Table of Content

20 February 2025, Volume 34 Issue 2

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Vegetation community characteristics and spatial differentiation in mountain grassland in Luoshan， Ningxia

Xin GONG, Xin-ru HUO, Wen LI, Yan-dong YANG, Chao LIU, Wei-chun QIN, Yan SHEN, Guo-hui WANG, Hong-bin MA

2025, 34(2):  1-15.  DOI: 10.11686/cyxb2024148

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The Ningxia Luoshan National Nature Reserve is the only water conservation forest area and regional green ecological protection barrier in the arid zone of central Ningxia. This reserve plays an important role in the protection of biodiversity， the prevention of soil erosion， and in ecological security. However， few studies have focused on the characteristics of the grassland plant community in Luoshan， or on the relationship between the characteristics of the grassland vegetation community and environmental factors. In this study， we analyzed the grassland plant community in the Luoshan Nature Reserve. We analyzed the composition of the plant community and its spatial differentiation， and the diversity characteristics of different types of grasslands and those at different altitudes. We also explored the relationship between the characteristics of the vegetation community and environmental factors. The results showed that： 1） The grassland plant community in Luoshan Nature Reserve was composed of annual and biennial herbs， perennial herbs， shrubs， and semi-shrubs， and perennial herbs accounted for the largest proportion of the community. The plant communities of desert steppe and typical grassland were dominated by grasses and weeds， while meadow steppe plant communities were dominated by weeds. As the altitude increased， except for the above-ground biomass of the community， the quantitative characteristics of the surveyed vegetation conformed to the ‘intermediate height expansion’ theory， and showed maximum values in the altitude range of 1600-2100 m. 2） As the altitude increased， the Margarlef richness index and the Shannon-Wiener diversity index of grassland plants increased to a certain point， reaching the highest values in the grassland sample plots at 2000-2100 m. This trend was unimodal， with the initial increase followed by a decrease （P<0.05）. Simpson’s dominance index and Pielou’s evenness index did not change significantly with increasing altitude （P>0.05）. There was no significant difference in species diversity among the meadow steppe， the typical steppe， and the desert steppe. 3） Annual precipitation， altitude， total soil nitrogen content， total soil phosphorus content， and average daily air temperature were important environmental factors that affected grassland vegetation characteristics in the study area. Among the environmental factors， annual precipitation and altitude were the main environmental factors affecting grassland vegetation， whereas total soil nitrogen content， total soil phosphorus content， and average daily air temperature were secondary environmental factors. The results of this study provide a basis for a deeper understanding of the distribution characteristics of grassland vegetation in the Luoshan Nature Reserve.

Changes in nitrogen uptake rate of plant species in different degradation stages of an alpine meadow on the Qinghai-Tibet Plateau

Jia-juan HUO, Ming-hua SONG

2025, 34(2):  16-26.  DOI: 10.11686/cyxb2024103

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Nitrogen （N） is an essential element for plant growth and reproduction， and it exists in various chemical forms in soils. The location of alpine meadows on the Tibetan Plateau is unique， where the climate is severe with low temperature. The low temperature restricts decomposition of soil organic matter and leads to scare available N in the soil， which further limits plant growth. Moreover， overgrazing causes grassland degradation and succession， resulting in severe loss of available nutrients in soil and changes in the N use patterns of plants. In this study， a ¹⁵N labeling experiment was conducted in an alpine meadow in Zeku County， Qinghai Province to trace plant utilization of ammonium nitrogen （NH₄⁺-N） and nitrate nitrogen （NO₃^--N） in plant communities exhibiting different degradation stages. Six degradation stages， including lightly， moderately， and severely degraded grasslands， and eroded， severely eroded grasslands， and bare black soil， were selected based on prior knowledge on plant community succession during the degradation of the alpine meadows. The uptake rates of NH₄⁺-N and NO₃^--N by the dominant sedge species Kobresia pygmaea were measured in the six degradation stages. Additionally， we also quantified the uptake rates of NH₄⁺-N and NO₃^--N by forb species Ligularia sibirica and Elsholtzia ciliata， the dominant species in patches in the later degradation stages. The results showed that along the degradation stages， the uptake rate of total inorganic nitrogen by K. pygmaea showed a fluctuating downward trend. The uptake rate of ammonium nitrogen was consistent with the trend of total inorganic nitrogen uptake rate， while the uptake rate of nitrate nitrogen showed a fluctuating upward trend. Except for the erosion and bare black soil stages， the uptake rate of ammonium nitrogen by K. pygmaea is significantly higher in underground organs than in aboveground organs. Except for the severe degradation and bare black soil stages， the uptake rate of nitrate nitrogen by K. pygmaea in underground organs was significantly higher than that in aboveground organs in all other stages. In the later stage of degradation， there was no significant difference in the uptake mode of nitrate nitrogen between patches dominated by K. pygmaea or patches dominated by forb species. However， the uptake rate of ammonium nitrogen was significantly higher in the patches dominated by the forb species than in the patches dominated by K. pygmaea. In patches， the dominant forb species， L. sibirica and E. ciliata， have significant differences in the uptake of ammonium and nitrate nitrogen. L. sibirica has a significantly higher uptake rate of NH₄⁺-N than NO₃^--N， while E. ciliata has no significant difference in the uptake rate of the two inorganic N forms. In summary， at different stages of degradation in the alpine meadow， plant species adopt different inorganic nitrogen acquisition strategies to adapt to soil nutrient conditions， by which maintains plant species coexistence. A deeper understanding of the absorption and utilization of soil inorganic nitrogen by plants at different stages of grassland degradation can provide insight into the mechanisms of species coexistence and guide the restoration of degraded grasslands.

