Table of Content

20 February 2022, Volume 31 Issue 2

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Change in grassland productivity in Qinghai Province and its driving factors

Ya-hui WANG, Wen-jia TANG, Sen LI, Hong-yan ZHAO, Jia-li XIE, Chao MA, Chang-zhen YAN

2022, 31(2):  1-13.  DOI: 10.11686/cyxb2021256

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In recent years， grassland in Qinghai province has been affected by climate change and variously impacted by a range of human activities， sometimes causing degradation and sometimes facilitating restoration. Here we report a survey of the spatial and temporal variation in grassland productivity across Qinghai Province for the period from 2001-2017. To extract data on grassland net primary productivity （NPP， MOD17A3HGF.006）， Sen’s slope together with the Mann-Kendall test （Sen-MK）， correlation analysis and residual analysis were used as decision nodes of a decision tree. Then we used the tree to evaluate grassland NPP time trends and their spatial heterogeneity during the study period and identify associated factors that may be change drivers. The results were as follows： 1） There were 11.41×10⁴ km² of grassland with significant （P<0.05） NPP trends in Qinghai Province during the 2001-2017 period. The areas of extremely significant （P<0.01） increase， significant （0.01≤P<0.05） increase， significant decrease and extremely significant decrease were respectively 11.88%， 17.25%， 0.20% and 0.08% of the grassland in the province. Remarkably， the overall change is a rise in NPP. 2） For the regions where grassland NPP trends were significant， the proportion explained by temperature was the largest （60.66%）， followed by human activities （23.45%） and human activities + temperature （9.49%）. Hence， temperature and human activities were the major factors driving significant grassland NPP trends. 3） Temperature， precipitation and human activities mainly had positive impacts on NPP. Human activities were the dominant factor linked with grassland degradation and were associated with 77.49% of the grassland area with a decreasing NPP trend. However， human activities have also achieved remarkable results in grassland restoration and ecological protection projects in Qinghai Province.

Effects of biochar addition on nutrient levels and humus and its components in dry farmland soils on the Loess Plateau

Zhan-dong PAN, Qian-qian MA, Xiao-long CHEN, Li-qun CAI, Xue-mei CAI, Bo DONG, Jun WU, Ren-zhi ZHANG

2022, 31(2):  14-24.  DOI: 10.11686/cyxb2020563

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Severe soil erosion in the Loess Plateau leads to a significant decrease in some soil nutrients and quality. Biochar can increase crop yield and soil biological activity， so it is widely used in soil improvement. However， it is not clear whether biomass charcoal can improve the physical and chemical properties of loessial soil by improving soil nutrient levels， and humus composition and content. This study investigates this question for a loessial soil on the Loess Plateau. The research was conducted at the Dry Farming Experiment Station of Gansu Agricultural University. A four-year field trial was set up with six biomass charcoal addition levels （0， 10， 20， 30， 40， 50 t·ha^-1） to determine the changes in soil nutrient levels， organic carbon components， combined humus composition and composition. It was found that addition of biochar at a rate of 20 t·ha^-1 or above significantly increased the soil heavy fraction organic carbon （HFOC）， light fraction organic carbon （LFOC）， organic matter and total nitrogen contents. Biochar addition had no significant effect on soil total phosphorus or potassium levels， but addition of biochar at 10 t·ha^-1 significantly increased soil available phosphorus and decreased available potassium. This effect was progressively reversed as the rate of biochar increased and the addition of biochar at 60 t·ha^-1 significantly increased the available potassium content but tended to reduce the available phosphorus content. When biochar was added at 20 t·ha^-1 and above， the content of soil loose combined humus （LCH） was increased by 47.50%-65.83% （P<0.05）； When biochar was added at rates in excess of 30 t·ha^-1， the content of humus constituent fulvic acid （FA） was increased by 78.79%-133.33% （P<0.05）. LFOC， HFOC and LCH were the components that contributed most to the increase of soil total organic carbon following biochar addition. Among these the interpretation rate of LFOC and HFOC to TOC were 72.55% and 89.74% respectively. This research provides increased understanding of the soil chemistry changes after addition of biomass charcoal in soil improvement and fertility improvement in dry farming areas of the Loess Plateau.

Module growth and biomass allocation of three typical Chenopodiaceae annuals in a typical desert-oasis ecotone of the Hexi Corridor in Gansu Province， China

