Table of Content

20 October 2022, Volume 31 Issue 10

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A study of grassland aboveground biomass on the Tibetan Plateau using MODIS data and machine learning

Zhe-ren JIN, Qi-sheng FENG, Rui-jing WANG, Tian-gang LIANG

2022, 31(10):  1-17.  DOI: 10.11686/cyxb2021386

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The Tibetan Plateau， often referred to as “the third pole of the world”， is located in the Southwest of China， and makes significant contribution to ecology and climate change in China and around the word. Our study evaluated the change in aboveground biomass （AGB） on the Tibetan Plateau from 2000 to 2020. We used multiple machine learning methods combined with MCD43A4 product data to simulate the aboveground biomass and analyzed the temporal and spatial characteristics of AGB in this region. The main results were as follows： 1） Among the constructed machine learning models， Rborist model demonstrated the highest accuracy， with an R² of 0.6484 based on screened variables， and eight variables were found to be highly correlated with biomass： precipitation in May， precipitation in June， average temperature in December， normalized difference phenology index （NDPI）， precipitation in April， maximum temperature in January， precipitation in August and precipitation in December； 2） AGB in the southeast of the Tibetan Plateau was higher than that in the northwest， with a decreasing trend from the southeast to northwest； 3） AGB on the Tibetan Plateau increased steadily from 2000 to 2020， with an overall positive movement. However， 61.38% of Tibetan Plateau grasslands showed a trend of unsustainability， 4.67% showed a slight deterioration trend， 1.19% showed a significant deterioration trend， and 32.76% were stable or showed a recovery trend.

Effects of different grazing patterns on soil carbon and nitrogen storage and sequestration in desert steppee

Yan-ming CHENG, Hong-bin MA, Jing MA, Zi-yuan MA, Jin-di LIU, Yao ZHOU, Wen-dong PENG

2022, 31(10):  18-27.  DOI: 10.11686/cyxb2021412

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It is important for scientific grassland management to know the effects of grazing on carbon and nitrogen storage and sequestration. Soil organic carbon and total nitrogen storage and carbon and nitrogen sequestration in the 0-40 cm soil horizon were studied in a Ningxia desert steppe under treatments of enclosure to prevent grazing， free grazing and warm season rotational grazing. It was found that： 1） After 5 years of grazing， the soil carbon and nitrogen contents were the highest （5.66±0.32 g·kg^-1 and 0.32±0.01 g·kg^-1， respectively） in warm season rotational grazing， and the lowest in free grazing. The organic carbon content increased with soil depth in warm season rotational grazing， but the differences between warm season rotational grazing and enclosure to prevent grazing and free grazing were not significant. The vertical variation of nitrogen content did not differ significantly among the three treatments. The C∶N ratio under free grazing was the highest （26.98±1.05）， while warm season rotation grazing was the lowest. Soil carbon and nitrogen storage for the 0-40 cm soil horizon ranked warm season rotation grazing>enclosure to prevent grazing>free grazing. 2） The carbon and nitrogen sequestration and sequestration rates ranked warm season rotation grazing>enclosure to prevent grazing>free grazing. 3） Pearson correlation analysis showed that soil carbon and nitrogen storage and retention were significantly correlated with aboveground biomass （P<0.05）. It is positively correlated with species diversity （P<0.01， P<0.001）. It was concluded that， from a perspective of soil carbon and nitrogen storage and retention， warm season rotational grazing is more conducive to the improvement of carbon sink capacity and sustainable development of desert steppe in the study area.

Effects of Caragana microphylla shrubs on the soil nitrogen-fixing microbial communities in steppe land

Chun-wen WANG, Fang ZHAO, Chen ZHANG, Li-na XIE, Cheng-cang MA

2022, 31(10):  28-40.  DOI: 10.11686/cyxb2021403

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Encroachment of woody species has become a common phenomenon in arid and semi-arid grassland worldwide. However， the effects of shrubs on soil nitrogen-fixing microbial （NFM） communities and the mechanisms underlying them are poorly known. Caragana microphylla （Fabaceae） is widely distributed in the Inner Mongolian Steppe. It is important to explore the effects on NFM communities. In this paper， we compared the differences of soil NFM communities outside and within the canopy areas of shrubs in different soil horizons of desert steppe （arid zone） and typical steppe （semi-arid zone） by traditional culture methods and molecular biology techniques. Furthermore， our study explored the mechanisms underlying the shrub effects in terms of the species selectivity， fertile-island effect， and the interaction of the shrub and aridity effects. It was found that C. microphylla significantly increased the abundance and richness of NFM communities， and also affected their community composition. The change in community composition was manifested as significant variation in abundance of 37.50%-58.33% of genera， as change in the dominant genera and their dominance position， as a large Jaccard dissimilarity index （0.40-0.76） for samples from outside and samples from within shrub canopies， and differences in the ordination of NMDS （non-metric multidimensional scaling） results inside and outside shrub canopies. Based on these data an ‘analysis of similarity’ test showed significant differences in NFM community composition outside and within shrubs. The effect of shrubs on NFM communities decreased with increasing soil depth， and increased with increasing aridity. Shrubs exerted a greater effect on NFM communities than aridity. The mechanisms underlying the C. microphylla effects on NFM communities were： 1） Shrubs had a selective effect on NFM species presence； 2） Shrubs affected NFM communities through soil physical and chemical characteristics； 3） Climate aridity enhanced the impact of shrubs on NFM communities； 4） Shrubs affected NFM communities through mitigating climatic impacts.

