Table of Content

20 July 2017, Volume 26 Issue 7

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Prediction of geographical distribution of Vitex trifolia var. simplicifolia under climate change based on the MaxEnt model

WANG Ya-Ling, LI Hao, YANG Xuan, GUO Yan-Long, LI Wei-De

2017, 26(7):  1-10.  DOI: 10.11686/cyxb2016356

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Vitex trifolia var. simplicifolia (Viticis fructus) is not only valuable as a medicinal plant, but also ecologically important. It can function as a wind break, and it stabilizes sand and soil, and it conserves water. Predicting the impact of climate change on the spatial distribution of V. trifolia var. simplicifolia may provide a scientific basis and reference for the sustainable use of this important plant. Using a Maximum Entropy (MaxEnt) model, we simulated the geographical distribution of V. trifolia under the current climatic conditions in China based on species presence data at 126 locations and data for 22 environmental factors. Then, we used the model to predict the future distributions of V. trifolia in two periods (2050s and 2070s) under four different climate change scenarios. The results showed that the MaxEnt model was highly accurate (mean area under ROC curve, 0.988). The main climatic factors influencing the geographic distribution of V. trifolia were altitude, mean diurnal air temperature range, precipitation in the coldest quarter, and precipitation in the driest month. The model simulations indicated that, under the four scenarios, V. trifolia will widen its distribution because of a rapid increase in suitable habitat areas and a slow increase in marginally suitable habitat areas. During the period of 2041-2060, the potential distribution area of suitable habitat would increase from the current ratio of 5.03% to 15.88%, 17.00%, 17.59%, and 23.11% under scenarios 1-4, respectively. The potential distribution area of marginally suitable habitat would increase from the current ratio of 8.86% to 11.09%, 10.31%, 11.53%, and 12.96% under scenarios 1-4, respectively. During the period of 2061-2080, the potential distribution area of suitable habitat would increase to 21.22%, 22.21%, 24.57%, and 30.66% under scenarios 1-4, respectively, and the potential distribution area of marginally suitable habitat would increase to 11.85%, 12.07%, 13.99%, and 14.66% under scenarios 1-4, respectively. In terms of the spatial distribution of the potential habitat area of V. trifolia, both the distributional range and the center of distribution of suitable and marginally suitable habitat areas would shift from coastal areas to inland. The distribution of suitable habitat area in Hunan and Jiangxi provinces would increase rapidly. Especially in Sichuan Province, where there is only a small percentage of marginally suitable habitat area currently, the potential marginally suitable habitat area would increase, and the suitable habitat area would appear and increase rapidly under climate change.

Soil erosion assessment based on the RUSLE model in the Three-Rivers Headwaters area, Qinghai-Tibetan Plateau, China

LIN Hui-Long, ZHENG Shu-Ting, WANG Xue-Lu

2017, 26(7):  11-22.  DOI: 10.11686/cyxb2016371

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Investigating soil erosion in the Three-Rivers Headwaters area is of great significance for the protection of the ecology, production, and function of the alpine meadow ecosystem on the Qinghai-Tibetan Plateau. In this study, we conducted a comprehensive analysis of soil erosion, its spatial characteristics, and the factors affecting it in the Three-Rivers Headwaters area. For these analyses, we used a ¹³⁷Cs tracing technique, GIS (Geographic Information System), and the RUSLE (Revised Universal Soil Loss Equation) model. The results showed that: 1) soil erosion factors showed spatial heterogeneity. Rainfall-related erosion showed drastic inter-annual changes, but generally increased from 2001 to 2012. Soil erodibility varied spatially, and soils with a high erodibility index accounted for 95.66% of the total area. The spatial distribution of slope and slope length were significantly influenced by the altitude. The vegetation cover and management factors showed spatial heterogeneity from the northwest to the southeast of the study area, and overgrazing was the main cause of serious underlying surface erosion. 2) In the validated RUSLE model, the correlation coefficient was 0.49 and the average root mean square error (ARMSE) was 75.29%. Although the RUSLE model tended to overestimate soil erosion, it was still one of the best choices to simulate alpine meadow soil erosion in the Three-Rivers Headwaters area. 3) The total average erosion volume estimated by the RUSLE model (2001-2012) was 3.1×10⁹ t/yr. Analyses of the erosion intensity classifications revealed the areas of moderate, strong, and extremely strong erosion. The three areas with the highest degrees of erosion were Tanggula township, and Zhiduo and Xinghai counties. 4) Taking into account the amounts of soil loss and market values, the estimated average economic loss of organic matter was 114354 RMB/km² in the study area from 2001 to 2012, the total annual economic loss was 39.9 billion, and economic losses caused by soil erosion were substantial across the whole study area. Therefore, it is very important to develop “classification, grade, segment, partition” soil erosion prevention and control procedures for the Three-Rivers Headwaters area of the alpine grassland on the Qinghai-Tibetan Plateau.

Monitoring of above-ground biomass in alpine grassland based on agricultural digital camera and MODIS remote sensing data: A case study in the Yellow River Headwater Region

GE Jing, MENG Bao-Ping, YANG Shu-Xia, GAO Jin-Long, YIN Jian-Peng, ZHANG Ren-Ping, FENG Qi-Sheng, LIANG Tian-Gang

