Table of Content

20 November 2016, Volume 25 Issue 11

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The NPP spatiotemporal variation of global grassland ecosystems in response to climate change over the past 100 years

GANG Cheng-Cheng, WANG Zhao-Qi, YANG Yue, CHEN Yi-Zhao, ZHANG Yan-Zhen, LI Jian-Long, CHENG Ji-Min

2016, 25(11):  1-14.  DOI: 10.11686/cyxb2016148

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Climate change has a significant effect on the spatial distribution, structure and function of ecosystems. To understand the effects and feedback mechanisms of climate change on a large spatial and temporal scale, the distribution, shift ranges and net primary production (NPP) of grassland ecosystems across the globe from 1911 to 2010 have been simulated using the Comprehensive Sequential Classification System (CSCS) and a segmentation model. Correlation analysis was also conducted to reveal the responses of grassland types to different climate variables. The results showed that the total global area of grassland ecosystems declined from 5175.73×10⁴ km² in the 1920s to 5102.16×10⁴ km² in the 1990s. The largest decrease, 192.35×10⁴ km², occurred in tundra & alpine steppe ecosystems. The areas of desert grassland, typical grassland and temperate humid grassland decreased by 14.31, 34.15 and 70.81×10⁴ km² respectively, while tropical savanna expanded by 238.06×10⁴ km². Climate warming forced most grasslands to shift northwards, particularly in the northern hemisphere. Global grassland NPP increased from 25.93 Pg DW/yr in the 1920s to 26.67 Pg DW/yr in the 1990s. In terms of each grassland type, the NPP of the tundra and alpine steppe, desert grassland, typical grassland and temperate humid grassland decreased by 709.57, 24.98, 115.74 and 291.56 Tg DW/yr respectively. The NPP of tropical savanna increased by 1887.37 Tg DW/yr. At the global scale, precipitation was the dominant factor affecting grassland NPP. In general, grassland ecosystems have been substantially affected by climate change over the past 100 years. Although the global grassland NPP showed an overall increasing trend, the structure and distribution of particular grassland ecosystems had been adversely affected by the warmer and wetter climate.

Soil moisture spatial distribution and infiltration characteristics of Nitraria nebkha in an oasis-desert ecotone

XI Jun-Qiang, ZHAO Cui-Lian, YANG Zi-Hui, GUO Shu-Jiang, WANG Qiang-Qiang, ZHANG Jian-Hui

2016, 25(11):  15-24.  DOI: 10.11686/cyxb2016083

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This study utilized Nitraria tangutorun nebkhas vegetation growing in a desert-oasis ecotone in Minqin to investigate space distribution of soil moisture content and the influence of soil physical properties, particularly soil hardness and crust thickness on water distribution and infiltration of the three evolutionary stages of soil formation; stable sand dune, sand dune formation and moving sand. The aim was to explore the effect of N. tangutorun nebkhas on soil moisture and to establish a theoretical foundation for protective systems for oasis-desert ecotones. The results as follows: 1) Soil hardness and crust thickness were highest in the stable dune, intermediate in forming dunes and least in moving sand. 2) Soil surface bulk density was 2.32, 2.30 and 1.95 g/cm³ in moving sand, forming dunes and stable dunes respectively; maximum water holding capacity, capillary water content, field capacity and total porosity was highest in the stable dune, intermediate in the forming dune and least in the moving sand. Soil physical properties in the subsurface layer were variable in all dune formation stages. 3) In the dry season, the lowest soil moisture contents occurred in soils from forming dunes and moving sand at 0, 70, 150 cm depth, maximum soil moisture occurred at 50, 130, 110 cm; in the rainy season, surface soil moisture content fluctuated while soil moisture at depth was relatively stable. 4) There were significant correlations between rainfall and infiltration in all three stages of soil formation (P<0.01). Water infiltration after rainfall events occurred immediately instable and forming dune soils whereas infiltration in moving sand only occurred when rainfall reached a critical threshold; with rainfall greater than 0.12 mm, infiltration was highest in the stable dune, intermediate in forming dune and least in moving sand.

Changes in organic carbon and nitrogen storage in alpine meadows under different grazing management regimes