Wen-ting GUO, Guo-hua WANG, Qian-qian GOU, Jing LIU

2022, 31(2):  25-38.  DOI: 10.11686/cyxb2020537

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Halogeton arachnoideus， Salsola ruthenica and Bassia dasyphylla are the dominant plants in the herb layer of artificial wind-breaking and sand-fixing vegetation in the desert-oasis ecotone， and they play an important role in maintaining the stability of the ecolosystem function in the transition zone. We studied the above three Chenopodiaceae annuals in the desert-oasis ecotone of Hexi Corridor， and through extensive sampling in the field， the characteristics of module growth and biomass allocation of the three species at different stages of the vegetative growth period were examined. The quantitative characters and biomass allocation of both above-ground and below-ground modules were analyzed， to reveal the growth strategies of the three species at different growth stages and provide reference for further understanding of their ecological adaptation mechanisms and development of conservation initiatives for the desert ecosystem. It was found that： 1） During the vegetative growth period， the three species differed in the patterns of variation in component growth and biomass accumulation. Above-ground and below-ground biomass showed strong variation with similar coefficients of variation， and leaves and lateral roots had the greatest variability in formation of above-ground and below-ground modules. 2） The module growth and biomass accumulation of the three species differed significantly at different stages of the vegetative growth period （P<0.05）. The growth of primary roots mainly occurred in early and mid-vegetative growth， while the growth of stems， leaves， branches and lateral roots mainly occurred in mid- and late-vegetative growth. 3） The quantitative traits of above-ground modules （stem height， branch number and leaf number） and the above-ground biomass of the three species showed an allometric relationship during the vegetative growth period， while the quantitative traits of below-ground modules （main root length and lateral root number） showed the allometric relationship in early growth， and the relationship was not significant in mid- and late-vegetative growth. 4） The root∶shoot mass ratio （R∶S） of the three species decreased gradually as the vegetative growth period progressed. The above-ground biomass distribution ratio was more than 86%， and the below-ground biomass distribution ratio was less than 14%， and larger plants have lower R∶S.

Capability evaluation of 47 common vetch cultivars （lines） as autumn green manure in Qinghai Province， Northwest China

Zi-ying CHEN, Dan-na CHANG, Mei HAN, Zheng-peng LI, Qing-biao YAN, Jiu-dong ZHANG, Guo-peng ZHOU, Xiao-feng SUN, Wei-dong CAO

2022, 31(2):  39-51.  DOI: 10.11686/cyxb2021278

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Common vetch （Vicia sativa）is one of the most important fertilizer and forage dual-purpose green manure crops in China. Pre-cropping common vetch with wheat （Triticum aestivum） is a significant combination of agriculture and animal husbandry in Qinghai， Northwest China. The nitrogen （N）， phosphorus （P）， and potassium （K） accumulation and aboveground biomass of 47 cultivars （lines） and soil available nutrients were analyzed at the branching and initial flowering stage under field conditions in Qinghai. Principal component and cluster analyses were used to evaluate the crop N， P and K absorption capacity in order to identify cultivars suitable for use in Qinghai. The ranges of values for fresh herbage yield， and total N， P and K accumulation were 21.33-47.31 t·ha^-1， 100.34-212.51 kg·ha^-1， 10.31-25.25 kg·ha^-1 and 63.89-140.41 kg·ha^-1， respectively， for the 47 common vetch cultivars at the initial flowering stage. The cultivar ‘Hungary’ had the highest fresh grass yield and N and K accumulation capacity. The performance of ‘Hungary’ for those traits exceeded that of the local main cultivar， ‘Ximu 333’， by 58.92%， 44.78%， and 54.40%， respectively. Cultivar ‘7501’ had the highest P accumulation capacity， which was 27.78% higher than ‘Ximu 333’. Principal component analysis showed that the top five ranking cultivars were ‘Hungary’， ‘Grassland 79-1’， ‘Qingshui River （Linen）’， ‘324’ and ‘Black 741 common vetch’. ‘Hungary’ had the highest score （6.84）， and ‘751’ had the lowest score （-3.87）. Cluster analysis showed that the absorption capacity of N， P and K differed among cultivars and clustered into three groups in each case. For N， the groups with higher， medium and lower N absorption capacity contained， respectively， 4， 33 and 10 cultivars. For P， the groups with higher， medium and lower absorption capacity contained， respectively 7， 28 and 12 cultivars. For K， the groups with higher， medium and lower absorption capacity contained， respectively 8， 37 and 2 cultivars. For the cultivar groups with higher N， P and K absorption capacity contained respectively four， seven and eight cultivars as noted above， and the average N， P and K absorption was， respectively， 200.62 kg·ha^-1， 23.10 kg·ha^-1 and 115.23 kg·ha^-1. Planting common vetch significantly decreased soil inorganic N， available P and K levels at branching and initial flowering growth stages. Overall， among the top-five-ranked cultivars of the principal component analysis noted above， ‘Hungary’， ‘Grassland 79-1’， ‘Qingshui River （Linen）’ and ‘324’ showed the highest N and K absorption capacities， and ‘Grassland 79-1’ and ‘Hungary’ showed the highest P and K absorption capacities. These cultivars are therefore proposed as candidate cultivars for further field evaluation in Qinghai.

Effects of different trampling intensities on three species of warm season turfgrass

Qiang XING, Jun QIN, Yong-hong HU

2022, 31(2):  52-61.  DOI: 10.11686/cyxb2021207

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Turf in open public parks can meet the needs of urban residents for recreational fitness， disaster mitigation and enhance the public health and safety and quality of life of urban residents. Lawns are subject to traffic of various kinds， especially foot traffic， and trampling causes both direct mechanical wear and indirect soil structure damage due to compaction. Resistance to trampling is the key factor determing the performance and service life of lawns. In this paper， three turfgrasses commonly used in Shanghai， namely Zoysia japonica ‘Belair’， Paspalum vaginatum ‘Sea Isle 2000’， and Cynodon dactylon x Cynodon transvaalensis ‘Tifdwarf’， were selected for evaluation， and an experiment involving exposure to different simulated trampling intensity and frequency during turfgrass peak growth from May to September was set up. At the end of the simulated trampling exposure a multivariate analysis of data on turfgrass wear resistance， soil compaction resistance and recovery ability was carried out using a multi-index membership function method. Under light trampling， the performance of the three turfgrasses ranked： Z. japonica ‘Belair’>P. vaginatum ‘Sea Isle 2000’>C. dactylon×C. transvaalensis ‘Tifdwarf’， and light trampling was beneficial and improved the quality of the lawn. Under moderate trampling the performance ranking was Tifdwarf>Sea Isle 2000>Belair. Tifdwarf showed the strongest resistance to trampling and was able to tolerate 80 simulated person-passes of intermittent trampling during the growth period from May to September. Under severe trampling Tifdwarf hybrid Bermudagrass showed resistance related to its fast daily growth and associated recovery ability. The study of the trampling resistance capacity of turfgrass species not only provides a theoretical basis for the development and utilization of trampling-resistant turfgrass needed in the large number of parks and green spaces being constructed in the current urbanization process， but also can be used to evaluate the carrying capacity and support long-term maintenance of parks and green spaces in the future.