2017, 26(7):  23-34.  DOI: 10.11686/cyxb2017010

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We collected grassland biomass and MODIS satellite remote sensing data, and calculated vegetation indices (VIs) from data obtained by an agricultural digital camera (ADC) in the Yellow River Headwater Region (YRHR) in August of 2015-2016. We explored the correlations between each of three ADC vegetation indices (NDVI_ADC, SAVI_ADC, and GNDVI_ADC) and field-measured grassland above-ground biomass (AGB), and selected the optimal ADC vegetation index to construct an AGB inversion model. Grassland AGB inversion models based on ADC vegetation indices and MODIS NDVI (denoted as NDVI_MOD) were constructed, and the accuracy of each model was evaluated by leave-one-out cross validation (LOOCV) to identify the optimal grassland AGB monitoring model. The NDVI_ADC was used to correct the NDVI_MOD to obtain the optimized grassland AGB model with high resolution and accuracy. The results showed that: 1) among the three VIs-based ADC indices, the NDVI_ADC was most closely related to the AGB of alpine grassland, followed by SAVI_ADC and GNDVI_ADC. 2) The NDVI_ADC-based AGB monitoring model (RMSEP: 383.55-393.18 kg DW/ha; r: 0.65-0.66) was more accurate than the NDVI_MOD model (RMSEP: 421.08-427.00 kg DW/ha; r: 0.55-0.58). Therefore, the grassland AGB inversion value from the NDVI_ADC-based model was much closer to the actual grassland AGB in YRHR, and the sampling values of NDVI_MOD were higher than those of NDVI_ADC as a whole. 3) Among the four models based on NDVI_ADC, the linear and power models showed better performance in grassland AGB simulations. The linear model (y=3248.93×NDVI_ADC-305.59, RMSEP=383.55 kg DW/ha, r=0.66) was more accurate than the power model, and the linear model provided a novel and simple method to estimate grassland biomass in the study area.4) There was a strong correlation between NDVI_ADC and NDVI_MOD; therefore, we could obtain an optimized grassland AGB model by using NDVI_ADC to correct NDVI_MOD. The optimized model was y=2455.54×NDVI_MOD-301.69. This model could be used to estimate the grassland biomass in YRHR on a large scale, and its precision was close to that of the field measurements.

Herbaceous plant species diversity and functional diversity in the forest-steppe zone of Hebei, China

GE Zhao-Xuan, SUN Guo-Long, YUAN Ye, HUANG Xuan-Rui, ZHANG Zhi-Dong

2017, 26(7):  35-44.  DOI: 10.11686/cyxb2017015

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Understanding the relationships between environmental/soil factors and plant species diversity and functional diversity is useful for identifying which factors have the strongest effects on plant communities. In this study, we first studied the relationships between different components of herbaceous plant species diversity (species richness, Shannon-Wiener diversity, and Pielou evenness) and functional diversity indices (functional richness, functional evenness, and functional dispersion). Then, we used methods of analysis of similarities (ANOSIM) and redundancy analysis to explore their variation across three vegetation types (grassland, shrub, and natural secondary forest) and different environmental gradients. The results showed that species richness and Shannon-Wiener diversity were significantly higher in grassland than in shrub and natural secondary forest (P<0.05); however, the lowest functional richness was in grassland (P<0.05) and the lowest functional evenness and functional dispersion were in shrub forests (P<0.05). There was no significant difference in Pielou evenness among the three vegetation types (P>0.05). Functional richness was negatively related to species richness and Shannon-Wiener diversity (P<0.01). Functional dispersion was significantly positively correlated with species evenness (P<0.01), whereas functional evenness had a non-significant correlation with all species diversity indices (P>0.05). The main factors affecting species diversity were soil water content, soil organic matter, soil pH, soil total nitrogen content, and aspect. The main factors correlated with functional diversity were soil organic matter, soil depth, soil water content, and altitude. Consequently, soil factors were the vital determinants of plant species diversity and functional diversity in the study area, and accounted for 29.1% and 29.8% of the total variance explained by environmental factors, respectively. The results showed that herbaceous plant species diversity and functional diversity varied independently in the study area. Species diversity was mainly determined by resource availability, whereas functional diversity was mainly related to niche differentiation (the effects of both environmental filters and species interactions).

Root distribution characteristics of Vetiveria zizanioides and Digitaria sanguinalis and their effects on the anti-erodibility of purple soil in slopelands

WANG Run-Ze, CHEN Yun, LI Tie, PENG Shi-Lei, LIU Zhi-Peng, SHAN Zhi-Jie

2017, 26(7):  45-54.  DOI: 10.11686/cyxb2016353

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The aim of this study was to investigate the characteristics of grass root distribution and its effects on soil anti-erodibility in purple soil areas. Two grass species, Vetiveria zizanioides and Digitaria sanguinalis, growing on slopelands were chosen as the experimental materials. Root and soil samples were taken from 0-10, 10-20, and 20-30 cm soil depths. Root parameters, soil shear strength, and anti-scourability of the root-soil system were measured to explore the relationship between root distribution and soil anti-erodibility. The values of overall root parameters and diameter parameters (root length density, root surface area density, root volume density, and root weight density) were higher for V. zizanioides roots than for D. sanguinalis roots in 0-30 cm soils. Compared with D. sanguinalis roots, V. zizanioides roots were more conducive to reducing soil bulk density, improving soil microaggregate composition, and increasing the soil organic carbon content. Soil shear strength and anti-scourability of the root-soil systems were highest in 0-10 cm soils and lowest in 20-30 cm soils. The values of both parameters were higher for V. zizanioides than for D. sanguinalis. A correlation analysis indicated that 1.0<d (diameter)≤2.0 mm was the critical diameter class affecting cohesion and the anti-scourability index, followed by d≤1.0 mm. The results of this study provide a theoretical basis for vegetation management strategies to conserve soil and water in purple soil areas.

