Table of Content

20 May 2019, Volume 28 Issue 5

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Analysis of spatio-temporal changes and climate-response of net primary production in Hulunbuir grassland

SHEN Bei-bei, DING Lei, LI Zhen-wang, XIN Xiao-ping, XU Da-wei, ZHU Xiao-yu, WANG Xu, CHEN Bao-rui

2019, 28(5):  1-14.  DOI: 10.11686/cyxb2018288

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The aim of this research was to quantitatively assess the productivity of Hulunbuir grassland and clarify the impact of climatic factors on the grassland growth processes. Our study used the MOD17A2H dataset and meteorological data to study the temporal and spatial variation of annual net primary productivity (NPP) and the relationship between NPP and climate factors in the grassland of Hulunbuir, China. We found that the annual mean value of NPP in Hulunbuir grassland gradually decreased from northeast to southwest. The average NPP value for the period 2000 to 2017 was 307 g C·m^-2, and the NPP during the 18 years has increased, with the lowest value being 242 g C·m^-2 in 2001, and the highest value being 372 g C·m^-2 in 2014. The high NPP values (>400 g C·m^-2) are mainly distributed in the eastern and western of Daxing'anling mountainous area with grassland type of lowland meadow; the median NPP values (250-400 g C·m^-2) are mainly distributed in the interlaced hills and high plains with grassland types of mountain meadow and temperate meadow steppe; the low NPP values (<250 g C·m^-2) are mainly distributed in southwest Hulunbuir where the grassland is categorized as swamp meadow and temperate steppe. The NPP of different grassland categories ranked in order: lowland meadow>mountain meadow>temperate meadow steppe>swampy meadow>temperate steppe. Climate change is also observed to be a large influence on NPP interannual variation. The correlation between NPP and precipitation is higher than that between NPP and temperature, indicating that precipitation is the more important contribution to NPP variation in Hulunbuir grassland. The response of lowland meadow and mountain meadow to climatic change is less pronounced than that of temperate meadow steppe and temperate steppe.

Plant community structure and species diversity differences in alpine grassland in the Qilian Mountains with different levels of degradation

ZHANG Jian-gui, WANG Li-de, YAO Tuo, LI Hai-yun, GAO Ya-min, YANG Xiao-mei, LI Chang-ning, LI Qi, FENG Ying, HU Yan-ting

2019, 28(5):  15-25.  DOI: 10.11686/cyxb2018302

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This research aimed to provide a theoretical basis for effective management, productivity improvement, biodiversity protection, and sustainable resource use in the restoration of Kangle grassland in the Qilian Mountains. The plant community structure and soil characteristics at selected sites with different levels of degradation were sampled and analyzed. Five diversity indexes (the Margalef index, Dominance index, Simpson index, Evenness index and Shannon index) were used to explore changes in species diversity. The results showed that: 1) As expected, aboveground biomass, vegetation height and ground cover, plant density, and plant frequency showed a decreasing trend (P<0.05), from lightly degraded grassland (LDG) to moderately degraded grassland (MDG) and from MDG to severely degraded grassland (SDG). 2) There were 39 species, 35 genera and 15 families in the study area. The plant community had strong ecological adaptability, which was mainly represented by the Fabaceae, Rosaceae, Poaceae, Asteraceae and Cyperaceae families. The dominant species of different degradation degrees were: LDG, Poa pratensis and Polygonum viviparum; MDG, Leymus secalinus and Kobresia humilis; SDG, K. humilis and L. secalinus. Poaceae had a key role in the stability of the community. 3) In defining functional groups in alpine grassland, it was found that forb plants were of primary importance, followed by graminoid plants, with harmful grass plants the least important. The importance values of forb plants at differing grassland degradation levels were 75.14% (SDG)>48.67% (LDG)>30.05% (MDG). The importance values of harmful grass plants at differing grassland degradation levels were 20.81% (LDG)>18.01% (SDG)>17.11% (MDG). 4) The highest species Dominance index within the SDG community was 0.23; the highest Margalef richness index of the LDG was 2.64 and the Shannon comprehensive index of the LDG community was 2.09. 5) With increased degree of degradation, the soil total phosphorus, total nitrogen, organic matter and water contents showed downward trends, while pH increased. In summary, with increasing degree of degradation, the change in grassland community structure exhibited a continuous single trend Kangle, while the major environmentally limiting factors changed.

