Table of Content

20 June 2023, Volume 32 Issue 6

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The grassland agriculture of Mongolia and its capacity to inform development in China

Zhi-peng HUANG, Yi HUANG, Quan-jun YANG, Chao XIA, Yan ZHANG

2023, 32(6):  1-15.  DOI: 10.11686/cyxb2022265

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Mongolia borders on northern China， has abundant grassland resources and grassland-based livestock husbandry is the pillar industry there. Based on the literature and statistical data， this study surveys the development status of grassland agriculture in Mongolia from three aspects： reform of the pastoral institutional system， the grassland resources， and the development of a grazing-based livestock industry. Our study also analyzes the differences between Mongolia and the Inner Mongolia Autonomous Region of China. Grassland agriculture in Mongolia has undergone three stages of institutional reforms， the post-transformation period began at 1990 and is ongoing till now. The grassland itself is collectively owned and the livestock is privately owned. Under the influences of climate change， over exploitation of grassland， expansion of cultivated land and urban areas， and mining pollution， the grassland area has decreased and the ecological status of the grassland is gradually deteriorating. The proportions for each of Mongolia’s five categories of livestock remain stable but with regional variability and differences. The growth in total livestock numbers is much higher in Mongolia than in Inner Mongolia， China. In recent years， the grazing-based livestock husbandry has faced a problem of an aging population. As a result， the proportion of animal husbandry output value within the national economy has gradually declined and the industrial chain urgently needs to be improved. Finally， this study proposes implications for Mongolia and offers information relevant to the development of grassland agriculture in China.

Responses of soil water conservation function and soil physicochemical properties to a range of degradation conditions in alpine meadows of the Three River Headwater Region

Yu SUN, Yong-sheng YANG, Qi HE, Jun-bang WANG, Xiu-juan ZHANG, Hui-ting LI, Xing-liang XU, Hua-kun ZHOU, Yu-heng ZHANG

2023, 32(6):  16-29.  DOI: 10.11686/cyxb2022291

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The soil water-holding capacity and physicochemical properties are important indicators of the water conservation function of soil， and it is important to understand how these factors change under various condition for the ecological protection and restoration of alpine meadows. In this study， we analyzed the effects of different degradation levels on the soil water-holding capacity and physicochemical properties of soil in alpine meadows， as well as correlations between these factors， in both field and laboratory-based experiments. The filed experiments were conducted in Maqin County， Guoluo Tibetan Autonomous Prefecture， in the Three River Headwater Region. The main findings were as follows： 1） The saturation water-holding capacity， capillary water-holding capacity， and field water-holding capacity of the 0-10 cm soil horizon of alpine meadows decreased with increasing severity of degradation. The degradation level had the most significant effect on the water-holding capacity in the 0-5 cm soil surface horizon. Compared with soil at the native vegetation site， soil at the heavily degraded site showed significantly decreased （P<0.05） saturation water-holding capacity， capillary water-holding capacity， and field water-holding capacity in 0-5 cm soil horizon decreased by 51.99%， 56.28%， and 59.93%， respectively. 2） With increasing severity of degradation， the total nitrogen， total phosphorus， and total carbon contents in the 0-5 cm soil horizon gradually decreased， but there was no significant change in total potassium content. Compared with soil at the native vegetation site， the soil at the heavily degraded site showed significantly decreased （P<0.05） contents of total C， total N， and total P in the 0-5 cm soil horizon decreased by 41.95%， 65.88%， and 21.82%， respectively. As the severity of degradation increased， the soil organic carbon content and total porosity showed a decreasing trend， and soil pH and bulk density showed a significant increasing trend. 3） A redundancy analysis showed that saturated water-holding capacity， capillary water-holding capacity， and field water-holding capacity were significantly correlated with total soil N and capillary porosity （P<0.05）， and the positive correlation with capillary porosity was highly significant （P<0.01）. The saturated water-holding capacity， capillary water-holding capacity， and field water-holding capacity were significantly negatively correlated with soil bulk density and pH （P<0.05）， Capillary porosity and soil total K were not correlated with the field water-holding capacity， but were the main factors determining saturated hydraulic conductivity. These findings indicate that alpine meadow degradation has the most significant effect on the top soil horizon and strengthening the protection of the top soil horizon is the key to maintaining the water conservation function of the soil.