Effect of Salix cupularis shrubs on soil nitrogen in the alpine sandy land of Northwest Sichuan

SHU Xiang-Yang, HU Yu-Fu, HE Jia, WANG Qin, JIA An-Du, SHE Shu-Feng, WANG Qian

2017, 26(7):  55-61.  DOI: 10.11686/cyxb2016343

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In this study, we evaluated the effect of Salix cupularis shrubs on the spatial heterogeneity of soil nitrogen, soil water content, and soil pH in the alpine sandy land of Northwest Sichuan, China. The soil water content was higher inside shrub canopies than outside. However, the soil pH was higher outside of shrub canopies than inside. Soil total nitrogen, available nitrogen, ammonium nitrogen, and nitrate nitrogen contents were significantly higher inside the shrub canopies than outside (P<0.05). Soil nitrite nitrogen was higher outside of shrub canopies than inside. These results indicate that the presence and distribution of S. cupularis shrubs can affect the nutrient patterns in soil.

Mutagenic effect of ⁶⁰Co-γ irradiation on turf characteristics of Paspalum vaginatum

LIU Tian-Zeng, XIE Xin-Chun, ZHANG Ju-Ming

2017, 26(7):  62-70.  DOI: 10.11686/cyxb2016352

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Seashore paspalum (Paspalum vaginatum) is a salt-tolerant plant that does not require good-quality water for irrigation. Therefore, it has the potential to greatly reduce fresh water consumption and waste. To date, however, no new seashore paspalum cultivars have been bred in China. Mutation is an important method for breeding new varieties of plants, including turfgrass. The objective of this study was to breed new strains of seashore paspalum with the ⁶⁰Co-γ radiation method. Sprigs of “Sea Isle 2000”, “Platinum”, “Supreme”, and “Salam” were radiated at five different radiation intensities, and then favorable mutants were screened by comparing leaf width, leaf length, plant height, stolon length, stolon diameter, and stolon density with those of unirradiated controls. Nine mutants were acquired by ⁶⁰Co-γ irradiation of sprigs of seashore paspalum. Compared with the control plants, the mutants showed greater plant height, leaf length, and leaf width. The turf qualities of the mutants “SI-50-1”, “PL-40-2” and “SLM-45-1” were better than those of the control. In conclusion, we have identified the appropriate radiation intensity of ⁶⁰Co-γ for mutation of seashore paspalum, and we have generated several new mutants of this important plant.

Genetic diversity analysis of Kentucky Bluegrass cultivars by RAPDs

TU Ming-Yue, LI Jie, HE Ya-Li, LI Xing, LI Jun, YUAN Xiao-Jun

2017, 26(7):  71-81.  DOI: 10.11686/cyxb2016374

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There are many commercial cultivars and wild germplasms of Kentucky bluegrass (Poa pratensis), an important cool-season turfgrass widely cultivated in temperate regions worldwide. In this study, 72 Kentucky bluegrass materials from China and elsewhere were collected and evaluated at the seedling stage by recording plant height, number of tillers, leaf width, and leaf color. All these traits differed significantly among the germplasms. Polymorphic bands were amplified from these germplasms by using random amplified polymorphic DNA (RAPD) primers. A total of 115 polymorphic bands (91%) was generated using 20 RAPD primers. The dendrogram grouped these germplasms into two main clusters. The first cluster contained four domestic varieties (‘KBG04’, ‘KBG03’, ‘Huhe 2’, and ‘Zahe’), while the second cluster contained the other varieties. The second group had a higher genetic similarity coefficient, and was divided into three subgroups: GroupⅠ consisting mainly of imported varieties, and Group Ⅱ and Group Ⅲ with mainly wild germplasms. The clustering analysis based on the RAPDs data was partly consistent with the source of the materials, but there was no correlation with seedling phenotypic traits.

Effects of alfalfa flavonoids as dietary additives on bacterial flora in the rumen of dairy cows

ZHAN Jin-Shun, WU Cai-Xia, LIU Ming-Mei, SU Xiao-Shuang, ZHAN Kang, ZHAO Guo-Qi

2017, 26(7):  82-89.  DOI: 10.11686/cyxb2016358

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The objective of this study was to examine the effects of alfalfa flavonoids on the bacterial flora in the rumen of dairy cows. Four primiparous Holstein cows fitted with ruminal cannulas were used in a 4×4 Latin square design and were fed a total mixed ration containing 0, 20, 60, or 100 g alfalfa flavonoids per day (group A-D, respectively). The experiment had four periods and each period lasted 24 days. The ruminal fluid was collected during each period. Total bacterial DNA was extracted from the ruminal fluid, and 16S RNA sequences were obtained using the Illumina MiSeq platform. In total, 52747 operational taxonomic units (OTUs) were generated, and 16142 OTUs were shared by four groups, accounting for 30.60% of the total OTUs. The largest amount of OTUs was in group A. As the amount of alfalfa flavonoids in the diet increased, the Shannon index first increased and then decreased, but the abundance-based coverage estimator and Chao 1 indexes were unaffected. Simpson’s index was significantly higher for group C than for groups A and D (P<0.05). There were more bacterial genera in group C than in groups B and A, but the number of phyla in each group was not affected by the amount of alfalfa flavonoids in the diet. At the phylum level, the relative abundance of SR1 tended to increase linearly (0.05<P<0.10), and the relative abundance of Synergistetes first decreased and then increased (0.05<P<0.10) as the amount of alfalfa flavonoids in the diet increased. At the genus level, the relative abundance of RC9 and SP3-e08 was higher in group B than in group A, while the relative abundance of Oribacterium was higher in group A than in group B. The relative abundance of Shuttleworthia increased linearly with increasing alfalfa flavonoids (P<0.05), and the relative abundance of Shuttleworthia was significantly higher in group D than in group A. In a clustering analysis, the bacterial community structure was similar in groups A and B, and in groups C and D. In conclusion, dietary supplementation with alfalfa flavonoids can change the composition and community structure of ruminal bacteria, thus affecting metabolism and nutrient digestion.

