Table of Content

20 January 2018, Volume 27 Issue 1

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Orginal Article

Responses of aboveground net primary productivity of the alpine meadow steppe to climate change: simulations based on the CENTURY model

GENG Yuan-bo, WANG Song, HU Xue-di

2018, 27(1):  1-13.  DOI: 10.11686/cyxb2017117

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The CENTURY model was used to simulate the dynamic changes in aboveground net primary productivity (ANPP) in the Haibei alpine meadow steppe, based on meteorological data from 1957 to 2014 and measured data from 1998 to 2014. The CENTURY model was coupled with five general circulation models (GCMs) to simulate the impacts of changes in climate and CO₂ concentration on the ANPP in three future periods in the RCP (the latest Representative Concentration Pathways) 4.5 and 8.5 scenarios. The results showed that: 1) The trends in the measured values and the simulated values of ANPP at the research site from 1998 to 2014 were highly consistent (Pearson’s correlation coefficient, 0.67; root mean square error, 19.62 g·m^-2), indicating that the CENTURY model is applicable to the alpine meadow steppe in Haibei. 2) Over the past 50 years, the annual mean minimum temperature, annual mean maximum temperature, and annual mean temperature have significantly increased (P<0.01) in the alpine meadow steppe, and there have been marked fluctuations in annual mean precipitation, with precipitation mainly concentrated in the vegetation growing season. The average value of ANPP in the alpine meadow steppe is 271 g·m^-2. The average ANPP has shown an overall increasing trend, but the trend was not significant (P>0.05). 3) There is a positive rate of change in the ensemble average of annual mean minimum temperature, annual mean maximum temperature, annual mean temperature, and annual mean precipitation during the three future periods: the 2030s (2016-2040), the 2050s (2041-2070), and the 2080s (2071-2099) at RCP4.5 and RCP8.5, relative to the baseline period (2001-2014). If CO₂ fertilization effects are excluded, the ensemble average ANPP of the alpine meadow steppe is predicted to increase by 2.21%, 11.53%, and 17.78% at RCP4.5, and by 8.34%, 21.68%, and 40.32% at RCP8.5, during the three future periods (2030s, 2050s, and 2080s, respectively), compared with the baseline period (2001-2014). If CO₂ fertilization effects are included, the ensemble average ANPP of alpine meadow-steppe is predicted to increase by 2.89%, 14.29%, and 24.28% at RCP4.5, and by 11.57%, 31.74%, and 57.29% at RCP8.5 during the three future periods (2030s, 2050s, and 2080s, respectively). The simulated ANPP results from five GCMs showed good consistency, and the uncertainty caused by combining climate models with the CENTURY model was in a reasonable range.

Remote sensing investigation and normalization monitoring of grassland resources in karst——a case study in Guanyang County

SHI Sha-na, TANG Chuan-yong, XIE Bing-geng, LIU Min, QIN Chang-wen

2018, 27(1):  14-21.  DOI: 10.11686/cyxb2017094

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This study reports research conducted in Guanyang county, in the Guangxi Zhuang Autonomous Region, to compile a database of grassland resources. Based on the results of the second national land survey, high resolution remote sensing images (Worldview-Ⅰ and Worldview-Ⅱ) and slope and soil data from the digital elevation model (DEM), we used the object-oriented method to identify the type, area and spatial distribution of grassland resources in the karst mountain area. By the analyzing the correlation between grassland resource classification and land use status classification and the results of the modified second annual national land survey, we successfully normalized the monitoring survey of karst mountain grassland resources and compared the results with the second survey and the annual national land change survey. The data showed that in 2012, the area of grassland resources in Guanyang county was 20829 ha, including 711 ha of tropical tussock, 16246 ha of tropical shrub tussock, and 3871 ha tropical shrub tussock, with scattered trees. These areas total 32125 ha less than was recorded in the first grassland resources survey in 1986. Through analysis of the land use change survey results from 2012 to 2016, the database of grassland resources in Guanyang county was updated. The area of grassland resources in Guanyang county in 2016 was 20744 ha, 85 ha less than in 2012. Agricultural development, unused land reclamation, urban expansion, and landslides and other natural disasters, were factors contributing to the reduction of the grassland area in Guanyang county. This study provides a scientific basis for the development and utilization of karst mountain grassland resources and government decision making.

Effects of grazing intensity on soil organic matter and microorganisms in the Zoige alpine meadow

CHANG Jing-jing, XU Li, XUE Jing-yue, YANG Hao, HE Nian-peng, ZHANG Jin-jing

2018, 27(1):  22-31.  DOI: 10.11686/cyxb2017112

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Human activities have significantly affected the structure and function of the Zoige alpine meadow ecosystem. In this study, we analyzed the effects of grazing intensity on soil organic matter (SOM) and the soil microbial community in the Zoige alpine meadow. Five grazing intensity treatments, which were based on vegetation coverage, were established: D₁, coverage of 0%-20%; D₂, coverage of 20%-40%; D₃, coverage of 40%-60%; D₄, coverage of 60%-80%; D₅, coverage of 80%-100%. The SOM and total nitrogen content at 0-10 cm soil depth significantly differed among the five grazing intensity treatments (P<0.05). With increasing grazing intensity, the amounts of bacteria, fungi, actinomycetes, and Gram-positive (G⁺) and Gram-negative bacteria (G^-) decreased. The highest ratio of G⁺/G^- was in D₃, while the lowest was in D₄. The microbial diversity index decreased in the following order: D₅>D₄>D₁>D₂>D₃. The diversity index was calculated from the soil phospholipid fatty acid profiles, and did not differ significantly among the five grazing intensity treatments (P>0.05). The soil microbe content was significantly positively correlated with SOM content. The grazing intensity was closely related not only to the productivity of the alpine meadow, but also to SOM and microbial communities. Therefore, it is important to restore and maintain soil productivity by controlling the grazing intensity in this region.