Carbon source utilization by soil bacteria at different lengths of time after introducing shrubs to the desert steppe

Yan-shuo CHEN, Yan-ping MA, Hong-mei WANG, Ya-nan ZHAO, Zhi-li LI, Zhen-jie ZHANG

2023, 32(6):  30-44.  DOI: 10.11686/cyxb2022298

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The aim of this study was to explore the impact of the introduction of shrubs over recent decades on the functional diversity of soil bacterial communities in the desert steppe. Therefore， the carbon utilization characteristics of soil bacteria in the 0-20 cm soil horizon were investigated and analyzed. Soil samples were collected from fenced grassland （17 yr）， and grassland at 6， 15 years， and 25 years after the introduction of shrubs. The soil samples were analyzed using the Biolog-ECO method. It was found that the soil total carbon content was up to 43.5% （P<0.05） higher in shrubland than in fenced desert grassland， but did not differ significantly among the three shrublands. The amounts of bacteria and microbial biomass carbon were highest in the 25-year shrubland. Sucrase activity in soil increased significantly with increasing number of years after shrub introduction. Compared with the soil bacterial community in enclosed desert grassland， those in the shrublands showed increased utilization of soil carbon sources （by 92.75%-181.73%）. The utilization capacity of six types of carbon sources by soil bacteria was significantly higher in the shrublands than in the enclosed grassland. Sugar， amino acids， and carboxylic acids were the three types of carbon sources preferentially utilized by soil bacteria. The introduction of shrubs into the desert steppe significantly increased the functional diversity of soil bacterial communities， especially in terms of the Shannon-Wiener richness index， Shannon’s evenness index， and Simpson’s dominance index， and the values of these indexes increased with increasing number of years after shrub introduction. The soil total carbon and nitrogen contents were significantly and positively correlated with the functional diversity of soil bacteria （P<0.05） after the introduction of shrubs. To summarize， nearly 30 years after shrub introduction， the bacterial utilization of carbon sources had significantly improved， accompanied by a shift of the main types utilized from amino acids and polymers in grassland to sugars and amino acids in shrubland.

Effects of co-sowing of Artemisia wellbyi and perennial grasses on the characteristics of vegetation and soil fungal communities in desertified grasslands in Tibet

Huan LIU, Kai DONG, Zeng-wangdui REN, Jing-long WANG, Yun-fei LIU, Gui-qin ZHAO

2023, 32(6):  45-57.  DOI: 10.11686/cyxb2022356

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The aim of this study was to determine the optimal proportion of plant species when using mixed-sowing for restoration of desertified grasslands on the Tibetan plateau and for improving the ecological effects of vegetation and soil during restoration. Artificial restoration experimental plots were established in the sandy grasslands of Tibet for this study. Seeds of the native Tibetan species Artemisia wellbyi and the perennial grass species Elymus nutans and Agropyron trachycaulhum were mixed at different proportions ［AG₁ （4∶1∶2）， AG₂ （4∶2∶1） and AG₃ （5∶1∶1）］ and sown at the experimental plots. The controls were unrestored sandy bare ground as the desertified control （CK） and natural grassland （NG） under in situ conditions. Three years after establishing these plots， the vegetation biomass and soil physical and chemical indexes were determined， and ITS sequencing technology and FUNGuild function prediction methods were used to characterize the community structure and functions of soil fungi. The main findings can be summarized as follows： 1） Compared with the control （unrestored sandy land）， the restoration treatments increased the above-ground plant biomass （AGB） and below-ground biomass （BGB） by more than three times， and significantly increased soil water content （WC）， and the contents of organic matter （OM）， alkali-hydrolyzale nitrogen （AN）， available phosphorus （AP）， and available potassium （AK） in soil （P<0.05）. 2） The soil fungal community structure and diversity varied among the three replanting treatments. The AG₃ treatment had the highest soil fungal diversity and its fungal community structure was most similar to that of natural grassland. 3） There were significant differences in the abundance of Basidiomycota and Mortierellomycota in soil between the restoration treatments and natural grassland （P<0.05）. The results of a redundancy analysis showed that BGB， AN， AP and pH were the main environmental factors affecting the horizontal community structure of the soil fungal phyla. The relative abundance of Basidiomycota was positively correlated with BGB and pH， and the relative abundance of Mortierellomycota was positively correlated with BGB， AN， and AP. 4） Based on FUNGuild functional predictions， three trophic functional groups （saprophytic， pathogenic， and symbiotic fungi） and five cross-trophic functional groups were detected in all soil samples. Pathogenic， saprophytic， pathogenic-saprophytic， pathogenic-saprophytic， and symbiotic trophic types were dominant. These results show that replanting with A. wellbyi and the perennial grasses E. nutans and A. trachycaulhum can increase plant biomass and restore desertified soil. Under these conditions， the restoration treatment with the best effect on soil nutrients and fungal abundance was sowing with a 5∶1∶1 mixture of A. wellbyi， E. nutans， and A. trachycaulhum seeds.