Effect of supplementary feeding on livestock and production efficiency of Hulun Buir short-tail sheep before lambing

LI Jiang-Wen, LI Zhi-Guo, JIANG Li-Hong, JIN Yu-Xi, WANG Shu-Xin, HAN Meng-Qi, YU Feng-Yuan, HAN Guo-Dong

2017, 26(7):  90-97.  DOI: 10.11686/cyxb2017027

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Winter feeding is a very important practice in sheep farming in Inner Mongolia grassland pastoral areas. The aim of this study was to determine the effects of supplementary feeding before lambing on sheep weight and body size, and economic benefits. Sixty pairs of Hulun Buir short-tailed sheep were selected as the test subjects. One month before lambing, the experimental group was fed with concentrated feed, and the control group was fed with only hay. Changes in the body weight, body size, and economic benefits of livestock within 100 days were analyzed. Variance analyses were conducted with SAS (statistics analysis system) and partial least squares regressions were conducted with SIMCA-P11 (simple principal component analysis). These analyses allowed us to determine the effects of prenatal feeding on the individual and production efficiency of livestock, and on the main body weight of livestock. The results showed that, in the 100-day period, the weight of females decreased and then increased. The chest circumference, chest width, body height, chest depth, body length, and body oblique length were significantly higher in the experimental group than in the control group at about 1 month after birth (P<0.05). The main indexes influencing the body weight of Hulun Buir short-tail sheep were chest width, body height, and chest depth; together, these factors explained more than 50% of the variance in body weight. The survival rate and the selling price of newborn lambs was significantly higher in the experimental group than in the control group (P<0.05). Supplementary feeding before lambing not only affected the body weight and body size indexes, but also played an important role in improving the survival rate and increasing economic benefits. These results provide a theoretical basis for the breeding and care of ewes and the precise elimination of livestock.

Effects of feeding with natural grass hay on meat quality of Wadi sheep in an arable region

MIAO Fu-Hong, LI Yong-Zhen, YANG Guo-Feng, LIU Hong-Qing, SUN Juan, LIN Ying-Ting

2017, 26(7):  98-105.  DOI: 10.11686/cyxb2016369

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The aim of this study was to investigate the effects of feeding with natural grass hay on the meat quality of Wadi sheep in an arable region. A total of 27 Wadi sheep [average body weight, (20.0±0.5) kg; 4 months old] were randomly divided into three groups: Group Ⅰ was fed with natural grass hay, Group Ⅱ was fed with maize silage and peanut vine, and Group Ⅲ was fed with maize silage and alfalfa. Each group was divided into three replicates, with three sheep per replicate. The experiment lasted for 105 d, and consisted of an adaptive period (15 d) and a trial period (90 d). There were no significant differences in fresh color, marbling, pH, and cooked meat rate (P>0.05) among the three groups. The water loss rate of Group Ⅰ was significantly lower than those of Groups Ⅱ and Ⅲ (P<0.05). Similarly, the shear force of Group Ⅰ was significantly lower than that of Group Ⅱ (P<0.05). There were no significant differences in crude protein, ether extract, or moisture (P>0.05) among the three groups. The ash content was higher in Group Ⅰ than in Group Ⅱ (P<0.05), but did not differ significantly between Group Ⅰ and Group Ⅲ (P>0.05). The total amino acids content did not differ significantly among the three groups (P>0.05), but the flavor amino acids content was higher in Group Ⅰ than in Group Ⅱ (P<0.05). These results show that feeding with natural hay can improve the edibility, flavor, and nutrient content of Wadi sheep meat. Therefore, this practice should be conducted in arable regions.

Effects of supplementary feeding in late pregnancy on Gansu Alpine Fine-Wool ewes

ZHANG Chang-Ji, ZHANG Yong, GUO Wu-Jun, ZHANG Li-Ping, GUN Shuang-Bao

2017, 26(7):  106-115.  DOI: 10.11686/cyxb2016302

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The nutrient intake of Gansu Alpine Fine-Wool ewes is often insufficient during late pregnancy. Therefore, three complementary concentrates (type Ⅰ, Ⅱ, and Ⅲ) with different energy and protein levels were designed and tested as supplementary feeds for Gansu Alpine Fine-Wool ewes during late pregnancy. Sixty healthy ewes with similar body weight in late pregnancy were randomly divided into four groups (A, B, C, and D). Each group comprised of 15 ewes with 1 ewe per replicate. Groups A, B, and C were fed with supplementary feed Ⅰ, Ⅱ, and Ⅲ, respectively, while group D was grazed on pasture according to the local practice. The experiment lasted for 68 days. The average daily weight gain of group A, B, C was 102, 109 and 114 g, respectively, and the lamb birth weight was 4.09, 3.91 and 4.40 kg, respectively. These values were higher than the corresponding values in group D. The serum glucose, triglyceride, and blood urea nitrogen concentration in ewes were significantly affected by supplementary feed Ⅲ (P<0.05). The total protein and aspartate transaminase contents were significantly affected by feed Ⅱ. The total nitrogen and rumen protein nitrogen contents in the rumen liquid of ewes were significantly higher in groups A, B, and C than in group D (P<0.05), and were significantly higher in group A than in groups B and C. The highest urea nitrogen content was in group B (P<0.05). The concentration and molar ratio of volatile fatty acids were significantly higher in groups A, B, and C than in group D (P<0.05), and the acetate/propionate ratio was significantly lower in groups A, B, and C than in group D (P<0.05). The rumen fluid pH and ammonia nitrogen concentration did not differ significantly among the four groups (P>0.05).

