT1 and GNT6 were identified as Sinorhizobium meliloti， GNT2 as Pararhizobium giardinii， and GNT4 as Pararhizobium herbae. Compared with a no-inoculation treatment， rhizobium inoculation increased the number of plant nodules by 2.06-3.64 times， the plant height by 0.75-3.17 times， the root length by 0.21-0.38 times and the plant dry weight by 0.55-2.82 times. The effective nodule number and nitrogenase activity under inoculation treatments were 11.33-18.00 nodules per plant and 5.71-10.97 μmol C₂H₄·g^-1·h^-1， respectively. The nodules under the non-inoculation treatment were ineffective nodules and did not have nitrogenase activity. The four strains could grow at pH 11， and the strain GNT2 grew best. The strains differed in their tolerance to NaCl. Strain GNT6 could tolerate 5% NaCl， and only strain GNT6 could grow at the low temperature of 4 ℃. Hence， strain GNT6 was determined to have potential to be applied in alpine grassland， and is identified in this research as a candidate strain to provide improved rhizobial strain resources for the restoration of alpine grassland.

Isolation and identification of four strains of Reaumuria soongorica root zone nitrogen fixing bacteria and their role in seedling growth promotion

Feng ZHANG, Pei-fang CHONG, Xin-guang BAO, Xue-ying WANG

2025, 34(3):  144-153.  DOI: 10.11686/cyxb2024170

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The aim of this research was to isolate nitrogen fixing bacteria in the root zone soil of desert plants， investigate their effects on nitrogen metabolism of Reaumuria soongorica seedlings， and verify the growth-promoting effect of the isolated nitrogen fixing bacteria. In this study， four strains of nitrogen fixing bacteria were isolated from the root zone soil of R. soongorica by the dilution-coated plate method， using Ashby’s solid medium. The taxonomic status and growth-promoting characteristics of the strains were identified by morphological， physiological and biochemical characteristics as well as by 16S rDNA sequence analysis. The results showed that strains designated Y3 and Y2 were Bacillus sp.， strain P4 was Enterobacter mori， and strain N12 was Enterobacter cloacae. Inoculation with the four strains of nitrogen fixing bacteria increased the activities of nitrate reductase （NR）， glutamine synthetase （GS）， and glutamate synthetase （GOGAT） in the leaves and roots of the R. soongorica seedlings. There were also differences in the root length and relative water content of leaves， and above-ground and below-ground fresh weight of R. soongorica seedlings after inoculation with the isolated bacterial strains （P<0.05）； among them， the nitrogen fixing bacterium P4 had the most significant growth-promoting effect， with the NR activity in leaves and roots increased by 31.9% and 34.6%， respectively （P<0.05）， the GOGAT activity by 25.6% and 25.1%， respectively （P<0.05）， and the GS activity by 23.3% and 24.3%， respectively （P<0.05）. Furthermore， root length， leaf relative water content， above-ground and below-ground fresh weight were increased （P<0.05）， respectively， by 27.9%， 20.7%， 33.3% and 33.2%. In conclusion， the four strains of nitrogen fixing bacteria exhibited ability to promote the growth and development of R. soongorica seedlings and improve their survival rate. The isolated strains represent high-quality resources for the development of microbial plant growth promoting agents.

Effects of different concentrations of silicon and calcium on the growth and physiological characteristics of Mentha spicata seedlings

Meng-qi WANG, Fei WANG, Wan-lu ZHAO, Yan-qi LIU, Can CUI, Jun-xin YAN

2025, 34(3):  154-163.  DOI: 10.11686/cyxb2024153

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In order to investigate the effects of silicon and calcium application on the growth of Mentha spicata seedlings， treatments comprising different concentrations of silicon （500， 1000， 2000 mg·kg^-1 applied as sodium metasilicate， NaSiO₃·9H₂O） and calcium （400， 800， 1200 mg·kg^-1 applied as anhydrous calcium chloride CaCl₂） were set up to determine the growth and physiological parameters of the seedlings. The results showed that， compared with the control group， all concentrations of silicon and calcium treatments， except 2000 mg·kg^-1 silicon， promoted the growth of M. spicata， with 1000 mg·kg^-1 silicon and 800 mg·kg^-1 calcium having the strongest promotional effect. Soluble sugar and soluble protein contents decreased after silicon treatment， 2000 mg·kg^-1 silicon significantly increased proline content， catalase and peroxidase activity， and malondialdehyde content and cell membrane relative permeability increased compared with the control； most of the calcium treatments increased levels of osmotic regulatory substances and antioxidant enzyme activities compared with the control， while malondialdehyde content and cell membrane relative permeability were decreased. Principal component and subordinate function analyses showed that 800 and 400 mg·kg^-1 calcium and 1000 mg·kg^-1 silicon promoted the growth of M. spicata. These results provide reference data for selecting suitable silicon and calcium concentrations in soil for M. spicata growth.

