Table of Content

20 October 2018, Volume 27 Issue 10

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Effects of species diversity and community structure on nitrogen use efficiency of mixed legume+grass pastures

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

2018, 27(10):  1-14.  DOI: 10.11686/cyxb2017483

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This study investigated species diversity and effects of species spatial distribution on forage yield in mixed grass+legume pasture communities. N fixation, N transfer and N utilization efficiency in leguminous forage under different planting patterns with intermixed grasses were evaluated to gain insight into N fixation ability, N transfer efficiency, N nutrition competition, interspecies compatibility and production performance. The results showed: 1) Both the forage yield and N yield in mixed pastures were significantly higher than in monoculture (P<0.05), However, productive capacity of mixed pastures did not increase with increasing number of grass species. A row spacing of 30 cm intercropping treatment+different line mixed treatment had higher productive capacity than other planting patterns. 2) The amount of nitrogen derived from air (W_N) declined with increasing grass content. The amount of nitrogen derived from legume (W_Nt) and percentage of nitrogen derived from legume (P_Nt) showed a curvilinear response with lowest values at intermediate levels of grass species, while, the percentage of nitrogen derived from air (P_N) and contribution of biological nitrogen fixation (C_BNF) were comparatively unchanged. Again, the treatment Row spacing of 30 cm+intercropping treatment had higher W_Nt, P_Nt and C_BNF values than other treatments. 3) No changes in competition ratio (C_Rpm) were observed, but the relative yield and relative yield total of legume increased with increasing grass species content in the mixtures. The relative yield and relative yield total of legume in row spacing of 30 cm+intercropping treatment were higher and the C_Rpm value was lower than for other spacing patterns. 4) Forage yield was significantly correlated with the W_Nt value (P<0.01), and relative yield total was negatively correlated with C_Rpm value (P<0.01). Therefore, species diversity had a limited impact on the productivity in mixed pastures, and high nutrient use efficiency species would be theoretically more important. Optimization of the spatial structure of legume-grass mixtures can improve biological N fixation, N transfer, N utilization, and N use efficiency. These principles potentially provide new methods to improve the productivity of mixed legume+grass pastures.

Effects of growth interaction effect of Leguminous and Gramineous pasture intercropping and absorption of nutrient and phosphorus on pasture expression

ZHANG De, LONG Hui-ying, JIN Jie, FAN Bo, ZHAO Xiu-mei, HAN Xue-qin

2018, 27(10):  15-22.  DOI: 10.11686/cyxb2017475

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This research was aimed at understanding the effects of intercropping on biomass accumulation and nutrient uptake of component species in grass-legume mixtures, and providing a theoretical basis for determining optimal planting configuration of different forage grasses in grass-legume mixtures. The design was a randomized block experiment, with species studied being Stylosanthes guianensis, Heteropogon contortus and Bothriochloa pertusa, and their nutrient absorption were studied. The results indicated that intercropping of H. contortus and B. pertusa with S. guianensis enhanced nutrient absorption ability and yields, compared with monoculture, due to the biological nitrogen fixation of S. guianensis. The grass biomass values in intercropping systems were 0.06% and 26.78% higher for H. contortus and B. pertusa, respectively, than for the same species in a monoculture system. Meanwhile, S. guianensis biomass values in the two intercropping systems were 9.70% and 12.83% lower than those in an S. guianensis monoculture system. For H. contortus intercropped with S. guianensis, the nitrogen and phosphorus absorption were 24.26% and 35.18% higher than those in H. contortus monoculture. Corresponding values of nitrogen and phosphorus absorption for B. pertusa intercropped with S. guianensis were 40.64% and 47.50% higher than those in B. pertusa monoculture. Compared with monoculture, S. guianensis intercropped with H. contortus or B. pertusa showed, respectively, a 3.58% and 20.66% decrease in phosphorus absorption, and an 8.31% and 28.94% decrease in nitrogen absorption, while the two intercropping modes had a land equivalent ratio>1. Intercropping of S. guianensis and H. contortus had higher yield and interspecific competitive ability than intercropping of S. guianensis and B. pertusa. For intercropping systems with a row space of 50 cm, there was an inhibitory effect on the growth of S. guianensis because of competition from the grasses. At this row spacing, S. guianensis was less competitive crop in an intercropping system with either of the two grasses. The results show that for grass-legume intercropping systems the appropriate planting density, and species combination improves the utilization of soil nitrogen and phosphorus, and enhances grass yield and forage quality through the inclusion of the legume component.