Determination of appropriate levels of exogenous fibrolytic enzyme supplementation for substrates with different non-fiber carbohydrate/neutral detergent fiber ratios based on in vitro gas production

CHEN Guang-Ji, SONG Shan-Dan, PENG Zhong-Li, WANG Pu-Chang, WU Jia-Hai, WANG Xiao-Li, GUO Chun-Hua, WANG Zi-Yuan, GAO Yan-Hua, LI Xiao-Dong, BAI Xue, FU Xi-San

2017, 26(7):  116-127.  DOI: 10.11686/cyxb2017055

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The objective of this study was to determine the appropriate level of exogenous fibrolytic enzyme (EFE) supplementation for substrates with different non-fiber carbohydrates/neutral detergent fiber (NFC/NDF) ratios. The experiment had a cross group design with two factors and five levels. Five substrates with different NFC/NDF ratios (0.85, 1.02, 1.19, 1.36, and 1.53; sub1-5) were supplemented with EFE at five levels (0, 2, 4, 8, and 16 mg/g dry matter/DM) and in vitro gas production, degradation, and fermentation profiles were determined. The results can be summarized as follows: 1) The NFC/NDF ratio influenced total in vitro gas production (GP₄₈) and gas production parameters (b, c, and L) (P<0.05). The interaction between NFC/NDF ratio and EFE level was significant for gas production parameters (P<0.05).In sub1, as the EFE level increased, GP₄₈, b, and c increased (linear and quadratic effect, P<0.05), and the highest GP₄₈, b, and c were in the 16 mg/g EFE treatment; L showed the opposite trend. In the sub2-4 treatments, the highest GP₄₈, b, and c were in the 4 mg/g EFE treatment. 2) The NFC/NDF ratio in the substrate significantly affected the dry matter disappearance rate (DMD), acid detergent fiber degradation rate (ADFD), neutral detergent fiber degradation rate (NDFD), and nitrogen degradation rate (ND) (P<0.05). The additive effects of EFE produced similar results, except for ND. In sub1, as the EFE dose increased, DMD, ADFD, and NDFD linearly increased (P<0.05). The maximum values of DMD, ADFD, and NDFD were in the 16 mg/g EFE treatment in sub1 and in the 4 mg/g EFE treatment in sub2-4 (P<0.05). 3) The fermentation profile differed significantly among substrates with different NFC/NDF ratios and different levels of EFE supplementation (P<0.05), and the two factors had a significant interaction effect (P<0.05) for all fermentation parameters, except for propionate. For sub1-4, as the EFE levels increased, the fermentation profiles of all parameters except for propionate increased or decreased (quadratic effect, P<0.05). In sub1, pH, ammonia-N, and the butyrate molar concentration were higher in the control group than in the 4, 8 and 16 mg/g EFE treatments, but the acetate molar concentration and acetate∶propionate ratio were higher in the 16 mg/g EFE treatment. The sub2-4 treatments showed lower pH and ammonia-N, and higher total volatile fatty acid (TVFA), acetate molar concentration, and acetate∶propionate ratio. 4) In the substrate with NFC/NDF=1.53, EFE supplementation had no effect on in vitro gas production, fiber degradation, or fermentation characteristics (P>0.05). The results of this study showed that the NFC/NDF ratio influenced the response to EFE supplementation; NFC/NDF=0.85, 16 mg/g EFE showed the best fiber degradation, and the optimum EFE dose was 4 mg/g for substrates with NFC/NDF ratios of 1.02, 1.19, and 1.36. There was no positive effect of EFE on the substrate with NFC/NDF=1.53.

Effects of seed position on seedling establishment in three medicinal licorice species

HAN Chun, LU Jia-Hui, ZHOU Ling-Ling, NIU Qing-Dong, SONG Feng, WANG Yue, YANG Xu

2017, 26(7):  128-137.  DOI: 10.11686/cyxb2016344

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The position effect of seeds within a plant is a common phenomenon, but its influence on seed germination and seedling establishment is not well known. The objective of this study was to determine whether there were differences in seed germination strategies and seedling growth among seeds obtained from different (upper, middle, and lower) positions of the plant for three medicinal licorice species (Glycyrrhiza glabra, Glycyrrhiza inflata, Glycyrrhiza uralensis).Seeds were collected from different positions on the plant, and then seed germination, seedling growth, seedling chlorophyll content, and chlorophyll fluorescence were measured. The main findings can be summarized as follows: 1) In G. glabra, the seedling emergence rates were higher for seeds from upper and middle positions than for seeds from the lower position. For G. inflate and G. uralensis, the seedling emergence rates were higher for seeds from middle and lower positions than for those from the upper position. The seedling survival rate did not differ significantly among the different collection positions. 2) The seedlings from the seeds with a high seedling emergence rate had higher total biomass, root length, and root∶shoot ratio than those of other seedlings, and a larger proportion of their biomass was allocated to below-ground parts, which can enhance seedling resistance and environmental adaptability. The seedling chlorophyll content and chlorophyll fluorescence parameters (F_v, F_m, F_v/F_m, F_v/F₀, electron transmission speed in the light reaction) were also higher in seedlings from seeds with a high seedling emergence rate. In addition, the fluorescence kinetics curve showed that these seedlings had a strong fluorescence intensity and high electron and light capture rates, which can enhance seedling establishment. In contrast, the seedlings from seeds with a low seedling emergence rate had greater plant height and more leaves to occupy space and intercept light. These results indicate that the seeds from different positions on the plant have different germination and seedling growth strategies, which are of great ecological significance for seedling establishment and population regeneration of wild licorice plants.