Effects of short-term yak grazing on soil fungal communities in an alpine meadow on the Qinghai-Tibetan Plateau

Yong-hong WANG, Li-ming TIAN, Yi AI, Shi-yong CHEN, Tserang-donko MIPAM

2022, 31(10):  41-52.  DOI: 10.11686/cyxb2021476

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Yak grazing is one of the major human disturbances， and decisions about grazing management and intensity play important roles in maintaining grassland health on the Qinghai-Tibetan Plateau. In order to clarify the effect of short-term yak grazing on soil fungal communities in alpine meadows， an experiment involving a range of grazing intensities was conducted in a typical alpine meadow of northwestern Sichuan. The experiment included a control group （no grazing）， light grazing （1 yak·ha^-1）， moderate grazing （2 yak·ha^-1）， and heavy grazing （3 yak·ha^-1）. After two years， it was found that the grazing treatments had changed the community structure of the soil fungi by increasing the relative abundance of Ascomycota and decreasing the relative abundance of Basidiomycota in the topsoil. Grazing treatments tended to enhance the diversity and richness of soil fungal communities， although differences among grazing intensities were not statistically significant. Variance partitioning analysis indicated that grazing intensity affected the community structure of soil fungi via alteration of soil nutrient status. Furthermore， the co-occurrence network showed that short-term yak grazing had no significant effect on the relative abundance of the main fungal groups， while grazing intensity affected the relative abundance of fungal groups through change in soil nutrient status.

Effects on soil nutrients and bacterial communities of different cover crops in an organic kiwifruit orchard in the Guanzhong region of China

Xu-mei JIN, Ying-ying WANG, Chong-yi LIU, Xin-yi CHEN, Ming-xiu LONG, Shu-bin HE

2022, 31(10):  53-63.  DOI: 10.11686/cyxb2021414

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This study investigated the effects of different cover crop combinations on soil nutrients and bacterial communities in organic kiwifruit orchards in the Guanzhong area. Four cover crop combinations were tested： 1） Lolium perenne+Vicia villosa；2） L. perenne+Melilotus officinalis； 3） L. perenne+Trifolium repens；and 4） Vulpia myuros. Natural grass was used as the control. The growth characteristics of grass species and the effects of cover crops on soil nutrients in the orchard topsoil （0-20 cm） were observed. The bacterial community structure was analyzed by high-throughput sequencing. It was found that V. myuros had the highest overwintering survival rate and the lowest number of weed plants in the plot. The soil organic matter of artificial grass was 6.46%-38.63% higher than that of natural grass. The combination L. perenne+V. villosa gave an obvious difference， and this treatment resulted in the most significant improvement in soil urease， sucrase and alkaline phosphatase activities， which were 3.37， 44.17 and 3.46 mg·g^-1·d^-1， respectively. Meanwhile， compared with natural grass， L. perenne+V. villosa， L. perenne+M. officinalis and L. perenne+T. repens increased the richness and diversity of soil bacterial communities. L. perenne+V. villosa had the most distinct bacterial community structure. In summary， planting L. perenne+V. villosa in organic kiwifruit orchards in Guanzhong area can be recommended to help improve soil organic matter and nutrient content to a certain extent， and to improve the soil micro-ecological environment.

Effects of phosphorus application on the growth and salt resistance of switchgrass under saline alkali conditions

Hai-feng HE, Na WU, Ji-li LIU, Xing XU

2022, 31(10):  64-74.  DOI: 10.11686/cyxb2021378

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This study investigated the effects of different levels of phosphorus application on the growth， development and drought resistance of switchgrass （Panicum virgatum） in the saline area of Yinbei， Ningxia. In a field experiment two ecotypes of switchgrass， “Alamo” and “Pathfinder” were compared at three levels of phosphorus application： No phosphorus （P₀）， low phosphorus （30 kg·ha^-1 P₂O₅） and high phosphorus （90 kg·ha^-1 P₂O₅）. There were three replications for each treatment. Changes in growth indexes， osmoregulatory substances and antioxidant enzyme activities were analyzed and compared at different stages of the reproductive period， and the switchgrass drought resistance was evaluated using the affiliation function method. It was found that with increasing phosphorus application levels， agronomic traits including as plant height， tiller number， leaf area index， dry matter accumulation and biological yield， and physiological characteristics such as SPAD value， malondialdehyde， soluble sugar content and peroxidase activity showed a general trend of gradual increase in both ecotypes. Compared to the P₀ treatment， the above nine parameters were increased by 7.74%， 10.21%， 14.64%， 11.88%， 22.22%， 3.85%， 74.29%， 14.70% and 57.77%， respectively. In the multivariate analysis， the mean value of the membership function for each drought tolerance index was largest under the low phosphorus treatment. Therefore， 30 kg·ha^-1 P₂O₅ equivalent is the ideal phosphorus application to improve the physiological characteristics， biological yield and salinity resistance of both ecotypes in this experiment.