Carbon sequestration characteristics of a warm shrub tussock grassland ecosystem in northwestern Henan

LI Lin, ZHAO Wei

2019, 28(5):  26-35.  DOI: 10.11686/cyxb2018309

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Dynamics of shrub populations are important factors affecting the carbon budget of natural grassland ecosystems. Shrub biomass and the soil carbon stock beneath shrubs are among the most uncertain components in grassland ecosystem carbon accounting. Warm shrub tussock is widely distributed in hilly areas in northwestern Henan and comprises a ‘typical' (i.e. reference) regional vegetation type. To elucidate the carbon sequestration characteristics of a warm shrub tussock grassland ecosystem, the carbon density of above ground shrub and herb biomass, and the associated soil carbon density were measured in seven plots of different areas in northwestern Henan, and ecosystem carbon density was calculated. The mean vegetation and mean soil organic carbon densities were 2360.07 and 4610.47 g C·m^-2, respectively. The vegetation carbon density for shrub vegetation was 981.63 g C·m^-2, while that of the herb layer was 1387.44 g C·m^-2. The carbon density was mainly contributed by the roots, which accounted for 93.04% of the total vegetation biomass. For shrubs, the root biomass was 41.51%, of total biomass; for herbs it was slightly more. The soil carbon density accounted for 62.80% of the total ecosystem carbon density. Across the seven plots measured, there were differences in the characteristics of ecosystem carbon sequestration. For vegetation carbon density, the plots ranked: P₁>P₅>P₂>P₄>P₆>P₇>P₃, but the difference was not significant (P>0.05). For soil carbon density the ranking was P₁>P₂>P₆>P₅>P₄>P₃>P₇, with significant differences between P₁ and P₄, P₃, and P₇ (P<0.05). The ranking for ecosystem carbon density was P₁>P₂>P₆>P₅>P₄>P₇>P₃, with P₁ being significantly different from P₄, P₃ and P₇ (P<0.05).

Effects of reclamation on the soil phosphorus fractions of alpine meadow in Northwest Sichuan

LEI Wei-qian, HU Yu-fu, YANG Ze-peng, HE Jian-feng, XIAO Hai-hua, SHU Xiang-yang, YANG Fan, LI Zheng-qing

2019, 28(5):  36-45.  DOI: 10.11686/cyxb2018285

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Alpine grassland in northwest Sichuan, dominated by Fritillaria cirrhosa and subject to 3 or 10 years development, was compared with nearby uncultivated natural grassland (Control) to explore the effects of development on the soil phosphorus fractions. Soil phosphorus tests were performed using a modified Hedley method. It was found that after development the levels of total phosphorus (TP), water-soluble phosphorus (H₂O-Pi), active phosphorus (NaHCO₃-P), potentially active phosphorus (NaOH-P), stable phosphorus (Dil. HCl-Pi) and highly stable phosphorus (Conc. HCl-P) were significantly lower than those of Control plots, while residual phosphorus (Residual-P) levels were significantly increased. These changes were most pronounced in the 0-20 cm soil layer. After 10 years of development, the levels of TP, H₂O-Pi, NaHCO₃-P, NaOH-P, Dil. HCl-Pi and Conc. HCl-P decreased by 16.48%, 78.98%, 57.43%, 26.06%, 16.38%, and 10.87% respectively, while Residual-P levels increased by 40.08% (P<0.05). H₂O-Pi, NaHCO₃-P and NaOH-P changed to a greater extent than the others, indicating the higher the activity, the greater the loss. With increased time under development, the ratios of H₂O-Pi, NaHCO₃-P, and NaOH-P to TP significantly decreased, while the ratios of Dil. HCl-Pi, Conc. HCl-P, and Residual-P to TP increased. In the early stages of development (0-3 years), TP and various phosphorus fractions changed faster than at the later stages (3-10 years), indicating that the losses of the various phosphorus fractions mainly occurred in the early stages of development (0-3 years).

Correlation between soil nutrient status and the bacterial community composition in alfalfa stands of different ages in the Yellow River irrigation area