Effects of forage planting and chickens on net carbon exchange and transformation of soil active carbon and nitrogen at different layers in paddy fields in south China in winter

WEI Jia-Bin, ZHOU Ling-Hong, XU Hua-Qin, TANG Qi-Yuan, FU Zhi-Qiang, CHENG Xiao-Lin, XIAO Zhi-Xiang, TANG Jian-Wu

2017, 26(7):  138-146.  DOI: 10.11686/cyxb2017020

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In this study, we investigated the effects of different forages and chickens on the transformation of soil active organic carbon and nitrogen and net carbon exchange in paddy fields in south China in winter. The five treatments were as follows: fallow (F), planted with ryegrass (R), planted with Chinese milk vetch (M), planted with ryegrass and presence of chickens (RC), and planted with Chinese milk vetch and presence of chickens (MC). Net carbon emissions increased in the short term under RC and MC, but these systems were carbon sinks (817.38 g/m² under RC and 472.90 g/m² under MC) before the planting of early rice. All treatments were weak methane sinks (3.06-22.88 mg/m²). The amount of fixed carbon was significantly higher in R and M than in F, RC, and MC. Compared with F, the R, RC, M and MC treatments significantly increased the contents of soil active carbon and nitrogen. Although the average contents of soil microbial biomass carbon were lower under RC and MC than under R and M, the average contents of soil soluble carbon were higher. The R, RC, M, and MC treatments increased the contents of soil organic carbon and promoted soil carbon sequestration. The results of this study revealed that integrated forage planting combined with the presence of chickens can not only improve soil active carbon and nitrogen, but also increase carbon sequestration in paddy fields in south China in winter.

Effect of plant growth regulators on germination and oxidase activity during storage of potato tubers

ZHONG Lei, DENG Jun-Cai, WANG Liang-Jun, ZHENG Shun-Lin, DOU Pan, WANG Xing-Long, YUAN Ji-Chao

2017, 26(7):  147-157.  DOI: 10.11686/cyxb2016338

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Studies on the effects of plant growth regulators on potato tubers during storage are important both for storing potatoes safely and for understanding the mechanisms of potato dormancy. In this research, the mid-to-longterm dormancy potato cultivar “Chuanyu 117” and the short-term dormancy cultivar “Favorita” were used as the experimental materials. Potato tubers were treated with three plant growth regulators: gibberellin A₃ (GA₃), chlorpropham (CIPC), or abscisic acid (ABA) for 30 min. Then, tuber germination and the oxidase activity in tuber flesh and bud bases were evaluated during storage. The results showed that GA₃ shortened the germination time of “Chuanyu 117” and “Favorita” by 10.42% and 26.92%, respectively, compared with that in the control (CK). In contrast, ABA and CIPC prolonged the germination time of “Chuanyu 117” by 10.42% and 106.25% respectively, compared with that in the CK. The germination time of “Favorita” treated with ABA was prolonged by 23.08% compared with that in the CK, and the tubers treated with CIPC did not sprout. Moreover, ABA significantly reduced the dormancy amplitude and led to neat tuber sprouting. The polyphenol oxidase (PPO) and peroxidase (POD) activities in tuber flesh and bud bases from cultivars with different degrees of dormancy increased and then decreased during the storage period. The peak activities of PPO and POD occurred during the bud-burst stage of germination, indicating that increased activity of PPO and POD represented physiological processes involved in the breaking of tuber dormancy and sprouting. The three plant growth regulators significantly affected the PPO and POD activities in bud bases and tuber flesh. The activities of PPO and POD in the bud bases were enhanced by GA₃. The activities of oxidases in different parts of non-sprouting tubers were reduced by ABA and CIPC. Application of ABA led to increases in PPO and POD activities during dormancy release, especially in “Chuanyu 117”. These findings reveal some of the physiological mechanisms involved in the breaking of dormancy and acceleration of germination by GA₃, and in the prolonging of dormancy by ABA and CIPC.

Characteristics of organic acids accumulation and oxalate metabolism in Kochia sieversiana under salt and alkali stresses

MA Ying, WANG Xiao-Ping, JIANG Hai-Bo, SHI De-Cheng

2017, 26(7):  158-165.  DOI: 10.11686/cyxb2016365

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In this study, seedlings of Kochia sieversiana were subjected to different salt and alkali stresses. The characteristics of organic acid accumulation and mechanisms regulating oxalate (OXA) metabolism were investigated by quantifying various organic acids and determining the activities of OXA metabolism-related enzymes. Seven kinds of organic acids (including OXA) accumulated in K. sieversiana under extended alkali stress. The accumulation of these organic acids was correlated with alkali stress (high pH), suggesting that they play roles in ion balance and pH regulation. The degradation pathway of L-ascorbic acid was not the main source of OXA. The cleavage of oxaloacetate by phosphoenolpyruvate carboxylase (PEPcase) probably played a minor role in OXA synthesis, but glycolate oxidase (GO) was the key enzyme for OXA synthesis. The activity of oxalate oxidase (OxO) involved in OXA decomposition was not a limiting factor for endogenous OXA accumulation. Taken together, these results showed that OXA accumulation in K. sieversiana under alkali stress was not because of reduced OXA degradation by OxO, but largely depended on OXA synthesis by GO.

Effects of combined applications of nitrogen and phosphorus on interspecies interaction, yield, and dry matter accumulation and translocation in maize in a maize-soybean relay intercropping system

ZENG Jin-Xi, WEN Xi-Chen, Muhammad Ali Raza, CHEN Guo-Peng, CHEN Cheng, PENG Xiao, MA Yan-Wei, LI Li, GUAN Si-Cheng, YANG Wen-Yu, WANG Xiao-Chun