Prediction of potentially suitable areas for Agropyron mongolicum to enhance its distribution

Cong-yan TIAN, Wen-qiang WANG, Bo YANG, Wen-guang HUANG, Yong-liang LIANG, Jun-long YANG, Xiao-wei LI

2025, 34(2):  27-40.  DOI: 10.11686/cyxb2024138

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Agropyron mongolicum， a plant under second-level key protection in China， posess strong drought resistance and adaptability. Hence， this species has significant value for the restoration of desert grassland vegetation and as a genetic resource for wheat （Triticum aestivum） breeding. Because A. mongolicum is sensitive to changes in environmental factors， it is important to identify its optimal habitat conditions to forecast its potential distribution under various climate scenarios； such information will provide crucial guidance for its conservation. In this study， a maximum entropy model was constructed using 119 accurate distribution records and data for 39 environmental variables. The model， which was implemented in ArcGIS software， was used to predict the current and future suitable growth areas for A. mongolicum under two different climate scenarios （SSP1-2.6 and SSP5-5.8）. The results show that precipitation of wettest month， seasonal variation coefficient of temperature， and soil pH are the primary natural factors influencing the distribution of A. mongolicum. At present， suitable growth areas for A. mongolicum are predominantly in northern China’s arid zones， with large populations distributed along the borders of Inner Mongolia， Shaanxi， and Ningxia. Under both projected climate scenarios， the suitable habitat for A. mongolicum is expected to shift westward to varying extents. Under future climate change scenarios， the overall distribution pattern of A. mongolicum’s potential growth areas will resemble the current one， but there will be substantial changes in suitability for A. mongolicum growth. Highly suitable areas for A. mongolicum are projected to migrate northward under these future climate scenarios， primarily to central Inner Mongolia. Consequently， conservation efforts for A. mongolicum should concentrate on areas which currently have dense communities and pay attention to potential future habitats in central Inner Mongolia.

The effects of carbon， nitrogen， and potassium addition on the decomposition characteristics of litter in desert grasslands

Xin-yi LUO, Kai-yang QIU, Tao JIN, Ping-an BAO, Ye-yun HUANG, Yi HE, Ying-zhong XIE

2025, 34(2):  41-53.  DOI: 10.11686/cyxb2024126

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Decomposition of litter is an important component process of energy flow and material cycling in grassland ecosystems. However it is not clear how litter decomposition in desert grasslands responds to the addition of carbon （C）， nitrogen （N）， and potassium （K）. Clarification of this relationship is needed to improve our understanding of the nutrient cycling process in desert grasslands. In this study， the mesh bag decomposition method was used in a randomized block design， to study the effects of exogenous C， N， and K addition on the litter decomposition characteristics of the dominant species Stipa breviflora and Leymus secalinus in Ningxia desert grassland. Litter decomposition was tested in soils fertilized with one of three rates of C （vermicompost， 30% C）， N （urea， 46% N） or K （KCl， 60% K） as follows： C₁ （0 g·m^-2·yr^-1）， C₂ （52.54 g·m^-2·yr^-1） and C₃ （705.09 g·m^-2·yr^-1） set at the experimental site； along with nutrient addition treatments. N₁ （0 g·m^-2·yr^-1）， N₂ （5 g·m^-2·yr^-1） and N₃ （20 g·m^-2·yr^-1）， three C， N， and K concentration gradients， K₁ （0 g·m^-2·yr^-1）， K₂ （9.0 g·m^-2·yr^-1） and K₃ （18.0 g·m^-2·yr^-1）. It was found that significant differences in the effects of C， N， and K addition on litter decomposition and different decomposition rates of litter from S. breviflora and L. secalinus （P<0.05）. Half-lives for L. secalinus decay ranged from 4.93 to 17.54 months and for S. breviflora from 10.76 to 20.51 months. The decomposition rates of litter from S. breviflora and L. secalinus began to slow down at 120 and 240 days， respectively. Leaves of the two grass species displayed different responses to the addition of C， N， and K nutrients. Under the K₃ and K₃+N₃+C₂ treatments， the decomposition rate of L. secalinus litter was faster， while under the CK and K₂+N₂ treatments， the decomposition rate of S. breviflora litter was faster. According to the exponential decay model， the predicted decomposition rate for L. secalinus litter is greater than for S. breviflora litter. The litter of both L. secalinus and S. breviflora decomposed quickly in autumn. In summary， there were differences in litter decomposition rates of the two grass species in the same habitat， and high additions of K and N and low additions of C promoted litter decomposition rates more strongly than other nutrient addition combinations.