Characteristics of soil seed banks in a typical grassland in the loess hilly region of Ningxia under different ecological restoration measures

ZHANG Rui, MA Hong-bin, JIA Xi-yang, ZHOU Yao, SU Ting-ting, CAI Yu-rong, ZHOU Jing-jing

2018, 27(1):  32-41.  DOI: 10.11686/cyxb2017295

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The soil seed bank is of great significance in the restoration of grassland vegetation. We investigated the density characteristics, species diversity, and similarity to the above-ground vegetation of the soil seed bank in the 0-15 cm soil layer under different restoration measures in a typical steppe in Ningxia. The restoration measures were F15 (exclosure for 15 years); S15 (contour trench, 15 years); Y15 (fish-scale pits, 15 years grassland), and F0 (long-term grazed grassland). The results showed that: 1) The soil seed bank was dominated by seeds of perennials. The F0 and S15 seed banks had the highest proportion of Gramineae seeds, and the Y15 and F15 seed banks had the highest proportion of Compositae seeds. 2) Compared with F0, the Y15, S15, and especially the F15 treatments had denser seed banks. The seed banks had different characteristics and seed pool densities. 3) Under the different restoration measures, the soil seed banks had the same degree of dominance, diversity, and evenness index, but the fish-scale pits treatment had a richer seed pool. The strongest similarity between the seed bank and existing vegetation was in the fish seed bank (0.81). 4) There were some differences between the soil seed bank and above-ground vegetation in terms of diversity, abundance, evenness, and dominance. The values of the similarity coefficient between the seed bank and above-ground vegetation were generally very low (0.37-0.55). The highest similarity between the seed bank and above-ground vegetation was in the fish-scale pits treatment; therefore, this was the best restoration measure for increasing the density and abundance of the soil seed bank in the loess hilly region of Ningxia.

Influence of herbivore exclusion on the soil seed bank and the aboveground vegetation characteristics of Agropyron mongolicum dominant desert steppe grassland

ZHAO Pan-pan, LI Guo-qi, SHAO Wen-shan, JIN Chang-qing

2018, 27(1):  42-52.  DOI: 10.11686/cyxb2017101

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Impacts of fencing on the soil seed bank (SSB) and the aboveground vegetation characteristics of an Agropyron mongolicum community in Yanchi County, Ningxia, were studied by germination, and vegetation survey techniques, respectively. The results showed that: 1) Herbivore exclosure significantly increased the SSB density. The total count of seeds in the SSB outside the enclosures was (1052±273) viable seeds·m^-2, but was (1885±100) viable seeds·m^-2 inside the enclosures. After herbivore exclosure, the number of annual species decreased by 8.2%, while seed density increased by 44.0%. 2) At sampling, there were 28 plant species (8 annuals+20 perennial species) present inside the enclosure and 32 species (7 annuals+25 perennial species) present outside the enclosure. 3) After enclosure, values for the Margalef richness index, Shannon-Wiener index, Pielou evenness index and Simpson dominance index of the SSB and the aboveground vegetation showed increasing trends, but the difference was not significant. However, the diversity of life form functional groups changed to some degree. 4) The similarity between seed banks of fenced and unfenced areas was 0.71, whereas the similarity between fenced and unfenced aboveground vegetation characteristics was 0.62, indicating that the impact of external disturbance on vegetation was greater than the impact on the seed bank. This study provides reference information useful for the restoration and management of vegetation in desert steppe areas.

Effect of sowing density of Bromus inermis on soil microbial characteristics and enzyme activities

LI Da, WANG Di, CHEN Jin-qiang, XIN Xiao-ping, XU Li-jun, YANG Gui-xia, TANG Xue-juan, GUO Ming-ying

2018, 27(1):  53-61.  DOI: 10.11686/cyxb2017265

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In this study, an experiment with different sowing densities of Bromus inermis: W₁(7.5 kg·ha^-1), W₂(15 kg·ha^-1), W₃(22.5 kg·ha^-1), W₄(30 kg·ha^-1) and W₅(37.5 kg·ha^-1) was conducted to investigate the effect of sowing density on soil microbial characteristics and enzyme (urease, phosphatase and catalase) activities. The aboveground biomass of B.inermis increased with sowing density to W₄(30.0 kg·ha^-1), and then was decreased at W₅ compared to W₄.There was no significant difference between the sowing densities in belowground biomass. For microbial biomass-C, the lowest values occurred at medium sowing densities. Microbial biomass-N in the 0-10 cm soil layer barely changed with sowing density, while in the 10-20 cm soil layer it decreased with increasing sowing density. The soil enzyme activity in the first cutting period was significantly higher than that in the second cutting period, but there was no significant difference among sowing densities within the same regrowth period. Soil microbial characteristics and enzyme activities were optimized at W₄ (30.0 kg·ha^-1).