Effects of drought stress on leaf senescence and the active oxygen scavenging system of oat seedlings

Yu-han WU, Wen-hui LIU, Kai-qiang LIU, Yong-chao ZHANG

2022, 31(10):  75-86.  DOI: 10.11686/cyxb2021410

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This research investigated the responses of leaf senescence and the active oxygen scavenging system following water deficit stress in oats， in order to provide a theoretical framework for evaluation of drought-resistance of oat varieties used on the Qinghai-Tibetan Plateau. A popular local Qinghai oat variety， Qingyan No.1， was used in the experiment. Water deficit stress was simulated with PEG-6000 at two concentrations （P₁₀ and P₂₀）_{and a nil-PEG （CK） treatment was also included. These treatments were applied to plants for 4， 7， or 10 days. The effects of drought stress on the photosynthesis parameters， chlorophyll content， carotenoid content， superoxide anion content， hydrogen peroxide content， antioxidant enzyme activities and non-enzymatic antioxidants were studied. It was found that： 1） With increase in drought stress， the chlorophyll （Chl） content of oat seedlings decreased significantly； superoxide anion content （O2^-） and hydrogen peroxide （H2O2） contents increased significantly； net photosynthetic rate （Pn）， transpiration rate （Tr）， intercellular CO2 concentration （Ci）， stomatal conductance （Gs）， maximum photochemical efficiency （Fv/Fm）， and actual photochemical efficiency （ΦpsII） decreased significantly； and chlorophyll initial fluorescence （Fo） and the non-photochemical quenching coefficient （NPQ） increased significantly. Water deficit stress initially increased plant water use efficiency， but this effect was short-lived and stomatal closure and damage to light reaction centers were the main reasons for the weakening of photosynthetic performance under water deficit. 2） With increase in PEG concentration， or duration of simulated water deficit stress， the activities superoxide dismutase （SOD）， and related enzymes dehydroascorbate reductase （DHAR）， glutathione reductase （GR）， and ascorbic acid peroxidase （APX） increased initially and then decreased， while glutathione peroxidase activity（GPX） continued increasing. However， levels of non-enzymatic antioxidants of oats were significantly higher under drought stress than in control plants. It was concluded that under mild drought stress or in early drought stress， ‘Qingyan No.1’oats remove reactive oxygen species and toxic substances mainly through enzyme antioxidants， while under severe stress， they are removed mainly through non-enzyme antioxidants.}

Response of photosynthetic characteristics and water use efficiency of Artemisia scoparia to rainfall changes in Eastern Ningxia desert steppe