Effects of conversion of alpine meadow to cultivated land on the soil microbial community in northwest Sichuan

Xiao-dong TU, Jun-fang CUI, Fu-hong KUANG, Chun-pei LI, Jiu-zhen DU, Hong-lan WANG, Xiang-yu TANG

2025, 34(2):  54-66.  DOI: 10.11686/cyxb2024116

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In the 1960s， extensive tracts of alpine meadows in the Zoige region of northwestern Sichuan were drained and converted into cultivated land， later utilized for cultivating genuine medicinal materials （for example Rheum tanguticum）. This change is significantly impacting soil physicochemical properties and microbial communities. Utilizing Illumina MiSeq sequencing technology， this study compares and analyzes the microbial community characteristics of the Zoige alpine meadows and soils used for R. tanguticum cultivation across soil depths of 0-60 cm. The effects of the land use change on soil physicochemical properties and microbial communities are investigated. Results indicate that the conversion of alpine meadow into cultivated land led to decrease in saturated moisture content， field capacity， and retention water content. The pH and total potassium content of soils used to grow R. tanguticum were significantly higher than meadow soil at several depths， while organic matter content was significantly lower in the 0-20 cm soil layer compared to meadow soil. Alkaline hydrolyzable nitrogen and total nitrogen content only significantly decreased at soil depths of 0-20 cm and 20-40 cm， respectively. Compared with meadow soil， R. tanguticum soil exhibited increased bacterial diversity and decreased fungal diversity. Cultivation of R. tanguticum significantly increased the abundance of Bacillus， reduced beneficial fungi， and increased potentially harmful fungi. Redundancy analysis highlighted available potassium， organic matter， available phosphorus， and total nitrogen as the main nutrient factors influencing soil microbial communities. Co-occurrence network analysis suggested that the conversion of meadow to cultivated land reduced the complexity of soil microbial communities， with bacteria forming more complex co-occurrence networks than fungi. The findings contribute significantly to the advanced understanding of the alterations in soil physicochemical properties and microbial communities following the reclamation of alpine meadows in Northwestern Sichuan， providing scientific data to assist in the formulation of sustainable management practices for R. tanguticum.

Effects of seasonal snow cover thickness on biomass allocation of four dominant late flowering plants in an alpine meadow

Ning ZHANG, Jin-niu WANG, Dong-liang LUO, Lin ZHANG, Bo XU, Yan WU

2025, 34(2):  67-80.  DOI: 10.11686/cyxb2024101

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The distribution of plant biomass among individual organs indicates the allocation of assimilation products， and is a driving mechanism of the differential growth of different organs， regulated by both external environment and internal factors. In alpine ecosystems the growing season is short and seasonal snow cover is a critical environmental factor with wide ranging implications for regulation of plant growth. This study was conducted in the Minjiang River headwaters on the eastern edge of the Qinghai-Tibet Plateau， to elucidate the growth strategies under different patterns of seasonal snow cover and their biomass trade-offs. For this purpose， data were collected on the biomass allocation to different organs （roots， stems leaves and flowers） of four dominant late flowering herb species （Gentiana farreri， Cremanthodium lineare， Allium sikkimense and Gentiana hexaphylla）. The findings revealed that： 1） The biomass of different components of the four plant species responded differently to different snow cover thicknesses. For C. lineare， biomass of all plant organs tended to be reduced in medium snow compared to shallow snow， with the reductions significant （P<0.05） for stem and leaf biomass. Moreover， under medium snow cover， C. lineare biomass accumulation failed to meet the threshold for seed set， leading to a decrease in population size. By contrast， biomass of all plant organs of G. farreri tended to be higher in medium snow than in shallow snow， with root and leaf biomass values significantly （P<0.05） increased. Similarly， A. sikkimense plant biomass was increased in deep snow compared to medium snow with the increases significant （P<0.05） for all plant organs-roots， stems， leaves and flowers， and for plant height. In addition， A. sikkimense consistently exhibited allometric growth relationships between the above- and belowground biomass ［α=0.208， α=0.262， P<0.05， where α denotes lg （above ground biomass）∶lg （below ground biomass）］. Meanwhile， G. hexaphylla plant biomass and allocation to plant parts was not significantly different in deep snow from that in shallow snow. With increase in depth of snow cover， investment in reproductive organs increased， but reproductive allocation decreased， indicating size-dependency. 2） Based on the response-effect trait model， the variations in plant form with different snow thickness mainly reflected different resource acquisition roles of stems and leaves， as well as the reproductive function of flowers. The niches of C. lineare， A. sikkimense， and G. hexaphylla were significantly correlated with their aboveground biomass allocation， belowground biomass allocation， and the ratio of belowground to aboveground biomass. Thicker snow cover enhanced resource availability， leading to an increased reproductive performance for A. sikkimense and a decreased one for G. farreri， whereas G. hexaphylla maintained a constant reproductive performance with change in snow cover. This demonstrates that changes in reproductive performance are governed by various factors and exhibit species-specific responses. 3） When A. sikkimense is in locations with deep snow， it faces a ‘seed-risk’ scenario. By raising the reproductive investment， it boosts its absolute investment in reproductive organs， exemplifying the traits of a classic late-flowering alpine self-pollinating plant. Conversely， G. farreri， a cross-pollinating species， reduces its reproductive investment in moderately snowy areas rich in resources， following a strategy known as pollen-risking.