Physiological responses of Kobresia humilis to different habitats in the alpine meadow of the Yellow River

LI Ji-lan, LI Xi-lai, MA Fu-jun

2018, 27(1):  62-72.  DOI: 10.11686/cyxb2017040

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Kobresia humilis is one of the dominant species in the alpine meadow. We analyzed the physiological and ecological characteristics of K. humilis growing in several different habitats in a small catch-pit with secondary tributaries draining into the Yellow River, near Nanqi village, Henan County, Qinghai Province. The habitats were hill top, hill slope, beach land, terrace 1, and terrace 2. We explored the interaction between K. humilis and soil factors in these habitats. Soil analyses showed that soil moisture, total nitrogen, total P₂O₅, available phosphorus, and organic matter were higher in the terrace 1, terrace 2, beach land, and hill top habitats, and lower on the hill slope. Beach land showed the lowest soil pH and total K₂O, and highest available potassium content. Therefore, soil fertility was higher in the terrace 1, terrace 2, and beach land habitats. Because of the different catch-pits in the various habitats, total biomass was higher in the terrace 1, terrace 2, and beach land habitats, and lower in the hill top and hill slope habitats. K. humilis was distributed in every habitat except on the floodplain wetland in terrace 1, and it was the dominant species in the beach land habitat. Its coverage, importance value, biomass, and proportion of total biomass were higher in the beach land habitat than in the hill slope habitat. Catalase activity and the contents of malondialdehyde, soluble protein, soluble sugars, proline, and carotenoids were higher in K. humilis from the hill top, hill slope, and terrace 2 habitats than in K. humilis from other habitats, but the chlorophyll a and b contents were lower. These indexes showed the opposite trends in the beach land habitat. Correlation analyses between soil factors and the physiological characteristics of K. humilis showed that some physiological characteristics were strongly correlated with soil moisture, pH, and total K₂O. According to these comprehensive analyses of K. humilis across a range of ecological habitats, we conclude that K. humilis is suited to growth on soil with low pH, and moderate moisture and nutrition status. It can adapt to its habitat by increasing its resistance and competitive abilities under the conditions of low soil moisture and low nutrient content.

Effects plant spacing pattern on root morphological and architectural characteristics of legume-grass mixtures

ZHU Ya-qiong, ZHENG Wei, WANG Xiang, GUAN Zheng-xuan

2018, 27(1):  73-85.  DOI: 10.11686/cyxb2017110

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In order to investigate the effect of root competition on production in mixtures of Onobrychis viciifolia and Bromus inermis, plant spacing and population density effects were varied so as to manipulate the underground competitive environment. The geometric morphology, topological structure and fractal characteristics of the root system were used to analyze and compare the changes in root structure of the two forage species in the competitive environment. The results showed that: 1) Mixed species sowing in alternate rows or increasing row spacing increased aboveground biomass of both forage species, and the root biomass and root:shoot ratio of B. inermis were also increased, while the root biomass and root:shoot ratio of O. viciifolia were not obviously changed. 2) Mixed species seeding within rows, and spacing increases resulted in increased formation of fine root (diameter≤0.16 mm) in B. inermis, and of roots in the category (diameter≤0.16-0.50 mm) of O. viciifolia. Thus the root length, root surface area and ratio of root length to root biomass increased for both species. Mixed species sowing within rows with a root barrier between, resulted in increased root diameter of both forage species, so that the root volume and ratio of root surface area to root biomass increased. 3) Under different mixed seeding patterns, the topological index (TI) of both forages was close to 1, the fixed topological index (q_a) was greater than 0.5, and the branching structures were of the fishtail shape. With increasing space between rows, there was a tendency for the topology of the roots of both forages to adopt the forked branch topology. 4) Root length, root surface, root biomass and aboveground biomass had a linear positive correlation between the two forage species, and there were significant correlations between root biomass and other root morphology parameters, and no significant correlations between root biomass and root:shoot ratios. Therefore, row spacing, planting pattern of species within rows, and population density effects changed the competitive interaction between the underground root systems of mixed B. inermis and O. viciifolia stands. Plasticity of root morphology was the ecological adaptation strategy that enabled effective utilization of water and nutrients, and more effective exploration of the root growth space.