Effect of grazing exclusion on soil organic carbon and stoichiometry characteristics of soil microbial biomass in sagebrush desert

Si-yuan LI, Yu-xuan CUI, Zong-jiu SUN, Hui-xia LIU, Hua-wei YE

2023, 32(6):  58-70.  DOI: 10.11686/cyxb2022267

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This research aimed to clarify soil microbial biomass eco-stoichiometry characteristics in desert montane grassland in the years following grazing exclusion. Soil organic carbon accumulation and its relationship in degraded desert grassland to soil organic carbon （SOC）， soil microbial biomass carbon （MBC）， nitrogen （MBN）， phosphorus （MBP）and their stoichiometric ratios were analyzed in the 0-50 cm soil layer of sagebrush desert grasslands from Xinyuan， Bole， Manasi， Hutubi and Qitai counties on the northern slopes of the Tianshan Mountains for 4-7 years following grazing exclusion. The relationships between soil organic carbon （SOC）， soil MBC， MBN， MBP and their stoichiometric ratios were analyzed by structural equation modeling （SEM）. It was found that the SOC content of sagebrush desert grassland in the 0-50 cm soil horizon after grazing exclusion was significantly reduced by 15.52% compared with the control （P<0.05）， while the overall changes of soil MBC， MBN， MBP， MBC∶MBN， MBC∶MBP and MBN∶MBP were not significant. SOC was significantly positively correlated with MBC， MBN， and MBP （P<0.01）， and negatively correlated with MBC∶MBN and MBC∶MBP， and the relationship between SOC and MBN∶MBP changed from significantly positive to negative after grazing exclusion （P<0.01）. SEM showed that soil MBC， MBN， MBP and their stoichiometric ratios data directly explained 46% of data variation for SOC accumulation， and MBN had the strongest effect on soil organic carbon （P<0.001）， while grazing exclusion reduced the effect of soil MBC and MBN on soil organic carbon accumulation and increased the direct effect of soil MBP. In conclusion， the effects of 4-7 years of grazing exclusion on soil microbial biomass eco-stoichiometry characteristics of sagebrush desert grassland were not significant， and MBN was the most influential determining factor for soil organic carbon accumulation.

Effects of phosphorus application and inoculation with arbuscular mycorrhizal fungi on alfalfa yield and phosphorus use efficiency