Effects of exogenous hormones on the proliferation of endophytic fluorescent labeled rhizobia in seeds and growth of the seedlings

Yuan-yuan DU, Wen-juan KANG, Shang-li SHI, Yi-lin HAN, Fu-qiang HE

2025, 34(2):  81-93.  DOI: 10.11686/cyxb2024102

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The formation， development， and seedling growth of alfalfa nodules are regulated by multiple plant hormones. The proliferation and growth promoting effects of hormones on exogenous rhizobia have been studied， but there is relatively little research on the proliferation and growth promoting effects of hormones on endogenous rhizobia. To address this knowledge gap， three concentrations of 3-indoleacetic acid （IAA）， 6-benzylaminopurine （6-BA）， and 28-homobrassinolide （HBR）， which promote the growth of rhizobium SM12531f， were evaluated. Alfalfa seeds containing cyan fluorescent protein labeled endophytic rhizobia SM12531f were soaked in solutions of one of these three concentrations， and planted. The effects of the exogenous hormones on the number of endophytic rhizobia in alfalfa plant tissue， plant nodulation， and plant growth were analyzed. The results showed that the optimal concentrations for promotional activity of these three hormones were 14 mg·L^-1 for IAA， 18 mg·L^-1 for 6-BA， and 2.97 mg·L^-1 for HBR. During the seedling stage， 6-BA and HBR were beneficial for the proliferation， nodulation， and growth of endophytic rhizobia in plants， and the former had a more significant growth promotion effect. The hormone 6-BA resulted in the highest number of endophytic rhizobia colonizing in the roots， with a colony density of 1167 cfu·g^-1 at a dilution of 100 times and aboveground fresh weight of 1.99 g·plant^-1. 6-BA was also beneficial to plants during the branching stage. The endophytic rhizobia formed 833 cfu·g^-1 in plants with an aboveground fresh weight of 5.03 g·plant^-1， when diluted 100 times in a ground root solution. Therefore， in these test conditions， the most suitable hormone for promoting proliferation and growth of alfalfa endophytic rhizobia was 6-BA at 18 mg·L^-1 concentrration. These results provide a theoretical basis for the precise utilization of the nodulation nitrogen fixation effect of endophytic rhizobia in seeds， and lays a foundation for the symbiotic breeding of alfalfa rhizobia.

Effects of different fertilization treatments on soil physical and chemical properties and enzyme activity of rare earth mine tailings after planting king grass

Xiang OU, Hai LIAN, Rong-qiang CHEN, Jing-yun QIU, Li-juan WU, Xian-hong CAO, Qiang ZHANG, Xiao-wen LEI

2025, 34(2):  94-108.  DOI: 10.11686/cyxb2024154

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The aim of this study was to determine the effect of different fertilization treatments on the growth of king grass （Pennisetum purpureum×Pennisetum americanum cv. Reyan No.4） planted as a strategy to rehabilitate soil in rare earth tailings. A field experiment was conducted with six treatments， namely chemical fertilizer （CK）， biogas slurry （Z）， decomposed cow dung （N）， decomposed cow dung+biogas slurry （N+Z）， earthworm castings （Q）， and earthworm castings+biogas slurry （Q+Z）. The effects of the different treatments on soil physical and chemical properties， soil enzyme activities， and the patterns of enzyme interactions were determined in three consecutive years. The results showed that： 1） In each group， the soil bulk density showed a downward trend over the three years， and the maximum moisture capacity， capillary moisture capacity， porosity， aeration， pH， and contents of organic matter， nitrogen， phosphorus， potassium， alkaline nitrogen， and available phosphorus showed an upward trend. In the third year of restoration， the Q+Z treatment had the strongest effect to improve soil bulk density， moisture capacity， porosity， aeration， pH， and available phosphorus and available potassium contents. 2） The activities of soil urease， acid phosphatase， and sucrase showed an increasing trend in the N， N+Z， Q， and Q+Z treatments over the three years， and their values were significantly higher than those in the CK group in the third year （P<0.05）. Soil dehydrogenase activity was significantly higher in the N+Z treatment than in CK in the first year. The activities of soil urease， acid phosphatase， and sucrase were higher in the Q treatment than in the other treatments. 3） The activities of soil urease， acid phosphatase， and sucrase showed highly significant negative correlations with soil bulk density， and highly significant positive correlations with soil pH， organic matter， available nutrients， moisture capacity， porosity， and aeration. The dehydrogenase activity showed a highly significant correlation with total phosphorus content， and significant correlations with total potassium， alkaline nitrogen， available phosphorus， and organic matter contents， and capillary moisture capacity， porosity， and aeration. Through a comprehensive evaluation using a fuzzy mathematics membership function method， it was found that the application of earthworm cast+biogas slurry was the most effective treatment to repair soil over three consecutive years. Therefore， this treatment was identified as the best fertilization treatment for cultivating king grass to repair the soil of ion-type rare earth tailings in Gannan.