Effects of autumn cutting on the non-structural carbon and nitrogen content in the root collar of alfalfa

ZHU Ai-min, ZHANG Yu-xia, WANG Xian-guo, TIAN Yong-lei

2018, 27(1):  86-96.  DOI: 10.11686/cyxb2017116

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To determinate the effect of autumn cutting management on alfalfa (Medicago sativa) growing in sandy soil in Horqin, changes in content of non-structural carbon and nitrogen compounds in the root collar of 8 alfalfa varieties with and without cutting were analyzed. The results showed that the starch and soluble sugar contents without cutting were significantly higher (P<0.05) than those cut at different times. Cutting on the 1st of November (when soil was regularly freezing and thawing) and October 15th resulted in higher free amino acid and soluble protein content compared to no cutting. However, cutting on December 1st (frozen soil) and no cutting resulted in higher free amino acid and soluble protein content than other cutting treatments. The free amino acid content after cutting on October 15th was significantly lower (P<0.05) than the uncut and cutting on October 1st resulted in significantly lower (P<0.05) soluble protein content than uncut plants. Both the free amino acid and soluble protein content with October 1st cutting initially increased, decreased and then stabilized. The different results from these cutting times may be related to alfalfa regrowth after cutting. Soluble sugar, starch, soluble protein, and free amino acid differed varieties, with cutting and without cutting. The C/N ratio without cutting was significantly higher (P<0.05) than that in cut plants. These results suggest that the cold winter temperatures in the Horqin region and the relatively light snow cover reduces transportation of above-ground carbohydrates to roots and that regrowth after cutting utilizes root nutrients. For these reasons, cutting in late autumn should be avoided to ensure sufficient accumulation. Alfalfa varieties with high root C/N content, such as Dongmu No.1, may offer advantages in this environment.

Leaf cuticular waxes in Poa pratensis and their responses to altitudes

YAO Lu-hua, NI Yu, GUO Na, HE Yu-ji, GAO Jian-hua, GUO Yan-jun

2018, 27(1):  97-105.  DOI: 10.11686/cyxb2017119

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Cuticular waxes are hydrophobic chemical compounds coating plant surfaces. They play key roles in protecting plants from various environmental stresses. Poa pratensis is well adapted to a wide range of mesic to moist habitats, in temperate to alpine conditions. However, little is known about its natural leaf wax profile or how the leaf wax profile changes in responses to change in the environment. In the current study, leaves of P. pratensis populations were sampled from different sites at altitudes ranging from 2600 m to 4200 m on two mountains. We analyzed the wax composition and calculated the chain length distribution of alkanes in cuticular wax and alkanes in the soil. The wax coverage from populations growing at 4200 m was higher than at lower altitudes. The most common components of cuticular waxes on leaves were primary alcohols, followed by alkanes and alkyl esters, with minor amounts of fatty acids and triterpenols. No linear relationship could be observed between altitude and the total wax coverage, nor between altitude and the amount of particular wax components. For plants growing at lower altitude, the overall abundance of primary alcohols in wax was reduced, while the abundance of alkanes increased. Our results suggest that higher altitude induces increased total wax coverage and changes the wax component composition. It is presumed these changes benefit P. pratensis by assisting adaptation to alpine environments.

Water and fertilizer interaction in Hemarthria compressa cultivation

JIN Jun-ying, ZHANG Wei-hua, WANG Da-ke, KOU Qing-qing, YUN Jian-wei, HUANG Jian-guo

2018, 27(1):  106-114.  DOI: 10.11686/cyxb2017103

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Water and fertilization management are the main agronomic decisions during artificial cultivation of Hemarthria compressa. Water treatments, including normal water supply, and light and moderate drought, and fertilization treatments, including no fertilizer, low, moderate and high fertilizer rates, were included in a pot experiment to study the effects of water and fertilizer and their interaction on the growth, yield, quality and some physiological indexes of H. compressa. The proline content of leaves was increased by reduced water supply, but was unaffected by fertilizer treatment. Under moderate drought without fertilizer, the proline content was the highest and the growth of H. compressa was the lowest, showing that the drought effect was serious, which indicates that proline accumulation is not always sufficient to overcome drought exposure effects in plants. Fertilizer resulted in increased relative water content of leaves, nitrate reductase activity, root vitality, uptake of nitrogen, phosphorus and potassium, and soil nutrient availability, which mitigated drought damage, and improved yield and quality. The light drought increased root:shoot ratio, the content of nitrogen and potassium, while there was no significant decrease in chlorophyll content, nitrate reductase activity, the phosphorus content of the plant and soil available nitrogen, phosphorus and potassium. Thus, the light drought with high fertilizer provided the best growth, yield and quality; whereas all these parameters were adversely affected in the various water treatments with no fertilizer or low fertilizer. To conclude, frequent short-term drought had no significant effect on the yield and quality, providing adequate fertilizer was applied. These findings may be relevant to achieving high yield and quality in artificial cultivation of H. compressa in the Three Gorges Reservoir area.

