Acta Prataculturae Sinica

Classification of Stellera chamaejasme communities and their relationships with environmental factors in degraded alpine meadow in the central Qilian Mountains， Qinghai Province

Yong-mei LIU, Xing-zhi DONG, Yong-qing LONG, Zhi-mei ZHU, Lei WANG, Xing-hua GE, Fan ZHAO, Jing-zhong LI

2022, 31(4): 1-11. DOI: 10.11686/cyxb2021310

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The invasion of Stellera chamaejasme has exerted an increasing impact on the alpine meadow ecosystem and animal husbandry on the Qinghai-Tibetan Plateau. In this study， we explored the relationships between S. chamaejasme communities and environmental factors on a local scale， using data for plant communities， soil characteristics， and topography collected from a typical degraded meadow in the central Qilian Mountains. The data were analyzed using two-way indicator species analysis （TWINSPAN）， detrended correspondence analysis （DCA）， and redundancy analysis （RDA）. The main findings were as follows： 1） TWINSPAN divided the 45 plots into three association types： Association Ⅰ-S. chamaejasme+Stipa purpurea+Kobresia capillifolia+Thermopsis lanceolata； Association Ⅱ- S. chamaejasme+S. purpurea+Potentilla chinensis+Saussurea pulchra； and Association Ⅲ-S. purpurea+Anemone rivularis+S. chamaejasme+Poa annua.2）The RDA analysis indicated that the distribution of S. chamaejasme was significantly affected by soil total phosphorus and soil total potassium content， followed by aspect. Soil nutrient contents played an important role in the spatial patterning of the three association types， and S. chamaejasme associations with high coverage were more susceptible to low-phosphorus and low-potassium conditions. 3）Species dominance in Associations Ⅲ， Ⅱ， and Ⅰ changed with the spread of S. chamaejasme， the importance values of the Poaceae forages P. annua and S. purpurea decreased （4.10， 3.12， 2.10），those of the Fabaceae species Gueldenstaedtia diversifolia and Medicago ruthenica initially increased and then decreased （0.28， 0.57， 0.25）， those of the Cyperaceaespecies K. capillifolia and Kobresia humilis increased （0.23， 1.18， 2.19）， and those of forbs and poisonous plants （S. chamaejasme， A. rivularis， T. lanceolata， Anaphalis lactea， and Morina kokonorica） markedly increased （6.10， 5.14， 10.08）. Over time， S. chamaejasme replaced S. purpurea and became the dominant species in Associations Ⅰ and Ⅱ， and the S. chamaejasme coverage increased （5.5%， 11.0%， 29.7%）. The results of this study reveal changes in the characteristics of plant communities in a degraded alpine meadow during S. chamaejasme invasion. These findings provide a scientific basis for the development of strategies to manage， restore， and develop the degraded alpine meadow and to effectively control S. chamaejasme.

Numerical classification and ordination of the desert steppe plant community in Etuokeqianqi， Inner Mongolia

Ling JIN, Ying LU, Hong-bin MA, Ying-zhong XIE, Yan SHEN

2022, 31(4): 12-21. DOI: 10.11686/cyxb2021007

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It is very important in grassland scientific management and biodiversity protection to understand the grassland community types， and their distribution and relationship with edaphic factors. In this research， 100 sample sites on the desert steppe of Etuokeqianqi in Inner Mongolia were investigated. We used two-way indicator species analysis （TWINSPAN） to classify the plant communities， and canonical correspondence analysis （CCA） to analyze the relationship between plant communities and soil factors. It was found that： 1） The flora types of desert steppe in the study area can be divided into Artemisia ordosica+Stipa breviflora， S. breviflora+Achnatherum splendens， Agropyron cristatum+A. splendens， A. ordosica+Sophora alpecuroides， Caragana liouana+Lespedeza potaninii， S. breviflora+Oxytropis aciphylla， S. alopecuroides+S. breviflora， Stipa grandis+Nitraria tangutorum. 2） CCA ordination results showed that the correlation between soil physical and chemical factors and the plant species ordination axis was driven by alkali hydrolyzable nitrogen， available potassium， total phosphorus， soil bulk density， total nitrogen， available phosphorus， organic matter and total carbon. Alkali hydrolyzable nitrogen and available potassium had the greatest impact on the distribution of plant communities at the study site. 3） The combination of TWINSPAN classification and CCA ordination elucidates the relationship between community distribution patterns and environmental factors， and thus provides reference information for ecological management and decisions fostering sustainable utilization of desert steppe in Etuokeqianqi， Inner Mongolia.