ZHANG Wen-wen, LIU Bing-ru, NIU Song-fang

2019, 28(5):  46-54.  DOI: 10.11686/cyxb2018781

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The soil bacterial community composition, abundance and diversity were studied in alfalfa stands between 1-6 years of age (i.e. established 2012-2017), in the Ningxia Yellow River irrigation area. The determination of the soil bacterial community characteristics was achieved by DNA extraction followed by PCR amplification, and sequencing using the HiSeq platform. The 16S rRNA amplifier sequencing technique was used in the study. The correlation between soil nutrients and bacterial population diversity was analyzed. The results indicate that there are about 40 phyla, 78 classes, 151 orders, 275 families and 416 genera of bacteria in the soils of the various alfalfa stands of different ages. At the phylum level, the dominant genera of bacteria detected were Proteobacteria, Acidobacteria and Bacteroidetes, accounting for 68% of the total bacterial population. The ranking of bacterial abundance and diversity with stand age was: 1 yr>5 yr>3 yr>4 yr>2 yr>6 yr. Soil pH, organic carbon, total nitrogen and alkali-hydrolysable nitrogen all decreased initially, and then increased with stand age, reaching their maxima at year 5. The result is basically consistent with findings of other studies of factors affecting bacterial community composition. Analysis using Spearman's correlation showed that organic carbon, total nitrogen and alkaline nitrogen were significantly (P<0.05) correlated with bacterial community composition. In general, the dominant taxa of soil bacterial communities present in the Yellow River irrigation area did not change with stand age, but population numbers and bacterial community diversity did vary from year to year, though not with any consistent trend over time. Soil organic carbon, soil alkali-hydrolysable nitrogen and soil total nitrogen were the main factors associated with changes in bacterial taxa present across years.

Characterization of a plant-growth-promoting rhizosphere bacterium, Gnyt1, and determination of its taxonomic status

LI Jian-hong, LI Xue-ping, LI Chang-ning, HAN Bing, XU Wan-li, YAO Tuo

2019, 28(5):  55-67.  DOI: 10.11686/cyxb2018005

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The aim of this research was to define the characteristics and taxonomic status of the plant-growth-promoting rhizobacterial strain, Gnyt1. The plant-growth-promoting properties, and biological characteristics were assessed, and taxonomic status determined from consideration of phenotypic, physiological and biochemical characteristics as well as 16S rRNA sequencing. We found nitrogenase activity in Gnyt1 up to 3193 nmol C₂H₄·h^-1·mL^-1. Inorganic and organic phosphorus could both be dissolved efficiently by Gnyt1. The bacterium can also produce three plant hormones: indole-3-acetic acid (IAA), gibberellin (GA₃) and trans-Zeatin (t-Z). Gnyt1 had a good tolerance to temperature and pH, but had no resistance to the antibiotics penicillin, streptomycin, roerythromycin, and cefradine. Gnyt1 also had no detected pathogenicity to the crop species Hordeum vulgare var. nudum, Lycopersicon esculentum, Brassica napus, Angelica sinensis, and Medicago sativa. The growth-promoting properties were found to be stable and Gnyt1 promoted the growth and yield of naked barley. Its taxonomic status was preliminarily identified as Bacillus mycoides. The results show that the Gnyt1 rhizobacterial strain has excellent overall properties, making it a strong candidate for further development and utilization.

Effect of shading on photosynthetic and antioxidant characteristics of Pueraria lobata

WU Xiao, HE Xiu-juan, WU Chao, DONG Yu-feng, ZHANG Yan, XU Yu, QIN Wei-dong, LÜ Jun, WANG San-gen, ZONG Xue-feng

2019, 28(5):  68-78.  DOI: 10.11686/cyxb2018722

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Light is the main environmental factor for plants to capture energy. Severely low light conditions can reduce the photosynthetic efficiency of plants leading to limited plant growth, and excess light can also hinder plant growth and development. An experiment was undertaken to investigate changes in photosynthesis parameters and antioxidant characteristics in Pueraria lobata under different shading treatments: control (100% natural light, T₁), mild shade (75% natural light, T₂) and moderate shade (50% natural light, T₃). Seedlings of P. lobata were collected and grown in a nursery, and then healthy seedlings of uniform-size seedlings were transferred to the shade shed when seedlings had 8 or 9 leaves. Each treatment was replicated 6 times. It was found that chlorophyll a, chlorophyll b, carotenoid content and total photosynthetic pigment content were increased with the increase of shading degree, while the change of chlorophyll a/b was opposite; The net photosynthetic rate (P_n), stomatal conductance (G_s) and transpiration rate (T_r) of P. lobata decreased with increased shading, while the intercellular CO₂ concentration (C_i) was increased. The chlorophyll fluorescence parameters of minimal fluorescence (F₀), maximal fluorescence (F_m), variable fluorescence (F_v), F_v/F₀, F_v/F_m and PSII actual photochemical efficiency (Φ_PSⅡ) of P. lobata were increased with increased shading. Meanwhile, soluble sugar, soluble protein, and free amino acid levels in P. lobata leaves decreased with increased shading degree, while malondialdehyde levels and electrical conductivity increased. The antioxidant enzyme activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX) and glutathione reductase (GR) decreased with increased shading. The results indicate that low light levels cause stress to P. lobata and it is necessary to avoid low light stress when P. lobata seedlings are establishing. The mechanisms of shading effects on photosynthetic and antioxidant systems of P. lobata and on its growth in different shading treatments, need further research.