Lin CHEN, Gao-lu CHEN, Nai-ping SONG, Xue-bin LI, Hong-yun WAN, Wen-qiang HE

2022, 31(10):  87-98.  DOI: 10.11686/cyxb2021409

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The growth and survival rates of plants are greatly affected by rainfall in desert steppe.This research investigated the soil water fluctuations after rainfall events for four consecutive years from 2017 to 2020 in an Artemisia scoparia population in an Eastern Ningxia desert steppe. We determined the effects of several simulated rainfall patterns （decreased by 30%， unchanged， increased by 30%） on the photosynthetic characteristics and water use efficiency of A. scoparia. The photosynthetic characteristics of A. scoparia including net photosynthetic rate， transpiration rate， stomatal conductance and intercellular CO₂ concentration were measured， and the intrinsic water use efficiency and instantaneous water use efficiency at leaf level were analyzed. It was found that trivial rainfall events （<5 mm） occurred frequently， accounting for 60.00%-82.54% of the rainfall frequency from 2017 to 2020. Heavy rain events （≥25 mm and <50.0 mm） and rainstorm events （≥50 mm） were few， and the average rainfall in a single rainfall event over the four years was only 3.3-6.5 mm. There were large differences in soil water content in different soil horizons under different treatments， and the variation of soil water content in the surface horizon （0-10 cm） was larger than that in the subsurface horizon （10-20 cm） and deep layer （20-60 cm）. The average soil water content in the subsurface layer （20 cm） was lower than that in the surface layer （10 cm）， and this reflected the high frequency of small rainfall events， the inability of water to infiltrate and penetrate， and the absorption and consumption of water by plants. The water content of the deep soil horizon changed little over time. The net photosynthetic rate increased with increase in photosynthetically active radiation. At photosynthetically active radiation levels of 400-1600 μmol·m^-2·s^-1， increase in soil water had a great influence on the net photosynthetic rate of A. scoparia. At photosynthetically active radiation levels higher than 1600 μmol·m^-2·s^-1， photosynthesis tended to be suppressed by increase in soil water and the rainfall treatment exhibited the largest decline. At photosynthetically active radiation levels above 400 μmol·m^-2·s^-1， the intercellular CO₂ concentration decreased linearly with increase in radiation， and at 1600 μmol·m^-2·s^-1， the intercellular CO₂ concentration reached its minimum. Transpiration rate and stomatal conductance did not change significantly with increase in light intensity， but the transpiration rate and stomatal conductance of A. scoparia under the rainfall enhancement treatment were higher than those under other treatments. Stomatal limitation increased with increase in photosynthetically active radiation， and decreased with increase in rainfall. Intrinsic water use efficiency and instantaneous water use efficiency of A. scoparia increased rapidly with increase in light intensity at light levels less than 400 μmol·m^-2·s^-1， but at higher light levels the growth rate slowed down. The intrinsic water use efficiency and instantaneous water use efficiency of A. scoparia reached their maxima at photosynthetically active radiation levels of 1600-2000 μmol·m^-2·s^-1. With increase in drought severity， the light intensity at which the maximum water use efficiency was observed decreased from 2000 to 1600 μmol·m^-2·s^-1， and when the light intensity was above 400 μmol·m^-2·s^-1， moderate drought improved the water use efficiency of A. scoparia.

Evaluation of soil heavy metal pollution under different land use patterns in the eastern Qilian Mountains

Ning-gang SAI, Juan QI, Yan-wei JIA, Mei-mei CHE, Juan-di YANG, Xiao-juan WANG, Chang-lin XU

2022, 31(10):  99-109.  DOI: 10.11686/cyxb2021394

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In this study we measured the levels of seven heavy metals in soils under different land uses in the eastern Qilian Mountains. By comparison with the background levels of soil elements on the Qinghai-Tibet Plateau， the degree of soil heavy metal pollution and the overall potential ecological risk was evaluated using the Nemero comprehensive pollution index and potential ecological risk coefficient. It was found that the average values of the seven measured heavy metal elements were higher than the background values. The average levels of Zn and Ni was higher at 196.67 mg·kg^-1 and 74.28 mg·kg^-1， respectively， these values being 3.20 and 3.00 times higher， respectively， than background values. Thus， it was concluded that an enrichment phenomenon of soil heavy metal elements is occurring. The Nemero comprehensive pollution index averaged for all land use categories was 2.84， which is classed as the pollution level is moderat. For farmland， the average pollution index was highest at 3.10， which is classified as a severe pollution level. The grassland pollution index was 2.71， and the wetland was lowest at 2.49， both of which are considered moderate pollution levels. The average comprehensive potential ecological risk coefficient for all land types was 94.31， with the risk coefficient of farmland being the highest （101.90）， while that of grassland was 92.22 and that of wetland was 73.29. The coefficient of variation for Zn in all soil types was the lowest. The coefficient of variation of Cd was the highest.

Effects of Epichloё endophyte on seed germination and seedling growth of Stipa purpurea under salt stress

Peng ZHANG, Xi REN, Si-yu MENG, Xiao-xing WEI, Gen-sheng BAO

2022, 31(10):  110-121.  DOI: 10.11686/cyxb2021492

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Stipa purpurea is one of the dominant grass species in alpine grassland in the Qinghai Lake basin， which is severely affected by salinity. S. purpurea maintains a high rate of Epichloё endophyte infection in native grassland， and Epichloё endophyte infection can improve salt tolerance of grasses. However， little research has been reported on Epichloё endophyte effects on the seed germination and seedling growth of S. purpurea under salt stress. This experiment studied the effects of salt stress on the germination and seedling growth of endophyte-infected （E+） and endophyte-free （E-） S. purpurea seeds. The experiment treatments included different concentrations of single salt （NaCl， Na₂SO₄， Na₂CO₃ and NaHCO₃） and compound salt （NaCl+Na₂CO₃） stress. It was found that the germination rate， germination power and germination index of S. purpurea seeds decreased progressively with successive increases in salt concentration， and the presence of Epichloё endophyte suppressed the downward trend for seed germinability. The intensity of seedling and radical growth inhibition increased with salt concentration and， the relative salt damage rate to seed germination also continued to increase. In addition， salt damage originating from Na₂CO₃ and Na₂SO₄ on seed germination and seedling growth of S. purpurea was higher than other salt types. Thus， Epichloё endophyte infection is one of the reasons why S. purpurea adapts to saline soil in Qinghai Lake Basin and becomes the dominant grass in alpine grassland. This information is relevant to ecological restoration of areas affected by soil salinization and identification of salt-tolerant grass germplasm and indicates the value of using the Epichloё endophyte symbiont with S. purpurea.

