Table of Content

20 February 2017, Volume 26 Issue 2

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Comprehensive risk assessment of snow disasters in Qinghai Province

MA Xiao-Fang, HUANG Xiao-Dong, DENG Jie, WANG Yun-Long, LIANG Tian-Gang

2017, 26(2):  10-20.  DOI: 10.11686/cyxb2016108

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We collected data on 19 factors, including social, economic, and meteorological factors, leading to snow disasters in Qinghai Province. A combination of subjective and objective methods was used to filter these data. Then, logistic regression models were used to further screen the initial factors and identify five risk assessment factors (per capita gross domestic product, annual average temperature, number of snow-covered days, maximum snow depth, and slope). These data were analyzed using ArcGIS to construct a snow disaster average risk zoning map from 2001-2007 for the Qinghai region, to illustrate the spatial distribution of different snow disaster levels. The results of the subjective and objective analyses indicated that the key factors leading to snow disasters were not only natural and meteorological factors, but also social economic factors. The average risk distribution of snow disasters, and risk factors (maximum snow depth, slope, number of snow-covered days) showed consistent trends, in contrast to the trends in the distribution of annual mean temperature and per capita gross domestic product. The risk of snow disasters was higher in the south and lower in the north of Qinghai Province. The high risk areas were mainly distributed in the south region of Qinghai Province including Chengduo, Yushu, Xiangqian, Dari, Gande, and Maqin, while the low-risk areas included the Qaidam Basin in the northwest and the eastern agricultural region. A high risk of snow disasters was associated with topography and geomorphology. Mountainous areas above 4000 m (including the Qilian, Kunlun, Tanggula, Bayankala, and Anyemaqen mountains) were high-risk areas for snow disasters in Qinghai Province.

Temporal and spatial patterns of emissions and pollutants from grassland burned in Inner Mongolia during 2005-2014

JIN Quan-Feng, JU Yuan-Hua, YANG Xia-Jie, WANG Wen-Hui, GUO Fu-Tao

2017, 26(2):  21-29.  DOI: 10.11686/cyxb2016337

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Fire is an important disturbance in ecosystems, and fires significantly affect the atmospheric environment and human health. Combining MODIS satellite data for the Inner Mongolia region during 2005-2014 and data from the Animal Husbandry Statistical Yearbook, we estimated the burnt biomass of regional grassland. The total emissions and spatial and temporal distribution of pollutants from grassland fires during 2005-2014 were also explored using emission factor, kernel density, and kriging interpolation methods. The results indicated that the density of burned grassland biomass differed within Inner Mongolia, decreasing from the northeast to the southwest parts of Inner Mongolia. The grassland fires were distributed unevenly, both spatially and temporally, in the study area. The grassland fires showed a stable annual growth and mainly occurred in March-April and September-October every year, showing two distinct peaks. Spatially, the distribution of fire point density gradually decreased from the northeast to the southwest parts of the study area. The proportions of total grassland fires in the various regions of Inner Mongolia were as follows: Hulun Buir (48.1%), Xing’an League (7.4%), Tongliao (2.8%), Chifeng (1.9%), Xilinguole (8.3%), Wulanchabu (3.8%), Baotou (4.3%), Hohhot (1.2%), Bayanzuoer (1.0%), Erdos (20.6%), Wuhai (0.3%), and Alashan (0.3%). During the period of 2005-2014, the total emissions of various substances were as follows: CO₂ (658.31 kt), CO (39.09 kt), NOx (846.18 t), CH₄ (1.22 kt), volatile organic compounds (1.87 kt), particulate matter smaller than 2.5 μm (2.49 kt), organic carbon (1.65 kt), and elemental carbon (197. 96 t). The emission of each type of pollutant varied spatially and temporally and was significantly correlated with the density distribution of fires. In this study, we explored the spatial and temporal dynamic changes in pollutants emitted from grassland fires in Inner Mongolia. This information will underpin further research on this regional environment by providing a robust database.

Effect of simulated trampling and rainfall on soil physical properties and microorganism abundance in an alpine meadow

CHAI Jin-Long, XU Chang-Lin, YANG Hai-Lei, ZHANG Jian-Wen, XIAO Hong, PAN Tao-Tao, WANG Yan, YU Xiao-Jun

2017, 26(2):  30-42.  DOI: 10.11686/cyxb2016140

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The aim of this study was to investigate the effects of yak and Tibetan sheep trampling and rainfall on the soil characteristics in an alpine meadow. In a field experiment conducted in an alpine meadow in Tianzhu, Gansu Province, simulated trampling and rainfall treatments were applied and the soil physical properties and microbial population were analyzed. The results showed that the soil compaction and bulk density increased at 0-10 cm soil depth with increasing trampling intensity and precipitation, while the saturated hydraulic conductivity decreased. The soil respiration rate decreased with increasing trampling intensity. The soil respiration rate was decreased by 37% and 45% under heavy trampling intensity by yaks and Tibetan sheep, respectively, compared with that in the control. The soil respiration rate significantly increased with increasing precipitation (P<0.05). As the trampling intensity increased, the bacterial abundance first increased and then decreased, while the abundance of fungi and actinomycetes gradually decreased. The abundance of all three types of microorganisms increased with increasing precipitation, and the number of microorganisms decreased in deeper soil layers. Below the 0-10 cm soil layer, there was no significant difference in soil physical properties between the two trampling treatments (P>0.05). Under the same precipitation conditions, trampling by yaks had a greater compaction effect on soil than did trampling by Tibetan sheep. Soil compaction and bulk density were increased by 20% and 39%, respectively, by Tibetan sheep trampling, and by 23% and 44%, respectively, by yak trampling, compared with their respective values in the control (untrampled). The magnitude of the increase in soil respiration rate, saturated hydraulic conductivity, and abundance of all three types of microorganisms were all lower under yak trampling than under Tibetan sheep trampling treatments at the same grazing intensity. Overall, soil physical properties and microbe abundance were strongly affected by increased livestock trampling and soil moisture. The soil physical properties at 0-10 cm depth were strongly affected by livestock trampling, and yaks caused greater soil compaction and more negatively affected microorganism distribution than did Tibetan sheep.