Xiao-xia AN, Ying-ying ZHANG, Chun-hui MA, Man LI, Qian-bing ZHANG

2023, 32(6):  71-84.  DOI: 10.11686/cyxb2022251

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In order to investigate the effects of phosphorus application and inoculation with arbuscular mycorrhizal fungi on dry matter yield， phosphorus content and soil alkaline phosphatase activity （AKP） of alfalfa， the soil available phosphorus and total phosphorus of alfalfa under different inoculation and phosphorus application regimes were analyzed. The relationship between alfalfa dry matter yield and inoculation and phosphorus application and the relationship between yield and various other indicators were further clarified. In this experiment， a two-factor completely randomized design was adopted. Four inoculation treatments were included： Single inoculation with Funneliformis mosseaes （Fm， T₁）， Glomus etunicatum （Ge， T₂）， double inoculation （Fm×Ge， T₃） and no fungal treatment （CK， T₀）. As the second factor， four phosphorus application levels were included： P₂O₅ 0 （P₀）， 50 （P₁）， 100 （P₂）， 150 （P₃） mg·kg^-1 making a total of 16 treatments defining the fungus-phosphorus interaction. Each treatment was repeated 10 times. It was found that： 1） With the same inoculation treatment， the dry matter yield， phosphorus content of leaves， stems and roots， soil pH value and alkaline phosphatase activity of alfalfa all initially increased first and then decreased with increasing phosphorus application. All reached the maximum value in the P₂ treatment， and the yield of the alfalfa P fertilization treatment was significantly greater than the no P fertilization treatment （P<0.05）. The content of available phosphorus and total phosphorus in rhizosphere and non-rhizosphere soil increased gradually with increasing phosphorus application rate， and the agronomic efficiency of alfalfa phosphorus fertilizer showed a decreasing trend with increase in phosphorus application rate. 2） With the same inoculation treatment， dry matter yield， phosphorus content of plant leaves， stems and roots， rhizosphere and non-rhizosphere soil available phosphorus， total phosphorus content， phosphorus use efficiency， soil alkaline phosphatase activity was significantly greater than that of uninoculated treatment （P<0.05）， and the soil total phosphorus and available phosphorus contents were maximised in the T₃ treatment. The pH value of soil in the double inoculation treatment was significantly lower than that in the uninoculated treatment （P<0.05）， and reached the minimum value in the T₃ treatment. Based on these results， the phosphorus application （P₂O₅） treatment of 100 mg·kg^-1， coupled with the mixed inoculation of the two arbuscular mycorrhizal fungi could could be recommended and this treatment effectively promoted the absorption of available phosphorus in the soil by the roots of alfalfa plants， improved the efficiency of phosphorus use， and enhanced dry matter yield in alfalfa.

Effects of three exogenous substances on the physiological and fluorescence characteristics of Stylosanthes guianensis under low-temperature stress

Shi-yang ZHANG, Feng-min LIU, Jun-tao CUI, Lei HE, Yue-yan FENG, Wei-li ZHANG

2023, 32(6):  85-99.  DOI: 10.11686/cyxb2022322

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The aim of this study was to determine whether spraying Stylosanthes guianensis plants with exogenous substances could improve their performance under low-temperature conditions. Abscisic acid， chitosan， and salicylic acid at different concentrations were sprayed onto 50-day-old S. guianensis plants， and their effects on the physiological indexes and chlorophyll fluorescence characteristics of leaves under low-temperature conditions were determined. The low-temperature treatment was applied to plants in a growth chamber， and consisted of 7 days of cold temperature （8 °C/5 °C days/nights） followed by 2 days of normal temperature （28 °C/25 °C days/nights） for recovery. It was found that spraying S. guianensis plants with exogenous substances at different concentrations significantly increased the photosynthetic pigment content， antioxidant enzyme activity， and soluble protein content of the leaves under low temperature； And significantly decreased the chilling injury index， relative conductivity， and malondialdehyde content. After 2 days of recovery at normal temperature， all indexes were restored to their respective pre-chilling levels. Compared with the control plants， those sprayed with 300 mg·L^–1 chitosan， 0.4 mmol·L^–1 salicylic acid， or 10 mg·L^–1 abscisic acid showed significantly increased values of F_v/F_m， φE₀， and PI_ABS （by 80.88%-122.57%， 119.87%-170.53% and 271.77%-580.49%， respectively） and significantly decreased φD₀ （by 26.39%-37.10%）. Based on a multivariate evaluation using a membership function analysis， the optimal concentrations of chitosan， abscisic acid， and salicylic acid to improve the low-temperature tolerance of S. guianensis are 300 mg·L^–1， 10 mg·L^–1， and 0.4 mmol·L^–1， respectively. Among the three exogenous substances， chitosan （at 300 mg·L^–1） significantly increased the chlorophyll content and the activity of photosystem II， reduced heat dissipation， and was most effective in alleviating low-temperature damage to S. guianensis.