Effects of Cd on antixoidant enzyme activities, and leaf photosynthetic and fluorescence characteristics in Pontederia cordata

XIN Jian-pan, LI Wen-ming, QI Xi, TIAN Ru-nan

2018, 27(10):  23-34.  DOI: 10.11686/cyxb2017463

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Plants of Pontederia cordata were cultivated in 1/2 strength Hoagland’s nutrient solution containing cadmium at concentrations of 0, 5, 25 or 75 mg·L^-1, to research cadmium tolerance and its physiological mechanisms. Changes with Cd exposure in antioxidant enzyme activities, leaf chlorophyll contents, photosynthetic gas exchange and chlorophyll fluorescence parameters in P. cordata leaves were measured. It was found that plasma membrane permeability tended to increase with cadmium concentration and with exposure time. Changes in activities of superoxide dismutase (SOD), peroxidase (POD) and hydrogen peroxidase (CAT) differed. CAT activity was seldom influenced by Cd, whereas activities of SOD and POD were increased by Cd. Leaves showed an obvious decrease in chlorophyll a (Chla), chlorophyll b (Chlb), and total chlorophyll (ChlT) contents and in chlorophyll a/b (Chla/b) ratio with Cd exposure, and this effect was also more marked with increasing Cd concentration and exposure time. Chla was more sensitive to Cd, and Chla reduction was primarily responsible for the reduction in the ChlT content and for the reduced Chla/b ratio. A Cd-induced decrease in net photosynthetic rate (P_n) of P. cordata leaves was observed and was associated with a decline in stomatal conductance (G_s). Linked to this effect, transpiration rate (E), and intercellular CO₂ concentration (C_i) of leaves were also decreased by increased Cd concentration and exposure time, while vapor pressure deficit (VPD) was increased. Also, higher Cd concentrations (25, 75 mg·L^-1) resulted in photoinhibition, decreasing the photosynthetic electron transport system activity, and thus leading to a decline in energy conversion and utilization efficiency of photosystemⅡ (PSⅡ). However, P. cordata can adapt to Cd exposure by enhancing thermal dissipation and activating non-activated PSⅡ reaction centers.

Responses of seed germination and rhizobia antioxidative enzyme activities in legumes to acidity and aluminum and NaCl stresses

WANG Deng-ke, YU Xiang-yu, ZHANG Xue-feng, HUANG Lei, LI Xiao-ting, HE Zhi-bin, KANG lin, WANG Dang-jun, YAO Lu-hua, GUO Yan-jun

2018, 27(10):  35-44.  DOI: 10.11686/cyxb2017493

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It is important for legumes to germinate and form nodules successfully under adverse soil conditions. In the current study, four summer legume crops used for green manure; Phaseolus calcaratns, Vigna radiata, Sesbania cannabina and Vigna unguiculata were utilised to investigate the responses of seed germination and the antioxidative enzyme activities of their rhizobia to soil acidity and NaCl stress. Four pH levels (4, 5, 6, 7), four Al³⁺ levels (0, 50, 100 and 200 mg·L^-1), and four NaCl levels (0, 40, 120 and 200 mmol·L^-1) were assessed for their effects on seed germination. Similarly, four pH levels (4, 5, 6, 7), five Al³⁺ levels (0, 25, 50, 75 and 100 μmol·L^-1), and five NaCl levels (0, 10, 20, 30 and 40 g·L^-1) were assessed for the influence on antioxidative enzymes. The results indicated that the seed germination and rhizobia antioxidative enzyme activities were significantly influenced by low soil pH and increased concentrations of Al³⁺ and NaCl. Overall, the antioxidative enzyme activities of rhizobia were more sensitive than seed germination to these stresses. Among the four plant species, seed germination and rhizobia of S. rostrat were comparatively sensitive to soil pH and Al³⁺ but was relatively tolerant to NaCl stress; those of P. calcaratns, V. radiate and V. unguiculata were relatively tolerant to low levels of NaCl and high levels of soil pH, whereas those of all plant species were sensitive to increased Al³⁺ concentrations. In acid or alkaline soils, higher concentrations of H⁺ and Al³⁺ or NaCl inhibited seed germination, retarded rhizobia growth, reduced the oxidation resistance of rhizobia, and limited the early growth of legume seedlings.

Effects of different grassland degradation levels on inorganic nitrogen and urease activity in alpine meadow soils

LI Ya-juan, LIU Jing, XU Chang-lin, CAO Wen-xia

2018, 27(10):  45-53.  DOI: 10.11686/cyxb2018098

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Four types alpine meadow, fenced grassland (FG), lightly degraded grassland (LD), moderately degraded grassland (MD) and heavily degraded grassland (HD), were selected to study the effects of grassland degradation on soil inorganic nitrogen characteristics and their seasonal dynamics in the eastern Qilian Mountain area. Samples of the 0-10 cm, 10-20 cm and 20-30 cm soil layers were collected from the four grassland types in spring, summer and winter. Soil total inorganic nitrogen, ammonium nitrogen (NH4+-N), nitrate nitrogen (NO3--N) contents and urease activities were measured. The results showed that grassland degradation has more influence on total inorganic nitrogen contents in the surface soils than deeper layers, but these effects varied by season. Compared with FG, the total inorganic nitrogen content of LD, MD and HD soils increased by 39.9%, 28.9% and 68.4% in spring and increased by 19.1%, 28.7% and 33.6% in summer. In winter, the total inorganic nitrogen content of these three kinds of grassland decreased by 20.4%, 27.2% and 47.4% respectively. The results also showed that grassland degradation has varying effects on the forms of soil inorganic nitrogen. In spring, grassland degradation significantly increased NH4+-N content in surface soils and there was little effect on NO3--N. In summer, NO3--N content increased significantly in surface soils while there was little effect on NH4+-N content. Degradation levels were also associated with seasonal differences in soil urease activity. Compared with FG, in spring the urease activities of LD and MD soils increased while HD decreased significantly. Soil urease activity increased gradually with increased degradation levels in summer and winter, which indicates that degradation increased soil inorganic nitrogen supplication and improved the soil nitrogen conversion process.