Response of plant community structure and biomass to long-term nutrient addition in a Stipa baicalensis steppe

Jun-yan LU, Mei HONG, Bayinnamula ZHAO, Wuyingga ZHAO, Wen-dong WANG, Shang-fei MA, Dian-lin YANG

2022, 31(4): 22-31. DOI: 10.11686/cyxb2021272

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The symptoms of Stipa baicalensis steppe degradation are decreases in plant diversity and soil nutrient loss caused by long-term overgrazing. However， it remains unclear whether returning lost nutrients could improve the community diversity and productivity of S. baicalensis steppe and restore the original vegetation. Therefore， in a long-term experiment， effects of N， P and K additions （100 kg·ha^-1·yr^-1） and various nutrient combination treatments were evaluated in 2010 in an S. baicalensis steppe located at Ewenki Banner， Hulunbuir City， Inner Mongolia. The results for three consecutive years （2017-2019） showed that： 1） Long-term addition of N， NK， NP and NPK significantly increased the relative importance value of Gramineae species （P<0.05）， decreased the relative importance value of forbs， and changed the dominant species from forbs to grasses. 2） N， NK， NP and NPK additions significantly increased the aboveground biomass of the community and of Gramineae （P<0.05）， and decreased the aboveground biomass of forbs （P<0.05）， while P enhanced the aboveground biomass of Leguminosae （P<0.05）. Plant biomass was more sensitive to nutrient addition in years with adequate precipitation. 3） Simpson index， Shannon-Wiener index， Pielou index and species richness decreased with the addition of NK， NP and NPK （P<0.05）. In conclusion， N is the most important limiting factor for aboveground biomass and species diversity in a S. baicalensis steppe community， P is the second most limiting factor after N， and K is the least limiting of the three. The effects of N， P and K combinations on the S. baicalensis steppe primary vegetation community were greater in years with adequate precipitation than in years with drought.

Preliminary study of a sufficiency index of soil N and recommended N fertilizer application rates for alfalfa in the Loess Plateau of China

Hong-ren SUN, Xian-guo WANG, Yao-jun BU, Nan QIAO, Bo REN

2022, 31(4): 32-42. DOI: 10.11686/cyxb2021077

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The aim of this research was to lay a scientific basis for alfalfa （Medicago sativa） soil testing and fertilizer recommendation in the Loess Plateau region of China. The research methodology included a literature survey of alfalfa fertilization experiments conducted on the Loess Plateau， extracting data on soil nitrogen content and forage yield of N fertilizer treatments and where no N fertilizer was added. An algorithm for scattered experimental data integration and a new formula based on nutrient balance were employed to develop a sufficiency index （SI） of soil N with a scale of 1 to 6 and the recommended N fertilizer application rates （RNFAR） for alfalfa in the study region. It was found that for the planting year of an alfalfa crop （Y₁） on the Loess plateau， the values for soil alkali-hydrolyzable nitrogen for SI levels 1 to 6 were， respectively， ≥73， 55-73， 39-55， 26-39， 13-26 and <13 mg·kg^-1. Values for soil total nitrogen for SI levels 1 to 5 for Y₁ were， respectively， ≥1.5， 1.1-1.5， 0.7-1.1， 0.4-0.7 and <0.4 g·kg^-1. Values for soil organic matter for SI levels 1 to 6 for Y₁ were， respectively， ≥19， 13-19， 9-13， 5-9， 2-5 and <2 g·kg^-1. For second and subsequent seasons， values for soil alkali-hydrolyzable nitrogen for levels 1 to 5 were， respectively， ≥79， 51-79， 30-51， 13-30 and <13 mg·kg^-1. For the whole crop life （WCL） of alfalfa， values for soil total nitrogen for SI levels 1 to 4 were， respectively， ≥1.9， 1.2-1.9， 0.5-1.2 and <0.5 g·kg^-1. Values of soil organic matter for SI levels 1 to 5 for the WCL were， respectively ≥24， 13-24， 6-13， 2-6 and <2 g·kg^-1. For a target yield of 9.0 t DM·ha^-1 and an N fertilizer use efficiency of 40%， the RNFAR for SI levels 1 to 6 were， respectively， 0， 68， 135， 203， 270 and 338 kg N·ha^-1， while for a target yield of 22.5 t DM·ha^-1 and an N fertilizer use efficiency of 40%， the corresponding values were， respectively， 0， 169， 338， 506， 675 and 844 kg N·ha^-1. This research has provisionally developed a system for calculating recommended fertilization rates for alfalfa crops on the Loess Plateau， based on soil nitrogen abundance and deficiency indicators and target crop yield and thereby provides a scientific framework for soil testing and nitrogen application to alfalfa crops in the region.

Effects of nitrogen and phosphorus fertilizer rates on forage dry matter yield and regrowth of alfalfa in seasonal cultivation systems