Effects of the Gm4CL2 gene on aluminum tolerance of Arabidopsis and alfalfa

Tao LIN, Li-jiao ZHANG, Rong-rong HAN, Yong-xiong YU, Cao-de JIANG

2022, 31(10):  122-134.  DOI: 10.11686/cyxb2022082

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4CL （4-coumarate： coenzyme A ligase） is a key enzyme in the lignin synthesis pathway， which has been shown to play an important role in biological and abiotic stress， mechanical damage resistance and other biological processes. However， the aluminum tolerance of Gm4CL2 has not been reported. In this work， Gm4CL2 of Glycine max cv. Tamba was chosen， and its full-length coding sequence was cloned by RT-PCR. The genetic relationship among Gm4CL2protein sequences was analyzed using multiple sequence alignment and phylogenetic tree analysis. Gm4CL2 was transformed into Arabidopsis thaliana and Medicago sativa by Agrobacterium-mediated floral dip and leaf disk method， respectively. Gene expression levels were detected using qRT-PCR. The results of sequence analysis revealed a 1668 bp Gm4CL2 full-length coding sequence， which encodes 555 amino acids and belongs to class I 4CL in dicotyledons. Real-time PCR results showed that Gm4CL2 expression was specifically induced at 50 μmol·L^-1 AlCl₃ （pH 4.5） in 0-2 cm root tips of G. max cv. Tamba seedlings， and the expression levels of AtMATE， AtSTAR1 and AtSTAR2 were significantly up-regulated in root tips of Arabidopsis overexpressing Gm4CL2 under aluminum treatment （P<0.05）. Under Al³⁺ stress， relative root elongation， activities of SOD （superoxide dismutase） and POD （peroxidase） and citrate secretion were significantly elevated， while Evans blue and chrome azure staining and the content of Al³⁺， ROS （reactive oxygen species） and MDA （malondialdehyde） were significantly lower in the roots of Arabidopsis overexpressing Gm4CL2 than in those of the wild type （P<0.05）. The relative root elongation， citrate secretion and biomass of alfalfa overexpressing Gm4CL2 were significantly higher， while Al³⁺ content and Evans blue staining were significantly lower than those of the wild type （P<0.05）. Cell wall composition analysis showed that pectin， and caffeic and ferulic acid contents in Arabidopsis roots overexpressing Gm4CL2 were significantly lower than those of the wild type under both Al³⁺ and non-Al³⁺ stress （P<0.05）. Under Al³⁺ stress， the content of lignin decreased， but the content of 4-coumaric acid increased in Arabidopsis roots overexpressing Gm4CL2 compared with the wild type （P<0.05）.

Identification and physiological study of variation in reproductive fertility in clonal lines of Medicago sativa cultivar ‘Qingshui’

Zi-li LI, Shang-li SHI, Yun A, Hui-hui ZHANG, Xiao-long LI

2022, 31(10):  135-144.  DOI: 10.11686/cyxb2021390

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A fertility analysis and identification and physiological characteristics of sterile material was undertaken in Medicagosativa cultivar ‘Qingshui’ to provide support for breeding sterile lines. Six clonal propagation lines （GN-A₁， GN-A₂， GN-A₃， GN-A₄， GN-A₅ and GN-A₆） with fertility variations were studied together with plants of normal fertility （CK）. At the full flowering growth stage， pollen grains were collected for I₂-KI staining to determine fertility and flower buds were analyzed for nutrient metabolism indexes （soluble sugar， SS； soluble protein， SP； starch， Sta and proline， Pro） and for indicators of membrane lipid peroxidation （catalase， CAT； peroxidase， POD； superoxide dismutase， SOD and malondialdehyde， MDA） at different development stages. It was found that the pollen vital staining rate of fertile CK plants was up to 98.37%， and pollen grains were full and spherical. The pollen staining rates of GN-A₁， GN-A₂， GN-A₃ and GN-A₆ plants were all lower than 5%， and the pollen grains were dried up and mostly had elliptical or irregular shapes， and these were preliminarily identified as sterile plants. The pollen staining rate of GN-A₄ and GN-A₅ plants were 54.80% and 63.60%， respectively with the majority of pollen grains elliptical， and relatively few dried grains. These were classified as typical semi-sterile plants. The supply of SS， SP， Sta and Pro of sterile plants （GN-A₁， GN-A₂， GN-A₃ and GN-A₆） was insufficient as the floral development period progressed. Indicators of membrane lipid peroxidation， POD and SOD activities in sterile plants were higher than those in the fertile plants for the whole floral development period， while CAT activity of sterile plants was higher than that of fertile plants at floral development stage Ⅰ and Ⅱ， and then decreased gradually. The content of MDA in the fertile plants was significantly higher （P<0.05） than that in the sterile plants at floral development stages Ⅰ， Ⅱ and Ⅳ. CAT， POD and SOD activities， and SS and SP levels showed variation in the flower buds of sterile plants， but were comparatively stable during the development of fertile plants， indicating that the changes of the measured physiological indexes were closely linked to reproductive fertility.