Short-term photosynthetic responses of Medicago ruthenia var. inschanicus to simulated yak and Tibetan sheep trampling and rainfall

XIAO Hong, XU Chang-Lin, ZHANG De-Gang, ZHANG Jian-Wen, YANG Hai-Lei, CHAI Jin-Long, PAN Tao-Tao, WANG Yan, YU Xiao-Jun

2017, 26(2):  43-52.  DOI: 10.11686/cyxb2016130

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To determine the effects of yak and Tibetan sheep trampling and rainfall on the photosynthetic characteristics of Medicago ruthenia var. inschanicus, the responses of single leaf area, chlorophyll content (SPAD value), and photosynthetic gas exchange parameters to short simulated yak and Tibetan sheep trampling and rainfall were studied with a two-factor (simulated trampling and rainfall) controlled experiment in a Tianzhu alpine meadow. The single leaf area, SPAD value, transpiration rate (T_r), stomatal conductance (G_s), and net photosynthetic rate (P_n) decreased with increasing yak and Tibetan sheep trampling intensity and declining rainfall, while the intracellular concentration of CO₂ (Ci) increased. Under the same rainfall conditions, the T_r, G_s, and P_n were all higher under a light trampling intensity of Tibetan sheep and yaks than in the control (no trampling), while the Ci was lower than that in the control. The magnitude of decreases in the single leaf area, SPAD value, T_r, G_s, and P_n, and increases in C_i were greater under heavy trampling by yaks than under heavy trampling by Tibetan sheep. Simulated rainfall alone or simulated trampling alone significantly affected the tested indicators, and the interaction between simulated rainfall and simulated trampling had a significant effect on single leaf area, T_r, G_s, P_n, and SPAD value (at the final trampling stage) of M. ruthenia var. inschanicus. These results showed that the photosynthesis of M. ruthenia var. inschanicus was promoted by light trampling, but inhibited by heavy trampling by Tibetan sheep and yaks. Compared with Tibetan sheep, yaks had stronger inhibitory effects on the photosynthetic activity of M. ruthenia var. inschanicus.

Land requirements for food in different regions of China

TIAN Tian, TANG Zeng, SUN Ting-Yan

2017, 26(2):  53-60.  DOI: 10.11686/cyxb2016102

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In this study, we analyzed the changes in food consumption and land requirements for food in different regions of China, based on statistical data. The results showed that the consumption of staple crops (grain) has decreased significantly, and the consumption of animal products has increased. The per capita land requirement for staple crop production has decreased from 1116.88 to 431.08 m² in eastern China, from 931.84 to 460.06 m² in central China, and from 985.97 m² to 446.55 m² in western China. The per capita land requirement for animal production has increased from 497.22 m² to 906.18 m² in eastern China, from 189.55 to 693.67 m² in central China, and from 226.23 m² to 666.75 m² in western China. The total land requirement for food is increasing, and eastern China needs more land to produce food than do central and western China. An analysis using a decomposition approach indicated that the changes in food consumption patterns have exceeded population growth to become the major driver of increased land requirements for food. Adjusting the food production structure and guiding the population towards healthy and sustainable food consumption are important measures to ensure food security and land resource security in the future.

Identification of Fusaruim acuminatum isolated from Medicago sativa root using the EF-1α sequence analysis method

YI Ming, LIANG Jia-Jun, SHI Jian, LI Hong-Jian, CHENG Ji-Min, JIAO Feng

2017, 26(2):  61-68.  DOI: 10.11686/cyxb2016100

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Alfalfa root rot causes serious reductions in alfalfa growth and yield. To identify the species of pathogenic fungus causing root rot disease, the root rot pathogen of Medicago sativa (alfalfa) collected from pasture in Dingbian County, Shaanxi Province, was analyzed by morphological observations, EF-1α sequence analysis, and inoculation tests. The mycelium and spores of a single colony of the pathogen growing on culture medium were observed under a microscope. Based on its morphology, the pathogen was identified as a Fusarium fungus. The genomic DNA was extracted from the pathogen using the cetyl-trimethylammonium bromide method, and the translation elongation factor gene was selected for PCR amplification, gel recycling, purification, cloning, sequencing, and phylogenetic analyses. A phylogenetic tree constructed using MEGA and sequences available in Genbank showed that the pathogen had the closest relationship with Fusarium acuminatum (99%). In the root inoculation test, the disease symptoms of roots inoculated with the isolated pathogen were the same as those characteristic of root rot disease of M. sativa in the field. Together, these results verified that the pathogen causing root rot disease of M. sativa in Shaanxi Province is F. acuminatum.