The relationship between growth characteristics and the quality of alfalfa under sprinkler irrigation in the northwest arid area of China

LI Yan, SU De-rong, LI Hong-tao

2018, 27(10):  54-65.  DOI: 10.11686/cyxb2017479

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Estimating forage quality with field measurements is useful for alfalfa production. In order to investigate the prediction of quality from growth characteristics, this experiment studied the growth and quality of alfalfa under different sprinkler irrigation levels. The experiment was conducted at the Shiyanghe Experimental Station for Water-Saving in Agriculture and Ecology of China Agricultural University in Wuwei, Gansu, over a period of two years. Three irrigation levels were applied: A₁ (100% measured evapotranspiration (ETc)), A₂ (66% of A₁), A₃ (33% of A₁) and A₄ (a rain-fed treatment). The results showed that plant height (H) and stem-leaf ratio (SLR) increased while the fresh-dry ratio (FDR) decreased with plant maturity. All these growth characteristics decreased with lowering levels of irrigation. In terms of quality, crude protein (CP) decreased but neutral detergent fiber (NDF) and acid detergent fiber (ADF) increased with plant maturity. NDF and ADF decreased and CP increased with lowering levels of irrigation. H and SLR had a significant linear relationship with quality (P<0.001). The coefficients of determination between quality and H (R²>0.900) were higher than those for SLR, while the results for FDR were not significant. These results imply that, when field management is good, alfalfa height could be used to estimate forage quality.

Spatio-temporal variations in grassland vegetation phenology in Xinjiang

ZHANG Ren-ping, GUO Jing, FENG Qi-sheng, LIANG Tian-gang

2018, 27(10):  66-75.  DOI: 10.11686/cyxb2017376

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Vegetation phenology is the most objective and sensitive indicator of environmental conditions and climate change. Therefore, grassland phenology research in Xinjiang has significance for understanding and predicting the dynamics of terrestrial ecosystems in this area. In this study, the spatio-temporal changes in grassland phenology in Xinjiang were evaluated using phenology data from the land cover dynamic product (MCD12Q2) for Xinjiang during 2001-2014. The main conclusions were as follows: 1) The perennial mean vegetation phenology in Xinjiang grassland showed obvious regional differences from low to high altitude. With every 1000 m increase in elevation, the SOG (start of the growing season) was delayed by 13 d, the EOG (end of the growing season) was advanced by 7 d, and the LOG (length of the growing season) was shortened by 20 d. 2) SOG occurred within 100th-136th days, EOG occurred within 256th-291th days, and the LOG occurred within 122-190 days. 3) Grassland SOG was advanced by 0.11 d·yr^-1, while the EOG was delayed by 0.14 d·yr^-1, and the LOG was prolonged by 0.25 d·yr^-1.

Effects of irrigation and nitrogen fertilizer on alfalfa quality

WEN Ya, ZHANG Jing, FENG Meng, GUO Zheng-gang

2018, 27(10):  76-83.  DOI: 10.11686/cyxb2017491

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The application of both nitrogen and irrigation have been shown to be beneficial to crop growth. A field experiment was carried out during 2015 in the Hexi Corridor to analyze the changeable characteristics of water use efficiency, quality and relatively feeding value of alfalfa under different irrigation regimes (W₁: 60% of conventional irrigation volumes; W₂: 80% of conventional irrigation; W₃: conventional irrigation) and nitrogen fertilizer levels (N₁: 0 kg·ha^-1; N₂: 40 kg·ha^-1; N₃: 80 kg·ha^-1; N₄: 120 kg·ha^-1). This study showed that the combination of different irrigation volumes and nitrogen fertilizer levels significantly affected the water use efficiency, crude protein content, neutral detergent fiber content and relatively feeding value of alfalfa but had no effect on aboveground biomass, crude fat content and crude ash content. Water use efficiency, crude protein content, neutral detergent fiber content and relatively feeding value of alfalfa all showed a downward trend (parabolic function) with increasing irrigation volumes and nitrogen fertilizer rate; the most beneficial combinations occurred in the W₂N₃, and W₂N₂ treatments which resulted in improved forage quality and relatively feeding value of alfalfa.