Li-min GAO, Chun CHEN, Yi-xin SHEN

2022, 31(4): 43-52. DOI: 10.11686/cyxb2021019

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In order to explore the effects of nitrogen and phosphorus fertilizer supply on forage dry matter yield and regrowth of alfalfa （Medicago sativa） in seasonal cultivation systems in the Jianghuai area， field experiments were conducted in 2017 and 2018 with 4 phosphorus （P₂O₅） rates （0， 50， 100， 150 kg·ha^-1） and 4 nitrogen （N） rates （0， 60， 120， 180 kg·ha^-1）. The forage dry matter yield and yield components， the content and accumulation of nitrogen and phosphorus in the shoot， and the regrowth characteristics at 6 days and 12 days after cutting were examined. It was found that： 1） The application of nitrogen and phosphorus fertilizers significantly promoted alfalfa growth. The forage dry matter yield increased with increasing nitrogen supply when P₂O₅ supply was lower. In the treatments with high P₂O₅ supply， the optimal nitrogen application rate for alfalfa growth was 120 kg·ha^-1. The dry matter yield increased significantly with increase in phosphorus application rate， and this effect was independent of nitrogen supply. 2） There were significant positive correlations between forage dry matter yield and shoot nitrogen content， shoot nitrogen accumulation， and shoot phosphorus accumulation. 3） Nitrogen and phosphorus fertilizer application significantly promoted alfalfa regrowth. For P₂O₅ application rates of 0， 50， 100 and 150 kg·ha^-1， the optimal nitrogen application rates for alfalfa regrowth were 180， 120， 120 and 60 kg·ha^-1， respectively. At 6 days after cutting， both the shoot length and leaf area were positively correlated with alfalfa biomass. At 12 days after cutting leaf area was positively correlated with alfalfa biomass. In conclusion， the application of phosphate fertilizer was beneficial for reducing nitrogen fertilizer rates in a seasonal alfalfa cultivation system in the Jianghuai area and the optimal nitrogen fertilizer application rate decreased as phosphate fertilizer application rate increased. Based on these data the most suitable combination of annual phosphorus and nitrogen application rates for seasonal alfalfa cultivation systems in the Jianghuai area was 100 kg·ha^-1phosphorus and 120 kg·ha^-1， nitrogen fertilizer. These results provide reference data for development of fertilizer management recommendations in seasonal alfalfa cultivation system in the Jianghuai area.

Effect of reducing chemical fertilizer and substitution with microbial fertilizer on the growth of Elymus nutans

Dong-rong HAN, Tuo YAO, Hai-yun LI, Min-hao CHEN, Ya-min GAO, Chang-ning LI, Jie BAI, Ming SU

2022, 31(4): 53-61. DOI: 10.11686/cyxb2021036

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This research aimed to identify the ideal ratio of microbial fertilizer （MF） and chemical fertilizer （CF） to promote growth of Elymus nutans. Compared with a typical CF application of 300 kg·ha^-1， this study explored fertilizer reductions of 20% or 40% （80%CF and 60%CF， respectively） and substitution with MF at rates of 60， 90， 120， 150 or 180 kg·ha^-1. Effects on agronomic characters， the root system and nutritional quality of E. nutans were evaluated. It was found that at the first harvest， 80%CF （240 kg·ha^-1） combined with 90 kg·ha^-1MF increased E. nutans plant height， stem thickness and hay yield by 34.86%， 44.83% and 3.08%， respectively compared with CK， while 80%CF combined with 120 kg·ha^-1MF increased the crude fat content of plants by 22.97% compared with CK and decreased acid detergent fiber content by 6.59%. 80%CF combined with 150 kg·ha^-1MF increased plant crude protein content by 36.09% and 80%CF （240 kg·ha^-1） combined with 90 kg·ha^-1MF decreased neutral detergent fiber content by 15.64%. At the second harvest， 80%CF combined with 60 kg·ha^-1MF increased total plant root length by 34.77% compared with CK； 80%CF combined with 90 kg·ha^-1MF increased plant height， stem thickness， hay yield and the total root surface area by 80.43%， 66.34%， 13.08% and 8.66%， respectively； 80%CF combined with 120 kg·ha^-1MF increased plant crude protein and crude fat content， total root volume， underground fresh weight and underground dry weight by 25.30%， 14.61%， 45.54%， 19.39% and 51.04%， respectively； 80%CF combined with 180 kg·ha^-1MF reduced acid detergent fiber and neutral detergent fiber content of plants by 8.13% and 8.88%， respectively， compared with CK. Through principal component analysis， the combined application of 20% fertilizer reduction （240 kg CF·ha^-1） and 90 kg·ha^-1 microbial fertilizer gave the best growth promotion effect on E. nutans.

Yield， forage quality and a multivariate evaluation of Avena sativa and Vicia villosa in different mixed planting patterns under drip irrigation in an arid area of Ningxia

Man-you LI, Yan-jun YANG, Bin WANG, Xiao-tian SHEN, Li-juan CAO, Xiao-yun LI, Wang NI, Jian LAN

2022, 31(4): 62-71. DOI: 10.11686/cyxb2021012

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This research compared the forage production and inter-species relationships between Avena sativa and Vicia villosa for randomly mixed， alternate-row intercropped， alternate-strip intercropped， and cross-drilled mixed cropped plantings of the two species and their monocultures under drip irrigation in arid areas of Ningxia. The experiment was laid out in a single factor randomized block design， and used principal component analysis （PCA） for multivariate evaluation to explore the best mixed planting mode for A. sativa and V. villosa. It was found that the four mixed sowing modes significantly increased the forage yield compared with monoculture （P<0.05）. Among the tested sowing patterns， alternate-row intercropped had the highest yields of fresh forage and hay， these being 36495 and 11906 kg·ha^-1， respectively. The mixed plantings significantly improved the forage quality compared with A. sativa monoculture. The relative feeding value of alternate-row intercroped forage （compared with A. sativa） was 115.89， which was exceeded only by V. villosa monoculture. For the four mixed sowing modes， the relative yield total values （RYT） were all greater than 1. Interspecific competition was weaker than intraspecific competition， A. sativa and V. villosa demonstrated a niche differentiation， with the alternate-row intercropped configuration being especially striking. According to PCA， the alternate-row sowing mode for A. sativa and V. villosa had the best multivariate score.