Effects of cadmium and arbuscular mycorrhizal fungi inoculation on the growth and nitrogen uptake of alfalfa (Medicago sativa)

LIU Fang, JING Shu-Xuan, HU Jian, XIAO Yan, ZHANG Ying-Jun

2017, 26(2):  69-77.  DOI: 10.11686/cyxb2016133

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A pot experiment in a greenhouse was conducted to investigate the growth and nitrogen (N) uptake of Medicago sativa inoculated with different arbuscular mycorrhizal fungi [Glomus aggregatum (Ga), Glomus etunicatum (Ge), Glomus intraradices (Gi), Glomus tortuosum (Gt), Glomus versiforme (Gv)] or un-inoculated in soil without or with cadmium at two concentrations (6 and 12 mg Cd/kg). Mycorrhizal colonization of alfalfa inoculated with Ga, Gi, and Gt was 33.90%, 19.17%, and 31.95% lower, respectively, in 12 mg Cd/kg soil than in 0 mg Cd/kg soil. In soil without Cd, the biomass of the Gt-inoculated plants was 33.19%, 64.74%, 57.29%, and 34.91% higher than that in the Ga, Ge, Gi, and Gv treatments, respectively. In 12 mg Cd/kg soil, the biomass of the Gt-inoculated plants was 16.67%, 34.07%, 32.96%, and 52.76% lower than that of those inocluated with Ga, Ge, Gi, and Gv, respectively. Compared with uninoculated plants, those inoculated with Gv showed significantly increased shoot height, number of nodules, shoot biomass, total biomass, shoot N content, and total N content (by 65.41%, 95.24%, 61.87%, 50.30%, 5.83%, and 71.55%, respectively) in soil containing 12 mg Cd/kg. The N₄⁺-N and N₃^--N concentrations in soil significantly decreased with increasing Cd levels in the Gv-inoculation treatments. These results showed that Gv inoculation promoted the growth and N uptake of alfalfa in Cd-contaminated soils, whereas Gt inoculation could not benefit the growth of alfalfa grown in soils containing more than 6 mg Cd/kg.

Identification of alfalfa root rot caused by Fusarium chlamydosporum and screening of antagonistic bacterial strains

BAI Yu-Jing, YAO Yu-Ling, ZHANG Zhen-Fen, YANG Cheng-De, XUE Li

2017, 26(2):  78-87.  DOI: 10.11686/cyxb2016111

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To identify the causal pathogens of alfalfa root rot with strong pathogenicity, pathogens were isolated from alfalfa (Medicago sativa) plants with alfalfa root rot growing in Wuwei City, Gansu Province. The pathogens were identified based on their morphology and by molecular methods. The results showed that the strain MXGF7 caused acute root rot of alfalfa. Most of its macroconidia were fusiform or sickle-shaped (3.3-4.7 μm×14.8-32.0 μm), and its microconidia were fusiform or dumbbell-shaped (2.9-4.2 μm×8.4-18.2 μm). The ITS sequence and the Fu3/Fu4 specificity gene sequence of the pathogenic fungus shared 99% similarity with those of Fusarium chlamydosporum, and so the pathogenic fungus was identified as F. chlamydosporum. We isolated 123 endophytic bacterial strains from alpine grassland in the Eastern Qilian Mountains, and evaluated their ability to antagonize the pathogenic strain of F. chlamydosporum. Sixty-one of the bacterial strains showed an antifungal ratio greater than 55%. The most antagonistic bacterium, strain 265ZY3, was identified as Bacillus amyloliquefaciens based in its morphology and 16S rDNA gene sequence.

Structural changes in leaves in Medicago sativa infected with Erysiphe pisi

ZHANG Yong-Mei, MA Hui-Ling, TANG Yun-Zhi

2017, 26(2):  88-94.  DOI: 10.11686/cyxb2016123

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To explore the relationship between plant cell structure and disease resistance, two alfalfa (Medicago sativa) cultivars with different levels of resistance were analyzed after inoculation with the powdery mildew fungus, Erysiphe pisi. Leaves were harvested at 0, 3, 7, and 10 days after inoculation, embedded in paraffin, and cut into sections to observe cell structural changes. The cellular structure of palisade tissue changed after infection with E. pisi. Palisade cells of the resistant alfalfa line changed from a single long cylindrical cell into several subrotund cells that were distributed evenly and arranged compactly. The mesophyll cell layer increased from 4-5-cells thick before infection to 7-8-cells thick after infection. There were two notable changes in the palisade cell structure of susceptible alfalfa. One was that long cylindrical palisade cells changed into several subrotund cells with a non-uniform distribution and more space between cells. The other was that palisade cells near vascular bundles retained their long cylindrical shape and stayed in a compact arrangement with only small spaces between cells.