Effects of intercropping ratio and regulated deficit irrigation on flag leaf traits of spring wheat at the grain filling stage in spring wheat-alfalfa intercropping

Tao ZHOU, Le MU, Kai-qi SU, Jun-yu ZHANG, Hui-min YANG

2022, 31(10):  145-153.  DOI: 10.11686/cyxb2022128

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In order to elucidate the advantages of legume-grass intercropping and provide reference data for development of appropriate grain and forage production practice in the Hexi Corridor area of China， this research investigated the effects of intercropping ratio and regulated deficit irrigation on flag leaf traits of spring wheat （Triticum aestivum） at the grain filling stage. Two spring wheat-alfalfa （Medicago sativa） strip intercropping configurations were evaluated： 12 rows of spring wheat and 4 rows of alfalfa （12W4A） per strip and 8 rows of spring wheat and 4 rows of alfalfa （8W4A） per strip. Sole spring wheat was used as control. There were four irrigation treatments： 450 （I₄₅₀）， 360 （I₃₆₀）， 270 （I₂₇₀） and 180 mm （I₁₈₀）. Flag leaf traits were measured at the grain filling stage to define the effects of intercropping ratio and regulated deficit irrigation on the flag leaf morphology and physiology of spring wheat. It was found that： 1） With the successive decreases in irrigation amount， flag leaf area of spring wheat tended to initially increase and then decrease， reaching a maximum at I₃₆₀. The specific leaf weight， leaf nitrogen concentration and chlorophyll content showed an upward trend， while leaf length∶width and leaf dry matter content did not change significantly. 2） In general， flag leaf area of spring wheat ranked 8W4A>12W4A； Specific leaf weight， leaf nitrogen concentration and chlorophyll content ranked 12W4A>8W4A. The canopy structure under 12W4A provided a suitable spatial ratio for the growth of spring wheat plants， and was conducive to the photosynthetic assimilation of flag leaves.

Effects of arginine level on rumen flora population structure and fermentation in weaning sika deer

Yu-jie FAN, Hua-zhe SI, Xiao-xu WANG, Qian-long YANG, Xin-yu ZHANG, Wei ZHONG, Kai-ying WANG

2022, 31(10):  154-166.  DOI: 10.11686/cyxb2021167

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This study investigated the effects of arginine level on rumen fermentation and flora population structure of weaning sika deer. Twelve three month old male sika deer with similar body weight were randomly divided into three groups of four. All groups were fed the same basal diet containing 12.28% crude protein （CP） with differing levels of arginine： 0.80% （A）， 1.08% （B）， and 1.26% （C）. The experimental period was 50 days. On the last day， 20 mL rumen fluid was extracted from each animal， rumen fermentation parameters were measured， and DNA was extracted to analyze rumen bacterial diversity. It was found that： 1） The content of ammonia nitrogen in rumen fluid of Group B was higher （P<0.01） than that in Group C， while the contents of acetic acid， butyric acid and isobutyric acid in Group B were lower （P<0.01） than those in Group A. The content of total volatile fatty acids in Group B was lower （P<0.05） than that in Group A and the ratio of acetate to propionate in Group B was lower （P<0.01） than that in Groups A and C. 2） The ACE index of Group B was higher （P<0.05） than that of Group C while the Chao1 index of Group B was significantly higher than that of Groups A and C （P<0.05） and the Simpson index of group B was higher （P<0.01） than that of Groups A and C and the Shannon index showed the opposite pattern. The bacterial diversity of Group A differed （P<0.05） from that of Groups B and C. 3） Taxonomically， at the phylum level， the relative abundance of Bacteroidetes in Group B was lower （P<0.01） than that in Group A， the relative abundance of Firmicutes was higher （P<0.05） than in Group A， and the relative abundance of Proteobacteria in Group B was higher （P<0.05） than in Groups A and C. At the genus level， the relative abundance of unidentified_Prevotellaceae did not differ （P>0.05） among the three groups， the relative abundance of Methanobrevibacter in Group A was higher （P>0.01） than in Groups B and C， the relative abundance of Succinivibrio in Group B was higher than in Group A （P<0.01） and Group C （P<0.05）. In conclusion， 1.08% dietary arginine level significantly improved the microbial richness of sika deer， changed the bacterial diversity and the taxonomic structure of dominant bacteria， and thus promoted rumen propionic acid fermentation， and enhanced the body energy supply.