Effects of grazing modes on the community structure and diversity of soil arthropod in an alpine meadow on the Qinghai-Tibetan Plateau

Cai-cai SUN, Quan-min DONG, Wen-ting LIU, Bin FENG, Guang SHI, Yu-zhen LIU, Yang YU, Chun-ping ZHANG, Xiao-fang ZHANG, Cai-di LI, Zeng-zeng YANG, Xiao-xia YANG

2022, 31(2):  62-75.  DOI: 10.11686/cyxb2021309

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Soil arthropods are an important component of the soil ecosystem and have been used as “indicators” of environmental change， because of their sensitivity to changes in the surrounding environment. Grazing is the main use of alpine grassland in the Qinghai-Tibet Plateau. Grazing affects both the physical and chemical properties of the soil， and also the biodiversity， including soil arthropods. This research investigated changes in the soil arthropod community structure and diversity associated with grazing by different animal species. Soil arthropods were sampled in July 2020 from a grazing experiment in an alpine meadow on the Qinghai-Tibetan Plateau. The grazing experiment included two single-species grazing treatments （yak only and Tibetan sheep only； YG， SG）， three mixed-grazing （MG） treatments （yak： Tibetan sheep ratios of 1∶2， 1∶4 and 1∶6） and an ungrazed control treatment （CK）. Soil samples were collected from 0-5 cm， 5-10 cm， and 10-15 cm soil depths， and the soil arthropods were separated by the dry funnel （Tullgren） method， identified， and the data statistically analysed. It was found that： 1） Of the total sampled soil arthropod population， 36.67% belonged to the taxonomic family Acaroidae and 41.14% belonged to the family Oiibatida. The highest densities of arthropods were found in the 0-5 cm soil layer. 2） The composition， community structure， density and diversity of the soil arthropod communities differed between the animal species grazing treatments. Compared with the control ， grazing decreased the proportion of Acaroidae， but increased the proportion of Oiibatida in the soil arthropod population. There were significant differences in soil arthropod community structure between CK plots and grazed plots. The species richness index， diversity index and the number of soil arthropods were highest， and the evenness index was lowest in the Tibetan sheep grazing treatment. 3） Soil arthropod evenness index was negatively correlated with soil total nitrogen， total carbon and available potassium （P<0.05 or P<0.01）， but positively correlated with soil organic matter and pH （P<0.05 or P<0.01）； soil arthropod richness index was negatively correlated with soil pH， but positively correlated with soil total nitrogen， available nitrogen and organic matter contents. Soil arthropod diversity index was negatively correlated with soil pH， but positively correlated with soil total nitrogen， available nitrogen， available phosphorus and organic matter contents. The mean density and the number of groups of soil arthropods were negatively correlated with soil pH， but positively correlated with soil total nitrogen， available nitrogen， available potassium and organic matter. 4） Soil total nitrogen， total phosphorus， total carbon， available nitrogen and available phosphorus levels were higher in the SG treatment. Available phosphorus and organic matter were highest in the CK plots. Soil water content and pH were highest in the MG1：6 treatment. In summary， only Tibetan sheep grazing had a positive effect in increasing soil arthropod density， community composition and community diversity in the alpine grassland ecosystem of the Qinghai-Tibetan Plateau.

Responses of root vessel anatomical structures to drought exposure for two Kobresia species in an alpine meadow habitat in Southeast Tibet

Chun-jiao YANG, Yu-zhen HAN, Zhong-kui LI, Da-cai ZHANG, Hong-bin WANG, Hong-lin LI