A high-grain diet promotes expression of MCT1 and Na⁺/K⁺-ATPase mRNAs in the ruminal epithelium of goats

LIU Jun-Hua, ZHU Wei-Yun, MAO Sheng-Yong

2017, 26(2):  95-101.  DOI: 10.11686/cyxb2016121

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The objective of this study was to investigate the effect of a high-grain (HG) diet on the ruminal epithelial structure and the transcript levels of genes encoding monocarboxylate transporters (MCTs) and a Na⁺/K⁺-ATPase in goats. Ten ruminally fistulated, castrated male goats were randomly assigned to either a hay diet (Hay,0% grain, n=5) or a HG diet (HG,65% grain, n=5) with continuous feeding for 7 weeks. Each week, at 0, 2, 3, 4, 6, 8 and 12 h after morning feeding, rumen fluid was collected to monitor the changes in ruminal pH. The rumen fluid collected at 0, 3, 6, and 12 h after morning feeding was used to determine the volatile fatty acid (VFA) concentration. The results showed that, compared with the control, the HG diet significantly reduced rumen pH, acetate concentration, and the acetate-propionate ratio (P<0.001), and significantly increased the concentrations of ruminal propionate, butyrate, and other VFAs (P<0.001). The HG diet significantly increased the length but decreased the width of rumen papillae. The surface of the rumen papillae did not differ significantly between the two groups. The HG diet caused substantial damage to ruminal epithelial cell mitochondria. Compared with the hay-fed group, the HG-fed group showed increased transcript levels of genes encoding MCT1 (P<0.001) and the Na⁺/K⁺-ATPase (P=0.001), but decreased transcript levels of the gene encoding MCT4 (P=0.041). There was no significant difference in the transcript levels of MCT2 between the hay-fed and HG-fed groups (P=0.305). Correlation analyses revealed that the transcript levels of the genes encoding MCT1 and Na⁺/K⁺-ATPase were negatively correlated with ruminal pH and acetate concentration, but positively correlated with total VFA, propionate, and butyrate concentrations. The MCT4 mRNA level was positively correlated with pH, but negatively correlated with total VFA, propionate, and butyrate concentrations. These results suggested that the changes in ruminal pH and VFA concentrations were associated with the changes in the expression levels of MCTs and Na⁺/K⁺-ATPase. These findings provide important information for understanding HG diet-induced ruminal epithelial function disorder in ruminants.

Molecular cloning and expression analysis of ZjCSD from Zoysia japonica

ZHANG Xue, SUN Xin-Bo, FAN Bo, ZHANG Yin-Bing, HAN Lie-Bao, XU Li-Xin

2017, 26(2):  102-110.  DOI: 10.11686/cyxb2016260

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Copper/zinc-superoxide dismutase (CSD) is a key enzyme involved in the plant response to abiotic stress. Its content and activity is closely related to the stress tolerance of plants. The ZjCSD gene was isolated from the transcriptome database of Zoysia japonica by homologous cloning. It encoded a protein of 152 amino acid residues. Bioinformatics analysis revealed that the protein encoded by ZjCSD gene was stable, hydrophobic, acidic, fat-soluble, and located in the cytoplasm. With typical Cu²⁺ and Zn²⁺binding sites, ZjCSD belonged to the plant SOD super family. A homology analysis based on the deduced amino sequence indicated that ZjCSD had a closer relationship with CSD from Setaria italica and Zea mays than with CSDs from other plants. The expression profiles of ZjCSD in different tissues and under different stress treatments were investigated by qRT-PCR. Transcripts of ZjCSD were detected in the root, stem, and leaf. The highest transcript levels were in the leaf. The ZjCSD mRNA levels were up-regulated by salt, drought, and cadmium stress, and down-regulated by lead stress. These results suggested that ZjCSD might play a role in drought, salt, and heavy metal stress tolerance in Z. japonica.

Heterosis, genetic and correlation analysis of main agronomic traits in F₁ population derived from crossing between Miscanthus sacchariflorus and M. lutarioriparius

AI Xin, JIANG Jian-Xiong, CHEN Zhi-Yong, QIN Jing-Ping, YI Zi-Li

2017, 26(2):  110-122.  DOI: 10.11686/cyxb2016370

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A F₁ population with 232 individuals was developed from a cross between Miscanthus sacchariflorus and M. lutarioriparius, two Miscanthus species significantly different in the main agronomic traits. A total of 12 traits including the number of nod (Non) , the length of leaf (Lol), the width of leaf (Wol), the length of main stem (Lms), the length of flower stalk (Lfs), the length of inflorescence (Loi), the plant height (Ph), the basal stem diameter (Sd), the number of tillers (Not), the average dry weight of single tiller (Wsl), the average dry weight of the biggest single tiller (Wbt), the weight of individual plant (Wop) were determined, and then subjected to genetic and correlation analysis using a mixed major gene plus polygene inheritance model. The results showed that each of trait produced a continuous, single peak and skewed distribution pattern, suggesting that they are quantitative traits. Except for the stem diameter (Sd), the other 11 traits exhibited a mid-parent heterosis, especially in which the Wop, Wsl, Loi, Not, Lms, Ph and Wbt even exhibited a heterobeltiosis, which indicates that the hybrid heterosis would be a major breeding method for Miscanthus. In addition, the mixed factors genetic analysis indicated that the performance of Lfs and Wbt might be controlled by a pair of major genes, and those of Wol, Lms, Ph, Not, Wsl and Wop by 2 pairs of major genes. The orders of the heritability of major genes for each trait are as follows: Wol (87.76%)>Wsl (81.48%)>Wop (65.12%)>Not (59.20%)>Lms (49.87%)>Ph (48.01%)>Lfs (47.75%) >Wbt (37.19%). Some yield-related traits comprising ‘Wop’, ‘Wsl’ and ‘Not’ are suitable to be selected in early generation because they are with a higher major gene effect. Correlation analysis among traits revealed that Wop is positively correlated with Non, Lms, Ph, Sd, Not, Wsl, and Wbt. Of those, Not, Wsl, Lms and Ph gave the highest correlation with Wop, and thus these traits could be selected indirectly according to their related trait performance in breeding practice.