Comparison of crop yield and forage quality of six oat varieties in Angren County， Shigatse

Hai-yan WU, Ni QU, Zhen QU, Tongsangcuomu, Dawazhuoga, Deyang, Nimazhuoga, Zhao-ming LIU, Yu-shou MA

2022, 31(4): 72-80. DOI: 10.11686/cyxb2021318

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In this research six oat （Avena sativa） varieties （Baiyan No.2， Qinghai 444， Qingyin No.1； Qingyin No.2， Jiayan No. 2， and sweet oat） were studied and 25 indexes of their agronomic traits， crop yields and nutritional quality were collectively evaluated by principal component analysis， in order to select suitable oat varieties with high crop yield and forage quality for farmer use in Angren County， Shigatse. It was found that among the six varieties evaluated， Qinghai 444 reached the wax-ripening grain development stage at harvest， while all other varieties were in the milk-ripening stage. Sweet oat and Qingyin No.1 both exceeded 147 cm in height and were significantly taller （P<0.05） than the other four varieties. The stem diameter of sweet oat （6.39 mm）， did not differ significantly （P>0.05） from Qinghai 444， Jiayan No.2 and Qingyin No.1， but was significantly （P<0.05） larger than Baiyan No.2 and Qingyin No.2. There was no significant difference in fresh weight or dry weight among the six varieties （P>0.05）. Sweet oat had the highest hay yield （18.42 t·ha^-1）， and Qingyin No.2 had the lowest hay yield （13.62 t·ha^-1）. The crude protein content of the six oat varieties ranged from 5.66% to 11.59%， and the crude fat content ranged from 2.94% to 3.50%. Qingyin No.2 had the highest relative forage quality， with values of 174.76， respectively. In principal component analysis， the first four components accounted for 91.78% of the data variation. In the multivariate evaluation， sweet oats had the highest overall score of 2.37， and is therefore recommended as the most suitable oat variety of those tested for both crop yield and forage quality in Angren County.

Differences in morphological and physiological characteristics in the abscission zone of shattering-prone and shattering-resistant genotypes of Elymus sibiricus

Rui WU, Wen-hui LIU, Yong-chao ZHANG, Min-jie LIU

2022, 31(4): 81-92. DOI: 10.11686/cyxb2021045

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This study examined contrasting shattering-prone and shattering-resistant germplasm lines of Elymus sibiricus in order to explore the morphological characteristics of the abscission zone and identify key factors affecting shattering. Samples were collected in batches from the two germplasm lines at intervals from milk stage until the maturity stage of grain development. The two germplasm lines with their contrasting shattering behavior were compared and morphological characteristics of the abscission zone， enzyme activity， dynamic shattering rate and physiological traits were evaluated. In this way， the differences in shattering-related traits between shattering-prone and shattering-resistant germplasm could be identified， as well as differences in the seedstalk and the spikelet stalk abscission zone. It was found that： 1） The abscission zone development of the shattering-prone germplasm was earlier than that of shattering-resistant germplasm， and the distinction was obvious. The development of the seed-stalk abscission zone was earlier and more obvious than the spikelet stalk abscission zone. Observation of the fracture surface of the abscission zone after shedding revealed that there was a ring structure in the abscission zone. 2） The hydrolase activity differed at each grain maturity stage after the milk stage， and the enzyme activity was generally higher in the later stages of seed maturity. The enzyme activity of shattering-prone germplasm was higher than that of shattering-resistant material， and the enzyme activity of the seedstalk was higher than that of the spikelet stalk， indicating that seedstalk shedding was dominant in the shattering process. 3） As the seed ripened， the incidence of shattering gradually increased. At any given development stage， the shattering rate of shattering-prone germplasm was always higher than that of shattering-resistant germplasm， and the shattering rate of shattering-prone germplasm accelerated from the 16th day after the milk stage of grain development. 4） During the process of seed maturation， the shattering rate was extremely significantly （P<0.01） negatively correlated with water content， conductivity and soluble sugar content and significantly （P<0.05） or extremely significantly （P<0.01） positively correlated with enzyme activity， germination rate and starch content. These findings indicate that physiological substances have a regulatory effect on the shattering of E. sibiricus. Based on the above physiological observations， the 16th day after reaching the milk stage of grain development was identified as the optimal harvesting time for E. sibiricus. At this stage of development， E. sibiricus seeds have high germination vigor but the peak period of seed loss from shattering is avoided.