Effects of plateau pika (Ochotona curzoniae) on alpine meadow in Tibet

ZHANG Wei-hong, MIAO Yan-jun, ZHAO Yu-hong, WANG Xiang-tao, XU Ya-mei, WEI Xue-hong, SUN Lei

2018, 27(1):  115-115.  DOI: 10.11686/cyxb2017100

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Plateau pika (Ochotona curzoniae) is one of the more abundant rodent species found in alpine meadow pastures in Tibet. Their foraging and burrowing activities accelerate the rate of degradation of alpine meadow pasture, and have a significant negative impact on the sustainable development of local pastoral farming. To quantify the impact of plateau pika, research was carried out in alpine meadow winter pastures at 4425 m altitude near Gengxing Township, Jiangda County, Nyingchi, Tibet (N 29° 87', E 93° 38'). The grassland type is referred to locally as ‘Bangjietang’ grassland. Data on pika burrow density, vegetation characteristics, and soil seed bank status were collected for two sites differing in degree of degradation (A, unfenced and more degraded; B fenced and less degraded) and within sites A and B for subplots impacted by pika activity, and subplots from which pika had been excluded by mesh cages. Pika burrow density was 547 ha^-1 (318 in use) at site A and 480 ha^-1(270 in use) at site B. Total area occupied by burrows and mounds was 161 m²·ha^-1 at site A and 120 m²·ha^-1 at site B. At site A, key data for plots unprotected and protected from pika, respectively, were: biomass 139 and 209 g DM·m^-2; species present 21 and 15; buried seed density 3929 and 4561 seeds·m^-2; species diversity index 2.28 and 1.63; and number of plant species represented in the seed bank 23 and 9. At site B, corresponding values were: 174 and 234 g DM·m^-2; species present 18 and 11; buried seed density 4559 and 5490 seeds·m^-2; species diversity index 1.95 and 1.19; and number of plant species represented in the seed bank 17 and 8. Plant species for which seed count in the seed bank was increased by pika activity were typically seed bearing and not rhizomatous. Hence it is concluded that plateau pika activity decreased grassland biomass and the number of buried seeds, but increased the species richness, particularly of seeded species. Additionally, the above effects of plateau pika activity were more pronounced at the more degraded site A than at the less degraded site B.

Small-scale genetic structural analysis of plateau zokor (Eospalax baileyi)

LIU Li, WANG Gui-zhen, ZHOU Yan-shan, CHU Bin, MA Su-jie, JI Cheng-peng, TIAN Yong-liang, HUA Li-min

2018, 27(1):  123-130.  DOI: 10.11686/cyxb2017068

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The plateau zokor is a subterranean rodent that is one of the unique native animals living on the Tibetan Plateau. Research on the genetic structure of zokor will be useful to understand its patterns of dispersal and genetic exchange. In this study, we focused on the genetic structure of four plateau zokor populations in the alpine meadow in the eastern Qilian Mountains in northwest China. We used microsatellite marker technology to study the genetic diversity and structure of these populations. The effective alleles (Ne) value was 83.6 in the four different geographic populations. The highest average observed heterozygosity (Ho) value was 0.32, and the expected heterozygosity (He) value was 0.50. The average polymorphism information content (PIC) value was 0.40, indicating that plateau zokor have medium-level genetic diversity. A genetic structure analysis divided the four populations into two groups; one group containing the MYT (Mayingtan) population; and the other group containing XNG (Xianannigou), MYR, and MYL populations (west and east of the Maying river, respectively). The genetic distance (F_ST) values were greater than 0.05 and gene flow values were lower than 1 in the four geographical populations. These results indicated that the island-type habitat has limited genetic exchange among plateau zokor populations. Rivers and roads may have restricted the movement and exchange of individuals among and within populations.

Assessment of genetic variability in prairie grass

SUN Ming, LEI Xiong, ZHANG Xin-quan, ZHANG Cheng-lin, WU Wen-dan, ZHAO Wen-da, YANG Xiao-peng, MA Xiao

2018, 27(1):  131-141.  DOI: 10.11686/cyxb2017260

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To estimate the selection effect and breeding potential of Bromus catharticus, 21 quantitative traits of 9 new strains and 2 varieties were used to calculate phenotypic coefficients of variation, genetic coefficient of variation, heritability and genetic improvement using analysis of variance, correlation analysis and cluster analysis. Analysis of variance showed that 17 traits reached significant among 11 accessions. Among them, 14 traits had a very high level of heritability; ranked (high to low) were dry matter yield, flag leaf sheath length, first leaf width, number of primary branches per panicle, penultimate leaf width, stem diameter, seed yield per plant, plant height and total number of flowers per panicle. The remaining 3 traits had medium or medium high heritability. Genetic analysis revealed that 11 traits had a high level of genetic improvement, including plant height, penultimate leaf sheath length, first leaf width, penultimate leaf width, stem diameter, tiller number, number of panicles per plant, spikelet number, number of primary branches per panicle, dry matter yield and seed yield per plant. Three traits, first internode length, flag leaf sheath length and number of florets per spikelet showed medium level of genetic improvement while flag leaf length and number of nodes per panicle showed low rates of improvement. Performance of the 9 new strains was generally better than the existing varieties, particularly in yield related traits including plant height, leaf size, stalk diameter, basal internode length, shoot number, dry matter yield and seed yield. Among the new strains, BCS1103 had the greatest plant height, dry matter yield and shoot numbers; BCS1106 possessed wide leaves, high shoot, panicle and spikelet numbers per plant, and high dry matter and seed yield; BCS1109 possessed the long basal internodes and leaf sheath, narrow leaves, thin stem, and high primary branche numbers. In the second group, B. catharticus cv. Qiannan showed better performances than B. catharticus cv. Jiangxia in yield related traits. We suggest that plant height, flag leaf width, tiller number, penultimate leaf width, stem diameter and number of panicles per plant are the most reliable traits when considering grass yield. When focusing on the grain yield, traits like tiller number, number of panicles per plant, dry matter yield and plant height might be more reliable and effective. The new prairie grass strains are likely to be released as new varieties due to their excellent performance.