2022, 31(2):  76-87.  DOI: 10.11686/cyxb2020530

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Xylem vessels in the vascular tissue of roots are the channels by which plants transport water， and the plasticity of their structure is an important mechanism for plants to adapt to the habitat， which will also impact the efficiency and safety of water transport. Kobresia humilis and Kobresia macrantha are two Cyperaceae species that differ in their soil moisture preferences， K. humilis being more tolerant of drier environments. This research investigated whether there is any difference in water transport efficiency and safety between these two Kobresia species. To answer this question， K. humilis and K. macrantha root samples were collected at six sample plots along a soil water gradient in an alpine meadow of Southeast Tibet. Collected root samples were embedded in paraffin， sectioned by microtome. The vessel diameter， lumen area and wall thickness of the two species of Kobresia were measured by microscopy and image analysis and a cell wall coefficient of reinforcement （cwr） for the vessels was derived. From these data an overall vessel density and hydraulic diameter were calculated， and histograms of diameter class distributions for the sampled roots were prepared. Correlation analysis， one-way ANOVA and principal component analysis were used to analyze and interpret the data. In K. humilis vessel wall thickness was significantly negatively and vessel density significantly positively （P<0.01） correlated with soil water content； In K. macrantha vessel wall thickness and cwr were significantly negatively and vessel lumen area and average diameter significantly positively （P<0.01） correlated with soil water content. Vessel wall thickness of both species was increased in dry soil conditions and decreased in wet soil conditions. Comparing K. humilis and K. macrantha， vessel lumen area and average diameter， stele hydraulic diameter were all very significantly less， while cwr and vessel density were very significantly greater in K. humilis than in K. macrantha （P<0.01）. K. macrantha is a species adapted to continuously wet environments， while K. humilis is adapted to drier soil conditions. The ratio of narrow vessel and middle vessel of K. humilis is similar， which has a strong ability to adjust efficiency and safety of water transport， while the ratio of middle vessel of K. macrantha is always the highest， with weak balance ability for efficiency and safety of water transport. A mechanistic hypothesis from these data for confirmation in future research， is that K. macrantha has greater average xylem vessel area and diameter in the root stele than K. humilis， which would be expected to decrease resistance to water flow. By contrast， narrower diameter， more reinforced xylem vessels in the root stele of K. humilis than K. macrantha would be better adapted to withstanding negative water potentials involved in extracting water from drier soils.

A study of chemicals released as volatiles or by rain leaching from Ipomoea cairica and their allelopathic effects

Jin-hui CHEN, Hui-yan MA, Yu CHEN, He HE

2022, 31(2):  88-100.  DOI: 10.11686/cyxb2020525

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The invasive alien plant Ipomoea cairica is widespread throughout South China. Allelopathy has been considered a key mechanism to explain the invasiveness of this species. In this research， bioassays showed that the germination of Bidens pilosa and Lactuca sativa seeds was significantly inhibited when mimicking the natural volatile and leaching conditions that would occur near plants of I. cairica. Substances released in these two ways were collected and analyzed by gas chromatography and mass spectrometry （GC-MS）. The volatiles from I. cairica contained 18 terpenes， of which caryophyllene （28.17%）， β-ocimene （16.59%）， α-pinene （13.65%）， and （+）-β-cedrene （9.43%） had the highest relative contents. The rain leachates were mainly phenolic acids， with the four with highest relative contents being cinnamic acid （39.21%）， succinic acid （15.15%）， propionic acid （11.12%） and lauric acid （9.38%）. Further analyses of these eight main chemicals were conducted to determine their actual concentrations in collected vapors and leachates. At these actual concentrations， laboratory bioassay results showed that cinnamic acid and lauric acids significantly inhibited the seed germination of B. pilosa and L. sativa seeds. In contrast， propionic acid and succinic acid didn’t show a significant adverse effect. Similarly， for the main volatiles present， the germination of B. pilosa and L. sativa seeds was significantly inhibited by treatment with （+）-β-cedrene and caryophyllene， while there was no noticeable effect when the seeds were treated with α-pinene or β-ocimene. In summary， some terpenes and phenolic acids were phytotoxic to other plant species when they were released as volatiles or by rain leaching from I. cairica.

Evaluation of agronomic traits and nutrient absorption of an F₄ recombinant inbred line of Chinese milk vetch （Astragalus sinicus）

Wen-jing REN, Yu-hu LV, Guo-peng ZHOU, Dan-na CHANG, Chun-yang XIANG, Wei-dong CAO

2022, 31(2):  101-110.  DOI: 10.11686/cyxb2020553

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In this research an F₄ inbred line of Chinese milk vetch was constructed using Minzi No.7 milk vetch （Astragalus sinicus） as the female parent and the variety Xinyang as the male parent. For 18 strains in this population， the agronomic traits and nutrient absorption status were evaluated in a pot experiment at the full flowering stage， in order to use the results as a reference for screening superior milk vetch strains. Differences between plant strains were found. Correlation analysis showed that fresh weight， dry weight and accumulation of nitrogen， phosphorus and kalium were highly correlated， and were drivers of plant nutrient absorption， while plant height， branch number and leaf number were important factors affecting the fresh weight and dry weight of the plant. Principal component analysis showed that the main indexes such as shoot fresh and dry weights， and accumulation of nitrogen， phosphorus and kalium in the shoots could be used as indexes of Chinese milk vetch performance. In cluster analysis with the distance coefficient d=25， the 18 tested strains could be classified into three groups， of which Group Ⅰ had 4 strains （m83xzh-1-4-4， m83xzh-1-4-6， m83xzh-1-4-8， and m83xzh-1-4-13） with excellent multivariate trait scores. The best performing Chinese milk vetch strain in this evaluation was m83xzh-1-4-4. For this strain， the total plant nitrogen， phosphorus and kalium nutrient accumulation， accumulation of phosphorus and kalium in the shoots and accumulation of nitrogen and kalium in the roots were highest among the18 strains tested and were 11.00 mg·pot^-1， 145.18 mg·pot^-1， 22.15 mg·pot^-1 and 15.27 mg·pot^-1， respectively. The herbage fresh yield of m83xzh-1-4-4 was 44.63 g·pot^-1 and ranked second among the 18 strains tested. This study provides technical data which may be useful in future breeding work to develop new milk vetch varieties.