LI Wen, CAO Wen-Xia, SHI Shang-Li, LI Xiao-Long, CHEN Jian-Gang, XU Chang-Lin

2016, 25(11):  25-33.  DOI: 10.11686/cyxb2015215

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A study has been undertaken to investigate changes in organic carbon and nitrogen storage under different grazing regimes in the alpine meadow ecosystem of the eastern margin of the Qinghai-Tibetan plateau. Organic carbon and nitrogen storage was measured in above-ground biomass, litter, roots and the 0-80 cm soil layer (divided 8 layers, and each layer was 10 cm) at four sites that represent different grazing management regions: non-grazing (NG), grazing rest during the growing stage (RG), traditional grazing (TG) and continuous grazing (CG). The results indicated that organic carbon and nitrogen in the 0-80 cm soil layer, roots, above-ground tissue and litter were significantly higher in NG, RG and TG than in CG. In general, the proportion of organic carbon in the alpine meadow ecosystem was the largest in soils (88.859%-98.242%), followed by roots (1.563%-8.742%), vegetation (0.172%-1.430%) and litter (0.022%-0.969%); similarly, the proportion of nitrogen was the largest in soils (97.331%-99.633%), followed by roots (0.316%-2.071%), vegetation (0.047%-0.442%) and litter (0.003%-0.157%). There were obvious differences in the vertical distributions of soil organic carbon and nitrogen storage under the four grazing regimes, with these differences mainly affecting the 0-40 cm layer and with no significant effect on deeper layers. Organic carbon and nitrogen storage was mainly distributed in the 0-40 cm layer, with grazing tending to move this storage to deeper layers. NG, RG and TG significantly increased storage in the alpine meadow ecosystem, while CG significantly reduced storage and was associated with a loss of carbon and nitrogen. Non-grazing and seasonal rest grazing can thus contribute to achieving carbon and nitrogen sinks on the eastern margin of the Qinghai-Tibetan Plateau and are important grazing management regimes for this and similar areas.

The effect of Erysiphe pisi infection on the pattern of oxidative burst and on anatomic structure of leaves in Medicago sativa

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

2016, 25(11):  34-42.  DOI: 10.11686/cyxb2016011

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Medicago sativa was inoculated with Erysiphe pisi. The colorimetric method was used to study the timing and intensity of ^·O2- and H₂O₂ bursts in leaves, and histochemical methods were used to study localization of ^·O2- and H₂O₂ accumulation. In addition, paraffin sections were made from infected leaves to observe structural changes in those leaves. It was found that after inoculation, ^·O2- and H₂O₂ bursts in Qingyang alfalfa (resistant cultivar) were observed as two peaks, appearing 4 and 48 h after inoculation for ^·O2- and 4 and 24 h after inoculation for H₂O₂, respectively, with the intensity of the first peak higher than that of the second peak. By contrast, in Debao alfalfa (susceptible cultivar), no obvious fluctuation in ^·O2- content appeared and only the one peak for H₂O₂ accumulation was seen. Staining to reveal zones of localization of reactive oxygen species (ROS) showed that blue-stained ^·O2- deposition sites did not occur at the surface of or inside of leaves, while brown-stained H₂O₂ deposition sites were observed in the cell wall of upper and lower epidermal cells, and the cytoplasm of infected mesophyll cells. Most importantly, we report here for the first time that the tissue structure of alfalfa leaves was changed after infection with E.pisi. Palisade cells changed from a long-cylindrical cell type to groups of several subrotund cells, so that it was difficult to distinguish the palisade tissue and spongy tissue cells. Our results show that for the different plant species and pathogen resistance combinations investigated, the timing and intensity of ROS accumulation differed, as did the identity of the chemical species generated in activating the defense reaction. The structural and morphological change of mesophyll cells may be one component of an effective response against powdery mildew infection in M. sativa.

Transformation of ZjADH gene into Arabidopsis thaliana and cold-tolerance analysis of transgenic plants

ZHANG Lan, TENG Ke, XIAO Guo-Zeng, LIANG Xiao-Hong, XU Li-Xin, YIN Shu-Xia, CHAO Yue-Hui

2016, 25(11):  43-49.  DOI: 10.11686/cyxb2016158

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To study the relationship between the ZjADH gene and plant cold tolerance, a plant expression vector 3302Y-ZjADH was constructed through DNA recombination technology. Transgenic Arabidopsis thaliana plants with glufosiante resistance were generated by floral dip method. PCR and qRT-PCR results showed that the target gene was successfully integrated with the genomes of Arabidopsis and could express efficiently. Both wild type and transgenic Arabidopsis plants were subjected to 4 ℃ to investigate their cold tolerance. Tests demonstrated that, compared with the wild type, the transgenic plants were more tolerant of cold stress. The free proline content in transgenic plants was significantly higher than the control, while the accumulation of ROS was much lower than the wild type. In addition, the expression levels of genes related to stresses like SOD, APX and LEA in transgenic plants were much higher than in the control. Results indicated that over-expression of ZjADH may improve the activities of superoxide dismutase (SOD), ascorbate peroxidase (APX) and late embryogenesis abundant proteins (LEA) to improve the cold tolerance of transgenic plants. In conclusion, the heterologous expression of ZjADH genes could reinforce the resistance of plants to cold stress. This study provides a theoretical foundation for future research on the ZjADH gene and the cultivation of cold-tolerant Zoysia japonica cultivars.