Effects of ascorbic acid and salicylic acid pelleting on germination characteristics in alfalfa seeds under NaCl stress

Cheng-ming OU, Mei-qi ZHAO, Ming SUN, Pei-sheng MAO

2022, 31(4): 93-101. DOI: 10.11686/cyxb2021018

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This research explored the mitigative effect of ascorbic acid （AsA） and salicylic acid （SA） pelleting against NaCl stress during germination of alfalfa （Medicago sativa） seeds. Alfalfa seeds were coated with various concentrations of AsA （1， 2， 4， and 8 mmol·L^-1） and SA （1， 5， 10， and 20 mmol·L^-1） and then were pelleted. There were two control treatments： CK₁ comprised seeds without coating or pelleting； CK₂ comprised pelleted uncoated seeds. The germination performance of the various seed coating treatments was compared under NaCl exposure at 1.25% and 1.50% concentrations， so as to identify the seed coating formula which most effectively alleviated the effects of salt stress on germinating alfalfa seeds. It was found that the mean germination time was extended and germination percentage， germination potential， seedling length and seedling weight of CK₁ decreased significantly （P<0.05） under NaCl exposure at 1.25% and 1.50% concentrations. AsA had no obvious alleviation effect under 1.25% NaCl stress but the 4 mmol·L^-1 AsA treatment increased the germination percentage and seedling length of alfalfa seeds under 1.50% NaCl stress. The 1 mmol·L^-1 SA treatment increased germination potential， germination percentage and seedling length of alfalfa seeds under 1.50% NaCl stress， while the germination percentage of alfalfa seeds was decreased with 20 mmol·L^-1 SA treatment. These results show that the alleviation effect of AsA and SA coating on NaCl stress was dependent on the concentration of the AsA and SA seed coatings and the level of NaCl stress and that NaCl stress was alleviated in alfalfa seeds by 4 mmol·L^-1 AsA and 1 mmol·L^-1 SA coating and pelleting. These results provide reference data on the mitigation effects of AsA and SA coating and pelleting of alfalfa seeds subject to mitigating NaCl stress.

Changes in soil fungal community structure under bermudagrass turf in response to traffic stress

Hong-jian WEI, Jie DING, Ju-ming ZHANG, Wen YANG, Yong-qi WANG, Tian-zeng LIU

2022, 31(4): 102-112. DOI: 10.11686/cyxb2021078

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In China， lawn sports grounds are regularly overused. Changes in the community structure of soil fungi can affect the growth， maintenance， and restoration of lawns. The aim of this study， therefore， was to explore the changes in soil fungal community structure change under turf in response to traffic stress. Common bermudagrass turf and Tifgreen bermudagrass turf were subjected to a traffic treatment of moderate intensity applied with a traffic simulator， and various factors including aboveground biomass， underground biomass， turf quality， soil pH， and soil hardness were measured. The relationships between soil fungal community diversity and environmental factors were determined. The results show that soil hardness and biomass were significantly higher in the no-traffic treatments than in the traffic treatments （P<0.05）. There were differences in fungal community diversity between the no-traffic and traffic treatments. At the phylum level， the relative abundance of Ascomycota was increased and of Basidiomycota was decreased in soils in the traffic treatments. At the genus level， the relative abundance of Trechispora was higher in the traffic treatments than in the no-traffic treatments. The genus with the highest relative abundance in the traffic treatments was Curvularia. Non-metric multidimensional scaling analyses showed that traffic stress and variety differences were the main factors affecting soil fungal community structure， with traffic stress being the most important factor. As determined using the linear discriminant analysis effect size algorithm， the top five fungal groups showing significant differences in abundance between the two bermudagrass cultivars were Ascomycota， Dothideomycetes， Pleosporales， Pleosporaceae and Curvularia in the traffic treatments； And Basidiomycota， Agaricomycetes， Trechisporales， Hydnodontaceaeand Trechispora in the no-traffic treatments. A redundancy analysis revealed a significant correlation between the diversity of the soil fungal community structure and environmental factors， with the main influencing factors being aboveground biomass， underground biomass， and soil pH. Traffic stress significantly affected the attributes of the turf， and the diversity of soil fungal community structure. Some attributes of the turf were significantly correlated with the diversity of the soil fungal community structure （P<0.05）. Ascomycota play a dominant role in the soil fungal community， and could be used as an indicator of a traffic-stressed lawn. The results of this study provide a theoretical basis for the management and conservation of turfgrass in southern China.

Isolation， identification， and biological characteristics of Fusarium perseae isolated from Potentilla anserina roots

Chen-qin LI, Jun-qiao LI, Xin-ci WANG, Yong-kun NIU, Jun-ru QU

2022, 31(4): 113-123. DOI: 10.11686/cyxb2021323

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The aim of this study was to isolate and characterize the causal pathogen of root rot from Juema （Potentilla anserina）. Samples were collected from the roots of Juema plants with root rot at the Juema artificial planting base in Huangyuan County， Qinghai Province， China. Strain D2 isolated from diseased samples was comprehensively evaluated in terms of its pathogenicity， morphology， rDNA-ITS sequence， and biological characteristics. The isolated strain D2 was identified as Fusarium perseae， a pathogenic fungus of Juema causing root rot. The optimum temperatures for mycelium growth， sporulation， and spore germination of strain D2 were 25， 30 and 25 ℃， respectively. The lethal temperature for mycelia was 64 ℃ （10 min）， and constant light conditions were not optimal for mycelial growth. Strain D2 was able to grow in a pH range of 5.0 to 12.0， and weak alkali conditions were more conducive to its growth and sporulation. The strain was able to use a variety of carbon and nitrogen sources， with fructose as the optimal carbon source and beef extract as the optimum nitrogen source. Some carbon and nitrogen sources promoted the production of a green pigment in strain D2. The types of nitrogen sources were ranked， from most to least efficient utilization by D2， as follows： Organic nitrogen>nitrate nitrogen>ammonium nitrogen. Ammonium nitrogen was more conducive to sporulation. These findings indicate that more attention should be paid to pastoral hygiene and water/fertilizer management to prevent the occurrence and spread of root rot at the Juema artificial planting base. These results provide a reliable basis for the diagnosis and prevention of the root rot in Juema.