Effects of fertilizer application during mid-growing season on vegetation community biomass and species diversity in meadow grasslands

Na LYU, Ji-xi GAO, Zheng-hai LI, Chun-he YOU, Xiao-man LIU, Biao ZHANG, Yu MO, Sa-ning ZHU, Yang PENG, Xue YANG

2025, 34(2):  109-122.  DOI: 10.11686/cyxb2024129

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Appropriate nutrient addition can improve grassland productivity and stability， but the effects of adding different amounts of nutrients on large-scale grassland communities are unclear. In this study， fertilization experiments were carried out in a field experiment on mildly degraded natural mowed grassland in Hulunbuir with a total area of 182673 m². Urea granules， calcium superphosphate granules， and potassium sulfate granules were used to supply nitrogen （N）， phosphorus （P）， and potassium （K）， respectively. Three nutrient addition treatments （A， B， C） and a control （CK） were established. The application rates of N， P₂O₅， and K₂O were 2.3， 1.2， and 0.75 g·m^-2， respectively， in treatment A； 4.6， 2.4， and 1.5 g·m^-2， respectively， in treatment B； and 6.9， 3.6， and 2.3 g·m^-2， respectively， in treatment C. No fertilizer was applied to the CK. The fertilizers were applied twice， once in mid-July and once in early August 2022 in the middle of the growing season. We compared the effects of these fertilization treatments on the characteristics of grassland communities. The results showed no synergistic effect of the treatments on the productivity and species diversity of the grassland. Treatment A did not significantly affect the community biomass， but significantly increased the community richness index. The community biomass was 201.73 g·m^-2 in CK， and was higher in treatment B （319.19 g·m^-2） and treatment C （328.52 g·m^-2）， although the community species diversity did not differ significantly between CK and treatments B and C. Treatments B and C significantly increased the biomass of dominant species and perennial bunch grasses. Treatment B significantly increased the biomass of perennial forbs. The increase in community biomass in treatments B and C was associated with increases in community species height and density. Treatments A， B， and C significantly enhanced the carbon， N， and P contents in the community. The contents of carbon， N， and P in the communities in treatments A， B， and C were all significantly and positively correlated with community biomass. In conclusion， fertilization mitigates the effects of nutrient-limiting factors on plant growth and enhances community biomass by increasing the biomass of key species in the community.

Comprehensive evaluation of agronomic traits and yield of eight Elymus sibiricus varieties in the Qinghai-Tibet Plateau

Wen-hu WANG, Guo-ling LIANG, Wen-hui LIU, Feng-yu WANG, Wen LI

2025, 34(2):  123-132.  DOI: 10.11686/cyxb2024118

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The aim of this research was to comprehensively evaluate the performance of Elymus sibiricus varieties in the Qinghai-Tibet Plateau. The work was conducted in Haiyan County of Qinghai Province， and analyzed the agronomic traits and forage yield characteristics of eight E. sibiricus varieties， using a TOPSIS model to identify superior varieties. In year two， varieties designated 16-364 and 17-195 had greater plant height than other varieties （108.1 and 109.0 cm， respectively）， while variety 16-093 had the highest grass height among the tested varieties （36.8 cm） and the greatest forage yield per plant （dry weight） （170.3 g）. Varieties 15-025 and 17-195 had the highest tiller numbers （123 and 124 tillers of per plant， respectively）. In year 3， variety 17-195 had the greatest plant height and crown breadth （122.7 cm and 140.8 cm， respectively）， while variety 16-093 had the greatest grass height and forage yield per plant （51.8 cm and 234.7 g， respectively）. Variety 15-025 had the highest tiller numbers （456 tillers per plant）. A structural equation model showed that plant height and tiller numbers were key factors affecting E. sibiricus forage yield. The TOPSIS model multivariate evaluation showed that the variety 16-093 ranked highest for forage productivity and stability， making it a suitable variety for cultivation in the study region. Therefore， variety 16-093 could be used as parent material for new variety breeding as a next step.

Characteristics of the soil phosphorus pool in continuously cultivated vegetable fields in the latosolic red soil zone of the Pearl River Delta

Jian-feng NING, Yong CHEN, Jian-wu YAO, Zi-wei LIANG, Rui-kun ZENG, Rong-hui WANG, Tong LI