Screening of Al-tolerant white clover germplasm and analysis of Al-tolerance evaluation indexes

Hua-hao FENG, Han WANG, Jian-zhen ZHOU, Han ZHANG, Tao TANG, Yan PENG

2023, 32(6):  100-111.  DOI: 10.11686/cyxb2022275

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In this study， we selected 82 white clover germplasm lines from Sichuan and Guizhou， as well as the widely used cultivars ‘Haifa’ and ‘Huia’ to evaluate the aluminum （Al） tolerance of white clover germplasm resources in southwest China， with a view to identifying superior germplasm resources for this region. Hydroponics was used to observe the growth parameters of different germplasm lines under Al exposure （4 mmol·L^-1） for 15 days at the seedling stage， then we preliminarily screened nine lines with differing Al tolerance by subordinate function analysis. We further observed the growth and physiological changes of nine germplasm lines under Al tolerance. Subordinate function analysis was used to calculate the Al tolerance scores of the nine selected germplasm lines and principal component analysis was used to compare the contribution rates of different evaluation indexes， and hematoxylin staining was carried out to observe the active Al content of the germplasm lines. It was found that the growth and physiological performance of white clover were inhibited when the white clover germplasm lines suffered from Al toxicity. With Al toxicity， the shoot length （SL）， root length （RL）， dry weight （DW）， greenness （G）， relative water content （RWC）， chlorophyll content （Chl）， photochemical efficiency （F_v/F_m）， and performance index （PI） of white clover were significantly decreased （P<0.05）； While the electrolyte leakage （EL） and malondialdehyde content （MDA） of white clover were significantly increased （P<0.05） and the root tips of white clover were stained with hematoxylin. The preliminary evaluation of relative growth indexes showed that the white clover germplasm lines with strongest Al tolerance were Tr016， Tr056， Tr060， Tr062， and Tr077， while Tr009， Tr021， Tr040， Tr048， and Tr075 had relatively weak Al tolerance. The multivariate evaluation further confirmed Tr016 and Tr060 had the strongest Al tolerance， on the contrary， Tr021 had poor at Al tolerance. The principal component analysis suggested that， for the Al tolerance evaluation of white clover， the relative SL， RL and DW could be regarded as growth identification indexes， while identification indexes for physiological stress could use photosynthetic parameters （Chl， F_v/F_m， PI） and MDA. The results provide data on white clover Al tolerance to support selection and breeding decisions， as well as a reference information for evaluation systems to detect Al tolerance.

Effect of arsenic stress on arsenic uptake and root morphological changes in seashore paspalum

Xiao-ming CHEN, Dong-ying HAN, Gui-long SONG

2023, 32(6):  112-119.  DOI: 10.11686/cyxb2022266

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The effects of two arsenic （As） concentration treatments （10 and 100 mg·kg^-1） on the growth and accumulative characteristics of five organs ［stem， new leaf， old leaf， coarse root （diameter， D>0.5 mm） and fine root （D<0.5 mm）］， of seashore paspalum （Paspalum vaginatum） were investigated in a pot experiment. It was found that： Under the high-As treatment， the growth of all organs of seashore paspalum was inhibited. The most obvious reduction was in the stem， which showed the characteristics of low tolerance and high intolerance. Coarse roots showed better As tolerance. The As content of plant tissue varied significantly between different seashore paspalum organs and was ranked fine roots>coarse roots>stems>new leaves>old leaves. The root response to As stress was that the growth of coarse roots was promoted and the growth of fine roots was inhibited. With increasing As concentration， the proportion of root length， root surface area and root volume of the D>0.5 mm root category gradually increased， while the proportion of diameter class D<0.5 mm decreased.

Effects of maize straw return combined with nitrogen on soil enzyme activity and nitrogen fertilizer use efficiency in western dryland wheat fields of Henan Province

Song-ke MA, Ke HUO, Dong-xia ZHANG, Jing ZHANG, Jun-hao ZHANG, Xue-ru CHAI, He-zheng WANG