Characteristics of stem and leaf functional traits of Rhododendron capitatum on the north slope of Zhagaliang， Gansu

Ke-tong YANG, Guo-peng CHEN, Jun-ren XIAN, Xiao-ya YU, Jin-wu ZHANG, Li WANG

2022, 31(2):  111-120.  DOI: 10.11686/cyxb2020536

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Alpine plants show unique functional plasticity in the process of adapting to environmental constraints such as high altitude， low atmospheric pressure and a short growing season. This research explored the morphological variation in twigs and leaves of Rhododendron capitatum along an altitude gradient to evaluate the functional significance of this variation for resource acquisition， survival and reproduction. In August 2019， various leaf and twig traits of 23 groups of R.capitatum were measured at altitudes from 3400-3700 m. It was found that with increase in altitude， the leaf dry matter content （LDMC）， density （LDE）， thickness （LT） and total leaf dry matter content （TLDMC） were increased. Leaf length （LL）， width （LW）， area （LA）， volume （LV）， dry weight （LDW）， stem length （SL）， stem dry weight （SDW）， total leaf dry weight （TLDW）， total leaf area （TLA）， stem slender ratio （SSR） and stem volume （SV） showed a “V” shaped altitudinal trend with the lowest values at around 3600 m altitude. Higher altitude significantly increased thickness （LT）， dry matter content （LDMC）， density （LDE）， but significantly decreased specific leaf area （SLA）， total leaf area （TLA） and total specific leaf area （TSLA）， respectively. There were significant correlations between most measured traits. The variance components of leaf traits between R. capitatum plants growing at the same altitude were significantly higher than those between plants at different altitudes. The smallest coefficient of phenotypic differentiation of twigs and leaves was 3.19% for stem dry matter content （SDMC）， the largest was 57.73% for leaf density （LDE）， and the average across traits was 20.65%. The results show that some traits of R. capitatum are not sensitive to elevation changes， and that a few key traits like leaf area （LA）， specific leaf area （SLA）， leaf dry matter content （LDMC） and leaf density （LDE） act as functional traits to adapt to alpine habitats. R. capitatum showed lower phenotypic variation among plants along elevation gradients than among plants at the same altitude.

An investigation of the main environmental factors affecting the natural drying of alfalfa for hay， and hay quality

Li-ying LIU, Yu-shan JIA, Wen-qiang FAN, Qiang YIN, Qi-ming CHENG, Zhi-jun WANG

2022, 31(2):  121-132.  DOI: 10.11686/cyxb2020529

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This article aims to provide a thorough analysis of the key conditions required for production of high-quality alfalfa hay， and to provide theoretical and technical guidelines for the production of good quality alfalfa hay in northern China. We evaluated the optimal environmental conditions for natural drying of alfalfa hay by measuring the drying rate， chlorophyll content and the main nutrient components： crude protein （CP）， neutral detergent fiber （NDF）， acid detergent fiber （ADF）， relative feeding value （RFV） and other indicators. Data were collected for different stubble heights and flowering stages and from the correlation between various hay characteristics and environmental variables， the main environmental factors that affect the natural drying of alfalfa were clarified. The results showed that： 1） During the natural drying of alfalfa， the main environmental factors that affected the drying rate of alfalfa were solar radiation intensity， temperature， air humidity and wind speed. The main factors that affected alfalfa chlorophyll content were solar radiation intensity， temperature and wind speed. The main factors that affected CP， NDF， ADF and RFV of alfalfa hay were temperature， air humidity and wind speed. Among these， temperature and wind speed had significant effects on CP， and air humidity had significant effects on NDF， ADF and RFV. Overall， temperature， air humidity， solar radiation intensity and wind speed were the main environmental factors affecting the drying rate of alfalfa hay. 2） Through a multivariate analysis of the drying rate， chlorophyll content and nutritive value data for alfalfa hay in each harvest period， the optimal ranges of environmental conditions for natural drying of alfalfa hay in northern China， or other areas with similar climate conditions， are： daily average temperature， 26.29-27.95 °C； daily average air humidity， 34.74%-36.71%； daily average solar radiation intensity， 268.36-422.33 W·m^-2 and daily average wind speed， 1.59-1.82 km·h^-1.