Effect of silicon supply on the salt tolerance of two tall fescue (Festuca arundinacea) varieties with different salt resistance levels

LIU Hui-xia, LIN Li-guo, WU Wen-li, LIN Xuan-dong, SONG Rui

2018, 27(10):  84-92.  DOI: 10.11686/cyxb2017466

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A study has been undertaken to explore the effect of silicon supply on the salt tolerance of two varieties of tall fescue (Festuca arundinacea), XD and K31. XD has stronger resistance to salinization than K31. A pot experiment was conducted to investigate the effect of silicon on the plants’ morphological indexes and protective enzyme activities under different salinization conditions. The results showed that plant height, tillers, leaf number, leaf length, leaf width, the aboveground biomass and water content of K31 and XD presented a decreasing trend with increases in salinity. The activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) firstly increased and then decreased with rising salinity. The activity of protective enzymes in XD and K31 peaked when salt concentrations were 150 and 100 mmol·L^-1. Silicon supplies significantly increased the tillers, leaf numbers, leaf length, plant height, aboveground biomass and water content, as well as SOD, POD and CAT activities, but the response of the two kinds of tall fescue varied under different salt concentrations. Silicon supplies significantly increased the tillers and leaf numbers of XD when salinity was below or at 50 mmol·L^-1, but they did not affect K31. However, the leaf length, plant height, aboveground biomass, SOD and CAT activities of XD significantly increased when salinity was below or at 100 mmol·L^-1. Silicon supplies also significantly increased the leaf length, plant height and aboveground biomass, SOD, POD and CAT activities of K31 when salt concentration was 150 and 200 mmol·L^-1. These results indicate that silicon supplies could enhance the salt resistance of both kinds of tall fescue and that the extent of enhancement varies with salt concentration and the degree of tall fescue resistance. Under higher salinization conditions, the improving effect of silicon supply on salt tolerance was stronger in tall fescue with weak salt tolerance. These results show that it is possible to expand the adaptive range of tall fescue by supplying silicon.

Effect of planting density on plant nutrients and their dynamics in PPS sorghum-sudangrass hybrids

HE Zhen-fu, HE Chun-gui, WANG Guo-dong, GE Yu-bin

2018, 27(10):  93-104.  DOI: 10.11686/cyxb2017469

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This study investigated the optimum planting density and harvest date of photoperiod-sensitive (PPS) sorghum-sudangrass hybrids in the rain-fed farming region of the Loess Plateau. Two hybrids, “Big Kahuna BMR” and “Monster”, were planted with 3 different densities (83300, 125000 and 166700 holes·ha^-1) on double ridge soil covered with plastic-film fully mulched. The contents of crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), total digestible nutrient (TDN) and brix (BX) were measured in the plants at different growth stages. Results showed that the growth and development process played a major role in the formation of plant nutritional ingredients. The nutritional difference between the 2 varieties was more significant in the early than late growing stages. The NDF, ADF and BX contents of “Big Kahuna BMR” were all lower than “Monster”, while its TDN contents were higher. CP content declined with increased planting densities. BX contents were more influenced by density in the early than middle or late stages. For the entire growth period, NDF and ADF contents in higher density plantings were significantly lower. In the late growth period (126 to 140 d after seeding), TDN contents progressively decreased as density increased. As density increased, the 2 varieties’ CP contents gradually decreased during the growth process, while BX contents increased. NDF, ADF and TDN contents trended as ascent-descent-ascent from 70 to 140 d after seeding. In the final period of 126 to 140 d, dry matter yield continued to increase but CP and TDN contents did not change significantly (although TDN decreased slightly). These dynamic changes in nutrient content and yield indicate the best harvest date for PPS sorghum-sudangrass. In terms of forage production, the optimum variety for spring sowing with a one-cut system for silage is “Big Kahuna BMR”, with 125000 holes per hectare the preferred density. For both varieties, the optimum harvest period is between 126 to 140 d after seeding (in early or mid-September), when “Big Kahuna BMR” is booting and “Monster” is flowering.

Research on exogenous NO and reverse regulation to the dynamic changes of antioxidant enzymes and isoenzymes in alfalfa seed germination under PEG stress

XIN Xia-qing, WEI Xiao-hong, HAN Ting, YUE Kai, ZHAO Ying

2018, 27(10):  105-112.  DOI: 10.11686/cyxb2017478

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To study the effects of exogenous NO and reverse regulation antioxidant enzyme activities and isoenzymes of alfalfa under PEG stress, alfalfa seeds were used as experimental materials, they were pretreated with nitric oxide donor sodium nitroprusside (SNP) or nitric oxide scavenger c-PTIO, the methods of spectrophotometry and isoenzyme electrophoresis were used to analyze the activities of antioxidant enzymes. The results showed that: under the PEG stress, the external application of 0.1 mmol·L^-1 SNP, the activities of POD were 32.72% lower than the PEG treatment on the 6th day; the activities of SOD and CAT were 10.48% and 23.60% higher than the PEG treatment on the 4th day respectively, so they could alleviate the oxidation damage on alfalfa seeds which caused by PEG stress. In addition, the exogenous of c-PTIO under drought stress inhibited the activity of antioxidant system during alfalfa germination stage. According to the number and intensity of isozymes, with prolonging the PEG stress time, the bands of POD isoenzymes activity increased, and only one strip on the second day, while 9 strips on the 4th day; the expression of isoenzymes of SOD and CAT were not significantly, but the strength of the enzyme band changed to some extent, the expression of S3 enzyme band was gradually weakened with prolonged the treatment time; CAT isoenzyme band had been kept at 2 bands all through, showed no significantly changes in strength. Therefore, exogenous NO rapidly responded to antioxidant enzymes during the germination of alfalfa under PEG stress and played an important protective role in the maintenance of oxygen free radical metabolism.