Effects of seeding rate on plant number, production performance, and quality of alfalfa

WANG Yan-Hua, WANG Cheng-Zhang, LI De-Feng, ZHENG Ai-Rong, QI Sheng-Li, LI Guan-Zhen

2017, 26(2):  123-135.  DOI: 10.11686/cyxb2016313

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To determine the effects of seeding rate on the quantity, production performance, and quality of different alfalfa varieties, we used a split-plot design with three seeding rates (15.0 kg/ha, 22.5 kg/ha, 30.0 kg/ha) as the main plot, and eight different fall-dormant alfalfa varieties as the subplots. The results showed that the wintering rate ranged from 85.53%-98.24%, and did not differ significantly among the three seeding rates for any of the alfalfa varieties. The dormant and semi-dormant alfalfa varieties had higher wintering rates than those of non-dormant alfalfa varieties. Therefore, dormant and semi-dormant alfalfa varieties should be cultivated in Henan Province. The seeding rate significantly affected the number of plants. As the seeding rate increased, the number of plants increased, especially in the first growing year (2011.10.5-2012.10.6). On the whole, as the number of cultivation years increased, the number of alfalfa plants decreased sharply at an early stage (2012), decreased slowly at the middle stage (2013), and stayed the same at the later stage (2014). The seeding rate did not affect the dry matter yield of alfalfa. In the first year, as the seeding rate increased, the dry matter yield of alfalfa increased slightly, but there was no significant difference among the three treatments. Over the three growing years, the dry matter yield was higher for the middle seeding rate (22.5 kg/ha) than for the other two seeding rates. The seeding rate affected alfalfa plant quality. The crude protein content, ether extract, and relative feed value increased with increasing seeding rate, and the neutral detergent fiber and acid detergent fiber contents decreased. The dry matter yield and nutritive value differed among the alfalfa varieties, with the 'Concept' cultivar showing the best yield and quality. In conclusion, it is advisable to cultivate semi-fall dormant alfalfa varieties in Henan Province, and the sowing density should be 22.5-30.0 kg/ha. In practice, suitable varieties and seeding rates should be selected according to the intended purpose of the crop.

Effect of coumarin on Italian ryegrass seed germination and seedling growth

YAO Dan-Dan, WANG Jing-Yi, ZHOU Qian, TANG Qian, ZHAO Guo-Qi, WU Cai-Xia

2017, 26(2):  136-145.  DOI: 10.11686/cyxb2016303

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To study the mechanism of allelopathy, the effects of coumarin on Italian ryegrass seed germination and seedling growth were evaluated in a sand-culture experiment. Compared with the control, coumarin treatment significantly (P<0.05) reduced the germination rate, root length, root dry weight, stem length, stem dry weight, and leaf dry weight of Italian ryegrass. The seedlings treated with coumarin showed significantly decreased indole acetic acid oxidase activity and lower chlorophyll content, compared with those in the control. The coumarin treatment also significantly (P<0.05) increased the water soluble carbohydrate content and protein concentration in seeds on days 4 and 6, increased catalase activity and starch content, and decreased peroxidase activity in Italian ryegrass seedlings during the early growth period. The results showed that an aqueous coumarin solution at a concentration of 100 μg/mL could control Italian ryegrass seed germination and seedling growth at the early stage, but it did not have a lethal effect. Coumarin inhibited endosperm function, disrupted the nutrient supply for seed germination, and destroyed cell membranes and cell walls in the endosperm, possibly leading to plasmolysis with water loss from cells.

Allelopathic effects of aqueous extracts from Xanthium spinosum on seed germination and seedling growth of Lactuca sativa var. longifolia

DONG Fang-Hui, LIU Ying, LENG Jia-Ming, YU Wei-Li, ZHAO Yu

2017, 26(2):  146-160.  DOI: 10.11686/cyxb2016188

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Xanthium spinosum is a noxious invasive weed that is spreading throughout Xinjiang Province. This plant threatens ecological safety, biodiversity, and agricultural development in affected areas. Because X. spinosum has shown strong adaptation to the divergent environment in the Ili River valley, samples of X. spinosum collected from this area were used as the research material in this study. To explore the allelopathic effects of this weed on vegetation succession and to determine the chemical mechanism of its noxious invasion, seeds of lettuce (Lactuca sativa var. longifolia) were treated with different concentrations of an aqueous extract of X. spinosum. The germination rate, germination energy, and germination index of lettuce seeds all decreased with increasing concentrations of the aqueous extract, and the germination speed was inhibited to different degrees. Compared with the control group, the seedlings treated with the extract at a concentration of 0.01 g/mL showed significantly inhibited root length. As the concentration of the aqueous extract increased, the root length of seedlings was significantly inhibited and there were significant differences in root length among the different treatments. The aqueous extract at a concentration of 0.08 g/mL showed the strongest inhibitory effect on seedling root length. The index of allelopathic effect (RI) decreased as the concentration of aqueous extract increased and the duration of the treatment extended. The results indicated that the aqueous extract of X. spinosum contained some allelopathic substances that inhibited seed germination and root elongation. The results of this study provide important information on the allelopathic effects of X. spinosum on vegetation succession and on the chemical mechanism of its invasion.