In vitro research on receptor regeneration and genetic transformation in Glycyrrhiza uralensis

HU Hai-Ying, ZHANG Rui, DUAN Yan-Hui, XIE Ying-Zhong

2016, 25(11):  50-56.  DOI: 10.11686/cyxb2015590

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A study has been undertaken to investigate the system of receptor regeneration and genetic transformation of Glycyrrhiza uralensis in vitro, in order to provide a preliminary experimental basis for breeding G. uralensis via genetic engineering. Using stem segments as explants, tests were done to select the most appropriate medium formula for adventitious bud differentiation, propagation and elongation. Furthermore, GUS and GFP genes were transferred into G. uralensis through Agrobacterium tumefaciens-mediated transformation methods. The results showed that the optimum formula for bud differentiation and proliferation was a Murashing and Skoog (MS) medium supplemented with 0.1 mg/L thidiaxuron, 0.1 mg/L 6-benzyladenine and 0.1 mg/L indole-3butyric acid. Using this formula, the differentiation rate of adventitious buds was 38.8% and the rate of multiplication 3.67. The most suitable formula for bud elongation was a MS medium containing 0.5 mg/L α-naphthalene acetic acid. Compared to stems without axillary buds, the differentiation rate of adventitious buds reached 100%. Moreover, these buds can survive in antibiotic containers and so become the optimal transformation explants. Stems with axillary buds were pre-cultured for 7 days in the differentiation medium, then infected by an Agrobacterium tumefaciens solution (OD₆₀₀=0.6) for 10 min and co-cultured for 3 days, following which the explants were transferred to a selective medium based on the differentiation medium and supplemented with 50 mg/L kanamycin and 250 mg/L carbenicillin. After 20 days, the GFP transient expression rate reached 78.88% and GFP expressed strongly by GFP detection. 5 transformed plants were selected randomly for testing and the presence of GUS and GFP genes in the genome were confirmed by polymerase chain reaction, indicating that 5 transformed plantlets had been successfully produced.

Investigation into the mechanism of Mo-mediatedCa²⁺ signaling during seed germination and antioxidation in Medicago sativa under drought stress

YI Qin, WEI Xiao-Hong, QIANG Xu, ZHAO Ying, DING Chun-Fa

2016, 25(11):  57-65.  DOI: 10.11686/cyxb2015591

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TheCa²⁺transduction pathways have been implicated in mediating stress response and tolerance in plants. In order to investigate the mechanism ofCa²⁺signaling mediated by nitric oxide (NO) during seed germination and antioxidation in Medicago sativa under drought stress, sodium nitroprusside (SNP, nitric oxide donor), CaCl2, and methylene blue (NO blockers) and LaCl3 (Ca2+ channel blockers) were used in this study, and alfalfa seeds were pre-soaked with these solutions. An index of germination was markedly decreased under drought stress induced by 15% polyethylene glycol treatment, but this effect was reversed after treatments with SNP and ^Ca2+. Moreover, 0.1 mmol/L SNP or 10 mmol/L CaCl2 alleviated drought stress damage. Compared to SNP or CaCl2 treatment alone, germination rate significantly increased by 8.96% and 19.67% respectively when the seeds were treated with both SNP and ^Ca2+. Furthermore, both SNP and CaCl2 treatments increased content of starch, soluble sugar, soluble protein and proline, and activities of amylase, superoxide dismutase, peroxidase and catalase, whereas malondialdehyde content decreased compared to that under SNP or CaCl2 treatment alone. The changes were slower for seeds receiving both NO andCa²⁺treatments than for NO orCa²⁺treatment alone. Interestingly, with added exogenousCa²⁺and methylene blue, the promotional effect ofCa²⁺was inhibited. In addition, the promotional effect of NO was inhibited by La3+. This indicates that NO mediated protein modifications in alfalfa seeds under drought stress through theCa²⁺signaling pathway.

Effects of various types of salt stress on ion absorption, accumulation and transportation in pea (Pisum sativum) seedlings

DONG Fang, CAO Jing, LI Xian-Ting, ZHANG Lin-Jie, YUE Xiao-Hong, GENG Jie, ZHANG Jin-Lin