Effects of drought stress on the root morphology and anatomical structure of alfalfa (Medicago sativa) varieties with differing drought-tolerance

ZHANG Cui-mei, SHI Shang-li, LIU Zhen, YANG Fan, ZHANG Zhen-ke

2019, 28(5):  79-89.  DOI: 10.11686/cyxb2018314

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This research studied the effects of drought stress on root morphology and anatomical structure of alfalfa (Medicago sativa) varieties with differing drought tolerance. At the seedling stage, M. sativa cv. Longzhong (strongly drought-tolerant), Longdong (moderately drought-tolerant) and Gannong No.3 (drought-sensitive) were exposed to 15 days of drought stress simulated by PEG-6000 with a water potential of -1.2 MPa. Root samples of each variety were collected every 3 days. With increasing stress exposure time, root tip number, root dry weight, total root length, total root surface area and xylem area of Longzhong as well as vascular bundle diameter and the areas of vascular bundle and phloem in roots rose continuously, as expected in growing seedlings. Meanwhile, for Longdong only the latter three measures rose continuously. For Gannong No. 3, total root length, total root surface area, and the proportion of cortex thickness to root diameter increased continuously while the root dry weight, primary and secondary xylem vessel diameters, vascular bundle diameter and vascular bundle area continuously decreased. After 6 days stress, total root length, total root surface area and root volume in Gannong No.3 were significantly lower than those in Longzhong and Longdong. After 9 days stress, the average root diameter, root volume and root dry weight, vascular bundle area, xylem area and the number of secondary xylem vessels were all significantly higher in Longzhong than in Longdong and Gannong No.3. The common responses of the tested alfalfa varieties to drought were an increased total root length and number of secondary xylem vessels. Moreover, Longzhong showed significant advantages of increased root volume and root tip number and improved root anatomical structure; Longdong was able to enhance vascular bundle diameter and the areas of vascular bundle and phloem to adapt to drought stress. In contrast, when the stress exposure time exceeded 9 days, the ability of Gannong No.3 plants to transport water was curtailed because of alterations in its internal conducting tissue.

The effect of plateau pika disturbance on plant community diversity and stability in an alpine meadow

XU Hai-peng, YU Cheng, SHU Chao-cheng, JIN Shao-hong, PANG Xiao-pan, GUO Zheng-gang

2019, 28(5):  90-99.  DOI: 10.11686/cyxb2018298

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Plant community diversity and functional redundancy are useful vegetation characteristics to consider when evaluating the community stability. A field survey was carried out to determine the disturbance effects of plateau pika on plant community diversity, functional diversity, functional redundancy and community stability of an alpine meadow. It was found that plateau pika disturbance increased plant species richness, functional diversity and functional redundancy, and decreased the plant diversity index, evenness index and community stability. In disturbed areas, plant species diversity, plant species richness, functional redundancy and community stability initially increased and then later decreased with increasing the plateau pika disturbance intensity. These results suggest that research into the effect of plateau pika disturbance on the plant community diversity and stability should consider not only the disturbance, but also the intensity of the disturbance.

A comparative study on digestibility and feed intake of Tibetan sheep of different types

JIAO Ting, WU Tie-cheng, WU Jian-ping, ZHAO Sheng-guo, LEI Zhao-min, LIANG Jian-yong, RAN Fu, JIU MAI Zha-xi, LIU Zhen-heng

2019, 28(5):  100-108.  DOI: 10.11686/cyxb2018297

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Feed intake is an important factor affecting the production performance of grazing livestock and plays an important role in determining outcomes in grassland ecosystems. This research compared groups of 4 sheep of differing age and sex (lamb, 1-, 2-, 3-, and 4-year-old ewes, wethers and stud stock, of Oula, Ganjia and Qiaoke types of Tibetan sheep). For these 21 groups of sheep, the feces output and organic matter digestibility were measured using the TiO₂ inert marker method and fecal nitrogen index method respectively in order to calculate grazing intake. The correlations between the various feed nutritive value, intake and digestibility data were also evaluated. The results showed that the average grazing intake of Oula, Qiaoke and Ganjia Tibetan sheep was 1032, 835 and 956 g·d^-1, respectively. Although the grazing intake of Qiaoke Tibetan sheep was significantly lower than that of Oula and Ganjia types (P<0.05), there was no significant difference among the three Tibetan sheep types in grazing intake per kg metabolic body weight or in the ratio of dry matter intake to body weight (P>0.05). The average organic matter digestibility of the Xiahe pasture when consumed by Oula, Qiaoke and Ganjia types of Tibetan sheep was 51%, 47% and 56%, respectively, and their average feces output was 561, 484 and 467 g·d^-1, respectively, with the difference in excretion of Oula Tibetan sheep being significantly higher than the values for the other two types of Tibetan sheep. The defecation, organic matter digestibility and grazing intake of the different types of Tibetan sheep were studied while grazing natural pasture in an alpine region in order to provide a sound scientific basis for the husbandry and management of Tibetan sheep.