Effect of grassland community types on population characteristics, morphology and resistance of the dioecious herb Anaphalis lacteal

LIU Hang-jiang, ZONG Ren-xu, LIU Jin-ping, YOU Ming-hong, XU Xiao-xia

2018, 27(10):  113-124.  DOI: 10.11686/cyxb2017485

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The population characteristics (number, density, area, distribution coefficient, sex ratio, biomass ratio, water distribution and the resistant traits of females and males) of Anaphalis lacteal were investigated in five different habitats: improved Elymus sibiricus grassland (A), improved Phalaris armdinacea grassland (B), natural grassland (C), natural meadow (D) and desertification grassland (E). The results showed that A. lacteal population characteristics varied with the different community properties found in the five habitats (such as the dominant species, density and coverage of the community, species saturation, height of the dominant species and the physical and chemical traits of soils). The order of effect by habitat community on A. lacteal population properties was area>density>sex ratio>age structure>number>distribution coefficient. The highest number and distribution coefficient of the A. lacteal population were in D, while the largest area and density were in C. Compared with E, the population numbers of C and D were 30.21% and 35.11% respectively, while the distribution coefficient of C was 36.04%. A. lacteal age structure, sex ratio, height, root number, leaf number and area, inflorescence and flowers, the number of males or females and the stem diameter and bracts layer of males were significantly different among the community types (P<0.05). The numbers of females varied between 2.22 and 7.03 times higher than males. Sex differences were found in height, stem diameter, root length, leaf number and area, florets number and the bracts layer (P<0.05). Significantly higher total biomass and flower distribution ratios but lower root distribution ratios were observed in males than females (P<0.05). The order of effects by community type on biomass distribution was flower>total biomass>leaf>root>stem for females and flower>stem>leaf>total biomass>root for males. The water contents of stem, leaf and flower were significantly higher in males than females. The order of effects by community type on water content was flower>stem>leaf>root for female, and leaf>stem>flower>root for males. H₂O₂ and malondialdehyde (MDA) contents were the lowest in A and B and total antioxidant capacity activity was the lowest in D. The E. sibiricus community composition had highly significant effects on H₂O₂ and MDA contents and on the T-AOC activity of males and females. MDA content was higher in males than females, but H₂O₂ content and T-AOC activity was higher in females (P<0.05). These results indicate that male and female individuals of A. lacteal can develop different growth strategies across habitats based on component characteristics, biomass ratio, water distribution and resistance physiology. These strategies may produce advantages in habitat adaptation, life history and population fitness.

Prediction of the potential geographic distribution of Leymus chinensis based on MaxEnt and collection and protection of germplasm

WU Zi-nian, HOU Xiang-yang, REN Wei-bo, WANG Zhao-lan, CHANG Chun, YANG Yu-ping, YANG Yan-ting

2018, 27(10):  125-135.  DOI: 10.11686/cyxb2018052

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There is an abundance of germplasm resources of Leymus chinensis in China; basic research on the collection and protection of this germplasm is significant for grassland ecological construction and animal husbandry development. The potential geographic distribution of L. chinensis globally was predicted using the ecological niche model (MaxEnt). Germplasm was collected using a grid sampling method and held in germplasm nursery. Potential geographic distribution was predicted by combining the known distribution and field investigation. The results showed that the potential suitable distribution of L. chinensis is constricted within Eastern Eurasia, the main suitable areas are concentrated in Northeast China, North China, Mongolia to southern Russia, USA, Canada, Pakistan, India, Nepal, Bhutan, Kyrgyzstan and Kazakhstan also have scattered low suitability distribution potential, accounting for 8.75% of the total global land area. In China, the potential suitable distribution area is mainly found in Inner Mongolia, Northern Xinjiang, Heilongjiang, Qinghai, Gansu, Xizang, Jilin, Hebei, Shanxi, Shanxi, Liaoning, Shandong, Northern Henan, Northwestern Sichuan, Ningxia, Beijing, Tianjin, scattered in Northern Jiangsu, Hubei, Northern Yunnan and Northern Anhui, accounting for 38.3% of the total global distribution area and 54.7% of the total China land area. A total of 483 wild L. chinense germplasm accessions were collected from 361 sample points and established in a germplasm nursery. The results will provide important resources for the study of the origin, formation, genetic structure, breeding, cultivation division and ecological restoration of L. chinensis.