2023, 32(6):  120-133.  DOI: 10.11686/cyxb2022269

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This experiment studied the effects on soil enzyme activities， nitrogen fertilizer use efficiency and wheat yield of straw return with nitrogen， in the wheat cultivar Luohan 22. A split field trial design was used with two factors， straw and nitrogen fertilizer. The main plot treatments were： Straw fully cleared （S₀） and straw return （S₁）. The split-plot treatments consisted of differing nitrogen fertilizer application rates： 0 （N₀），120 （N₁）， 180 （N₂）， 240 （N₃） and 300 kg·ha^-1 （N₄）. Soil urease， sucrase， catalase and protease activities of 0-20 cm and 20-40 cm horizons were determined and the wheat yield， the nitrogen fertilizer agricultural utilization rate， nitrogen fertilizer apparent recovery rate， nitrogen fertilizer partial productivity and nitrogen absorption efficiency were measured. It was found that： 1） Compared with nitrogen fertilization treatment alone， the soil enzyme activities， nitrogen fertilizer use efficiency and wheat yield were increased by straw return. The wheat yield under S₁N₃ was the highest， and was 36.92% greater than S₀N₀. 2） Soil enzyme activity showed a trend of initial increase and then decrease with increasing rate of nitrogen application. Urease and sucrase had the highest activities in N₂， while all other soil enzymes had the highest activity at N₃. The soil enzyme activities gradually decreased with increasing soil depth. 3） The agronomic efficiency and apparent recovery of nitrogen fertilizer initially increased and then decreased with successive increases in nitrogen application rate， with the highest values observed in N₂， while the partial nitrogen productivity and nitrogen absorption efficiency decreased gradually with increasing nitrogen application rate. 4） The soil enzyme activities were positively correlated with the wheat yield and the apparent recovery of nitrogen fertilizer. In each reproductive period， urease activity was positively correlated with nitrogen absorption efficiency and nitrogen fertilizer partial productivity during the jointing period， while activities of all other soil enzymes were negatively correlated. Straw return combined with 180-240 kg·ha^-1 nitrogen fertilizer was shown to reduce excess nitrogen loss， improve the soil environment and result in efficient utilization of nitrogen resources in rainfed wheat fields of western Henan Province.

Identification of potential autotoxic substances in pea soil and analysis of their autotoxic effects

Shao-ying MA, Gui-ping CHEN, Na WANG, Lei MA, Rong-fang LIAN, Sheng LI, Xu-cheng ZHANG

2023, 32(6):  134-145.  DOI: 10.11686/cyxb2022388

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Autotoxicity is one of the main problems in continuous cropping. The aims of this study were to identify potential autotoxins in soil where pea （Pisum sativum） had been cultivated and to explore their autotoxic effects. We collected rhizosphere soil from two pea genotypes （cultivars Ding wan 10 and Yun wan 8） in the field， and used gas chromatography-mass spectrometry （GC-MS） to identify potential autotoxins in these soil samples. Then， the effects of potential autotoxins at different concentrations on the seed germination， seedling growth， and physiological indexes of pea （cultivars Ding wan 10 and Yun wan 8） were evaluated using a hydroponic system. Erucamide was detected as a potential autotoxin in both pea genotypes. Erucamide at a concentration of 0.1 mmol·L^–1 promoted the germination of Ding wan 10 seeds， and erucamide at concentrations of 0.10， 0.25 and 0.50 mmol·L^–1 promoted the germination of Yun wan 8 seeds. It was found that erucamide at different concentrations significantly decreased the activities of superoxide dismutase （SOD） and peroxidase （POD）， and increased the malondialdehyde （MDA） content in Ding wan 10. A high concentration of erucamide significantly increased the MDA content in Yun wan 8， and decreased the proline （Pro） content and POD activity in pea roots. These analyses of the allelopathic effects of potential autotoxins on pea plants revealed that erucamide inhibited the growth of two pea genotypes， with a stronger inhibitory effect on Ding wan 10 than on Yun wan 8. Thus， erucamide is a potential autotoxin in pea rhizosphere soil， and its effects depend on its concentration. A low concentration can promote seed germination but higher concentrations can inhibit seed germination and plant growth. The degree of promotion and inhibition varies among different pea genotypes.