2016, 25(11):  66-75.  DOI: 10.11686/cyxb2016019

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In order to investigate the physiological mechanisms of ion absorption, accumulation and transportation in pea seedlings under various types of salt stress (NaCl, mixed sodium salts and mixed chlorine salts, the control treatment was Hoagland nutrient solution), the characteristics of absorption and accumulation of ions in three varieties of pea (‘Yinwan NO.1’, ‘S5001-1’ and ‘737’) seedlings were studied using a hydroponic method. Key findings were: 1) Under NaCl and mixed sodium salt stress, Na⁺ contents in shoots and roots were significantly higher than control, whereas contents of K⁺ and Ca²⁺ were significantly lower. Under mixed chlorine salt stress, Na⁺ contents in shoots and roots did not differ significantly from those of control plants. However, contents of Cl^-, K⁺, Ca²⁺ and Mg²⁺ were significantly higher than for the other two salt treatments. 2) Under the control treatment, K⁺ was absorbed and accumulated prior to other ions in three varieties of pea, followed by Ca²⁺. Under NaCl and mixed chlorine salt stress, K⁺ was absorbed and accumulated prior to other ions, followed by Na⁺ and Cl^-. Under mixed sodium salt stress, Na⁺ and K⁺ was absorbed and accumulated prior to other ions, followed by Ca²⁺, while the characteristics of transportation and accumulation of salt ions among three varieties of pea were different under various types of salt stress. 3) Under NaCl and mixed sodium salt stress, the selective absorption coefficients SA_K,Na、SA_Ca,Na and SA_Mg,Na in the three varieties of pea were significantly higher than in control plants, while significantly lower than under mixed chlorine salt. The ST_K,Na and ST_Ca,Na in ‘S5001-1’ seedlings were significantly higher under NaCl and mixed sodium salt stress than in control plants, whereas the ST_K,Na and ST_Ca,Na in ‘Yinwan NO.1’ under mixed sodium salt and mixed chlorine salt treatments were significantly lower than for controls. The ST_K,Na of the three varieties of pea were similar under mixed chlorine salt stress. The study showed that the accumulation of Ca²⁺, K⁺ and Mg²⁺ in shoots under NaCl and mixed sodium salt stress was lower than control, whereas the ability of roots of pea seedlings to absorb and transport Ca²⁺, K⁺ and Mg²⁺ was weakened in response to salt stress. Under mixed chlorine salt stress, the absorption and accumulation of Ca²⁺, K⁺ and Mg²⁺ in shoots was higher than under the other two salt treatments (NaCl and mixed sodium salts), whereas in roots they were significantly lower than under other two salt treatments.

Effects of long-term nitrogen addition on photosynthetic characteristics and leaf traits of Stipa baicalensis in Inner Mongolia, China

LIU Hong-Mei, LI Jie, HUANGFU Chao-He, CHEN Xin-Wei, YANG Dian-Lin

2016, 25(11):  76-85.  DOI: 10.11686/cyxb2016110

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Atmospheric nitrogen deposition is an important component phenomenon of global change, and induces a series of ecological problems. We conducted a field manipulation experiment to study the photosynthetic response and change in leaf functional traits after long-term nitrogen addition in an S.baicalensis grassland in Inner Mongolia. This study was conducted from 2010-2015. Five treatments including N₀ (0 kg N/ha), N₃₀ (30 kg N/ha), N₅₀ (50 kg N/ha), N₁₀₀ (100 kg N/ha) and N₁₅₀ (150 kg N/ha) were set up and forty-eight plots, sized 8 m×8 m, were established with 2 m strips between each plot. The objective was to determine how photosynthetic characteristics and leaf traits vary with nitrogen addition and what causes these differences. Photosynthetic traits and leaf traits differed among different nitrogen addition treatments. Net photosynthetic rate (P_n), stomatal conductance (G_s), transpiration rate (T_r), photosynthetic nitrogen use efficiency (PNUE), photosynthetic energy use efficiency (PEUE) under N₃₀, N₅₀, N₁₀₀, and N₁₅₀ treatments were lower or significantly lower than those under N₀. Specific leaf area (SLA), leaf N content (N_mass), leaf construction cost (CC_mass), leaf N∶P under N₃₀, N₅₀, N₁₀₀, N₁₅₀ treatments tended to be higher or were significantly higher than those under N₀. Correlation analysis showed that P_n was positively correlated with G_s, T_r, PNUE, PEUE, leaf P content (P_mass), N_mass and soil N, P while P_n was negatively correlated with SLA, N_mass, CC_mass, soil water content and soil pH; N_mass was positively correlated with SLA, CC_mass and soil N, P, and N_mass was negatively correlated with PNUE, PEUE, P_mass, soil water content and soil pH. In conclusion, long-term nitrogen addition induced decreases in P_n and nutrient use efficiency of S. baicalensis, and increases in leaf CC_mass and N∶P. Soil water content and pH decreased with nitrogen addition. This suggests that water content and soil pH are two important factors affecting photosynthetic characteristics and leaf traits of S.baicalensis under different nitrogen addition regimes.

Ecophysiological mechanisms associated with drought tolerance and post-drought recovery in warm- and cool-season turfgrasses