Effects of additive types and combinations on silage quality of whole-plant rape after harvesting and air-drying

Di ZHOU, Shuai YANG, Xin-xin ZHANG, Jing YUAN, Yan-xia GAO, Jian-guo LI, Bo WANG, Guang-sheng ZHOU, Ting-dong FU, Jun YE, Li-guo YANG, Guo-hua HUA

2022, 31(4): 124-135. DOI: 10.11686/cyxb2021035

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The aim of study was to develop an effective additive formulation for ensiling whole-plant rape. A rape crop was harvested at the final flowering stage and air-dried in the field for 3-4 days， then ensiled as the moisture content dropped below 70%， with different additives used in different silage batches. Fermentation outcomes were evaluated for seven additive treatments： Control （no additive）， a solid inoculum treatment （S）， a liquid inoculum treatment （L）， a solid inoculum+liquid inoculum treatment （SL）， a solid inoculum+liquid inoculum+corn flour treatment （SLC）， a solid inoculum+liquid inoculum+brown sugar treatment SLB， and a corn meal treatment （C）. Sensory characteristics， chemical composition and animal rumen degradation rate were measured and data was evaluated using multivariate analysis. It was found that the sensory characteristics of the silage rape were excellent in all treatments， including the control. As judged by pH and moisture data， the SLC and SLB treatments were the most stable （P<0.05）. Analysis of chemical composition showed that neutral detergent fiber （P>0.05） and acid detergent fiber contents （P<0.05） were lowest in the SLC treatment， and that the dry matter content was significantly higher in SLC than in other treatments （P<0.05）. Results from rumen degradation of silage samples using the nylon bag method showed that the degradation of dry matter， crude protein， neutral and acidic detergent fiber in all treatments increased with digestion time （P<0.05）. After 60 days fermentation， the rumen degradation rate of dry matter， crude protein and neutral and acid detergent fiber differed significantly （P<0.05） between additive treatments， with the SLC treatment having the highest degradation rate （72 h）（P<0.05）. In summary， whole-plant rape harvested and air-dried to a moisture content under 70% made stable， high quality silage. Addition of S， L or more complex SLC additives mixed thoroughly with the chopped rape further increased the whole-plant rape silage nutritional value and rumen digestibility. The study provides technical data on the preservation of rape silage， which has great potential to help address the shortage of feed resources in the herbivore animal industries and support the conversion of “oil-to-feed”.

Effects of Lycium barbarum by-products on fermentation quality and microbial diversity of alfalfa silage

Huan ZHANG, Yi-xiao MU, Gui-jie ZHANG

2022, 31(4): 136-144. DOI: 10.11686/cyxb2021053

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In order to develop additives that improve the fermentation quality of alfalfa silage， the fermentation quality and microbial diversity of alfalfa silages prepared with addition of different Lycium barbarum by-products （LBP） were studied. Alfalfa silage was prepared without （CK） and with 40 （T₁）， 60 （T₂）， and 80 （T₃） g·kg^-1 LBP. After 60 days of fermentation， the nutrient levels， fermentation quality and microbial diversity of the silages were determined. It was found that the concentrations of acid detergent fiber in the LBP silages significantly （P<0.01） decreased， while polysaccharide significantly （P<0.01） increased as the proportion of LBP increased in the alfalfa silage. The pH value and ammonia nitrogen∶total nitrogen ratio of CK silages were 4.91 and 8.58%， respectively. As the proportion of LBP increased in the alfalfa silages， the contents of ammonia nitrogen， acetic acid and pH significantly （P<0.01） decreased， while lactic acid level and the ratio of lactic acid to acetic acid significantly （P<0.01） increased. The silage aerobic stability was improved in LBP treatments， although the addition of LBP at 80 g·kg^-1 decreased aerobic stability compared with addition of 40 and 60 g·kg^-1. The dominant alfalfa silage bacterial genera were Lactobacillus， Weissella and Pediococcus. The relative abundance of Lactobacillus in LBP treatments was lower than in the CK treatment， while the relative abundance of Weissella and Pediococcus in LBP treatments was higher than in the CK treatment. The results confirm that LBP addition can improve alfalfa silage fermentation quality and aerobic stability， and change microbial community structure. The 60 g·kg^-1 LBP treatment was more effective than other tested treatments in enhancing silage fermentation.