Analysis of the key exogenous IAA-induced gene expression levels and metabolic pathways involved in long-distance translocation of Cd in Poa pratensis

Ting CUI, Yong WANG, Hui-ling MA

2023, 32(6):  146-156.  DOI: 10.11686/cyxb2022276

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This research aimed to investigate the effects and molecular mechanisms of indole-3-acetic acid （IAA）-induced decrease of the long-distance translocation of cadmium （Cd） from the roots to the shoots in Kentucky bluegrass by analysis the differentially expressed IAA-induced genes （DEGs） and metabolic pathways involved in response to Cd stress. The species Poa pratensis was used as the study material and 400 nmol·L^-1 IAA was sprayed on the leaves of plants subjected to 600 μmol·L^-1 of Cd stress. Plant heights， root lengths， and Cd concentrations in the roots and leaves were measured， and transcriptome sequencing was performed in both the Cd+ IAA and Cd treatments. Real-time quantitative polymerase chain reaction （RT-qPCR） was used to verify the accuracy of the RNA-seq. It was found that exogenous IAA significantly increased the plant heights and root lengths， and inhibited the long-distance translocation of Cd from roots to leaves. There were 1294 genes with significantly IAA-modified expression under Cd stress in Kentucky bluegrass. The expression levels of RT-qPCR had a high correlation with RNA-seq data. Gene ontology （GO） enrichment analysis showed that the genes involved in response to heat， cold， Cd， and virus exposure were induced by IAA. The molecular chaperone HSP70， protein kinase mitogen-activated protein kinase （MAPK）， and transcription factor myeloblastosis46 （MYB46） were very obviously up-regulated by IAA application. In addition， genes involved in the glutathione metabolism and lignin biosynthesis pathways were also up-regulated by exogenous IAA. This may be indicative of increased glutathione synthesis and lignification of the cell wall and further increase the vacuolar compartmentalization and decreased the Cd entry into cells， and further decrease the Cd concentration in leaves. This study provides reference data on mechanisms of IAA-induced translocation and distribution of Cd.

Effects of plateau pika （Ochotona curzoniae） disturbance on the relationship between plant species diversity and soil ecological stoichiometry in alpine meadows

Cai-feng LIU, Yuan-yuan DUAN, Ling-ling WANG, Yi-mo WANG, Zheng-gang GUO

2023, 32(6):  157-166.  DOI: 10.11686/cyxb2022271

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The relationship between plant species diversity and soil ecological stoichiometry is key to maintaining plant community structure in grasslands. Although plateau pika （Ochotona curzoniae） disturbance has been reported to have impacts on plant species diversity and soil C， N and P contents， whether plateau pika disturbance influences the relationship between plant species diversity and soil ecological stoichiometry in alpine meadows is not yet well documented. In this study， an experimental survey in the Gannan area of Gansu Province and the Qinghai Lake basins of Qinghai Province was conducted to investigate the effects of plateau pika disturbance on plant species diversity， soil ecological stoichiometry and their relationship in alpine meadows. In this research， paired-plots were used to collect data and soil samples. The results of this study showed that plateau pika disturbance significantly increased species richness index， soil organic carbon， total nitrogen， total phosphorus contents， soil C∶N and C∶P （P<0.05）， but had no significant effect on species diversity index， species evenness index and soil N∶P. In addition， plateau pika disturbance increased the positive correlation of species richness index and species diversity index with soil C∶N （P<0.05） and weakened the positive correlation between species richness index and soil C∶P （P<0.05）. The relationship between species diversity index and soil C∶P changed from a logarithmic relationship in the absence of plateau pikas to a quadratic relationship in the presence of plateau pikas （P<0.05）， and the relationship between species richness index and soil N∶P changed from an insignificant correlation in the absence of plateau pikas into a significant negative correlation with a quadratic function in the presence plateau pikas （P<0.05）. The relationship between species diversity index and soil N∶P was a significant positive correlation with a quadratic function in absence of plateau pikas， and became an insignificant correlation in the presence of plateau pikas （P<0.05）. The findings of this study verify that plateau pika disturbance has impacts on the relationship between plant species diversity and soil ecological stoichiometry. Our research provides basic information on multiple parameters， relevant to maintenance of plant community structure in alpine meadows in the presence of plateau pikas.