Physiological and biochemical responses of Bothriochloa ischaemum seedlings to salt stress at seedling stage and definition of salt tolerance threshold

Shou-yu GAO, Wen-jing LIU, Yu-ying LI, Qing-yuan XIANG, Jia-jun XU, Lei-qi SHU, Zhao-zhong LI

2025, 34(3):  164-174.  DOI: 10.11686/cyxb2024177

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Soil salinization is one of the important limiting factors restricting the development of the pastoral industry in northern China. Developing local grass germplasm resources with strong saline-alkali resistance is an effective means to overcome difficulties utilizing saline-alkali land. This study investigated the salt-tolerance mechanisms and salt-tolerance threshold of Bothriochloa ischaemum cv. ‘Taihang’ seedlings. Nine NaCl salt stress treatments were set up， and plant height， root length， aboveground biomass and other 13 other plant traits were measured. Salt-tolerance threshold was calculated by principal component analysis. The results showed that NaCl stress had a greater influence on the growth of the shoots of B. ischaemum seedlings， but the root system was more sensitive to Na⁺ and K⁺. With increase in both stress exposure time and NaCl concentration， the activities of peroxidase and superoxide dismutase in leaves initially increased and then decreased， and reached their maxima on the 8th and 10th day， respectively， in a treatment of 210 mmol·L^-1 NaCl. The contents of malondialdehyde and soluble sugar showed an upward trend over time， while chlorophyll content showed a downward trend. After principal component analysis （PCA）， the first two sets of PC scores （root length and dry weight） were selected to establish regression relationship. From this evaluation it was found that the dry weight of aboveground parts was the most suitable criterion for evaluating salt tolerance， and the salt tolerance threshold of B. ischaemum seedlings was approximately 207.53 mmol·L^-1. This study provides preliminary insight about the salt tolerance mechanism of grasses and for planning of subsequent research on the impact of exposure duration and salt concentration on salt tolerance in B. ischaemum.

Classification system of inter-silva grasslands in Northern China

Yi-fu LI, Bin SUN, Zhi-biao NAN, Shi-rong LIU, Zhi-hai GAO, Xiao-dong HUANG, Mei-nan ZHANG, Chang-long LI, Jing-bo ZHANG, Shui-rong WU, Beng-yu WANG

2025, 34(3):  175-188.  DOI: 10.11686/cyxb2024197

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Inter-silva grasslands， serving as a critical transitional zone between forest and grassland ecosystems or grassland within forest land， have significant ecological importance. However， a widely accepted concept and a unified standard classification framework for inter-silva grasslands is not well recognized， neither domestically nor internationally， and this lack of recognition leads to constraints on their ecological conservation and rational utilization. Based on a comprehensive analysis of the state-of-the-art research findings from around the world along with extensive field surveys in typical forests of northern China， this study proposes a scientific definition of inter-silva grasslands. Inter-silva grasslands are defined as grassland patches of varying sizes and forms that occur within or on the edges of large forests， or that are interspersed with sparse trees or shrubs. Considering the geographic environmental features， usability， and visibility derived from medium to high spatial resolution remote sensing imagery， this classification system for northern China’s inter-silva grasslands includes four classes： forest gap grasslands， forest edge grasslands， sparse forest grasslands， and shrub grasslands， with further subdivision into twelve distinct subclasses. This study provides a conceptual framework to support the ecological protection and sustainable use of inter-silva grasslands in northern China.

The evolution of China’s maize seed industry， relevant industrial policies and implications for grassland agriculture development