Effect of compound Lactobacillus and mixture ratio on fermentation quality and rumen degradability of mixed tomato pomace and alfalfa silage mixed storage

Ting WANG, Lei SONG, Xu-zhe WANG, Chun-hui MA, Bao-jun DU, Fan-fan ZHANG

2022, 31(10):  167-177.  DOI: 10.11686/cyxb2021411

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This study explored the effect of mixture ratio and inoculation with compound Lactobacillus on the quality of mixed tomato pomace and alfalfa silage in order to provide a theoretical basis for improving resource utilization and broadening forage resources in this region. The vacuum bag method was used to prepare the mixed silage samples for testing. There were ten experimental treatments； five mixture ratios ［tomato pomace∶alfalfa=3∶7 （T₁）， 4∶6 （T₂）， 5∶5 （T₃）， 6∶4 （T₄）， 7∶3 （T₅）］， each mixture ratio either without or with added compound Lactobacillus culture made up from a 1∶1 of Lactobacillus brucei and Lactobacillus plantarum， 1×10⁶ CFU·g^-1. The Lactobacillus culture was evenly added and the five inoculated treatments were designated JT₁， JT₂， JT₃， JT₄ and JT₅，5 replicates in each group， 2 kg in each bag. After 60 days of fermentation， the bags were opened for sensory evaluation； The nutritional quality， fermentation quality， and rumen degradability were analyzed. The membership function analysis method was used to evaluate the optimal treatment. It was found that， the smell and texture of mixed silage of tomato pomace and alfalfa were improved by inoculation with compound Lactobacillus. Sensory evaluation results for the mixed silage treatments T₁， JT₁， T₂ and JT₂ were excellent. When inoculated with compound Lactobacillus， the dry matter （DM）， crude protein （CP）， lactic acid （LA） and acetic acid （AA） of the mixed tomato pomace and alfalfa silage were significantly increased （P<0.05）， and water-soluble carbohydrate （WSC）， neutral detergent fiber （NDF）， acid detergent fiber （ADF）， pH， propionic acid （PA）， butyric acid （BA）， ammonia nitrogen∶total nitrogen （NH₃-N∶TN） were significantly decreased （P<0.05）. Among the tested mixed silage treatments， the DM and CP contents of JT₂ were the highest， the WSC content of T₂ was the highest， the NDF and ADF contents of JT₂ were the lowest， pH values of JT₁ and JT₂ treatments were lower， LA contents of JT₁ and JT₂ were higher， the AA contents of T₁ and T₂ were lower and the PA and BA contents and NH₃-N/TN of JT₁ and JT₂ treatment were lower. After rumen degradation for 24 hours， the dry matter degradability （DMD）， neutral detergent fiber degradability （NDFD） and acid detergent fiber degradability （ADFD） of mixed tomato pomace and alfalfa silage were significantly increased （P<0.05） by inoculation with compound Lactobacillus culture. The DMD and NDFD of JT₁ and JT₂ treatment were higher than other treatments， and the ADFD of JT₂ was the highest. It was concluded that the nutritional quality， fermentation quality and rumen degradation rate of tomato pomace and alfalfa mixed silage were significantly improved by inoculation with compound Lactobacillus. On membership function analysis of 14 measured indexes of each mixed silage treatment， JT₂ （tomato pomace∶alfalfa ratio=4∶6， inoculated with compound Lactobacillus culture， dry matter content=30.64%） was identified as the best treatment， and this formulation can be recommended for wider use.

In vivo degradation characteristics of dry matter and crude protein of four morphological fractions for five varieties maize harvested at two maturity stages

Dong-sheng GUO, Shao-xun TANG

2022, 31(10):  178-188.  DOI: 10.11686/cyxb2021402

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Maize stalk is an important source of roughage for ruminants， and its nutritional degradation characteristics are affected by variety and maturity of the maize， and also related to the composition of the component morphological parts of the maize stalk. This experiment provides data support for the utilization of maize stalk in ruminant livestock by analyzing the rumen degradation characteristics of dry matter （DM） and crude protein （CP） of different morphological parts of maize stalk at two maturity stages. Five varieties of maize： Kexiangyu No.11 （conventional maize）， Gaoyou 115 （high oil maize）， Kexiangnuoyu No.1 （waxy maize）， Huqing No.1 （forage maize） and Kexiang Tianyu No.1 （sweet maize） were selected in this experiment. Samples of the four morphological parts of leaf blade， leaf sheath， stem and husk were collected on day 17 day （milk maturity stage） and day 31 （wax maturity stage） after tasselling， and an in situ degradation technique was used to analyse the kinetic parameters of DM and CP rumen degradation in all samples. It was found that the rapidly degrading fraction （a values） of DM of leaf blades， leaf sheaths， and stems， and the a values of CP of leaf blades and husks at the wax maturity stage were higher （P<0.001） than corresponding values at the milk stage， while the slowly degrading fraction （b values） of DM of leaf blades， leaf sheaths， and stems， b values of CP of leaf blades， leaf sheaths and husks， and the effective degradability （ED） values of the husk DM at the wax maturity stage were significantly lower （P<0.001） than those of the milk stage. The a， b and ED values of the DM and CP of the different morphological parts of the new maize cultivars were similar to or higher than those of the conventional maize. Differences in DM and CP degradation kinetic parameters were also observed among different morphological components. The ED values decreased in the order of stem>husk>leaf sheath>leaf blade. In conclusion， extending the maturity period mainly affects the a and b values of DM and CP of maize stalk. Among different varieties， the ED of DM and CP was higher in high-oil and waxy maize.