2025, 34(2):  133-148.  DOI: 10.11686/cyxb2024161

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Phosphorus （P） is an essential nutrient for crops， and is a key factor that is monitored in the control of non-point pollution. It is important to clarify the characteristics of the soil P pool to devise strategies to manage P levels and reduce P-related non-point pollution in intensively cultivated vegetable fields. In this study， we determined the characteristics of the soil P pool in the perennial vegetable fields in the latosolic red soil zone of the Pearl River Delta. A total of 89 soil samples were collected from the surface layer （0-20 cm） of vegetable fields located in the suburbs of Guangzhou， Jiangmen， Zhaoqing， and Huizhou. The composition of the soil P pool in the samples was determined using a modified Hedley method. Correlation analyses were conducted to reveal relationships between soil properties and the P pool. The results show that the proportions of inorganic P （Pi）， organic P （Po）， and residual P in the soil P pool were 88%， 8.1% and 3.9%， respectively， indicating that Pi was the dominant form in the soil P pool. The concentrations of these forms were as follows： Pi （1176.78 mg·kg^-1）， Po （109.03 mg·kg^-1）， and residual P （52.19 mg·kg^-1）. The Pi pool consisted of several fractions， namely H₂O-Pi， NaHCO₃-Pi， NaOH-Pi， Dli HCl-Pi， and Con HCl-Pi， with concentrations of 46.35 mg·kg^-1， 264.64 mg·kg^-1， 427.45 mg·kg^-1， 274.82 mg·kg^-1， 163.52 mg·kg^-1， respectively； and proportions of 3.32%， 20.74%， 31.29%， 16.32%， and 14.13%， respectively， in the total P pool. The fractions in the Po pool were NaHCO₃-Po， NaOH-Po， and Con HCl-Po， with concentrations of 27.24 mg·kg^-1， 62.35 mg·kg^-1， and 19.44 mg·kg^-1， respectively； and proportions of 2.33%， 5.70%， and 1.56%， respectively， in the total P pool. The dominant form in both the Po and Pi pools was NaOH-P， specifically NaOH-Pi in the Pi pool and NaOH-Po in the Po pool. In terms of soil P availability， the concentrations of labile P， moderately labile P， and recalcitrant P were 338.23 mg·kg^-1， 764.62 mg·kg^-1， and 235.15 mg·kg^-1， respectively. The proportions of labile P， moderately labile P， and recalcitrant P in the total P pool were 25.3%， 57.1%， and 17.6%， respectively. The sum of labile P and moderately labile P accounted for more than half of the total P pool in almost all the 89 soil samples， suggesting that labile P and moderately labile P were the main P types in the soil. On the whole， the soil in the perennial vegetable fields in the latosolic red soil zone was rich in P in highly available forms. Significant positive correlations and concentration effects were detected between soil properties （organic matter， total nitrogen， available nitrogen， available potassium， cation exchange capacity） and labile P and moderately labile P contents. The soil P pool accumulates via anthropogenic activities i.e. fertilization and cultivation， and is also affected by the soil’s intrinsic properties. Considering the climate characteristics in the Pearl River Delta， including heavy rainfall， the application of P nutrient management strategies is suggested to reduce the risks of P pollution in vegetable field soil.

Construction of a high-precision cultivated land identification model based on machine learning-using Zhangye City， Gansu Province as an example

Jing-jing MAI, Qi-sheng FENG, Rui-jing WANG, Sen-yao FENG, Zhe-ren JIN, Zhong-xue ZHANG, Tian-gang LIANG, Jia-ming JIN

2025, 34(2):  149-162.  DOI: 10.11686/cyxb2024110

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Cultivated land is a vital foundation resource for agricultural production and ensuring food security. Accurate identification of cultivated land is of great significance for the conservation of cultivable land resources and the sustainable development of agricultural production. In order to construct a high-precision cultivated land identification model， this study used Sentinel-1/2 data together with the spatial cloud computing platform and built combinations of different feature types. Through feature importance analysis， cultivated land identification features were then evaluated to identify the optimal feature set. Random Forest （RF）， support vector machine （SVM）， and classification and regression tree （CART） models were employed to identify the cultivated land in Zhangye City， Gansu Province for the year 2021. Simultaneously， the classification accuracy of each classifier was compared and analyzed. The results show that using a combination of vegetation index features， radar features， and topographic features improved the classification accuracy to 91.32%； Features that performed well in cultivated land identification in the study area included elevation， radar polarization channel VH， and normalized difference water index （NDWI）. In the cultivated land identification of Zhangye City， RF algorithm demonstrates clear advantages， with an overall accuracy of 90.04% and a Kappa coefficient of 0.79. Based on the RF model， the cultivated land area associated with Zhangye City is estimated to be 585000 ha， accounting for 15.4% of the total area. The methodology developed in this study achieves accurate identification of cultivated land in Zhangye City and offers a tool for cultivated land mapping in the region.

Effect of nitrogen application rates on root growth and organic acid secretion in two rice varieties with different eating quality

Hao-jing LI, Dan-ke ZHANG, Hai-run LI, Jing CAO, Guo-wei XU

2025, 34(2):  163-173.  DOI: 10.11686/cyxb2024142

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The application of nitrogen fertilizer affects the growth， yield， and quality of rice （Oryza sativa）. The aim of this study was to determine the effects of different nitrogen application rates on root growth and organic acid secretion in two rice varieties with different eating quality. A pot experiment was conducted with the rice varieties ‘Zhengdao C42’ （high flavor quality） and ‘Xudao 3’ （medium flavor quality）. The experiment was established with a control and three nitrogen fertilization treatments： 0 （N₀）， 120 （N₁₂₀）， 240 （N₂₄₀）， and 360 （N₂₄₀） kg N·ha^-1. The rice plants were analyzed to determine root length， root surface area， root oxidation activity， root exudation， the contents of zeatin and zeatin riboside （Z+ZR）， and abscisic acid （ABA）， and total organic acids in root exudates. The results showed that the root surface area， root oxidation activity， Z+ZR contents， and total organic acids in root exudates showed trends of initially increasing and then decreasing as the rate of nitrogen fertilizer application was increased. In both rice varieties， the maximum values of all measured indexes were in the N₂₄₀ treatment. The root surface area， root oxidation activity， Z+ZR content， and total organic acids in root exudates were increased by 148.0%， 48.5%， 16.0%， and 86.5%， respectively， in Xudao 3 in the N₂₄₀ treatment at the heading stage； and by 103.7%， 72.5%， 17.8%， and 98.0%， respectively， in Zhengdao C42 in the N₂₄₀ treatment at the heading stage， compared with their respective controls at the same stage. The ABA content first decreased and then increased as the nitrogen application rate increased， and was lowest in the N₂₄₀ treatment. Comparisons of the two varieties showed that the root oxidation activity， root exudation， Z+ZR content， and total organic acids in root exudates were 40.7%， 74.7%， 9.7%， and 34.1% higher， respectively， in Zhengdao C42 than in Xudao 3. The root length and root surface area were lower in Zhengdao C42 than in Xudao 3. The root surface area， root oxidation activity， root exudation， Z+ZR content， and total organic acid content in exudates showed significant or extremely significant negative correlations with amylose content， and significant or extremely significant positive correlations with gel consistency. The ABA content in root exudates showed an extremely significant positive correlation with amylose content， but a negative correlation with gel consistency. For both rice cultivars， root growth and organic acid secretion showed the best results in N₂₄₀ treatment. These results provide guidance for nitrogen management during the cultivation of high-quality eating rice.