Effects of lactic acid bacteria and alkyl polyglycoside on yellow corn stover silage quality and fermentation in vitro

YANG Da-sheng, WANG Shui-ping, HAN Xue-feng, TANG Shao-xun, TAN Zhi-liang, YIN Meng-jie, LUO Dong-mei

2019, 28(5):  109-120.  DOI: 10.11686/cyxb2018341

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The aim of this experiment was to study the effect of lactic acid bacteria and alkyl polyglycoside addition on the quality of yellow corn stover silage and its' in vitro fermentation characteristics. A 3×3 factorial design, i.e. three lactic acid bacteria levels (0, 1×10¹⁰, 2×10¹⁰ CFU·kg^-1) and three alkyl polyglycoside levels (0, 0.10, 0.20 g·kg^-1) with three replicates per treatment was employed in this study. After the yellow silage from corn stover had completed fermentation, its rumen degradation characteristics were evaluated by in vitro fermentation techniques. It was found that the levels of lactic acid, acid detergent fiber, and dry matter in silage, specific surface area and total score of sensory evaluation significantly (P<0.05) increased, while the ratio of ammonia to total nitrogen significantly (P<0.05) decreased with increased addition of lactic acid bacteria. The potential maximum gas production (P<0.05) and the total volatile fatty acids significantly (P<0.01) increased, while the rate of gas production was significantly (P<0.05) reduced with increased lactic acid bacteria supplementation. With increased rate of alkyl polyglycoside addition, the total score and the content of acid detergent fiber and dry matter of the silage, the Zeta potential and electron mobility of microorganism in fermentation liquor and the in vitro dry matter disappearance of the silage were significantly (P<0.05) increased. The lactic acid bacteria interacted (P<0.05) with the alkyl polyglycosides with respect to crude protein content and pH value of the silage, and the proportion of acetate, isobutyrate, butyrate, valerate, and isovalerate in vitro fermentation. In conclusion, when the dosage of lactic acid bacteria was 2×10¹⁰ CFU·kg^-1 and the amount of alkyl polyglycoside was 0.20 g·kg^-1, the quality of yellow corn stover silage could be guaranteed and the degradation characteristics were be improved.

A comparative study of yield and nutritive value of nine imported oat varieties in the Valley region of Tibet, China

ZHANG Guang-yu, MA He-ping, SHAO Xiao-ming, WANG Jiang-wei, SHEN Zhen-xi, FU Gang

2019, 28(5):  121-131.  DOI: 10.11686/cyxb2018300

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A field experiment measuring yield and nutritive value was conducted to select oat varieties suitable for cultivation in the Valley region of Tibet. Varieties tested were: Aba, Qingyin No.1, Qingyin No.2, Qinghai 444, Qingyan No.1, Linna, Bianfeng, Jiayan No.2, and Qinghai sweet oat; these were planted on 8th May 2016 in 3 m×4 m plots with 3 replicates. Yield measurements included fresh weight, dry weight (DW), dry matter%, plant height, leaf/stem, and nutritional quality of the nine varieties at heading, booting and maturity stages. Nutritive value measurements included crude protein (CP), ether extract (EE), crude ash (Ash), acid detergent fiber (ADF), neutral detergent fiber (NDF), and lignin (ADL), measured at maturity. For above-ground DW at maturity, the varieties could be divided into groups of high yield (>26 t·ha^-1; Qingyan No.2, Linna, Bianfeng, and Jiayan No.2), medium yield (22-26 t·ha^-1; Qingyin1 No.1, Qingyin No.2, Qinghai 444, and Qinghai sweet oat), and low yield (<22 t·ha^-1; Aba). With respect to the nutritional quality results, the ranges observed for CP, EE, Ash, ADF, NDF, and ADL content were, respectively, 4.5%-7.2%, 21.7%-57.3%, 4.5%-5.7%, 24.9%-35.4%, 58.2%-80.5% and 30.6%-42.0%. Among variety differences in nutritive value observed were: CP, Qingyan No.1, Qingyin No.2 and Jiayan No.2 significantly lower than other varieties; ADF, Bianfeng lower and Qinghai sweet oat higher than others; NDF, Bianfeng higher and Linna lower than other varieties; EE, Qinghai 444 higher than other varieties. Based on grey relational analysis of yields and nutritional quality, it was concluded that Qinghai 444, Qingyan No.1 and Aba oats are the best performing varieties in this region.

