Table of Content

20 March 2020, Volume 29 Issue 3

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A study of the spatiotemporal dynamic of land cover types and the driving forces of grassland area change in Gannan Prefecture and Northwest Sichuan based on CCI-LC data

LI Yuan-chun, GE Jing, HOU Meng-jing, GAO Hong-yuan, LIU Jie, BAO Xu-ying, YIN Jian-peng, GAO Jin-long, FENG Qi-sheng, LIANG Tian-gang

2020, 29(3):  1-15.  DOI: 10.11686/cyxb2019263

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Land cover change is key information when evaluating ecosystem health and such data is of great significance to planning sustainable development. Remote sensing is an effective way to achieve rapid and dynamic monitoring of land cover changes on a large scale. In this study, field measurement data and Landsat 8 OLI images were used to evaluate the classification accuracy of ESA Global land cover products (CCI-LC) in Gannan Prefecture and Northwest Sichuan, using the CCI-LC data to analyze the spatiotemporal dynamic of land cover types from 1992 to 2015, and the factors driving changes in grassland area changes was studied, considering both natural and artificial factors. The results indicated that: 1) The overall accuracy of CCI-LC products in Gannan Prefecture and Northwest Sichuan is 76.79%. Among the six land cover types (grassland, forest, bare land, water, permanent snow and ice, artificial surfaces), the user accuracy of grassland is the highest (94.88%). 2) From 1992 to 2015, the grassland area showed a generally decreasing trend, with a marked change during the period 1994-2001, with an overall decrease in area of 6760.53 km² and a rate of loss of -0.53%·year^-1. 3) From 1992 to 2000, the main changes in land cover types in the study area involved grassland, forest and artificial surfaces, and grassland area was mainly reduced in this period; from 2000 to 2010, the changes in land cover type in the study area were more diverse. The grassland cover was again reduced in most instances, but at a greatly reduced rate compared to 1992-2000; from 2010 to 2015, the transformation of land types was more complex, but a common pattern was transfer of grassland to forest and artificial surfaces. 4) Agricultural GDP and animal husbandry GDP are the main driving factors of grassland area change in Gannan Prefecture and Northwest Sichuan, and both of them are negatively correlated with grassland area. This study provides a macroscopic, rapid and low-cost remote sensing monitoring method to analyze the dynamic changes in land cover types over a long time period.

An analysis of the Tengger Desert spermatophytic flora characteristics

MA Quan-lin, ZHANG Jin-chun, LI De-lu, YANG Hao-tian

2020, 29(3):  16-26.  DOI: 10.11686/cyxb2019483

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Tengger Desert has a complex flora with a rich species composition and as it is located in the transitional zone between desert and grassland in central Asia. Based on a large number of site investigations, and reference to relevant plant and specimen databases and literature, we catalogued the spermatophytic flora and species geographical distribution categories in Tengger Desert through application of the basic principles of floristic geography. We found that the spermatophytic flora of Tengger Desert fitted in the middle transitional zone of Northwest China, and had the characteristics of a typical desert flora, including 382 natural spermatophytic species, belonging to 201 genera and 60 families. Floristic dominance was obvious in Tengger Desert where the floristic species tended to be concentrated in dominant families with more than 10 species, accounting for 64.40% of all the species. Floristic plants were highly differentiated, and there were as many as 178 genera represented by single species and oligos, accounting for 88.56% of all the genera. The Tengger desert flora contained a complex mix of genera from 14 global distribution categories and a further 9 sub-categories, including among others: cosmopolitan (40 genera), pantropic distributed (19 genera) and north temperate distributed (26 genera). The proportion of genera of temperate origin was 44.78%, which indicated the typical temperate zone characteristics of the Tengger Desert flora. Genera of paleo-mediterranean origin were also an important influence, comprising 21.39%, of the flora. The family representation was dominated by types with world distribution, including 38 globally widespread families. The proportions of globally dominant and representative families present in the Tengger Desert were 77.78% and 40.00%, respectively, which is consistent with the harsh desert climate in the region. The tropical component comprised 11 families, accounting for 18.33% of all the families, which showed that the flora of Tengger Desert has tropical links. However, the floristic origin of Tengger Desert was ancient and contained some new evolutionary forms, including primitive families of polycarpous plants, as well as some ancient relic species and many types with discontinuous distribution. In addition, there were relatively young and evolving families. Overall, the data indicate a very complex origin of the Tengger Desert flora.