You-he FAN, Si-yu YUE, Zhi-biao NAN, Yu-bing FAN

2025, 34(3):  189-203.  DOI: 10.11686/cyxb2024176

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Maize （Zea mays） is one of the most important grain crops and feed crops in China， and the development of the maize seed industry is important to stabilize maize yield， improve farmers’ incomes， and promote the development of livestock production and aquaculture in this country. Exploring the development history of the maize seed industry and relevant industry policies can provide insights for the optimal and efficient development of grassland agriculture. This study systematically reviews the No. 1 Central Documents and national agricultural policy documents from 1982 to 2023， and summarizes the development history of China’s maize seed industry， and of maize straw and silage maize forage utilization. Analysis of the progress in policy support， technological advancement， industrial scale， market demand and other topics is presented， and the report explores the supportive role of the maize industry in the development of grassland agriculture. The study found that： through the promotion of high-yield and high-quality maize varieties， the productivity of agriculture and animal rearing operations has been improved， providing more forage resources for animal production and promoting the coordinated and sustainable development of food security and grassland agriculture. Increased utilization of maize straw and silage maize forage has provided a vital complement to the feed supply for animal production and for the development of grassland agriculture， and has thus mitigated the negative impacts of increased animal numbers in the agro-ecological environment. National policies should focus on promoting the construction of forage bases， strengthening cross-regional grass-livestock coupling， and promoting grassland livestock production and grassland ecological recovery. Meanwhile， a collaborative development mechanism for forage and maize seed industry should be created to facilitate the co-revitalization of grass seed and maize seed industries， and to further realize the win-win outcomes of a high-quality agricultural ecology industry footprint， and higher economic benefit. In the future， the development of China’s maize seed industry should focus on promoting scientific and technological innovation， improving seed quality， protecting the ecological environment and promoting the sustainable use of resources， in order to realize the coordinated development of maize industry and grassland agriculture.

Current situation and prospects for drought-resistance breeding in Medicago sativa

Cai-jin CHEN, Ming-fang BAO, Wen-hu WANG, Ji-hong SHANG, Yan-xia ZENG, Xiao-di SHA, Xin-zhong ZHU, Xue-min WANG, Wen-hui LIU

2025, 34(3):  204-223.  DOI: 10.11686/cyxb2024105

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Alfalfa （Medicago sativa）， a tetraploid perennial herb of the legume family， is widely cultivated around the world and protein forage resource for herbivores of the highest quality. The development of the alfalfa industry is of major importance for agricultural industries and animal husbandry worldwide. However， with the frequent occurrence globally， of extreme climate events such as drought and water shortage， drought has emerged as a key factor limiting alfalfa performance in many regions. Development of varieties with strong drought resistance can not only maintain high and stable yield， but also help to conserve water resources. Therefore， this research focused on reviewing the collection and preservation of alfalfa germplasm resources and evaluation of drought resistance both in China and abroad. The current evaluation and registration status of drought-resistant varieties， as well as the problems and challenges of breeding for drought-resistance， are reviewed in order to promote breeding of drought-resistant alfalfa varieties in China. Our study aims to provide technical support and reference information for the development of drought-resistance in alfalfa breeding in China.

Effects of three plant growth regulators on shade tolerance of Zoysia japonica

Xin-yi LIN, Ni WANG, Tuo CHEN, Yi-lan SONG, Yao-dong LU, Zhao-xia DONG

2025, 34(3):  224-232.  DOI: 10.11686/cyxb2024192

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Light serves as the essential energy source， underpinning the processes of photosynthesis， growth， and nutrient assimilation within plant systems. However， urban green spaces frequently present challenges such as overshadowing of lawn areas by towering structures， which can seriously impede the lawn’s capacity for normal growth and development. This research studied the maintenance and management of a Zoysia japonica cv. ‘Guanglv’ lawn under shaded conditions. Foliar sprays of the mixed herbicide indaziflam （50 mL·ha^-1）+trifloxysulfuron （22.5 mL·ha^-1）， paclobutrazol at 120 mL·ha^-1 and trinexapac-ethyl at 50 mL·ha^-1 were conducted under artificial shading （80% shade）. This study comprehensively evaluated the effects of three plant growth regulators on the external morphology and physiological characteristics of ‘Guanglv’ zoysiagrass. Traits measured included daily growth rate， leaf width， leaf green color intensity， percent green cover， superoxide dismutase activity， peroxidase activity， and malondialdehyde content. It was found that under continuous shading， ‘Guanglv’ zoysiagrass displayed a range of stress symptoms， including etiolation， narrowing and lengthening of leaves， a reduction in relative chlorophyll content， a marked decrease in turf ground cover， elevated levels of malondialdehyde， and diminished activity of antioxidant enzymes. Among the growth regulators tested， the combination of 50 mL·ha^-1 indaziflam+22.5 mL·ha^-1 trifloxysulfuron and 50 mL·ha^-1 trinexapac-ethyl proved the most effective. These treatments not only ameliorated the adverse stress symptoms in zoysiagrass under shaded conditions， but also increased antioxidant enzyme activity， effectively enhancing the environmental adaptability， stress resistance， and shade tolerance.