YU Jing-Jin, LI Ran, LIU Meng-Xian, YANG Zhi-Min

2016, 25(11):  86-93.  DOI: 10.11686/cyxb2016162

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Warm-season grasses had superior drought tolerance and post-drought recovery, compared to cool-season turfgrasses. In this study, seashore paspalum (Paspalum vaginatum cv. ‘2000’) and Kentucky bluegrass (Poa pratensis cv. ‘Excursion II’) were chosen as research material. Leaf relative water content (RWC), water use efficiency (WUE), net photosynthetic rate (P_n), stomatal conductance (G_s), transpiration rate (T_r), specific leaf area (SLA), osmotic adjustment (OA) and root length were measured to clarify the mechanisms of their differential drought tolerance. Seashore paspalum had superior drought tolerance as shown by higher RWC (11%), P_n (33%), T_r (52%), G_s (119%) and WUE (27%). Total root length in the 0-20 cm soil layer under Kentucky bluegrass was reduced significantly more after 20 d drought stress than under seashore paspalum, suggesting the former was less drought-tolerant. During post-drought recovery, seashore paspalum had higher RWC (9%), T_r (43%), G_s (154%) and WUE (34%), as well as lower SLA (8%) than Kentucky bluegrass. Further, total root length in the 0-20 cm soil layer showed the same changes as that during drought stress. The results indicated that lower water loss, higher water use efficiency and the fact that root growth in 0-20 cm soil layer was less reduced under drought, were the main reasons for the superior drought tolerance and post-drought recovery ability of seashore paspalum, compared to Kentucky bluegrass.

Effects of gibberellic acid on forage quality of rice (Oryza sativa) straw

DONG Chen-Fei, GU Hong-Ru, DING Cheng-Long, XU Neng-Xiang, ZHANG Wen-Jie

2016, 25(11):  94-102.  DOI: 10.11686/cyxb2016014

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In this study, two different rice (Oryza sativa) varieties, Liangyoupeijiu (late maturing indica) and Nanjing 44 (early maturing japonica), were used to investigate the mechanisms of gibberellic acid (GA) regulation of the forage value of rice straw during late growth. GA was applied 15 days after anthesis at a rate of 45 g/ha. The endogenous plant hormones [such as GA, 3-indole acetic acid (IAA), and abscisic acid (ABA)], superoxide dismutase (SOD) and peroxidase (POD) activities, and malondialdehyde (MDA) content in the first top leaf were assessed on the 3rd d and 14th d after GA application. Forage quality and fermentation quality of rice straw were also assessed after rice harvest. The results indicated that the forage value Liangyoupeijiu and Nanjing 44 were significantly improved by GA application as a result of reduced senescence. However, there were significant cultivar differences; the green leaf area per tiller of Liangyoupeijiu was significantly higher than that of Nanjing 44 (P<0.01); nonstructural carbohydrates (NSC) and crude protein (CP) content in the straw of Liangyoupeijiu were significantly higher than those of Nanjing 44 (P<0.05). The MDA content of GA treated Liangyoupeijiu was significantly lower than that of the control (P<0.05), while the SOD and POD activities of GA treated plants were significantly higher than those of the control (P<0.05). The GA content and the GA∶ABA ratio of GA treated plants of Liangyoupeiju were significantly higher than those of the control (P<0.05) and Nanjing 44. It was concluded that application of GA during late growth could significantly improve the forage quality of rice straw. The effects of GA were greater in Liangyoupeijiu than in Nanjing 44.

Effects of winter green manure crops with and without chicken rearing on microbial biomass and effective carbon and nitrogen pools in a double-crop rice paddy soil

ZHOU Ling-Hong, WEI Jia-Bin, TANG Xian-Liang, CHENG Xiao-Lin, XIAO Zhi-Xiang, XU Hua-Qin, TANG Jian-Wu

2016, 25(11):  103-114.  DOI: 10.11686/cyxb2016032

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This study examined the short term effects of the crop rotation systems known as “winter green manure with double cropped rice” and “winter planting and chicken raising with double cropped rice” on paddy soil microbial biomass and dissolved organic C and N. The goal of a winter planting and chicken raising in rice double cropping systems is to return green manure and chicken manure to soils and reduce the amount of fertilizer during the rice growing period. Five winter treatments were included: fallow (F), planting ryegrass (R), planting milk vetch (M), planting ryegrass and rearing chickens (RC), planting milk vetch and rearing chickens (MC). In general soil microbial biomass and dissolved organic C and N were increased significantly, compared to a winter fallow, by a green manure crop and further increased when chickens were also reared, although values were subject to dynamic seasonal fluctuation. Specifically, the maximum values for soil microbial biomass C were 492.22, 464.91, 432.34, 435.48 and 378.02 mg/kg for the treatments RC, MC, R, M and F, respectively; while the corresponding maxima for microbial biomass N were 118.20, 101.03, 70.13, 85.46 and 61.12 mg/kg, respectively. The maxima for dissolved organic N were 1001.47, 926.21, 832.80, 870.75 and 719.86 mg/kg; and the maxima for dissolved organic C were 278.95, 266.40, 246.13, 249.84 and 201.58 mg/kg, for RC, MC, R, M and F, respectively. The dynamics of microbial biomass C, N and dissolved organic C were different at different growth stages. Microbial biomass C peaked at the transplanting, booting and filling stage of late rice. Microbial biomass N peaked at the tillering and heading stage of early rice, and the booting stage of late rice. While the dissolved organic C peaked at seedling stage of early rice and it was higher during the period of raising chickens and after chicken removal from the paddy field. In summary, compared to a winter fallow paddy field, planting green manure and raising chickens significantly increased microbial biomass and soil dissolved organic carbon and nitrogen, which indirectly indicates that winter manure and chicken rearing systems can improve the soil organic carbon, and soil labile organic carbon contents, as well as nitrogen levels and nitrogen mineralization rate. Plant nutrients needed by the rice crop during the rice growing season can thus be provided by a winter planting and chicken raising.