Effect of increasing precipitation on seed germination characteristics in the soil seed banks of Seriphidium transiliense desert grassland

Bademuqiqige, SUN Zong-jiu, LI Pei-ying, TIAN Meng, WU Yong-mei

2018, 27(10):  136-146.  DOI: 10.11686/cyxb2017486

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This study explored the adaptation mechanisms for seed germination of Seriphidium transiliense desert soil seed banks under six different precipitation treatments -CK, increased 5% (W₅), increased 10% (W₁₀), increased 15% (W₁₅), increased 20% (W₂₀) and increased 25% (W₂₅). The response of species composition, seed germination dynamics and density were measured at 0-5 cm and 5-10 cm layers, and the Sorensen similarity coefficient between the soil seed banks and aboveground vegetation was also analyzed. The results showed that species number and total germination density in the 0-5 cm layer increased with rising precipitation levels. Compared with CK (3 species, 146.5 grain·m^-2), the number of germination species in the 0-5 cm layer increased by 3.7 times in W₂₀ and 4.3 times in W₂₅, while total seed germination density increased by 65.2% and 195.6% respectively and on average total germination quantities occupied 2.8% of the soil seed bank (7.2×10³ grain·m^-2). Seed germination in the 5-10 cm layer changed at the same rate as the 0-5 cm layer, with total germination seed quantities occupying 6.2% of the storage bank (1.2×10³ grain·m^-2). Increased precipitation improved the germination density of Geranium transversale, Kochia prostrate and Taraxacum monochlamydeum. Sorensen similarity between the soil seed bank and aboveground vegetation also increased with rising precipitation, with the highest coefficient being 0.81. In summary, increased precipitation stimulated germination density in the S. transiliense desert soil seed bank, increased the number of germination species and the similarity coefficient between the soil seed bank and aboveground vegetation, all of which benefit the succession and restoration of degraded grassland.

Screening and genetic diversity analysis of chloroplast non-coding regions in Leymus chinensis

YANG Yan-ting, HOU Xiang-yang, WEI Zhen-wu, QIAO Zhi-hong, CHANG Chun, REN Wei-bo, WU Zi-nian

2018, 27(10):  147-157.  DOI: 10.11686/cyxb2018022

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The aim of this research was to screen for and classify polymorphic loci of chloroplast non-coding fragments in Leymus chinensis. The study evaluated 9 L. chinensis populations from different geographical locations to identify polymorphic loci from 12 chloroplast DNA (cpDNA) non-coding fragments, and then genetic diversity of the polymorphic cpDNA fragments was analyzed. The results showed that the polymorphic loci of ndhF-rpl32, trnL-trnF, trnC-ycf6 and aptI-aptH were rich, and they had a relatively fast evolution rate. Hence, they could be regarded as ideal molecular markers for future research on population genetics and phylogeography. Based on combined sequences there were 15 haplotypes identified. The haplotype diversity (Hd) and nucleotide diversity (Pi) were 0.928 and 0.00101 respectively. The genetic differentiation coefficient Fst was 0.58884 with the low gene flow (Nm=0.17). Tajima’s D and Fu’s Fs values of neutrality tests were negative (Tajima’s D=-1.0854; Fu’s Fs=-5.301), indicating that L. chinensis had experienced historical population expansion. Analysis of molecular variance showed that most of genetic variation was distributed among populations. The Mantel test showed a significantly positive correlation between genetic and geographical distance (r=0.449, P<0.05). The genetic differentiation coefficients Nst (0.386)>Gst (0.234) implied a significant phylogeographic structure for the populations. The neighbor-joining tree based on combined sequences showed that all haplotypes divided into two major clades, H2 and H10 clustered into a category. The network for cpDNA haplotypes based on combined sequence data showed that the relationships among H2 and H12, and H10 and H12 were further than others, which was similar to the pattern identified by the neighbor-joining tree. These results will be useful for future research on germplasm resources and phylogeography.

Effect of different levels of alfalfa meal on productivity and reproductive performance of primiparous sows

QI Meng-fan, LOU Chun-hua, ZHU Xiao-yan, CHEN Wen-xue, SHI Ying-hua, WANG Cheng-zhang