Disease resistance evaluation of 32 alfalfa varieties in Xinjiang

Yue-yang ZHANG, Fang LI, Wei-wei LIANG, Yan-zhong LI

2022, 31(2):  133-146.  DOI: 10.11686/cyxb2020519

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This research aimed to identify disease resistant， high-yielding alfalfa （Medicago sativa） varieties suitable for planting in Xinjiang and was conducted in Hutubi， Changji City， Xinjiang in 2018 and 2019. Disease incidence and disease indexes were scored on two dates in both years for 32 alfalfa varieties. In total， yield data for 5 cuts were collected and plant survival percentage was measured in 2019. Diseases observed included： Phoma leaf spot and black stem， powdery mildew， alfalfa yellow leaf blotch， Stemphylium leaf spot and Cercospora leaf spot. Among these， the most important were powdery mildew， Phoma leaf spot and black stem， and alfalfa yellow leaf blotch， with the highest incidence of these three diseases being 97.08%， 100.00% and 57.14%， respectively. The resistance of each variety to each disease was evaluated following standardized scoring systems， and “gray incidence degree analysis” was used to analyze the characteristics of each variety and provide a combined trait score based on disease resistance， yield and survival. The 32 tested varieties were categorized as having “high resistance” （HR）， “resistance” （R）， “medium resistance” （MR）， “low resistance” （LR）， or as “susceptible” （S） to each of the three main diseases. Among the 32 tested alfalfa varieties， for resistance to Phoma leaf spot and black stem， the numbers of varieties in each of these 5 categories were： 17 HR， 8 R， 4 MR， 1 LR and 2 S. For alfalfa powdery mildew， the numbers of varieties in each category were： 0 HR， 1 R， 8 MR， 5 LR and 18 S. For alfalfa yellow leaf blotch， there 29 HR varieties， 3 R varieties and no MR， LR， or S varieties. The total yields over two seasons for the different varieties ranged from 22.48 t·ha^-1 for “Longdong” to 29.52 t·ha^-1 for “Longwei 3010”. No freezing injury occurred in any of the tested varieties； all survived well. Plant survival was greater than 80% for all varieties and was above 90% for 22 varieties. The five varieties with the highest combined trait scores from gray analysis were “Phabulous” （score 0.942）， “WL363HQ” （0.897）， “Zhongmu No.3” （0.877）， “Aohan” （0.853） and “Dryland” （0.850）， while the five lowest-scoring varieties were Salt-tolerant Star （score 0.650）， WL343HQ （0.679）， Shockwave （0.699）， Instict （0.718） and Longdong （0.721）.

The effect of sowing rate and row spacing on the yield and quality of alfalfa in the Ningxia Yellow River irrigation area

Bin WANG, Yu-qi YANG, Man-you LI, Wang NI, Yi-rui HAI, Shun-xiang ZHANG, Xiu DONG, Jian LAN

2022, 31(2):  147-158.  DOI: 10.11686/cyxb2021236

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This research explored the optimal sowing rate and row spacing configuration for high-quality and high-efficiency production of alfalfa （Medicago sativa） in the Ningxia Yellow River irrigation area. In a three-year experiment， a two-factor randomized block design was used to study the effects on the yield and quality of alfalfa， of different sowing rates （S₁： 13.5 kg·ha^-1， S₂： 18.0 kg·ha^-1， S₃： 22.5 kg·ha^-1） and row spacing configurations （R₁： 15 cm equal row spacing， R₂： 20 cm equal row spacing， R₃： rows spaced two narrow and one wide 15 cm+15 cm+20 cm， R₄： rows spaced one narrow and one wide 15 cm+20 cm）. It was found that the number of branches， leaf∶stem ratio， hay yield， crude protein， neutral detergent fiber content and relative feeding value of alfalfa were significantly affected by both sowing rate and row spacing （P<0.05）. The results of three-year experiment showed that the sowing rate and row spacing had significant effects on the branch number， leaf stem ratio， hay yield， crude protein， neutral detergent fiber content and relative feeding value of Alfalfa （P<0.05）. The hay yield （18.41 t·ha^-1） and crude protein content （21.00%） were the highest when sowing rate was S₂ and row spacing was R₃. The contents of neutral detergent fiber （36.50%） and acid detergent fiber （26.59%） were the lowest when the row spacing was R₂. Relative feeding value （171.98） was the highest when sowing rate was S₂ and row spacing was R₂. These findings are based on averaged data from the three years. A principal component analysis （PCA） showed that the drymatter yield， leaf∶stem ratio， branch number and neutral detergent fiber level of herbage were more responsive to the alfalfa sowing rate and row spacing treatments contribution rate of alfalfa were larger， and the plant height and acid detergent fiber responses were smaller. The treatment combination S₂R₃ （sowing rate of 18.0 kg·ha^-1 and row spacing of 15 cm+15 cm+20 cm） was the optimal sowing rate and row spacing combination for alfalfa forage production in this region for maximization of hay yield and forage nutritional quality.

A study of yield interactions in mixed sowings of alfalfa and three perennial grasses

Hui-hui ZHANG, Shang-li SHI, Bei WU, Zi-li LI, Xiao-long LI

2022, 31(2):  159-170.  DOI: 10.11686/cyxb2021175

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This study investigated the yield and competitive interactions in three mixed-sown combinations of alfalfa （Medicago sativa） and a perennial grass （M. sativa+Poa pratensis， M. sativa+Bromus inermis and M. sativa+Festuca arundinacea）. The mixtures were established at legume∶grass ratios of 7∶3， 5∶5， and 3∶7， and monocultures of alfalfa and the three grasses were also included as a contrast. Data on biomass and key morphological traits of each species in the various monocultures and mixed sowings were collated and analyzed to investigate the competitive interactions between alfalfa and the three grass species， so as to provide a theoretical basis for the development of management guidelines for high yield and high quality of mixed sown pasture. Results indicated that the relative yield （RY） values of alfalfa in the three mixed sowing combinations were higher than 1.0 and that alfalfa had a competitive advantage over the grasses. The growth of the grass in the combinations of M. sativa+P. pratensis and M. sativa+B. inermis was suppressed by alfalfa， while grass in M. sativa+F. arundinacea combination grew synergistically with alfalfa. For the three legume∶grass ratios tested in the mixed-sown plots， the RY for the alfalfa component ranked 3∶7>5∶5>7∶3 and RY for the grass component ranked 3∶7>7∶3>5∶5. For the alfalfa component， responses to the mixed sowing systems included reduced plant height and increased stem diameter and leaf area. For the grass component， plant height increased and stem diameter reduced were also observed but leaf area was increased in mild competition and decreased in more intense competition. These responses resulted in a high （>1.0） total relative yield （RYT） value under different mixed sowing ratios. The species in the mixed sown plots adapted to the variations in the interspecific relationship by adjusting their morphological characteristics， and these adjustments provided the mechanism for the achievement of synergistic growth and yield increase. Among the three mixed sown combinations， M. sativa+F. arundinacea exhibited a greater biomass-increasing effect than the others， especially with the legume：grass ratio of 3∶7. In contrast， in the mixed sowings of M. sativa+P. pratensis and M. sativa+B. inermis， the legume∶grass ratio of 7∶3 had the highest biomass-increasing effect.