Effects of sweet sorghum silage and whole-plant corn silage on the forestomach microecology of mutton sheep

De-zhi YANG, Chen WANG, Ming-jie HOU, Hu-cheng WANG

2022, 31(4): 145-154. DOI: 10.11686/cyxb2021021

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The aim of this study was to evaluate the effects of sweet sorghum silage and whole-plant corn silage on the forestomach microecology of mutton sheep. Healthy Dorper ewe lambs aged from 3 to 4 months （33.40±1.68 kg） were selected and randomly divided into two groups with seven sheep in each group： a sweet sorghum silage group （SS group） and a whole-plant corn silage group （CS group）. Ewes were all fed in the same shed and had free access to water. The experiment included a 15-day pre-treatment adaptation period and a 90-day feeding-trial period. At the end of the trial period， 4 sheep in each group were slaughtered and samples of digesta and tissues from the forestomach （rumen， reticulum and omasum） were collected. Fermentation parameters， microbial expression， epithelial color and tissue structure were determined. It was found that： 1） The dry matter intake of the CS mutton sheep was significantly higher than that of SS group （P<0.05）. 2） After feeding the SS and CS silages to the mutton sheep for 90 days， there was no significant difference in the pH value of the forestomach contents （P>0.05）. In the contents of the reticulum， the NH₃-N and total volatile fatty acid （TVFA） concentrations of the SS group were significantly higher than in the CS group （P<0.05）， while the butyric acid content in the CS group was significantly higher than in the SS group （P<0.05）. 3） The occurrence levels of Prevotella brevis， Prevotella ruminicola， Fibrobacter succinogenes and Rumincoccus flavefaciens in the rumens of the SS group were significantly higher than in the CS group （P<0.05）. 4） Diet treatment significantly affected the forestomach epithelial color； the epithelium of forestomach tissues was darker in the CS group than in the SS group （P<0.05）. 5） The rumen papillae in the SS group were significantly wider than in the CS group （P<0.05）. The thickness of the reticulum mucosa， submucosa and muscular layer of the sheep did not differ significantly （P>0.05） between the two silage types， although the thickness of the valve epithelial mucosa in the CS sheep was significantly higher than in the SS group （P<0.05）. In conclusion， compared with CS group， the feed intake of SS sheep was lower. The rumen TVFA levels， the occurrence of fibrinolytic bacteria in the forestomach and the width of rumen papillae in the SS group were significantly higher than in the CS group， while the color of forestomach epithelium was lighter in SS sheep and the degree of keratinization was lower. The differences observed in SS treatment （compared with the CS group）， were beneficial to the gastrointestinal health of mutton sheep.

Effects of exogenous nutrient addition on alpine meadow soil arthropod communities

Xin LI, Xue WEI, Chang-ting WANG, Xiao REN, Peng-fei WU

2022, 31(4): 155-164. DOI: 10.11686/cyxb2021331

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This study aimed to determine the effects of exogenous nutrient addition on soil arthropod communities in the alpine meadows. Three nutrient addition treatments （nitrogen， N； phosphorus， P； and combined nitrogen and phosphorus， NP） were established in Hongyuan County， northwest Sichuan， China， in late May 2012. Each nutrient treatment was applied at three concentrations： 10 g·m^–2 （N₁₀， P₁₀， and NP₁₀）， 20 g·m^–2 （N₂₀， P₂₀， and NP₂₀）， and 30 g·m^–2 （N₃₀， P₃₀， and NP₃₀）， with six replicate plots of 3 m×3 m. Another six 3 m×3 m plots in natural alpine meadow served as control plots. The nutrient treatments were added every year for continued eight years. The soil arthropods and soil environmental factors in each plot were evaluated in August 2017 and 2020. Soil arthropods were extracted from the soil samples for 48 h at 38 ℃ using the Tullgren method in the laboratory. The main findings were as follows： 1） N， P， and NP additions in the alpine meadow increased the individual density and diversity of soil arthropods， with the strongest effects in the 20 g·m^-2 and NP treatments； 2） The abundances， taxonomic richness， and Shannon’s diversity index of the soil arthropod communities in the N-addition and P-addition treatments increased significantly from 2017 to 2020 （P<0.05）， while the abundance and taxonomic richness of soil arthropod communities in the NP-addition treatment declined significantly from 2017 to 2020 （P<0.05）， but no significant change was detected for Shannon’s diversity index （P>0.05）； 3） The abundance of Entomobryomorpha was significantly increased in the N-addition and P-addition treatments （P<0.05） and the abundances of Oribatida and Mesostigmata were significantly increased in the NP-addition treatment （P<0.05）； 4） The results of multiple regression analysis and canonical correspondence analysis showed that the main environmental factors influencing the composition of soil arthropod communities were the contents of soil total N， total P and soil organic matter， pH， aboveground biomass， and plant community cover. Our results showed that the soil arthropod communities respond differently to different exogenous nutrient additions and nutrient gradients； and that the diversity of soil arthropods in alpine meadows can be promoted by N-addition and P-addition but restrained by mixed N and P additions after continued eight years additions. We recommend that the additions of mixed N and P to the alpine meadows should be controlled at 20 g·m^–2 per year and should not exceed eight years.