2018, 27(10):  158-170.  DOI: 10.11686/cyxb2018021

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The objective of this study was to explore the effects of different proportions of alfalfa meal in the diet of replacement gilts and pregnant sows on production and reproductive performance. 640 healthy gilts (Landrace×Large white) 110 days of age and 45 kg live weight were randomly divided into four treatment groups; control group (0% alfalfa meal), 5% alfalfa meal group, 10% alfalfa meal group and 15% alfalfa meal. Each treatment was replicated 4 times with 40 pigs in each replicate. The gilts offered 5% alfalfa meal had the best daily weight gain and estrus percentage. These animals were selected for on-going assessment and divided into a control group-Ⅰ(0% alfalfa meal), 10% alfalfa meal group, 15% alfalfa meal group and 20% alfalfa meal group following estrus and artificial insemination. The replacement gilts in the initial control group were retained in the control group (0% alfalfa meal) during the gestation period. There were 5 treatments with 4 replicates each treatment and 3 pigs in each replicate during pregnancy. The results showed that in replacement gilts weighing 45-70 feed intake of the alfalfa meal groups was lower than the control group, with greater reductions as alfalfa meal proportion increased. The daily gain and feed conversion rate in the 5% alfalfa meal group were significantly higher than those of 10% and 15% alfalfa meal groups (P<0.05), however, there were no differences between 5% alfalfa and control group. The weight gain cost of the 5% alfalfa meal group was lower than the control group. At 70-130 kg live weight, both feed intake and the daily gain in the three alfalfa meal groups were lower than the control group; the 10% and 15% alfalfa meal groups were significantly lower than the control group (P<0.05), declining linearly as alfalfa meal increased. The F/G (ratio of feed to gain) and the weight gain cost of the 3 alfalfa meal groups were higher than the control group, and had an increasing tendency with increasing % of alfalfa meal in the diets; the 15% alfalfa meal group was significantly higher than the control group (P<0.05). The estrus rate of gilts in the 5% alfalfa group was improved, but there were no difference among the 4 treatments. In pregnancy, the back fat thickness of the all alfalfa meal groups were significantly higher than the control group and the control group- Ⅰ(P<0.05). The live birth litter size of control group-Ⅰand the 10%, 15%, 20% alfalfa meal groups was significantly higher than that of control group, and the newborn litter weight was increased by 14.9%, 6.9%, 12.3% and 24.5% respectively, while the % of weak piglets declined by 53.44%, 36.39%, 87.37% and 62.78%, respectively. It was concluded that the growth performance of gilts fed 5% alfalfa meal was not affected but estrus rate and reproductive performance were improved. During pregnancy, live birth litter size, birth litter weight and piglets' health were greatest in the group fed 20% of alfalfa meal in the diet.

Evaluation of import dependency risk for livestock products in China based on food security

WU Yuan, GAO Song, GAO Ya-ling, LIN Hui-long

2018, 27(10):  171-182.  DOI: 10.11686/cyxb2017528

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The protection of China’s livestock product supply security to protect China’s food security is an important objective for China and ‘moderate import’ levels is one of the important ways of protect the supply security of livestock products in China. To define ‘moderate imports’ we need to analysis the import relevant risks of livestock products. Based on the import dependency evaluation model, we studied the import dependence of pork, chicken, mutton, beef and fresh milk. We found that five kinds of livestock products have import dependency risk. Pork risk comes from the United States, Germany, Denmark, Spain and Canada; risk with chicken comes from the United States, Brazil, Argentina and Poland; lamb risk comes from Australia, New Zealand and Uruguay; beef risk comes from Uruguay, Australia, New Zealand, Argentina and Canada; fresh milk risk comes from Germany, France, New Zealand and Australia. In order to reduce the risk of import dependency China, in the short-term, should develop livestock products import market strategy and focus on importing forage instead of imported livestock products; longer-term China should, under the premise of guaranteeing ‘rations security’, adjust agricultural industry structures, vigorously develop grassland agriculture and reduce dependence on the international market.

Effect of crop rotation patterns on field soil properties and medicinal material yield for Angelicae sinensis in alpine regions

YUAN Hong-chao, GUO Feng-xia, CHEN Yuan, BAI Gang, LIANG Wei

2018, 27(10):  183-193.  DOI: 10.11686/cyxb2018138

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Continuous cropping causes Angelica sinensis (DG) medicinal yield to reduce year by year. In order to study the effects of crop rotation patterns on soil factors and the medicinal yield of A. sinensis, data on relevant soil and yield factors were collected from residue sites where A. sinensis is grown in rotation with other medicinal crops such as Gentiana macrophylla (QJ-DG) and Notopterygium incisum (QH-DG), and compared with data from sites where A. sinensis is grown in continuous cropping systems (DG-DG, or control). The data were assessed by membership function and cluster analysis so to provide an objective basis for classifying the rotation pattern. It was found that the rotation patterns had significant effects on the soil properties and the medicinal yield of A. sinensis. The QJ-DG rotations effectively improved the soil properties, resulting in higher organic matter, but lower total K and P. Notably, increased soil organic matter in these systems was linked to improved soil water retention which in turn increased patent medicine plant rate by 94.10%, fresh individual root weight by 53.46% and total fresh medicinal yield by 125.56%, compared with DG-DG. However, in contrast, QH-DG rotations showed higher pH and lower total organic content, but higher organic content rich in P and K, and lower soil water retention appeared in the DG-DG control sites. Thus data from all sites were clustered into three categories ranked for medicinal productivity of A. sinensis as QJ-DG>DG-DG>QH-DG and comprehensive scored as QJ-DG (0.8132)>QH-DG (0.3315)>DG-DG (0.2051) in the cluster analysis. In summary, the crop rotation used has affected soil properties and growing A. sinensis in rotation with G. macrophylla improved the soil environment, resulting in the higher medicinal root yield.