Diversity and diffusion dynamics of the ground-dwelling carabid beetle community in alfalfa fields and boundary edges of their adjacent crops

ZHANG Yan-Rong, HU Wen-Chao, LV Miao-Miao, HONG Bo, GUAN Xiao-Qing, HE Da-Han

2017, 26(2):  153-160.  DOI: 10.11686/cyxb2016114

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We conducted a pitfall trap survey in alfalfa fields and the boundary edges of their adjacent crops in Northwest China from May to July 2014-2015, to investigate the species and individuals in the ground-dwelling carabid beetle community. We selected four different habitat interfaces: alfalfa-wheat, alfalfa-corn, alfalfa-tree land, and alfalfa-fallow grassland. The component species, community diversity, and diffusion dynamics of carabid beetles in these habitats were analyzed. During the field research, we collected a total of 9239 carabid beetles belonging to 21 species. Chlaenius pallipes, Harpaluscal ceatus, and Chlaenius touzalini were the dominant species, accounting for 41.17%, 18.77%, and 17.07% of the total number of individuals, respectively. The four habitat interfaces were ranked based on carabid abundance index as follows: alfalfa-tree interface>alfalfa-wheat interface=alfalfa-corn interface>alfalfa-fallow interface. Similarly, the four types of alfalfa fields were ranked based on their Shannon-Wiener diversity index as follows: alfalfa field adjacent to wheat>alfalfa field adjacent to tree land>alfalfa field adjacent to corn>alfalfa field adjacent to fallow land. The alfalfa field adjacent to wheat also showed the highest evenness and dominance indices. The Shannon-Wiener index was higher at the edge of alfalfa fields than in their adjacent crop fields, indicating that the ground-dwelling carabid beetle community showed significant seasonal migration dynamics between the edge of alfalfa fields and their adjacent crop fields. The results indicated that different habitat interfaces, alfalfa mowing, irrigation, and other agricultural operations significantly affect the migration dynamics of ground-dwelling predators.

Dry matter production and water use of winter wheat-forage catch crop rotation systems on the Longdong Loess Plateau

DENG Jian-Qiang, LIANG Zhi-Ting, LIU Yuan-Bo, WANG Zi-Kui, SHEN Yu-Ying

2017, 26(2):  161-170.  DOI: 10.11686/cyxb2016131

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A field experiment was conducted to study the effects of winter wheat/forage catch crop rotation systems on dry matter production and water use. This experiment was conducted at the Qingyang Experimental Station of Lanzhou University, which is located in the central part of the Loess Plateau. Four crop rotation systems were tested: fallow/winter wheat (Triticum aestivum)/vetch (Vicia sativa)/winter wheat (F-W-V-W); fallow/winter wheat/rape (Brassica campestris)/winter wheat (F-W-R-W); rape/winter wheat/vetch/winter wheat (R-W-V-W); and rape/winter wheat/rape/winter wheat (R-W-R-W). The results showed that the system productivity of R-W was 27% higher than that of F-W. Compared with F-W, R-W showed 1100 kg/ha greater crude protein yield, but there was no significant difference in the yield of winter wheat stubble. Among the four cropping systems, the R-W-R-W rotation system showed the highest dry matter production, crude protein yield, water use efficiency, and protein water use efficiency [30.68 t/ha, 3.25 t/ha, 7.80 kg/(mm·ha), and 0.92 kg/(mm·ha), respectively]. The yield and water consumption of rape were higher than those of vetch, indicating that precipitation after the winter wheat crop was used more efficiently by rape. However, the protein content of vetch was 22.4% higher than that of rape. This result highlighted the importance of evaluating the relationship between dry matter production and crude protein yield to judge the benefits of different rotation systems.

Effects of wheat/maize/soybean intercropping and nitrogen fertilizer on growth and nitrogen uptake of maize