2017, 26(7):  166-176.  DOI: 10.11686/cyxb2016510

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The aim of this study was to investigate the effect of nitrogen and phosphorus application on maize in a maize-soybean relay intercropping system. A pot experiment was conducted in 2013 and 2014, and interspecies interactions, dry matter production and accumulation, and grain yield were assessed. The experiment consisted of four nitrogen levels [N₀ (0), N₁₂₀ (120 kg/ha), N₁₈₀ (180 kg/ha), N₂₄₀ (240 kg/ha)] and four phosphorus levels [P₀ (0), P₃₅ (35 kg/ha), P₇₀ (70 kg/ha), P₁₀₅ (105 kg/ha)]. Furthermore, to evaluate the root interaction between maize and soybean, the two plants were grown with or without a root barrier between them. The main findings were as follows: 1) The interaction between N and P significantly affected the inter-specific interaction of maize and soybean in the relay intercropping system, reduced inter-specific competition between maize and soybean, increased the land equivalent ratio, increased the aggressiveness and nutrition competition ratio, and increased the uptake of N and P. The interaction between N and P significantly increased the yield and resource utilization (land equivalent ratio>1). The interactive effect of N and P was more prominent than the effect of N or P alone in the intercropping system. 2) The effects of the N×P interaction on dry matter accumulation in each growing period of maize increased with increasing N and P application rates up to N₁₈₀ (180 kg/ha) and P₇₀ (70 kg/ha), and then decreased when N and P application rates were N₂₄₀ (240 kg/ha) and P₁₀₅ (105 kg/ha). The treatment of N₁₈₀ (180 kg/ha) and P₇₀ (70 kg/ha) significantly decreased maize dry matter accumulation before maturity, but promoted dry matter accumulation and translocation to the grain, and improved the harvest index of maize. 3) Inter-specific interactions and interactive effects of N and P were significant, and increased the yield by increasing the number of kernels per ear and the number of ears per maize plant. Among all the N and P fertilizer levels, N₁₈₀ (180 kg/ha) and P₇₀ (70 kg/ha) considerably improved the maize yield from 1.65% to 20.43% in the relay intercropping system, compared with sole cropping. On the basis of these results, we recommend nitrogen and phosphorus applications at the rates of N₁₈₀ (180 kg/ha) and P₇₀ (70 kg/ha) to substantially improve ear traits, increase dry matter translocation to the grain at maturity, and achieve the maximum yield of maize in a maize-soybean relay intercropping system.

Nutrient contents and yields of photoperiod-sensitive sorghum-Sudangrass hybrids grown in summer after a winter wheat crop

HE Chun-Gui, HE Zhen-Fu, WANG Fei

2017, 26(7):  177-189.  DOI: 10.11686/cyxb2016376

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The aim of this study was to investigate the nutrient contents and yields of three photoperiod-sensitive sorghum-Sudangrass hybrids cropped after winter wheat in the Longdong dryland area, Gansu Province. The three sorghum-Sudangrass hybrids were Monster, BJM, and Big kahuna (with a brown midrib). The plants were grown with three dibbling modes: no tillage and no mulching (NN), tillage and no mulching (TN), and tillage with plastic mulch (TP), and were mown once (one-cut, C₁₁) or twice (two-cuts, C₂₁, C₂₂). The nutrient contents and yields were determined for the three varieties grown with different sowing patterns and mowing frequencies. The contents of various nutrients, including crude protein (CP), soluble sugars (SS), neutral detergent fiber (NDF), acid detergent fiber (ADF), total digestible nutrients (TDN), and relative feeding value (RFV) showed complex variations among the three sowing methods, the two mowing methods, and their combinations. There were no consistent trends in the contents of most nutrients. In practice, the most effective cultivation method should be selected based on the need for particular nutrients. The contents of the main nutrients (CP and TDN) showed the same trends as dry matter yields in the same treatments. Therefore, high dry matter yield was associated with higher contents of the main nutrients. The yields of CP and TDN were significantly higher for the plants mown once than for those mown twice. The yield of BJM was higher than those of the other two varieties. The yields were higher in the TP sowing mode than in the other two sowing modes. The highest yields of TDN (10.97 t/hm²) and CP (1.25 t/hm²) were from Monster in the TP system mown once. The CP yield from BJM mown once with the TP sowing mode was 1.11 t/hm² (not significantly different from that of Big Kahuna, P>0.05). Therefore, under these experimental conditions, the best production pattern was the TP dibbling mode, mown once (1 week before the early frost), and BJM for use in silage. However, the best production pattern for green harvest was Monster and the TP dibbling mode with two mowings.

CRISPR/Cas9: A gene targeting technology and its application in the study of plant genetic function

BAO Ai-Ke, BAI Tian-Hui, ZHAO Tian-Xuan, SU Jia-Hao

2017, 26(7):  190-200.  DOI: 10.11686/cyxb2016430

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CRISPR/Cas (clustered regularly interspaced short palindromic repeats) was derived from the adaptive immune system of bacteria and archaea to resist attacks from invasive viruses and exogenous DNA. Comparing zinc finger nuclease (ZFN) and transcription activator-like effector nuclease (TALENs), the type II CRISPR/Cas9 system mediated by RNA breaks new ground for gene editing due to its efficiency, low cost and ease of operation for the study of genetic function. This review summarizes recent research and progress of the structure, mechanisms and application of CRISPR/Cas9 for the study of genetic function and crop breeding. We also investigate the potential future development of CRISPR/Cas9.

Litter and its functions in grazing ecosystems

MA Zhou-Wen, WANG Ying-Xin, WANG Hong, A Bu-Man, ZHANG Zhen-Ming, HOU Fu-Jiang

2017, 26(7):  201-212.  DOI: 10.11686/cyxb2016342

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Plant litter is the main medium at the soil-grass interface in grassland ecosystems, and is one of the key factors regulating above-ground ecological processes. Plant litter dynamics are important for grassland species diversity and productivity, as well as for the restoration of degraded grasslands. Livestock affect litter dynamics through feeding, trampling, and their excretions, which can reduce litter accumulation and accelerate its decomposition. These activities vary depending on the stocking rate, grazing season, grazing system, and animal species. Litter affects the selective feeding and hoof pressure of livestock. Plant litter can provide favorable sites for microorganisms and small herbivores, thus affecting the structure and function of the grassland ecosystem. Litter dynamics can also change the physical and chemical properties of soil and affect nutrient cycling. Soil nutrient status and allelochemicals in plant litter can affect seed germination and seedling growth, which contribute to grassland community structure and succession. In this paper, we review the literature related to litter and its role in grazed-grassland ecosystems to understand the interactions among grazing animals, litter, soil, and plants in these environments. Our long-term aim is to provide a theoretical basis for the sustainable management of grassland ecosystems.