Comparison of the effects of nitrogen fertilizer on the yield and feeding quality of Italian ryegrass (Lolium multiflorum) in saline and non-saline soil

XU Neng-Xiang, DONG Chen-Fei, DING Cheng-Long, CHENG Yun-Hui, ZHANG Wen-Jie, GU Hong-Ru

2016, 25(11):  115-123.  DOI: 10.11686/cyxb2016027

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This study investigated the effects of nitrogen fertilizer on the forage yield and quality of Italian ryegrass (Lolium multiflorum) in saline soil and non-saline soil conditions. The experiment was carried out at Jinhai Farm, Liuhe Experiment Station, Jiangsu Academy of Agricultural Sciences, Nanjing, Jiangsu Province. Nitrogen fertilizer treatments were; N₀ (Control), N₁ (100 kg/ha), N₂ (150 kg/ha) and N₃ (200 kg/ha). Pasture was sampled at the stem elongation (first cut) and heading stages (second cut) and assessed for yield and quality related straits. The results indicated that the effects of nitrogen on grass yield and forage quality in saline soil and non-saline soil were different; yield and quality of Italian ryegrass in non-saline soil were better than those in saline soil. In vitro dry matter digestibility (IVDMD), crude protein (CP) and nonstructural carbohydrates (NSC) content of Italian ryegrass in non-saline soil were higher than those in saline soil, and higher from the first cut than the second cut. The CP content increased with increasing nitrogen application while NSC content decreased with increasing nitrogen. Starch content from saline soil was higher than non-saline soil. The IVDMD of nitrogen treatments was higher than that of the control but there were no differences between nitrogen treatments. The neutral detergent fiber (NDF) content of Italian ryegrass in saline soil was higher than that in non-saline soil and higher in the second cut than the first. Dry matter (DM) of Italian ryegrass in saline soil was significantly higher than that in non-saline soil, and that of the second cut higher than the first. The forage yield in non-saline soil was higher than that of saline soil, and that of the second cut higher than the firs. Grass yield increased with increasing nitrogen fertilizer but yield responses to nitrogen were in saline soil were higher than that in non-saline soil.

Influence of mowing time on yield and quality of spring and autumn sown oat hay

ZHANG Ying, CHEN Zhi-Fei, ZHANG Xiao-Na, SONG Shu-Hong, YANG Zhuo, YANG Yun-Gui

2016, 25(11):  124-135.  DOI: 10.11686/cyxb2016020

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A experiment was carried out to determine the effect of cutting time on yield and nutritional quality of autumn oat (varieties were Keyan1, T045, UITIMA, Baiyan9) and spring oat (varieties were Keyan1, Baiyan5, Baiyan9, Dancer) in determine the best cutting time for autumn and spring sown oats in the Guanzhong area. The results showed that fresh weight and dry weight of all varieties increased over time. Autumn sown Keyan 1 produced the best yield when cut at the heading stage, (P≤0.05; fresh yield was 1625 g/m² and hay yield was 524 g/m² and crude protein content was 12%. Spring sown Baiyan 9 has the best performance when cut at the jointing stage when fresh yield was 0.73 kg/m², hay yield 0.16 kg/m² and protein content, 15.42%. Protein contents of different varieties ranged from 9% to 19% across cutting times. Protein contents of Keyan1, Baiyan 5, Baiyan 9, and Dancer were 19%, 10%, 15%, 14%, respectively and significantly higher when cut at the jointing stage (P≤0.05) compared with other cutting times.

Effects of livestock grazing on rodents in grassland ecosystems

SU Jun-Hu, NAN Zhi-Biao, JI Wei-Hong

2016, 25(11):  136-148.  DOI: 10.11686/cyxb2015587

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Knowledge of how livestock grazing affects rodents is important if a solution to the problem of maintaining grassland biodiversity while controlling degradation resulting from rodent damage is to be found. This review summarizes the research on the effect of livestock grazing on rodents in China and other countries up to 2015. Soil physical and chemical properties are changed by both livestock trampling. Changes in vegetation affect rodent food resources and their abundance as do changes in plant nutrient content and secondary defense compounds; rodent predation risk is modulated by decreased vegetation height and structural complexity. The cascading effect of these changes alters rodent microhabitat, feeding behavior, distribution, reproduction and life history traits; this results in changes in the structure of rodent populations, population dynamics and its regulation process as well as community composition structure and biotic interactions leading the community succession. Future research should focus on the effect of grazing on the coupling mechanisms of grass-livestock-rodent interactions and the effects of different grazing systems on rodents. The objective should be to identify effective rodent management techniques to achieve sustainable management of grassland ecosystem.