CHEN Yuan-Xue, WANG Ke, ZHAO Ya-Ni, WANG Jia-Rui, XU Kai-Wei

2017, 26(2):  171-179.  DOI: 10.11686/cyxb2016125

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The aim of this study was to evaluate the effects of wheat/maize/soybean intercropping and nitrogen levels on maize growth and nitrogen (N) uptake. We conducted a double-factor randomized block experiment with two planting patterns (sole cropping and wheat/maize/soybean intercropping), with three N levels (0, 180, and 360 kg/ha) in 2013 and four N levels (0, 90, 180, and 270 kg/ha) in 2014. The overall aim was to determine the effect of N fertilizer and intercropping on maize yield, and then to further improve the wheat/maize/soybean intercropping system. The results showed that: 1) intercropped maize in the N₀ and N₉₀ treatments showed 20.5% and 7.5% lower yields, respectively, than that of sole-cropped maize (i.e., an intercropping disadvantage). In the N₁₈₀, N₂₇₀, and N₃₆₀ treatments, there was no significant difference in maize yield between the sole cropping and intercropping planting patterns. As the nitrogen supply increased, the dry matter content in maize first increased and then decreased. The maximum dry matter accumulation rate in maize was at the spinning to harvest stage. Compared with sole-cropping, intercropping significantly and negatively affected the stem growth of maize in all N treatments. The maize stem growth rate was 12.5% lower in the intercrop than in the sole crop at the jointing stage, but this effect was mitigated when the amount of N fertilizer applied was 180 kg/ha or greater. The maize biomass and N accumulation in maize were significantly lower in the intercropping system than in the sole cropping system, and N transformation from nutritional organs to the seeds was also lower in the N₀ and N₉₀ treatments than in the sole cropping system. In the N₁₈₀, N₂₇₀, and N₃₆₀ treatments, the maize biomass and N accumulation in maize did not differ significantly between the two cropping systems, while the N transformation rate was higher in the intercropping system than in the sole cropping system. The highest N optimum transport index was in the N₁₈₀ and N₂₇₀ treatments, indicating that these treatments were most favorable for N-transporter function. In conclusion, it is important to provide the right amount of N to provide stability to the wheat/maize/soybean relay-planting system. Optimizing the amount of N supplied can increase maize yield, improve the efficiency of N absorption and transport, and reduce the effects of the growth and N absorption of maize on wheat. Under the conditions of this study, the amount of N fertilizer required for intercropped maize was 180 kg/ha.

Fertility and nitrification characteristics of two typical paddy soils after application of milk vetch (Astragalus sinicus) for 8 years

WANG Yan-Qiu, GAO Song-Juan, CAO Wei-Dong, LI Jing-Huan, NIE Jun, XU Chang-Xu, BAI Jin-Shun, ZENG Nao-Hua, ZHOU Guo-Peng

2017, 26(2):  180-189.  DOI: 10.11686/cyxb2016281

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Two green manure experiments in Hunan and Jiangxi provinces were conducted in this study. The soil types at the two experimental sites were purple alluvial soil in Hunan and yellow clayey soil in Jiangxi. Soil properties, nitrification activity, potential nitrification rate, and the abundance of AOA (ammonia-oxidizing archaea) and AOB (ammonia-oxidizing bacteria) amoA gene transcripts were determined to evaluate the effects of application of milk vetch for 8 years on soil fertility, nitrification characteristics, and ammonia oxidizers. The two experiments had the same treatments: 1) no fertilizer and milk vetch (CK); 2) milk vetch but no chemical fertilizer (GM); 3) chemical fertilizer but no milk vetch (CF); 4) chemical fertilizer and milk vetch (GM+CF). The results showed that the application of milk vetch improved the pH of both the paddy soils; i.e., the pH of acidic soil in Jiangxi was increased and that of alkaline soil in Hunan was decreased. Application of milk vetch increased the soil organic matter, total nitrogen, ammonium nitrogen, and available phosphorus. The two paddy soils had different nitrification abilities, both the nitrification activity and potential nitrification rate were much higher in purple alluvial soil than in yellow clayey soil. In purple alluvial soil in Hunan, the nitrification activity ranged from 0.269 to 0.325 μg/(g·h) in all the treatments, and there was no significant difference among the treatments. The potential nitrification rate in purple alluvial soil reached 10.25% at the fifth week of incubation, and the GM+CF treatment inhibited nitrification ability to some extent. In yellow clayey soil in Jiangxi, the nitrification activity ranged from 0.010 to 0.021 μg/(g·h) in all the treatments. The potential nitrification rate in yellow clayey soil increased after the third week of incubation and reached 5.41% by the fifth week. Compared with the control, winter green manuring improved the soil nitrification activity and potential nitrification rate, and had almost the same effects as the CF treatment. The GM+CF treatment had the strongest effect to promote the nitrification ability of yellow clayey soil. Transcripts of AOA were predominant in both purple alluvial soil and yellow clayey soil, and the abundance of AOA-amoA transcripts was significantly higher in purple alluvial soil than in yellow clayey soil. The application of milk vetch did not significantly affect the abundance of AOA-amoA and AOB-amoA transcripts in purple alluvial soil, but increased their abundance in yellow clayey soil, similar to the effects of milk vetch to promote nitrification activity and the potential nitrification rate.

Effect of additives on the quality and aerobic stability of rice straw silage

GUO Hai-Ming, XIA Tian-Chan, ZHU Wen, ZHANG Yong, YE Jun-An

2017, 26(2):  190-196.  DOI: 10.11686/cyxb2016124

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The effects of different additives on the fermentation and aerobic stability of rice straw silage were studied under laboratory conditions. The treatments were no additive (CK); Lactobacillus (L); a mixture of Lactobacillus and cellulose (LC); a mixture of Lactobacillus and molasses (LM); and a mixture of Lactobacillus, cellulose, and molasses (LMC). The Lactobacillus, cellulose, and molasses were applied at the rate of 5×10⁵ cfu/g, 0.6 IU/g, and 20 mg/g fresh weight, respectively. After 90 days of ensilage, the quality of rice straw silages was assessed and their chemical composition was determined. The pH value, NH₃-N, and organic acid contents in fermented juice were determined and the aerobic stability of the silages was evaluated. The comprehensive score was significantly higher for the silages with additives than for the control silage (P<0.05). Compared with the control silage, the LC and LMC silages showed significantly (P<0.05) lower acid detergent fiber content, resulting in higher residual water soluble content. Compared with the control silage, the L, LM, LC and LMC silages showed higher lactic acid concentrations, especially the LC and LMC silages (P<0.05). The total acid content was significantly lower in the control silage than in the LC and LMC silages, but did not differ significantly among the control, L, and LM silages (P>0.05). The aerobic stability and aerobic deterioration did not differ significantly between the control silage and those with additives (P>0.05). In conclusion, the results showed that addition of Lactobacillus increased the lactic acid content and comprehensive evaluation score of silage. Addition of molasses and/or cellulose with Lactobacillus improved the quality of rice straw silage.