Identification and functional analysis of ApCtsk1 encoding cathepsin K in Acyrthosiphon pisum

Rui MA, Yi-ting WU, Yan LI, Zhan-zi YU, Lei LIU, Sen-shan WANG

2025, 34(2):  174-183.  DOI: 10.11686/cyxb2024147

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The aim of this research was to explore the function of ApCtsk1 in pea aphid （Acyrthosiphon pisum） and evaluate its potential as a target for the prevention and control of this pest. The amino acid sequence characteristics of the putative ApCtsk1 protein were analyzed using tools at various websites （NCBI， ExPASy Proteomics Server） and a phylogenetic tree was constructed using MEGA 11. The transcript levels of its encoding gene were determined in aphids at different stages of development and in different tissues by RT-qPCR analysis. The biological function of ApCtsk1 in the development and reproduction of A. pisum was investigated using an RNA interference gene knock-down strategy. In the phylogenetic analysis， ApCtsk1 was clustered with cysteine proteases from other members of the Aphididae in the Hemiptera. High transcript levels of ApCtsk1 were detected in fourth instar nymphs， and in the abdomen， ovary， and cuticle of adult aphids. Compared with A. pisum in the control group， those in the ApCtsk1-knockdown group showed an increased mortality rate （22.22% higher）， decreased body length and body width （decreased by 12.56% and 13.22%， respectively）， abnormal body color， and slower movement. In addition， the aphids with knocked-down ApCtsk1 showed the lethal phenomenon of molting failure， which affected their fecundity. These changes resulted in delayed reproduction and decreased reproduction over time. Our findings show that ApCtsk1 plays an important role in the development， survival， and reproduction of A. pisum.

Gene cloning and drought resistance identification of the gene HgS5 in Halogeton glomeratus

Xin-yao WANG, Ya-ping PENG, Li-rong YAO, Jun-cheng WANG, Er-jing SI, Hong ZHANG, Ke YANG, Xiao-le MA, Ya-xiong MENG, Hua-jun WANG, Bao-chun LI

2025, 34(2):  184-195.  DOI: 10.11686/cyxb2024106

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To address environmental challenges involving escalating frequency and severity of drought， it is of utmost importance to develop a deep understanding of drought-resistance genes in plant genomes. Based on our initial laboratory analysis of transcriptome sequencing data from Halogeton glomeratus， the HgS5 gene exhibited the highest expression level and differential fold change following salt stress. This study focused on the HgS5 gene， conducting bioinformatics analysis and subcellular localization of the protein encoded by this target gene. We employed qRT-PCR to assess the relative expression of the target gene in the leaves and roots of Arabidopsis thaliana， and achieved heterologous expression in A. thaliana using Agrobacterium as a vector. In this experiment， we cloned the HgS5 gene from H. glomeratus and validated its drought resistance in A. thaliana. It was found that the HgS5 gene comprises 1738 base pairs， encoding 370 amino acids. The encoded protein is acidic and hydrophilic， lacking a transmembrane region. Featuring 116 promoter cis-acting elements， the HgS5 gene shares a A_thal_3526 conserved domain with homologous genes related to Carnegiea gigantea， Amaranthus tricolor， and Beta vulgaris. Subcellular localization indicated that the HgS5 gene is primarily expressed on the cell membrane. Fluorescence quantitative analysis showed that the HgS5 gene is predominantly expressed in the roots of A. thaliana， with a significantly increased expression level compared to other groups at 6 days （P<0.05）. The drought resistance assessment revealed a notable enhancement in drought tolerance in A. thaliana overexpressing the HgS5 gene， evident in a slower wilting rate of the plants. The HgS5 gene conferred resistance to dry conditions by influencing enzyme activity， initially increasing and subsequently decreasing the activities of superoxide dismutase， peroxidase， and catalase in the roots of A. thaliana. To summarize， the gene HgS5 plays a pivotal role in the process of drought resistance. The aim of this study was to provide a theoretical basis for further exploration of the molecular response mechanism of the HgS5 gene to drought stress.