Interaction effects of exogenous salicylic acid, abscisic acid and Epichloё on Achnatherum inebrians symbiosis under low temperature stress

LIU Jing, CHEN Zhen-jiang, LI Xiu-zhang, ZHOU Jing-le, LIU Li, LI Chun-jie

2018, 27(1):  142-151.  DOI: 10.11686/cyxb2017106

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Achnatherum inebrians is an intoxicating grass found in the native grasslands of Northwest China. It forms a symbiotic relationship with Epichloё endophyte which can promote plant growth and improve abiotic and biotic stress resistance. In the present study, endophyte-infected (E⁺) and endophyte-free (E^-) seedlings of A. inebrians were grown at 5 ℃ for one month and exposed to exogenous salicylic acid (SA) and abscisic acid (ABA); the physiological response of seedlings was assessed. The results showed that, comparing with the control, ABA and SA treatments increased the total chlorophyll content, proline acid content, soluble sugar content, superoxide dismutase activity and peroxidase activity but decreased malondialdehyde content. After 4 days of growth under SA stress, Epichloё significantly (P<0.05) increased proline content and superoxide dismutase activity, by 51.8% and 62.1%, respectively. After 6 days of SA stress, the chlorophyll content, malondialdehyde content, soluble sugar content and peroxidase activity were significantly (P<0.05) improved in E⁺ seedlings (23.0%, 25.4%, 23.7% and 18.0% higher than those of E^- seedlings, respectively). Epichloё significantly (P<0.05) increased the chlorophyll content, proline acid content, soluble sugar content, superoxide dismutase activity and peroxidase activity under ABA treatment but significantly (P<0.05) reduced malondialdehyde content after 6 and 8 days of stress; the malondialdehyde content of E⁺ seedlings treated with ABA⁺ were 21.1% and 34.3% lower respectively than E^- seedlings treated with ABA^-. In conclusion, the interactions between ABA and SA and Epichloё endophytes alleviated the damage of low temperature stress on A. inebrians seedlings.

Identification and biological attributes of seed-borne bacteria isolated from lucerne cv. Gannong No.3

ZHANG Zhen-fen, SHI Shang-li

2018, 27(1):  152-160.  DOI: 10.11686/cyxb2017107

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Eight bacterial strains (ZSR9-16) were isolated from surface-sterilized seeds of Gannong No.3 lucerne using the dilution plate method. Biological functions including indole acetic acid (IAA) production, nitrogen fixation, phosphate solubilization and ability to decompose cellulose were determined for all strains. The results showed that six strains (ZSR9-12 and ZSR14-15) had the ability to produce IAA, solubilize phosphorus, fix nitrogen and decompose cellulose; ZSR9 was better than other strains. Strain ZSR13 had weak IAA production. ZSR16 had good IAA production, phosphorus solubilization, cellulose decomposition and nitrogen fixation. The morphology, phenotype and 16S rDNA sequence of all 8 strains were analyzed and revealed that they belonged to three different genera. Six Bacillus strains included B. subtilis ZSR9, B. safensis ZSR10, B. mojavensis ZSR11, B. licheniformis ZSR12, B. pumilus ZSR14 and B. atrophaeus ZSR15. ZSR13 and ZSR16 belonged to Enterobacter sp. and Terribacillus sp., respectively. These strains will be potentially very useful for improving production of lucerne.

Identification, tolerance to abiotic stress and host plant effects of endophytic bacteria HX-2 from Agastache rugosa

JIANG Xu-wen, LI He-qin, TAN Yong

2018, 27(1):  161-168.  DOI: 10.11686/cyxb2017095

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To identify microbial resources and provide a theoretical basis for high-yielding Agastache rugosa crops, an endophytic bacteria, HX-2, was isolated from healthy leaves of A. rugosa and identified through morphological observation and 16S rDNA sequence analysis. Indole acetic acid production, phosphate solubilization, salt and copper tolerance, and the effects on seed germination and seedling growth of A. rugosa were assessed in vitro and in vivo. The isolated bacterium was identified as Bacillus megaterium which is able to produce indole acetic acid and dissolve inorganic phosphorus. It was tolerant of pH’s ranging from 5.0 to 9.0, 0.5% to 8% NaCl and 0 to 6 mmol·L^-1 Cu²⁺. After inoculation with HX-2, seed germination energy, seed germination percentage, seedling height, root length, leaf area, seedling fresh and dry weights, chlorophyll content, root vigor and stem diameter of A. rugosa improved by 22.6%, 18.0%, 17.1%, 18.2%, 14.7%, 22.8%, 25.0%, 10.0%, 19.2% and 10.4%, respectively (P<0.05). These results suggest that HX-2 is a growth promoting bacteria which can be developed as a microbial fertilizer for agricultural production.