Research progress on seagrass and seagrass ecosystems

WANG Suo-Min, CUI Yan-Nong, LIU Jin-Xiang, XIA Zeng-Run

2016, 25(11):  149-159.  DOI: 10.11686/cyxb2016025

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Seagrasses are underwater flowering plants widely distributed in shallow seas often forming vast seagrass based ecosystems. Seagrass ecosystems are one of the most productive aquatic ecosystems in the world and a globally significant carbon store due to the unique features of seagrass which allow efficient photosynthesis underwater. Seagrass ecosystems provide a range of important ecological service functions and they act as biological sentinels used to assess the health of coastal ecosystems. Recently, rapidly decreases in the number of individual seagrass species and the number of seagrass meadows caused by the multiple stressors including natural factors and human effects had led to a situation where 14% of all seagrass species are at risk of extinction and about one-third seagrass meadows have disappeared worldwide. In response to this decline, there has been a significant increase in the number of marine protected areas during the last decade, including seagrass monitoring and restoration projects which aim to prevent the extinction of individual seagrass species and prevent the large scale loss of seagrass meadows throughout the world. Current restoration projects involve habitat improvement through reduction in eutrophication or alteration of hydrology and the use of artificial transplantations which can be an effective method of restoration. Seagrass monitoring and restoration projects have achieved some positive preliminary results and provide useful guidelines for seagrass restoration. However there are challenges including limited theoretical approaches, appropriate technology, and uncertainty of outcome from seagrass transplantation and restoration projects and cost. This paper reviews the research on seagrasses and seagrass ecosystems globally, clarifies their importance to the biosphere and the risks to their survival to raise the awareness of the public, government and international agencies of the need to protect seagrass ecosystems.

AtmiR156a regulates the vegetative growth and forage quality of chicory (Cichorium intybus)

LI Xiao-Dong, CAI Lu, ZHANG Yu, WANG Qian, MO Ben-Tian, HAN Yong-Fen, WANG Xiao-Li

2016, 25(11):  160-166.  DOI: 10.11686/cyxb2016128

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Chicory is an important forage plant for animal husbandry in south China. The yield of chicory is closely related to the length of the plants’ vegetative growth phase. In this study, Arabidopsis AtmiR156a was over-expressed in chicory and a total of 140 independent lines of transgenic plants were obtained. PCR analysis detected 94.3% positive expression in these plants. q-PCR analysis showed that, compared with the wild-type chicory used as control, the expression of AtmiR156a was promoted by 7.9 times in the transgenic plants. Germination rates for the AtmiR156a over-expressed lines were similar to that of the control, but the leaf emergence rate was significantly faster. Bolting time and flowering time were delayed by 20.2 and 27.3 days respectively in the AtmiR156a over-expressed lines. However, plant height was reduced, which led to similar annual forage yields for both the wild type and transgenic plants. Forage quality was analyzed via a first cutting of leaves. The results showed that crude protein content was 3.7% higher and fiber content was 2% lower in the AtmiR156a over-expressed lines; other quality traits showed no significant differences from the control seedlings. Our results establish an efficient method for the genetic transformation of chicory. The experiment also created a pool of late-flowering and fast-growing germplasm resources, laying a foundation for the breeding of high-yield and cutting-resistant chicory varieties. The results provide a reference for theoretical studies and practical applications aiming to improve chicory performance through the use of genes from other crops.

Effects of cutting stage and additives on the fermentation quality and CNCPS protein fractions of alfalfa silage

LI Zhen-Zhen, BAI Chun-Sheng, YU Yi-Dong, YU Zhu

2016, 25(11):  167-172.  DOI: 10.11686/cyxb2016029

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The effect of microbial and chemical additives on the quality of alfalfa silage were tested in this study. Alfalfa was harvested at budding and early-flowering stage and wilted to approximately 70% moisture content and treated with four additive treatments; distilled water (control), 10⁵ cfu/g Lactobacillus plantarum and 50 mg/kg cellulase (LP+C50), 10⁵ cfu/g L. plantarum and 100 mg/kg cellulose (LP+C₁₀₀) and 6 mL/kg formic acid+propionic acid (FA+PRA), with 3 replications. Silages were analyzed after 30 d of ensiling. This study indicated that alfalfa harvested at the early flowering stage had lower pH (P<0.05), butyric acid (BA) and NH< sub >3-N (P<0.01) than those harvested at budding with significantly less non-protein nitrogen (PA) and unusable protein (P<0.01). All three additives significantly increased the fermentation quality of alfalfa by decreasing the pH and content of NH₃-N (P<0.01). Alfalfa silage treated with LP+C had significantly higher lactic acid and lactic acid/acetic acid (P<0.01) while BA was not detected in the FA+PRA treatment. All additives had higher water soluble carbohydrate (WSC) and crude protein (CP) and less neutral detergent fiber (NDF) and acid detergent fiber (ADF) (P<0.01) than the control. Applying LP+C₁₀₀ and FA+PRA markedly decreased the concentration of non-protein nitrogen and unusable protein, and increased the content of true protein in silages (P<0.01). The results suggest that alfalfa silage treated with FA+PRA had the highest quality, followed by LP+C₁₀₀ treated silage.