Advances in breeding of pea (Pisum sativum) with resistance to pea weevil (Bruchus pisorum) and its integrated management

WANG Chang, HE Chun-Gui, ZHANG Li-Juan, YANG Xiao-Ming

2017, 26(7):  213-224.  DOI: 10.11686/cyxb2016360

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Pea (Pisum sativum) is an important economic legume crop that is cultivated around the world for its high nutritional value. The pea weevil (Bruchus pisorum) is the most destructive pest of pea crops worldwide. The boring of pea weevil larvae can destroy more than 50% of the cotyledon parts in pea grains, leading to empty grains, poor seed germination, and poor seed quality. The pea weevil has become one of the most serious factors restricting the sustainable development of the pea industry. Genetic resources for pea weevil resistance have not been found in cultivated pea varieties, but have been detected in wild pea. Genetic studies have revealed that the inheritance of resistance to pea weevil is controlled by at least three recessive genes. In other studies, α-amylase inhibitor (α-AI) and neoplastic pod (Np) mutants of pea showed a degree of resistance to pea weevil. Although transgenic pea lines have been developed, their potential threats to human and animal health mean that chemical pesticides are still the most efficient methods to control pea weevil. In this paper, we review recent advances in pea weevil research, including breeding for resistance and integrated management systems. We discuss the current state of research on pea weevil in China and the problems remaining to be solved.

Effects on soil respiration and soil factors of different mowing frequency on Stipa grandis steppe

WAN Zhi-Qiang, YANG Jiu-Yan, YAN Yu-Long, GU Rui, YANG Jie, GAO Qing-Zhu

2017, 26(7):  225-231.  DOI: 10.11686/cyxb2016154

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The Stipa grandis steppe is a characteristically central Asian grassland. In grassland ecosystem, soil has a significant impact on plant community dynamics. The study area comprised Maodeng pasture near Xilin-haote, Inner Mongolia characterized as S. grandis steppe. We established four different mowing treatments in 2009 which were continued until 2013. Mowing frequencies were twice a year (TAY); Once a year (OAY); Once two year (OTY); No mowing (NM). Soil samples were collected to determine soil nutrient status in August 2013. Soil moisture (gravimetric), soil respiration rate and soil microbial number were measured in June, July and August, respectively. The results indicated that soil moisture of NM was the highest across all treatments. Soil organic matter content in the 20-30 cm and 30-40 cm depth bands in the TAY treatment was significantly higher than all other treatments; total soil nitrogen was also highest in the TAY treatment. There was significantly difference in soil respiration rate among cutting systems; OAY and NM produced higher soil respiration than that of remaining treatments; soil respiration was lowest in July for all systems. Soil microbial activity in NM treatments was significantly higher than in the cutting systems in both June and August. No mowing was beneficial to soil microbial activity, soil nutrients and soil respiration, but was not conducive to the growth of S. grandis. Annual mowing produced the optimal outcome in terms of productivity in the short and long term.

Contribution of herbage and sludge-microbes to remediation of polycyclic aromatic hydrocarbons

ZHANG Li-Xiu, LI Yan, LI Cheng, SHI Wei, ZHAO Ou-Ya, LI Cheng, CHEN Miao-Miao, WANG Xiao-Min, YANG Zhi-Xin

2017, 26(7):  232-238.  DOI: 10.11686/cyxb2016508

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A pot experiment was conducted to investigate the contribution of alfalfa (Medicago sativa), smooth brome (Bromus inermis), and sludge microbes to the remediation of polycyclic aromatic hydrocarbons (PAHs). After 5 months, the total removal rate of polycyclic aromatic hydrocarbons (PAHs) by sludge microbes was 20.52% in the absence of forage grass, and the removal rate of PAHs with different rings was as follows: six rings≈four rings≈three rings>five rings≈two rings. The total removal rate of PAHs by grass-sludge microbes was 83.74% (alfalfa) and 78.73% (smoothbrome). Therefore, the addition of a grass significantly increased the average PAH removal rate by almost three times compared with that of sludge microbes alone. The highest degradation rate was for the six-ring PAHs. In the absence of sludge microbes, the degradation rate of PAHs by alfalfa and smoothbrome was 63.22% and 58.21%, respectively (on average, 33.90% less than that of the grass-sludge microbes combination).The grasses showed the highest PAH removal rate for five-ring PAHs. Further analyses of the contribution rates of grass and sludge microbes to PAH degradation showed that 1.35% of PAHs was removed by direct absorption, 24.67% by microbes, and 79.46% through grass-sludge microbial interactions, transpiration, and the effects of root secretions. The treatments were ranked from highest sludge alkaline phosphatase activity to lowest as follows: non-sterilized sludge+alfalfa treatment (J+M)≈non-sterilized sludge+smooth brome treatment (J+W)>non-sterilized sludge treatment (J)>sterilized sludge treatment (CK) (P<0.05), consistent with the order of the treatments based on PAHs degradation. In conclusion, the use of grass and sludge microbes was more effective for removing PAHs from contaminated sludge than either grass or sludge microbes alone. The combined action of grass and microbes removed PAHs as a result of their interactions and transpiration.