Effect of nitrogenous fertilizer on the antioxidant systems of grassland species in the Karst mountains

LIAO Jian-jun, SHEN Xiao-yun, HUO Bin, XIONG Kang-ning

2018, 27(1):  169-176.  DOI: 10.11686/cyxb2017275

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To identify the effect of different nitrogen fertilizer on grassland, fertilization and grazing treatments were applied to perennial grassland grazed by Wumeng semi-fine wool sheep in Weining County. The results showed that copper content in grasses was relatively low, but was higher than the minimum requirement for sheep. Application of nitrogen significantly increase nitrogen content (P<0.01) in herbage but there were no differences among different forms of nitrogen. Ammonium sulfate significantly increased the sulfur and zinc content (P<0.01) of herbage, but significantly decreased the selenium content (P<0.01). At the end of grazing experiment, copper, iron and selenium concentration in the blood of sheep grazing grassland treated with ammonium sulfate was significantly lower (P<0.01) than in sheep grazing ammonium nitrate treated grassland; blood zinc and sulfur were also significantly higher (P<0.01). Sheep grazing ammonium sulfate treated pasture had significantly lower (P<0.01) blood hemoglobin and hematocrit capacity than sheep grazing pasture treated with ammonium nitrate and the control (no fertilizer); antioxidant enzymes including serum ceruloplasmin, serum superoxide dismutase and serum glutathione peroxidase were significantly lower (P<0.01) than in sheep grazing the pasture treated with ammonium nitrate and the control. Malondialdehyde (MDA) content was also higher (P<0.01). There were no differences in other blood mineral element concentrations, blood indexes and serum biochemical values. It was concluded that fertilizer selection should be based on soil mineral content; grassland with low copper content is not suitable for ammonium sulfate fertilizer. Ammonium sulfate fertilizer significantly affected the antioxidant system function.

Effects of feeding high concentrate diets on glucose and lipid metabolism in the liver of lactating goats

LUO Yan-wen, TIAN Ping, HUA Can-feng, TAO Shi-yu, NI Ying-dong

2018, 27(1):  177-186.  DOI: 10.11686/cyxb2017109

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The aim of this study was to investigate the effects of short-term and long-term feeding with a high concentrate diet on glucose and lipid metabolism in the liver of lactating goats. Sixteen mid-lactating goats were randomly divided into three groups: one group was fed with a high concentrate diet for 4 weeks (HS; 65% concentrate diet, n=4); one group was fed with a high concentrate diet for 19 weeks (HL; 65% concentration diet, n=7); and the control group was fed with a low concentrate diet during the whole experimental period (LC; 35% concentrate diet, n=5). Compared with the LC group, the HS and HL groups showed significantly increased levels of plasma glucose and hepatic glycogen and markedly decreased triglyceride (TG) levels in plasma, but total cholesterol (Tch) in plasma showed no significant difference (P>0.05). The concentrations of hepatic TG and Tch were significantly increased in the HS group (P<0.05) but not in the HL group (P<0.05). Compared with the LC group, the HL group showed significantly upregulated transcript levels of the genes encoding pyruvic carboxylase and glucose transporter 2 in the liver (P<0.05). In the HS group, the transcript levels of genes encoding pyruvic carboxylase, sterol regulation element-binding protein-1, stearoyl-CoA desaturase, diacylgycerol acyltransferase, and 3-hydroxy-3-methyl glutaryl coenzyme A reductase in the liver were markedly increased, as was the protein level of phosphoenol pyruvate carboxykinase 2. The transcript levels of the gene encodingsterol regulation element-binding protein-2 tended to be higher (0.05<P<0.1), while those of the genes encoding carnitine palmitoyltransferase-1 and cholesterol 7α-hydroxylase were markedly decreased in the HS group compared with the LC group (P<0.05). These results suggested that short-term feeding with a high concentrate diet enhances gluconeogenesis and promotes lipogenesis in the liver, while long-term feeding with high concentrate dietincreases gluconeogenesis, but does not affect lipid metabolism in the liver.

Effects of alfalfa flavonoids on apoptosis of bovine mammary epithelial cells induced by lipopolysaccharide

ZHAN Jin-shun, CHEN Xiao-lian, ZHAN Kang, SU Xiao-shuang, ZHAO Guo-qi

2018, 27(1):  187-194.  DOI: 10.11686/cyxb2017098

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The aim of this study was to examine the effect of alfalfa flavonoids (AF) on apoptosis of bovine mammary epithelial cells (BMECs) induced by lipopolysaccharide (LPS). The BMECs were exposed to 4 treatments; medium containing 0 μg·mL^-1 LPS and AF (control), 1 μg·mL^-1 LPS (L), 1 μg·mL^-1 LPS and 75 μg·mL^-1 AF(L+F), and 75 μg·mL^-1 AF(F), respectively. The BMECs were cultured in cell incubator at 37 ℃, 5% CO₂. The results were as follow: 1) AF supplementation significantly reduced the viability of BMECs stimulated by LPS for 12 h (P<0.01). 2) LPS significantly increased the concentration of ROS in cells (P<0.01), whereas AF supplementation significantly reduced the concentration of ROS in cells induced by LPS (P<0.05). 3) LPS significantly increased the relative expression of IL-1β, IL-6, TNF-α, TLR2, TLR4 and MyD88 in cells (P<0.01), but the relative expression of IL-1β, IL-6, TNF-α and TLR2 in cells induced by LPS was significantly reduce by AF supplementation (P<0.01 or P<0.05). 4) LPS significantly increased the expression of p53, Caspase3, p38 and P-p38 proteins in cells (P<0.01 or P<0.05), whereas AF supplementation inhibited the expression of p53 and p38 proteins in cells induced by LPS (P<0.05). The results showed that AF could improve the viability of cells and inhibit apoptosis by reducing the concentration of ROS and that AF might play a role in protecting cells against inflammatory injure by inhibiting the TLR2/MyD88 signaling pathway.