A study of UAV remote sensing technology for classifying the level of plateau pika damage to alpine rangeland

Rui HUA, Rui ZHOU, Daerhan BAO, Ke-chi DONG, Zhuang-sheng TANG, Li-min HUA

2022, 31(4): 165-176. DOI: 10.11686/cyxb2021057

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The plateau pika is a unique small mammal and a key species among the fauna of the alpine rangeland ecosystem on the Qinghai Tibetan Plateau. Therefore， there is a need to monitor and evaluate the level of damage to alpine rangeland caused by the plateau pika. In this study， unmanned aerial vehicle （UAV） technology validated by field observation was used to monitor and evaluate the level of plateau pika damage to rangeland in Maqu county of Gansu Province. Several variables， including the number of pika holes， aboveground biomass， vegetation cover， and proportion of edible forage in the aboveground biomass， among others， were extracted from UAV images by self-designed software. Then a multi-factor index system， comprising the number of pika holes， aboveground biomass， vegetation cover and proportion of edible forage was developed to categorize the degree of damage by plateau pika. Finally， a low altitude remote sensing monitoring methodology suitable for collecting data on plateau pika damage was devised. The system is ready for implementation as a technical tool for efficient and accurate monitoring of plateau pika damage. The main results were： 1） The accuracy of photo interpretation for the pika hole number and vegetation cover was 95% and 93%， respectively， based on field verification. 2） The visible-band difference vegetation index （VDVI） was selected as the best vegetation index for estimating aboveground biomass； for the estimation model constructed， the accuracy was 86.54%. 3） A damage scale was formulated to classify plateau pika damage in the study area （damage to rangeland index， DRI） into five levels as follows： Level I， no damage； Level Ⅱ， light damage； Level Ⅲ， moderate damage； Level Ⅳ， severe damage and Level V， extreme damage.

Inversion of grassland aboveground biomass in Tianzhu Zangzu Autonomous County based on a machine learning algorithm

Ge-xia QIN, Jing WU, Chun-bin LI, Zhen-xia JI, Zheng-chao QIU, Ying LI

2022, 31(4): 177-188. DOI: 10.11686/cyxb2021072

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Effective， accurate， and large-scale monitoring of grassland aboveground biomass （AGB） using machine learning algorithms is currently a very active field of research， but different machine learning algorithms vary greatly in performance depending on training samples and hyper-parameter settings. The research utilized grassland AGB data collected field， combined with remote sensing data， meteorological data， terrain data for the same period. Thirteen indicators with strong correlation with grassland AGB were selected as input variables for analysis using deep neural network （DNN）， random forest （RF）， gradient boosting regression tree （GBRT）， vector support machine （SVR）， artificial neural network （ANN） and Gaussian process regression （GPR） algorithms for AGB inversion. At the same time， the application potential of 6 models were evaluated from the aspects of model prediction accuracy， stability， sample sensitivity， and characteristics of AGB space-time changes in grasslands during the 2020 Tianzhu County growth season （April-September） and their response to climate. It was found that： 1） The multivariate performance of DNN in grassland AGB inversion was the best， but the stability was poor， and the sensitivity to samples was high； the comprehensive performance of GPR was inferior to DNN， and its stability and accuracy were good； the simulation accuracy of GBRT and RF was high， and its stability was poor； the accuracy of SVR and ANN was relatively poor and the stability of SVR was high， and the stability of ANN was poor. 2） The grassland AGB ranged from 50 to 250 g·m^-2. The spatial heterogeneity of AGB was large and variable over time. In general AGB showed a downward trend from northwest to southeast. 3） Except for temperate desert steppe， the AGB in mountain meadow， alpine meadow and temperate steppe species showed a significant positive correlation with air temperature. Precipitation had no obvious effect on AGB of alpine meadow， temperate grassland and mountain meadow， but had a great effect on AGB of temperate desert grassland. With decrease in precipitation， AGB tended to decrease. The above results provide technical information to support decisions on choice of method and parameter setting when remotely monitoring grassland biomass.

The knowledge domain and emerging trends in plant root exudates： a bibliometric analysis based on CiteSpace

Xiao-jia WANG, Jin ZOU, Bing CAO, Jia-xin LIU, Xue-rui FENG, Yun-mao LI, Shang-yu LI

2022, 31(4): 189-199. DOI: 10.11686/cyxb2021071

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Root exudates are important carriers for substrate and metabolite exchange and information transmission between plants and soil. This study accessed a total of 4047 publications on root exudates in the core journals whose contents were included in Web of Science from 1998 to 2020， and used CiteSpace software to identify research themes and topics of current interest. It was found that： 1） The total publications and average citations per paper of the surveyed research showed a linear increase with time； 2） Institutions from the USA and China were the most active in this field， followed by Germany， Japan， Australia and France， occupied the most dominant positions； 3） Chinese Academy of Sciences， Nanjing Agricultural University， CSIC， and University of Western Australia are obvious leaders in terms of the total number of publications and average citations per research paper. Plant Sciences， Soil Sciences， Agronomy， Environmental Sciences， Microbiology and Ecology were the most frequently used subject categories. The Netherlands journal Plant and Soil is a clear leader in the total number of publications （256） and h-index， and thus very influential in academia； 4） Plant root exudates research was most often linked with keywords “rhizosphere”， “plant”， “soil”， “organic acid”， and “allelopathy”. Finally， based on current research， we infer that future research will move towards a focus on plant-soil-microbe interactions and mechanisms mediated by root exudates， and this will have important implications for elucidating the dynamics of rhizosphere microecology and for providing practical guidelines for plant culture and crop husbandry.

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