The study of plant growth promoting rhizobacteria (PGPR) from several Poaceous species in the East Chi-lien Mountains of China

LI Jian-Hong, LI Xue-Ping, MA Wen-Wen, YAO Tuo, SUN Jian-Jun, JIANG Yong-Mei, ZHANG Jian-Gui, SHI Shang-Li

2016, 25(11):  173-177.  DOI: 10.11686/cyxb2016090

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This research studied the quantity and distribution of bacteria in the rhizosphere of seven Poaceous species from the east Chi-lien Mountains. The research employed a cultivation method, and mainly studied nitrogen fixing bacteria. It was found that there were large numbers of bacteria in rhizospheres of all 7 plant species studied. The total number of rhizosphere bacteria counted ranged from 2.5×10⁶ cfu/g to 17.07×10⁶ cfu/g, with Agropyron cristatum and Leymus secalinus having the lowest rhizosphere nitrogen-fixing bacterial populations and Poa alpigena having the highest, with the other 4 species intermediate. A total of 201 nitrogen-fixing strains were isolated from the 7 grass species studied. The quantity of bacteria and PGPR present a distribution trend: “root system surface (RP)>root surface soil (RS)>histoplan or interior of roots (HP)”.

Effects of natural grass hay on the growth, carcass traits and economic profitability of Wadi sheep in arable regions

LI Yong-Zhen, MIAO Fu-Hong, SHEN Zhi-Qiang, LIN Ying-Ting, LI Guo-Cai, SUN Juan

2016, 25(11):  178-184.  DOI: 10.11686/cyxb2016002

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A total of 27 Wadi sheep weighing (20±0.50) kg at age 4 months were randomly divided into 3 groups to investigate the effects of natural grass hay on their growth, carcass traits and economic profitability in arable regions. The three treatment groups were fed with natural grass hay (Ⅰ), maize silage and peanut vine (Ⅱ), and maize silage and alfalfa (Ⅲ). The experiment lasted 105 d, including a preliminary trial period (15 d) and the trial period proper (90 d). The results showed that there was no significant difference in total and average daily weight gain among the three treatments. The feed to gain ratio of treatment Ⅰ was 4.55% and 11.29% lower than treatments Ⅱ and Ⅲ (P<0.05) respectively. There were no significant differences in the animals’ increasing body height, body length and chest among the three treatments. There was no significant difference in dressing percentage; treatment Ⅰ was 1.22% higher than Ⅱ and 2.33% lower than Ⅲ. There was no significant difference in carcass net muscle percentage; the highest was 37.83% in Ⅰ, which was higher than Ⅱ and Ⅲ by 2.97% and 1.26% respectively. There was no significant difference in meat-bone ratio, with Ⅰ higher than Ⅱ by 1.56% and lower than Ⅲ by 3.35%. The eye muscle areas were similar in the three treatments, with Ⅰ the highest, 0.57% higher than Ⅱ and 7.30% higher than Ⅲ. The profitability of treatment Ⅰ was the highest at 492.15 yuan, higher than Ⅱ and Ⅲ by 41.31 yuan and 150.74 yuan respectively. In conclusion, natural grass hay can promote the growth, carcass traits and profitability of Wadi sheep.

Evaluation of the associative effects of rape straw, corn and soybean meal using an in vitro gas production technique

ZHANG Yong, XIA Tian-Chan, CHANG Yu, HUANG Wen-Ming, GUO Hai-Ming, YE Jun-An

2016, 25(11):  185-191.  DOI: 10.11686/cyxb2015555

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This study was conducted to investigate the associative effects of different mixtures of rape straw, corn and soybean meal on rumen fermentation. Rape straw was mixed with 0%, 15% and 30% proportions of corn; the straw was also mixed with soybean meal using the same proportions. The mixtures were incubated in vitro using the Reading Pressure Technique (RPT) to evaluate the best combination according to rumen fermentation parameters and associative effects. The results showed that with rising proportions of corn, the yield rates of acetate, propionate and volatile fatty acid (VFA) also increased, but that the ratio of acetate to propionate decreased. Rumen pH, NH₃-N, VFA, acetate, and the ratio of acetate to propionate of treatments with 30% corn and 30% soybean meal were significantly lower than the other treatments (P<0.01), but their total gas production, potential gas production, rate of gas production, acetate, propionate, VFA, and organic matter digestibility (OMD) were higher than the other treatments (P<0.01). When the associative effects of gas production, NH₃-N, VFA, OMD and the synthetic associative effects (AEs) were used as evaluation indexes, the value of associative effects of the 30% corn and 15% soybean meal treatments were the highest (P<0.01), indicating that these mixture ratios provide the most acceptable balance of energy and nitrogen.