Plant root decomposition and its responses to biotic and abiotic factors

LUO Yong-Qing, ZHAO Xue-Yong, WANG Tao, LI Yu-Qiang, ZUO Xiao-An, DING Jie-Ping

2017, 26(2):  197-207.  DOI: 10.11686/cyxb2016136

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The plant root system plays an important role in ecosystem matter exchange and energy flux, and root decomposition is one of the main contributors to these processes. Matter accumulates in roots and is then released back into the roots’ surroundings, including the atmosphere and soil, via the decomposition process. Root decomposition is affected by multiple biotic and abiotic factors. In terms of biotic factors, the chemical characteristics of roots are among the main factors affecting their decomposition. Other factors such as root lifespan, size/diameter, and the abundance and types of fungi and other microbes in soil also affect plant root decomposition, and their effects can be explained by their ability to alter the chemical characteristics of plant roots. Root exudates and changes in the abundance and activities of soil microorganisms that degrade plant roots affect the root decomposition rate. In terms of abiotic factors, water and temperature are the main factors affecting root decomposition. Other factors related to climate change, for example, nitrogen deposition and carbon dioxide concentrations, will affect the root decomposition rate to different degrees, the extent of which is currently unknown. In this study, we reviewed the process of matter release during plant root decomposition, and summarized the current knowledge on how different biotic and abiotic factors affect plant root decomposition. Finally, we proposed some related perspectives based on the current status of plant root decomposition research.

Biological research on alfalfa in modern China

SUN Qi-Zhong, LIU Qian, TAO Ya, XU Li-Jun

2017, 26(2):  208-214.  DOI: 10.11686/cyxb2016067

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Like research on other crops, research on alfalfa has developed rapidly in modern China. However, there is still much to learn about this important crop. We consulted a large body of literature to classify alfalfa varieties in China and summarize the history, cultivation, and use of this crop. Many studies have been conducted on the origins of alfalfa, the range of alfalfa species and varieties, and on the utilization of this crop. Some studies have compared different alfalfa species such as Medicago sativa, Medicago lupulina, and Medicago minima, and others have focused on the development of bacterial nodules on alfalfa in northwest China, as well as the habitat, adaptation, and moisture and fertilizer requirements of this important plant. Western science and technology and local studies have resulted in the rapid and widespread dissemination of scientific knowledge about alfalfa in relevant journals, newspapers, and other media. All of this information has laid the foundation for further research on alfalfa, and for the development of strategies to increase its cultivation and use in modern China.

Fatty acid characteristics of forage silages from the Hulunbeir Meadow Steppe

NA Ya, SUN Qi-Zhong, WANG Hong-Mei

2017, 26(2):  215-223.  DOI: 10.11686/cyxb2016115

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To determine the types and amounts of fatty acids in silages produced from vegetation on the Hulunbeir Meadow Steppe, 40 wild forages were ensiled and their fatty acids contents were analyzed by gas chromatography after 45 days. The main fatty acids in the 40 forage silages were six long-chain fatty acids, especially palmitic acid and linolenic acid. The linoleic acid contents ranged from 0.1735% to 40.2036%. The ether extract and total fatty acids contents of the 40 silages ranged from 1.3507% to 10.8523% and from 0.0376% to 3.2505%, respectively, and the saturated fatty acid and unsaturated fatty acid contents ranged from 0.0252% to 1.5333% and from 0.0515% to 1.7172%, respectively. There was no obvious correlation between ether extract contents and the contents of the six main fatty acids, while there were complex correlations among the different fatty acids. There were pronounced differences in fatty acids composition and proportions among the 40 different forages, and the nutritive values of fatty acids of forages also differed depending on the genera and families of the vegetation.

Relationship between shrub encroachment and soil properties in the typical steppe of Inner Mongolia

ZHANG Zhi-Hua, LI Xiao-Yan, JIANG Zhi-Yun, WANG Yan-Mei

2017, 26(2):  224-230.  DOI: 10.11686/cyxb2016249

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The aim of this study was investigate the soil properties of shrub-encroached grassland and non-encroached grassland in Inner Mongolia. Compared with the non-encroached grassland, shrub-encroached grassland had higher soil bulk density and sand content, and lower silt, clay, organic matter, total nitrogen, and total phosphorus in the 0-60 cm soil layer. The differences in soil composition and soil nutrient contents were significant in the 0-60 cm soil layer in the enclosed treatment and in the 0-10 cm soil layer in the heavy grazing treatment. The extent of shrub encroachment was significantly and positively correlated with sand content and bulk density, but significantly and negatively correlated with soil grain size distribution and soil nutrient content. The above results suggest that soil properties have important effects on shrub encroachment. Poor and coarse-textured soil may be beneficial for shrub establishment and growth.