Effects of hydrothermal treatment on in vitro fermentation， methanogenesis and microbiota of soybean straw

Cheng-fu ZHOU, Shui-ping WANG, Bai-zhong ZHANG, Xiu-min ZHANG, Rong WANG, Zhi-yuan MA, Min WANG

2022, 31(2):  171-181.  DOI: 10.11686/cyxb2020538

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The aim of this study was to investigate the effects of hydrothermal treatment on in vitro fermentation， methanogenesis and microbiota of soybean straw. The chemical compositions， the degradation characteristics， the fermentation parameters and the microbial ?ora were estimated for the soybean straws with and without hydrothermal treatment using an automatic ruminal fermentation system with 72 h of incubation. It was found that： The hydrothermal treatment reduced the concentrations of neutral detergent fiber （P<0.001）， acid detergent fiber （P<0.001） and hemicellulose （P<0.001） in the soybean straw， and increased the concentrations of neutral detergent soluble fiber （P<0.001）， water soluble carbohydrates （P<0.001）， arabinose （P<0.001） and galactose （P<0.001）. The hydrothermal treatment increased dry matter degradability （P<0.001） and volatile fatty acid concentration （P<0.05）， and decreased the acetate：propionate concentration （P<0.001）， the gas production of methane （P<0.001） and hydrogen （P<0.001） and the populations of fungi （P<0.01）， methanogenic bacteria （P<0.05） and Fibrobacter succinogenes （P<0.05）. The results indicate that the hydrothermal treatment disrupted the cellulose-hemicellulose-lignin structural matrix of soybean straw， thereby increasing the soluble matter content， improving the ruminal degradation， leading to reduction in the number of fungi and methanogens， and decreased methane production.

Effects of dietary protein levels on ruminal fungal community structure and function in Tibetan sheep

Xun-gang WANG, Xiao-ling ZHANG, Tian-wei XU, Yuan-yue GENG, Lin-yong HU, Na ZHAO, Hong-jin LIU, Sheng-ping KANG, Shi-xiao XU

2022, 31(2):  182-191.  DOI: 10.11686/cyxb2020545

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This study aimed to investigate the effects of dietary protein levels on ruminal fungal community structure and function of Tibetan sheep. A total of eighteen 12-month-old， healthy， castrated Tibetan sheep with similar initial body weights （31.71±0.72） kg were randomly divided into three treatment groups， with 6 sheep in each group. During the whole experiment， the sheep were fed diets with low， medium or high dietary crude protein （CP） levels （LP group， 10.06%CP； MP group， 12.10%CP； HP group， 14.12%CP） and similar metabolizable energy. The experiment took place over 120 d with a 15 d adaptation period and 105 d measurement period. It was found that： 1） The final body weights， average daily gains， and average daily feed intake of the LP group were lower than those in MP and HP groups （P<0.05）， while the feed conversion ratio in LP was higher than that in MP and HP groups （P<0.05）. 2） A total of 1547415 clean gene tags were obtained from 18 samples， and the total number of OTUs detected by a cluster analysis was 4073. The diversity index of the rumen fungi in Tibetan sheep was not significantly （P>0.05） affected by the dietary protein levels. 3） At the phylum level， the most dominant fungal phyla from the ruminal samples were Ascomycota， Basidiomycota， Mortierellomycota and Neocallimastigomycota. At the genus level， Penicillium， Acauliun， Cladosporium， Fusarium and Alternaria were detected as highly abundant taxa in the rumen. 4） A total of 33 biomarkers were identified at various taxonomic levels based on linear discriminant effect size analysis （LEfSe）. 5） The main function of the rumen fungal flora， as predicted by FUNGuid， was saprophytic activity. In summary， higher dietary protein levels significantly improved daily weight gain of Tibetan sheep， but had no significant effect on microbial diversity and community structure.

Effects of dietary concentrate level and chromium-methionine supplementation on ruminal fermentation， and ruminal bacterial and fatty acid composition in Tan lambs