Research progress on remote sensing discrimination techniques for grassland botanical species

Meng-ge HUANG, Xin-hong WANG, Ling-ling MA, Xue-hua YE, Xiao-hua ZHU, Wei-ping KONG, Ning WANG, Qi WANG, Guang-zhou OUYANG, Qing-chuan ZHENG, Xiao-xin HOU, Ling-li TANG

2023, 32(6):  167-185.  DOI: 10.11686/cyxb2022278

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Grassland is an important resource bank for regional economic development and a crucial ecological reservoir for the security of China’s land-based ecological environment. Remote sensing technology is rapid， efficient， and low-cost， and therefore provides the mainstream technical means for large-scale grassland monitoring. The use of remote sensing technology to discriminate grassland species is an important way to monitor the population dynamics and botanical community succession in grassland. Such information is conducive to the timely and accurate detection of changes in the grassland ecological environment and provides an important reference for the scientific management of grassland ecosystems and the construction of an ecologically aware civilization. This study focuses on the problem of remote sensing discrimination of grassland species， clarifies the technical process of grassland species discrimination and introduces the latest research progress. Technical difficulties are covered from three perspectives： The characteristics of the main remote sensing data sources for grassland species discrimination and their acquisition techniques， important grassland species discrimination features and their mining techniques and the current commonly used grassland species discrimination methods and models. This study concludes that hyperspectral and LiDAR remote sensing and their fusion technologies have application prospects in the remote sensing discrimination of grassland species， and that the deep mining of multidimensional features and the effective combination of complementary features can improve the accuracy of grassland species discrimination. This study identifies the main problems of the current remote sensing discrimination technology for grassland species， and opens the prospect of the future precise discrimination of grassland species through remote sensing technology and thereby provides a theoretical reference for a thorough understanding of the field of remote sensing identification of grassland species and in-depth research on grassland species discrimination.

Accumulation and functions of polyamines in plants under drought stress

Wen-juan WANG, Shang-li SHI, Long HE, Bei WU, Chan-chan LIU

2023, 32(6):  186-202.  DOI: 10.11686/cyxb2022303

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Drought stress is one of the major abiotic stresses that causes reductions in crop yields. Polyamines are a class of low molecular weight aliphatic nitrogenous bases in plants. They have strong biological activity and are involved in a range of physiological processes such as plant organogenesis， embryogenesis， bud differentiation， leaf senescence， pollen tube growth， and fruit development and ripening. They also play important roles in plants under drought stress. In this paper， we review research on the anabolism and catabolism of polyamines， their functions under abiotic stress， and differences in their accumulation among species/varieties of plants under drought stress. We also discuss studies on the effects of exogenous polyamines and those using transgenic approaches to elucidate the roles of polyamines at the physiological level. The body of research on polyamines has shown that they enhance drought resistance by improving plant growth and development， photosynthetic capacity， accumulation of osmoregulatory substances， and antioxidant capacity， and that they participate in signal transduction at the molecular level in plants under drought stress.

Grassland investigation， monitoring and evaluation： international experience and insight

Ya-xian ZHANG, Jiang-wen FAN, Sui-zi WANG, Hai-yan ZHANG

2023, 32(6):  203-213.  DOI: 10.11686/cyxb2022273

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Grassland investigation， monitoring and evaluation （GIME） is the foundation for understanding the current situation and development dynamics of grassland resources. China’s GIME system has problems of a weak foundation， slow update and tardy development， which lead to an obscure information base and unclear definition of trends relating to grassland resources in China. Therefore the need for more sophiticated management of grassland can’t be met. The wider management of China’s grassland resource is at the stage of institutional reform and functional transformation. Based on experience from countries that possess abundant grassland resources， optimization and refinement of a GIME system would be conducive to the improvement of national grassland oversight. This study systematically summarizes the experience from construction of GIME systems in America， Canada and Australia and this experience offers valuable guidance for development of grassland supervision systems in China. International experience implies that certain practices， such as implementing multi-time scale fine monitoring， setting ample monitoring indicators， researching and applying advanced technologies， building a field observatory network， developing an integrated data management platform and a mechanism of data sharing， expanding the application range of outcomes， forming professional technical teams， and encouraging public participation， will better fulfill demands for multi-objective and more sophisticated grassland management for different stakeholders， and as such which deserve widespread promotion.