Techniques of N₂O emission reduction in farmland and their synergistic application with green manure

Rui LIU, Dan-na CHANG, Guo-peng ZHOU, Song-juan GAO, Qiang CHAI, Wei-dong CAO

2025, 34(2):  196-210.  DOI: 10.11686/cyxb2024111

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Nitrous oxide （N₂O） is one of four the main gases linked to global warming， and agricultural production is the largest anthropogenic source of N₂O emissions. N₂O mainly originates from nitrification and denitrification processes in soil and is predominantly influenced by soil pH value， O₂ concentration， CO₂ concentration， moisture， texture， temperature， and exogenous carbon （C） and nitrogen （N） input. In recent years， China has achieved remarkable results in using green manure to reduce chemical N fertilizer application and drive soil health. However， study of the role of green manure in N₂O emission is still in the early stages. The impact of planting and incorporating green manure on soil N₂O emission depends on factors such as the varieties of green manure and the physicochemical properties of the soil. Among them， the influence on soil mineral N is the greatest factor. Generally， green manure can efficiently absorb soil mineral N in the fallow period， and its incorporation into the soil can reduce chemical N fertilizer application， thus decreasing N₂O emission. However， green manure releases large amounts of N during its decomposition， which may increase soil N₂O emissions. Combined with appropriate N₂O emission reduction approaches， N₂O emission in green manure-based systems can be reduced according to planting systems， crop varieties， climate conditions and soil types. In southern China’s rice-green manure rotation area， chemical N could be reduced by 40%， when adding alkaline amendments such as biochar. In northern China’s main crop-green manure rotation area， chemical N could be reduced by 15%-20%， through adding chemical inhibitors and combining mechanical deep application of chemical N fertilizers. For main crops rotated or intercropped with green manure systems in Northeast and Northwest China， chemical N could be reduced by 13%-48%， by adding nitrification inhibitors， with integrated water-fertilizer management practices and no-tillage. In main crops rotated with green manure systems of Southwest China， chemical N could be reduced by 15%-20%， through techniques such as slow-release fertilization， use of chemical inhibitors， and others. In this study we have focused on the feasibility of N₂O emission reduction by combining green manure practices and exogenous reduction approaches to N₂O emission， to provide practical guidance for reducing N₂O emission in green manure-based systems.

Optimizing agricultural structure and accelerating the development of the forage industry

Jia-ting WANG, Duo-wen SA, Lin-hui SHAO, Zong-li WANG

2025, 34(2):  211-220.  DOI: 10.11686/cyxb2024233

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With the continuous improvement of the living standard of urban and rural residents， the consumption structure of agricultural products is gradually changing， the proportion of meat food is increasing year by year， and the proportion of ration crops is decreasing. Based on the historical background of agricultural supply-side structural reform， reviews the changes of grain production， forage planting， animal husbandry and animal product supply before and after agricultural supply-side structural reform， summarizes the effect of grain-to-feed policy in the supply-side structural reform of agriculture， interprets the development plan and policy of herbivorous animal husbandry， and optimizes the three-dimensional structure of“grain-economy-feed”， the prospect of forage industry development was prospected in the aspects of increasing forage， cattle and sheep， and improving the scientific and technological support level of forage， which provided theoretical support for the study of high quality forage industry and modernization of agriculture and animal husbandry in our country.

Effects of nitrogen addition on soil microbial nutrient limitation characteristics in grassland in the Loess Hilly Region

Yun-huan JIA, Wen-ying HU, Jian DENG, Xue ZHAO, Zi-yue CHEN, Ya-nan WANG, Jiang-wen LI, Xiao-xi ZHANG

2025, 34(2):  221-232.  DOI: 10.11686/cyxb2024146

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Increasing atmospheric nitrogen deposition is affecting the soil nutrient balance. This may result in decreased nutrient availability to soil microbes. However， the effect of nitrogen deposition on the characteristics of nutrient limitation for soil microbes in grassland in the Loess Hilly Region is still unclear. The objective of this study was to investigate the effects of nitrogen deposition on soil microbial nutrient limitation in this region. A field-based controlled experiment simulating nitrogen deposition was conducted， and the soil microbial biomass， nutrient-transforming enzyme activities， and soil physicochemical properties were determined. This allowed us to elucidate the characteristics of nutrient limitation for grassland soil microorganisms， and its influencing factors， under different nitrogen addition levels. The results showed that nitrogen addition led to a decrease in soil pH， and altered the soil nutrient balance. More specifically， nitrogen addition increased the soil organic carbon and total nitrogen contents， but did not significantly affect the total phosphorus content. In addition， nitrogen addition enhanced the contents of soil available nutrients， with a greater increase in the available phosphorus content than in the soluble carbon and mineral nitrogen contents. This resulted in a relative shortage of carbon and nitrogen as available nutrients. Notably， the soil microbial biomass and extracellular enzyme activities decreased under low nitrogen addition but increased under high nitrogen addition. Further analyses using an enzyme stoichiometric model indicated that with increasing amounts of nitrogen addition， nitrogen limitation for soil microorganisms was intensified， while carbon limitation was alleviated. Microbial carbon limitation also affected the microbial carbon utilization efficiency. The imbalance of soil total and available nutrients caused by nitrogen addition jointly affected the characteristics of nutrient limitation for soil microorganisms by regulating microbial biomass and enzyme activity. In conclusion， these findings provide new information about the characteristics of soil nutrient cycling in grassland as affected by increasing nitrogen deposition.