Transcriptomic analysis of the self-incompatibility mechansim in Paspalum vaginatum by comparison with an artificial self-compatible mutant

QIAN Chen, LIU Zhi-wei, ZHONG Xiao-xian, WU Juan-zi, ZHANG Jian-li, PAN Yu-mei

2019, 28(5):  132-142.  DOI: 10.11686/cyxb2018304

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The warm-season turfgrass seashore paspalum (Paspalum vaginatum) is rapidly gaining recognition as having a potentially important contribution in a range of turf and environment conservation applications. However, self-incompatibility (SI) creates issues for seed production in seashore paspalum, consequently limiting the feasibility of large scale planting. The mechanism of SI response in P. vaginatum is still largely unknown. In addition, the lack of genomic and transcriptomic information makes it highly challenging to clarify the mechanism of SI in seashore paspalum. In order to further understand the mechanism of SI in seashore paspalum, we created a self-compatible (SC) mutant (SP2008-3) and compared the first transcriptome of SI seashore paspalum (variety Adalayd) and the SC mutant using Illumina sequencing technology. Transcriptome analysis using RNA-sequencing was performed to profile gene expression patterns in Adalayd and SP2008-3 (the SC mutant). A total of 68.17 million raw reads were obtained, and de novo assembly produced 117619 Unigenes. All assembled Unigenes were annotated by querying against public databases. 58810 Unigenes (50%) were found to be homologous to genes in the NCBI non-redundant protein (Nr) database. In further orthologous analyses, comparison of the transcriptomes found 1303 Unigenes that showed significant differences in transcript abundance between Adalayd and SP2008-3. These Unigenes were functionally annotated within the Gene ontology (GO), Kyoto encyclopedia of genes and genomes (KEGG) pathways. A large number of notable genes potentially involved in SI responses showed differential expression. We conclude these genes may encode critical regulators of SI responses. Examples of these genes include 14 CaM (Calmodulin, calcium-dependent protein kinases and CBL-interacting protein kinases), 3 F-box and 5 THL (Thioredoxin). Our data represent a genetic resource for the discovery of genes related to SI in seashore paspalum. To our knowledge, this is the first study of the transcriptome of seashore paspalum focusing on SI. This resource will be very useful for future studies on the mechanisms of SI in seashore paspalum.

Textual research on the cultivation and utilization of alfalfa in North China and adjacent areas in modern times

SUN Qi-zhong, LIU Qian, TAO Ya, LI Feng, XU Li-jun

2019, 28(5):  143-150.  DOI: 10.11686/cyxb2018276

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North China and its adjacent areas are major centres of 20th century agricultural transformation in China. Obvious changes in agricultural technology were evident, partly driven by Western learning spreading to the East. Alfalfa is a major forage crop in North China and its adjacent areas (Hebei, Chahar, Beiping, Tianjin, Henan, Shanxi, Suiyuan, Shandong and Northern Jiangsu), and played an important role in this agricultural development. The article synthesises textual criticism of agriculture-related works and scientific information from modern research, to understand the evolution of the cultivation and utilization of alfalfa in North China and adjacent regions in the modern times. We found that Qi Ru-shan examined the dialectal rendition of alfalfa in North China, and noted that alfalfa was often read as Kisu, rather than Mùxu. According to our incomplete examination of the records, alfalfa was planted in 72 counties (offices and districts) in North China in recent years. Shandong had the highest count (27 Counties), followed by Hebei (19 Counties), and Shanxi (11 Counties). These three Provinces account for 78% of the total records. Because alfalfa has been cultivated in the region for more than a millennium, some local varieties have emerged, including ‘Jinnan', ‘Weixian', ‘Wudi' and ‘Huaiyin', among others. In order to facilitate alfalfa planting in North China, the government has also created a number of policies to encourage alfalfa planting. Alfalfa has a growth pattern well suited to the climate in the North China region, and is both fed to livestock during the growing season and conserved as hay. When young, alfalfa is also suitable for human consumption. Alfalfa also plays an important role in the improvement of land with saline or alkaline soils, especially in the Shandong saline soil reclamation area and Northern Jiangsu saline soil reclamation areas. Alfalfa is normally cultivated by sowing seed in a well prepared seed bed of fine tilth. Once established, it is typically cut three times a year, with a sickle bar mower. Alfalfa stands can persist for more than 10 years, but stand longevity is reduced by waterlogging.