Coupling degree as a measure of land use efficiency under two interaction patterns between arable farming and pastoral grazing systems in the agricultural-pastoral transition zone in Southern Tibet

XU Cheng-qi, XU Hai-peng, JIN Shao-hong, SHU Chao-cheng, GUO Zheng-gang

2018, 27(10):  194-203.  DOI: 10.11686/cyxb2017465

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The coupling of spatially separated arable farming and pastoral grazing systems is one of the effective ways to increase the overall productive capacity of larger geographic regions in a climate transition zone. The coupling model of land use was used in this study to quantify the coupling degree of socio-economic benefits and ecological-environmental benefits under two interaction patterns of farming and pastoral grazing systems in Southern Tibet: (i) ‘breeding’ animals in a pastoral grazing region, and ‘fattening’ them in farming region, or (ii) ‘carrying forage’ from a farming region to pastoral grazing region for consumption by livestock. This study showed that the socio-economic benefits and ecological-environmental benefits from breeding animals in a pastoral grazing region and fattening them in a farming region gradually increased from 2008 to 2016. The ecological-environmental benefits of carrying forage from arable farming regions to livestock in pastoral grazing regions also showed a rising trend during the same period. However, the socio-economic benefits of the latter system displayed a wave-like dynamic state. The coupling degrees for the two interaction patterns of arable farming and pastoral grazing were in a state of coordinated development; however, the pattern of breeding animals in pastoral grazing regions and fattening them in arable farming regions was more sustainable than that of carrying forage from farming regions to pastoral regions for livestock use. These results provide a paradigm to quantify the coupling model of land use efficiency under two alternative interaction patterns linking arable farming and pastoral grazing land use in neighboring regions.

Cultivation and utilization of alfalfa in the Ming Dynasty

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

2018, 27(10):  204-214.  DOI: 10.11686/cyxb2017501

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Alfalfa was recorded in many classical publications including Jiuhuang Bencao, Bencao Gangmu, Qunfang Pu, Nongzheng Quanshu, Emperor Chronicles from the Ming Dynasty and Local Chronicles, indicating that alfalfa was important, studied commonly and cultivated widely. Based on the ancient codes and records of alfalfa in the Ming dynasty, plant textology principles and methods were applied to create modern research findings concerning alfalfa during this period. This included alfalfa distribution and state of cultivation, ecological and biological characteristics, cultivation and utilization. This revealed that in the Ming dynasty alfalfa was planted in Shanxi, Shannxi, Hebei, Henan, Shandong, Anhui, Jiangsu, Gansu and Ningxia provinces and in Beijing. The countries planting alfalfa the most were Sanjin, followed by Qin and Lu, and Yan and Zhao. The accurate description of alfalfa plant morphology, flower color, pod attachment, and pod and seed shape had reached levels seen in modern phytology; they were excellent. The alfalfa tap toot was recognized. Purple and yellow flowered varieties were recorded in the Ming Dynasty. Alfalfa was often planted with buckwheat, because of its ability to fix nitrogen. Alfalfa was typically planted in July or August and cut three times a year, but when cultivated for seed production was cut once a year. Alfalfa went into an exuberant period three years after planting, and was turned over after 7 or 8 years because of declining production. It was cut for horse and cattle forage when it flowered, indicating that farmers were aware of the optimum time to harvest. Alfalfa was also used when offering tributes.

Root architecture of eight Gramineae plant species in the Benggang area of Changting County

LI Si-shi, SI Xiao-jing, JIANG Fang-shi, LIN Jin-shi, CAI Xue-zhi, WU Yu, HUANG Yan-he

2018, 27(10):  215-222.  DOI: 10.11686/cyxb2017490

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In order to explore the root architecture of herbaceous plants in the Benggang area, eight Gramineae species were studied (Imperata cylindrica, Eulalia speciosa, Miscanthus floridulus, Eriachne pallescens, Cynodon dactylon, Paspalum wettsteinii, Pennisetum sp. and Vetiveria zizanioides). Six root architecture parameters were analyzed and comprehensively evaluated using principal component analysis. The results showed that the average diameter of the tested herbaceous roots was between 0.36 and 0.63 mm. There were no significant differences in the total root length of E. speciosa, M. floridulus, E. pallescens, P. wettsteinii and V. zizanioides. The total root surface area, total root volume, root tip numbers and crossing numbers varied by plant species. The total root surface area of Pennisetum sp. was the largest and that of I. cylindrica the smallest. The root tips and crossing numbers of Pennisetum sp. were also the largest. Average diameter, total root surface area and total root volume were the main factors influencing root architecture. The composite score order of the eight species’ roots was Pennisetum sp.>P. wettsteinii>E. speciosa>M. floridulus>V. zizanioides>E. pallescens>C. dactylon>I. cylindrica. These results help to provide a scientific basis for the screening, allocating and popularizing of herbaceous plants for the control of erosion.