Advances in seed breeding and production of Setaria sphacelata cv. Narok

ZHANG Mei-yan, XUE Shi-ming, NAN Zhi-biao

2018, 27(1):  195-203.  DOI: 10.11686/cyxb2017197

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Setaria sphacelata cv. Narok has been cultivated extensively in tropical and subtropical areas around the world, and has favorable forage attributes of good palatability, regeneration, and persistence. It is tolerant to grazing, drought, cold, water logging, diseases, and insect attack, and so it has been widely grown as grassland for long-term grazing and cutting. Narok has a cultivation history of more than 30 years in China, and it is one of the elite cultivars for grassland establishment and improvement, karst rocky desert restoration, and herbivore production in Southern China. However, its disadvantages are its low seed yield and degraded genus characters. Therefore, our research goal is to improve the yield and quality of Narok seeds. In this paper, we discuss the utilization status, genus rejuvenation, and seed yield components of Narok, and describe some of the crucial technologies for Narok seed production, including fertilization, clipping, and seed harvesting. We conclude that further research should focus on the selection of high-quality plant materials, and on the optimization of fertilizer regimes, clipping, and seed harvesting technologies for the breeding and seed production of Narok. The results of this study provide technical support for the seed breeding and production of Narok in China.

Advances in studies of calcium-dependent protein kinase (CDPK) in plants

WU Zhi-gang, WU Shu-jia, WANG Ying-chun, ZHENG Lin-lin

2018, 27(1):  204-214.  DOI: 10.11686/cyxb2017211

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Ca²⁺ is an important secondary messenger in signal transduction in plant cells. When plants are exposed to fluctuating environmental conditions Ca²⁺ signals are perceived and decoded by Ca²⁺ sensors (CaMs, CaMLs, CBLs and CDPKs) to elicit the expression level of related genes. Calcium-dependent protein kinase (CDPK) is a Ca²⁺ sensor playing a pivotal role in plant development, pollen tube elongation and responses to abiotic and biotic stimuli. It has the unique ability to directly transmit cytolic Ca²⁺ signals to downstream phosphorylation events in diverse substrates which can mediate interaction with 14-3-3 proteins to modulate protein functions. Most CDPKs have significant subcellular distribution, allowing them to “feel” local Ca²⁺ concentration and to act specifically with their target cells. 14-3-3 proteins are highly conserved in eukaryotic cells, which in most cases need to bind to different targets and be phosphorylated to modulate their activity. Through protein-protein interactions, 14-3-3 proteins are involved in many significant physiological processes in plants. Recent studies have revealed that the role of CDPK in phosphorylating sites in mediating 14-3-3 protein binding to form CDPK/14-3-3 complex, and have also highlighted the role of the CDPK/14-3-3 complex in regulating primary metabolism, plant hormone synthesis and flowering. In this paper, CDPK structure, subcellular localization, target protein, biological functions, especially the cross regulation between CDPK and 14-3-3 and their synergistic effect in plant signaling pathway will be discussed in depth. Our study aims are to provide a reference and indicate new directions for future CDPK research.

Characteristics of annual variation in net carbon dioxide flux in a sandy grassland ecosystem during dry years

NIU Ya-yi, LI Yu-qiang, WANG Xu-yang, GONG Xiang-wen, LUO Yong-qing, TIAN De-yu

2018, 27(1):  215-221.  DOI: 10.11686/cyxb2017231

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Grassland ecosystems are a major component of terrestrial ecosystems in arid and semi-arid regions and play an important role in regional carbon balances. Continuous observation (from 2015 to 2016) of carbon dioxide flux was conducted using the eddy covariance technique in the ‘Horqin Sandy Land’ grassland ecosystem. The study period coincided with the drought in the study area and the annual rainfall during the study was 60% of the historical average. Key results were: 1) The maximum daily absorption rates were -6.68 and -9.58 g·m^-2·d^-1, respectively, in 2015 and 2016, while the release rate was 5.69 and 5.21 g·m^-2·d^-1. 2) The amount of CO₂ absorption was -120.54 and -139.83 g·m^-2 during growing season and the emission was 230.33 and 212.82 g·m^-2 during the non-growing season. 3) The Horqin sandy grassland ecosystem was a carbon source when considered from an annual perspective. The net carbon release in 2015 (109.79 g·m^-2·yr^-1) was slightly greater than that in 2016 (72.99 g·m^-2·yr^-1). 4) There were significant correlations between net ecosystem exchange (NEE) and air temperature, soil temperature, and soil moisture. However, the response of NEE to environmental temperature and humidity was not consistent across the two years.