Status of research into the abiotic stress tolerance of Elymus species

WANG Pei, CHEN Jiu-hong, WANG Ping, MA Qing, TIAN Li-hua, CHEN You-jun, ZHOU Qing-ping

2019, 28(5):  151-162.  DOI: 10.11686/cyxb2018219

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Elymus is an economically important genus belonging to the tribe Triticeae, within the grass family, Poaceae. In China it is mainly found at altitudes of 2000-5200 m. Most species in this genus have potential as forage grasses, as they have a high feeding value. Some species show wide adaptability and excellent abiotic stress tolerance, including salt tolerance, drought resistance, and cold resistance, among others. Elymus also has a rich genetic diversity. Therefore, members of this genus are not only important species for ecological restoration, but can also provide excellent genetic resources for improvement of other grass and cereal crop species. Worldwide, there are over 30 species of Elymus, of which thirteen species are distributed in China, including Elymus sibiricus, Elymus nutans, Elymus dahuricus, Elymus breviaristatus, Elymus cylindricus, and others. In the past few years, on account of increased abiotic stress caused by global change arising from human activities, more and more researches have focused on the resistance to abiotic stresses of Elymus, including salt tolerance, drought tolerance, low temperature tolerance, resistance to heavy metals and multiple stress tolerance. Most of this research on abiotic stress tolerance of Elymus species has been carried out by Chinese researchers, and has involved a comparison between different species, and/or different varieties or germplasm lines from Elymus or related species. There is also a suite of commonly investigated physiological indicators, such as electrolyte leakage, chlorophyll content, accumulation of proline and other osmoregulatory substances, and activities of antioxidase, and related enzymes. These studies have employed a variety of analysis methods and evaluation systems, which has led to conflicting results in some cases. In addition, there has been little research into the mechanisms conferring tolerance to environmental stresses, apart from some exploration of chilling tolerance in E. nutans. This review summarizes the research progress in the last few years into abiotic stress tolerance of Elymus, and identifies the existing gaps in knowledge and the direction for future research. In this way it is hoped to lay the foundation for further extraction and utilization of the diverse genetic resources of Elymus.

Short term effects on ecosystem CO₂ exchange in a semi-arid grassland agro-pastoral ecotone, following differing levels of nitrogen application

DONG Xiao-xiao, BO Yuan-chao, SUN Jian-ping, ZHANG Xiao-lin, WANG Chang-hui, DONG Kuan-hu

2019, 28(5):  163-170.  DOI: 10.11686/cyxb2018409

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This study investigated the short-term effects of different nitrogen (N) application rates in a semi-arid grassland ecosystem in an agro-pastoral ecotone in Youyu County, Shanxi Province, China. A randomized complete block experiment was set up with 8 nitrogen levels (0, 1, 2, 4, 8, 16, 24, and 32 g N·m^-2, denoted N₀, N₁, N₂, N₄, N₈, N₁₆, N₂₄, N₃₂, respectively), and 6 replicates (48 plots in total). Ecosystem net CO₂ exchange (NEE) and ecosystem respiration (ER) under the different treatments were monitored using the static chamber method, with a fixed base for the portable chamber located in each plot before the start of the growing season, and chamber dimensions 50 cm×50 cm×50 cm. Gross ecosystem CO₂ capture was calculated from those primary data by difference, and was taken as gross ecosystem productivity (GEP). Nine measurements were undertaken at approximately two weekly intervals between June and September. Over this period, short-term N addition (except N₃₂, which had a detrimental effect) significantly increased the net carbon uptake, with peak response seen in N₁₆ and N₂₄ treatments. The responses of ER and GEP to different N addition were more sensitive than NEE. There was a significant positive correlation between 10 cm soil temperature and ER (R²=0.319, P<0.0001), while the soil moisture for the upper 10 cm was significantly positively correlated with NEE (R²=0.420, P<0.0001) and was significantly negatively correlated with GEP (R²=0.202, P=0.0004). Therefore, short-term nitrogen addition increased the net carbon uptake of this semi-arid in the agro-pastoral ecotone, grassland ecosystem. Our study provides some reference data for grassland ecosystem carbon source/sink relationships in this region.