Progress in research and practice of restoration of degraded grassland around the world

Li GAO, Yong DING

2022, 31(10):  189-205.  DOI: 10.11686/cyxb2022077

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Grassland is one of the most important terrestrial ecosystems on earth， and brings humankind a series of ecosystem services， including food production， climate regulation， air purification， water conservation， wind prevention and sand fixation. Nearly half of the grasslands in the world are affected by climate change and human factors， and thus display different degrees of degradation. This degradation has become one of the world’s ecological and environmental problems. Much research on restoration of degraded grasslands has been carried out around the world with findings often leading to change in practice， and great progress has been made. However， at the beginning of the UN Decade on Ecosystem Restoration （2021-2030）， a new generation of restoration research and practice projects is needed to cope with global environmental challenges. This paper summarizes the research and practice of degraded grassland restoration around the world， in the hope of learning from the existing grassland restoration work. On this basis， it is anticipated that we can map out the main direction of future research on degraded grassland restoration， and formulate reasonable restoration plans for degraded grassland， so as to provide reference information for new grassland restoration research and practice in the context of global change.

The relationships between desert shrubs and soil fauna and their responses to precipitation changes in arid regions： A review

Zhi-xia GUO, Ren-tao LIU, Wen-zhi ZHAO

2022, 31(10):  206-216.  DOI: 10.11686/cyxb2021389

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In a desert ecosystem， shrub regeneration was facilitated as part of a vegetation restoration program. Shrub regeneration was found to be one of the most efficient， economical， lasting and stable measures for desertification control in these regions. The soil fauna is an important component of soil biota in desert ecosystems， and play important roles in material recycling， energy flow and information transfer. Shrub establishment had beneficial effects on soil faunal distribution and shrubs also acted as “fertilizer islands” in the restoration of degraded ecosystems. Our study focused on the relationships between soil faunal distributions and shrub microhabitats. Firstly， we catalogued the distribution of desert shrubs and their effects on the distribution of soil faunal communities. Secondly， we probed into the underlying mechanisms of the effects of shrubs on soil faunal distribution and how these processes responded to precipitation changes in these regions. From these data we extrapolated responses under future global climate change and proposed some key topics for future study. They are： 1） The feedback of soil faunal distribution in particular shrub microhabitats on aboveground plant growth and development and related ecophysiological attributes； 2） Identification of new methods to examine the relationships between soil fauna and desert shrubs under precipitation changes； 3） The ecosystem service benefits of particular soil faunal diversity distribution patterns between shrub microhabitats in arid regions.

Priority effects on plant community assembly and ecological restoration significance

Xiao-hong YAN, Jian-ming NIU, Yuan-heng LI, Feng-yan YI, Shi-xian SUN, Ke JIN, Xi-liang LI

2022, 31(10):  217-225.  DOI: 10.11686/cyxb2021393

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Plant community assembly is a key ecological process in the restoration of degraded ecosystems. However， how to reconstruct the plant community， so as to accelerate the restoration of ecosystem processes and functions， remains a key problem that is in urgent need of a solution. The ‘priority effect’ is defined by whether species that arrive early have positive， negative or neutral effect on establishment， growth， or reproduction of species that arrive later in plant community assembly. The priority effect plays an important role in regulating the process of community structure improvement， the functional maintenance and the community succession dynamics. To the present time， studies on the priority effect have been mainly focused on North America and some European countries to better understand the impact of alien species invasion and answer questions relating to grassland diversity conservation， artificial grassland construction and management， among others. However， such research has not been conducted in China. Based on a systematic literature review， this paper summarized the current status of research on priority effects in plant community assembly， identifying the driving factors， response mechanisms and quantitative methods used. It was found that the strength and direction of priority effects were influenced by species identity， community assembly order， environmental factors and interactions between community members. Niche preemption and niche modification have been proved to be the two major driving mechanisms for priority effects. Currently there are some knowledge gaps in this research field， such as the impact of choice of study area， the limitations of shorter experiment duration， and the effects of interactions between biotic and abiotic factors. We conclude by proposing future research directions in this area， taking account of the urgent needs for vegetation restoration in China. Thus， our study provides some new insights for future researchers and new ideas for ecological restoration practice.