Ya-dong JIN, Hai-xia ZHAO, Rui-qi GUI, Qing MA, Yu-xiang ZHOU

2022, 31(2):  192-202.  DOI: 10.11686/cyxb2020522

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This study evaluated the effects of dietary concentrate level and chromium methionine（Cr-Met）supplementation on ruminal fermentation and fatty acid composition， and ruminal bacteria abundance in Tan lambs. Forty male Tan lambs ［（21.00±1.23） kg body weight， 5 months of age］ were randomly assigned to four treatment groups with 10 lambs in each treatment. The treatments were： a low-concentrate （LC） diet （concentrate∶forage， 35∶65） without Cr-Met supplementation； a high-concentrate （HC） diet （concentrate∶forage， 55∶45） without Cr-Met supplementation； groups fed the HC diet with 0.75 or 1.50 g·d^-1·lamb^-1 Cr-Met （HCM and HCH， respectively）. Ruminal fluid was collected on day 65 with an oral stomach tube about 3 h after the morning feed and samples used for fermentation analysis， fatty acid composition determination and bacterial DNA extraction. It was found that： 1） Ruminal pH， acetate proportion and acetate∶propionate were greater （P<0.05） with the LC diet whereas microbial crude protein， propionate and valerate proportions were greater （P<0.05） with the HC diet. The acetate∶propionate was greater （P<0.05） in the HCM group than in the HC group. 2） For the HC diet， the DNA abundances of Butyrivibrio fibrisolvens vaccenic acid subgroup（Butyrivibrio VA） and Ruminococcus flavefaciens were decreased （P<0.05）， compared with the LC diet， whereas the DNA abundance of Anaerovibrio lipolytica was increased （P<0.05）. For lambs fed the HC diet， DNA abundances of B. fibrisolvens stearic acid subgroup， Butyrivibrio VA， Butyrivibrio proteoclasticus，and A. lipolytica showed a linear decrease （P<0.05） with increasing Cr-Met supplementation level； However， the DNA abundance of R. flavefaciens showed a linear increase （P<0.05）. 3） Compared with the LC group， the concentrations of t11 C18：1， trans C18：1， c9t11 CLA， t10c12 CLA， C18：2n6， and C18：3n3 were decreased by the HC diet without Cr-Met supplementation whereas the concentration of C18：0 was increased. There was a linear increase in t11 C18：1 and trans C18：1 with increasing Cr-Met supplementation level in lambs fed the HC diet. The results suggest that the HC diet inhibited the growth of ruminal bacteria involved in the ruminal biohydrogenation process， and the addition of Cr-Met had a potentially positive effect on conjugated linoleic acid （CLA） synthesis in body tissue.

Effects of drought stress on root characteristics structure and physiological characteristics of Potentilla bifurca var. glabrata

Peng-fei GAO, Jing ZHANG, Wei-fang FAN, Bing GAO, Hong-juan HAO, Jian-hui WU

2022, 31(2):  203-212.  DOI: 10.11686/cyxb2020521

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In this research a natural water control method was used to study the effects of different drought treatments on the phenotypic characteristics， ultrastructure and physiological indexes of roots of Potentilla bifurca var. glabrata and to explore the drought tolerance of this species. It was found that under drought stress， the total root length， total surface area， total volume and average diameter of P. bifurca var. glabrata increased continuously over days 0-25. The root dry weight increased over days 0-15 d， but decreased significantly over days 20-25 d （P<0.05）. With increased drought stress， the root cell wall was deformed and damaged， the mitochondria disintegrated and disappeared， and starch grains appeared and continuously expanded. Malondialdehyde （MDA） content and proline content were increased over days 0-25. Soluble protein content and superoxide dismutase （SOD） activity increased significantly over days 0-15， and decreased significantly over days 20-25 d （P<0.05）. After rehydration， the contents of proline and soluble protein decreased nonsignificantly （P>0.05）， while MDA content and SOD activity decreased significantly （P<0.05）. Generally speaking， P. bifurca var. glabrata can endure natural drought for 20 d and has strong drought resistance. These results provide information for the breeding of drought-tolerant plants in Northeast China.

Lipid peroxidation and carbon and nitrogen characteristics in leaves and roots of alfalfa （Medicago sativa） in response to water and nitrogen addition

Jie BAI, Zhen-feng ZANG, Cong LIU, Kan-zhuo ZAN, Ming-xiu LONG, Ke-zhen WANG, Yang QU, Shu-bin HE

2022, 31(2):  213-220.  DOI: 10.11686/cyxb2020539

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In order to study the response of alfalfa （Medicago sativa） leaves and roots to water and N addition， two contrasting water availability regimes were set up under greenhouse conditions： water stress （WS） with soil maintained at 35%±5% field water capacity （FWC） and well-watered （WW， 70%±5% FWC）. Treatments of 0， 5 and 10 mmol·L^-1 N （Nn， Nm and Nh， respectively） were established under each watering regime. The responses of physiological parameters of alfalfa leaves and roots and their C and N characteristics to different water conditions and exogenous N addition were then studied at the three N levels. It was found that WS and exogenous N increased malondialdehyde content in alfalfa leaves， but had no significant effect on the root system. WS and N addition did not affect C content in alfalfa leaves， but N addition increased C content in roots. The content of N in alfalfa leaves did not differ between water treatments， but root N content was increased under the WS treatment. Exogenous N addition not only increased leaf N content， but also increased root N content. However， leaf N content was more sensitive to exogenous N addition under the WW treatment， while root N content was more sensitive to exogenous N addition under the WS treatment， which indicates that the response of alfalfa leaf and root C and N status to N addition was regulated by soil moisture conditions. The C∶N of alfalfa roots was higher than that of leaves， and was more sensitive to soil water status and exogenous N addition. The WS treatment resulted in significantly less negative root δ¹³C， but had no significant effect on leaf δ¹³C. δ¹⁵N tended to be reduced with exogenous N addition， but this effect was statistically significant in roots under WS treatment and in leaves under WW treatment. In conclusion， compared with leaves， alfalfa root physiological parameters and C and N characteristics displayed more active responses to water and exogenous N addition， and played a more important role in growth. The results are helpful to fully understand the response strategies of alfalfa organs to water and exogenous N addition， and provide a theoretical basis for formulation of water and fertilizer management systems that more precisely meet alfalfa requirements in dry farming areas of China.