Herbage accumulation, and nitrogen and phosphorus absorption responses of three forage species following addition of nitrogen and phosphorus fertilizer

LONG Hui-ying, ZHANG De, ZENG Li-ping, JIN Jie, HE Guang-xiong

2019, 28(5):  171-177.  DOI: 10.11686/cyxb2019008

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Herbage drymatter accumulation, and nitrogen and phosphorus absorption responses of three forage species following addition of nitrogen as urea (N) or phosphorus as superphosphate (P) fertilizer were studied over 2 seasons (2015 and 2016), in a field experiment with a randomized block design. The leguminous forage, Stylosanthes guianensis cv. Seabrana, and the forage grasses black spear grass (Heteropogon contortus) and ‘kong ying' grass (Bothriochloa pertusa) were compared with nil-fertilizer and N or P fertilizer treatments. In general, fertilizer application (especially N) delayed crop phenological development by 5-10 days. Averaged over the two growing seasons, addition of either N or P fertilizer increased forage yield by approximately 11%, but data were variable, and the yield, except B. pertusa responses to N and P were not statistically significant. Crop N and P yields (kg·ha^-1) of S. guianensis were almost double those of the two grasses tested, but only in the case of N addition to B. pertusa, was there a significant fertilizer-induced increase in forage N or P yield. Root mass of H. contortus was reduced by N or P fertilizer (P<0.05), especially by N addition. This study has provided a theoretical basis for planning the application of nitrogen and phosphorus in sub-tropical forage production. In this article, proper application of nitrogen and phosphorus is beneficial to increase the yield of the three herbages.

Effects on silage quality of mixing different ratios of rice straw with alfalfa and wheat bran

LUO Ying-jie, CHEN Gui-hua, MU Lin, HU Long-xing, ZHANG Zhi-fei, GAO Shuai, WEI Zhong-shan

2019, 28(5):  178-184.  DOI: 10.11686/cyxb2018570

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To investigate the influence of different ratios of rice straw on the fermentation quality of alfalfa and wheat bran mixed silage, this study conducted a series of experiments in which different ratios of rice straw (0, 5%, 10%, 15% and 20%) were added to the mixed silage and its fermentation quality, nutritional quality, and aerobic stability were analyzed after 30 days. It was found that: 1) There were significant differences in pH, water soluble carbohydrates (WSC), acid detergent fiber (ADF) and NH₃-N/TN between the control group (0) and the other groups (P<0.05). When the ratio of rice straw is increased, the pH, ADF, neutral detergent fiber (NDF) and aerobic stability of the mixed silage tended to increase while the values for crude protein (CP), WSC, relative feed value (RFV) and V-Score decreased. 2) As determined from the V-Score, silage quality for the 0 and 5% treatments was superior, quality of the 10% and 15% treatments was fairish and quality of the 20% treatment was considered to be inferior. 3) After 64 and 72 h aerobic exposure, the 0 and 5% treatments were 2 ℃ above ambient temperature, while the aerobic stability times for the 10%, 15% and 20% treatments were all above 168 h. Furthermore, after 4 days of aerobic exposure, the 0, 5%, 10% and 20% treatments exhibited a rapid change of pH, but for the 15% treatment the pH did not change much. In conclusion, the recommended mixing ratio for incorporation of rice straw into mixed alfalfa-wheat bran silage, is not more than 5% rice straw.

A comparative study on nutrient solutions suitable potted alfalfa plants in a greenhouse

CHENG Feng-hua, HU Jin-ling, SHI Min, DANG Shu-zhong, LI Yan-zhong

2019, 28(5):  185-191.  DOI: 10.11686/cyxb2018734

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Healthy potted alfalfa plants grown in a greenhouse are commonly used in pathogenicity tests. The growth of such test plants is strongly influenced by the environmental conditions, especially nutrient supply. In order to determine the most suitable nutrient solution for the healthy growth of potted alfalfa plants, two-day-old seedlings were transplanted into pots filled with sterilized soil, and supplied either compound fertilizer (CF), Hoagland's solution (HS), tap water (TW), or distilled water (DW). Plant growth status, plant heights and other data were recorded during the next four weeks, and biomass of seedlings at the end of the fourth week was determined. It was found that CF was obviously superior to other treatments; in this treatment, the plant growth status was the healthiest, and the leaves of the CF plants had no discoloration or dryness. Moreover, the growth rate of these plants was up to 1.15 cm·d^-1 with on average 4.28 branches per plant whereas the growth rate of TW plants was just 0.28 cm·d^-1 with no branches formed. The leaves of the TW plants were more or less dry or had even died by the end of the 4th week. Hoagland's nutrient solution proved inferior to the plant growth fertilizer. There were no significant differences between the DW and TW plants. Compared with TW plants, plant height, fresh weight, ground dry weight, root fresh weight, root dry weight, root surface area, root diameter, numbers of leaves and internode numbers of CF plants were increased, respectively, by 256%, 731%, 655%, 384%, 445%, 101%, 27%, 84% and 112%, with P<0.05 in all cases. For comparison, corresponding plant size increases for HS plants were 88%, 117%, 188%, 105%, 117%, 40%, 7%, 30% and 40%, respectively (P<0.05).