Size distribution of soil aggregates in different grassland desertification categories in Yanchi County, Ningxia

MA Xiao-jing, GUO Yan-ju, ZHANG Jia-yu, XU Ai-yun, LIU Jin-long, XU Dong-mei

2020, 29(3):  27-37.  DOI: 10.11686/cyxb2019419

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This study evaluated the particle size distributions of mechanically stable and water stable aggregates in the 0-40 cm soil depth in different categories of desert steppe grassland in the Haba Lake Nature Reserve in Yanchi County, Ningxia. Potentially desertified grassland, lightly desertified grassland, moderately desertified grassland and severely desertified grassland were studied. The stability characteristics of soil aggregates were evaluated using aggregate destruction rate (PAD), mean weight diameter (MWD), geometric mean diameter (GMD), fractal dimension and soil erosion factor data. It was found that the mechanically stable aggregates in the 0-20 cm soil layer and the water stable aggregates in the 0-40 cm soil depth of each grassland desertification category were dominated by <0.25 mm micro-aggregates with the percentage of these being 45.78%-88.36% and 48.05%-97.79% respectively. The <0.25 mm mechanically stable and water stable micro-aggregate contents, PAD, fractal dimension and erosion factor in the 0-40 cm soil depth all increased with increasing grassland desertification, while the MWD and GMD gradually decreased, and the soil structure was variable. The soil stability increased with depth in the soil profile, especially in the potentially and lightly desertified grassland, which indicated that the land desertification in this grassland mainly occurs in the upper 20 cm of the soil profile. The stability of soil aggregates was positively correlated with organic carbon content, total nitrogen content (P<0.01), and silt and clay particles (P<0.05), and negatively correlated with soil bulk density (P<0.01). With the erosion of fine soil particles and transportation of nutrients such as carbon and nitrogen in the process of grassland desertification in Yanchi County, soil structure and physical stability is reduced.

Interactive effects of climate warming and species diversity on the invasiveness of the alien weed Alternanthera philoxeroides

WU Hao, ZHANG Chen, DAI Wen-kui

2020, 29(3):  38-48.  DOI: 10.11686/cyxb2019277

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Global warming has, in many cases, accelerated the spread of introduced invasive plant species, while the species diversity can produce bio-resistance to the invasive species. Exploring the effects of climate warming-biodiversity interactions on biological invasions is beneficial for predicting invasion outcomes and formulating effective bio-control measures. Here, 59 sampling plots were selected across a geographic range from 21° N to 37° N in China, the objective was to study the relationships between species diversity and invasiveness of the alien weed Alternanthera philoxeroides in field community. Temperature and species diversity data were examined in artificial community, to examine the effects of increased temperature and native plant species diversity on A. philoxeroides invasion. It was found that: 1) Values of Shannon-Wiener diversity index within A. philoxeroides communities ranged from 0-2.434, and the coverage and branches of A. philoxeroides both significantly decreased as species diversity increased, while the latitude and latitude×species diversity interaction did not significantly affect the invasiveness. 2) Increased temperature was associated with a significant reduction of both height and maximum stem length of A. philoxeroides, as well as the heights of resident plants Digitaria sanguinalis, Sonchus oleraceus and Eleusine indica. Increased species diversity significantly reduced the height, numbers of clonal ramets and maximum stem length of A. philoxeroides, thus weakened its invasiveness. An interaction between latitude and species diversity significantly increased A. philoxeroides branches when growing in the monoculture, and a species-specific interaction with latitude significantly shortened the maximum stem length of S. oleraceus in the artificial community. 3) Increased temperature had no significant effect on either A. philoxeroides or native plant species biomass. A. philoxeroides biomass decreased with increased species diversity, but its root/stem ratio increased, indicating that A. philoxeroides allocated relatively more resources to underground storage in response to the interspecies competition. In conclusion, these results indicate that a higher biodiversity is helpful for reducing A. philoxeroides invasiveness, but increased temperature may weaken the competitive resistance of resident plants. Thus, protection of native plant species diversity should receive more attentions to counteract the potential facilitating effects of global warming on the spread of A. philoxeroides.

Differences in physiological responses and regeneration strategies of male and female Humulus scandens plants during wintering

HE Lin-jiang, HUANG Xi-ye, LIU Jin-ping, YOU Ming-hong, YANG Xiao-qin

2020, 29(3):  49-59.  DOI: 10.11686/cyxb2019275

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This research studied the wild dioecious climbing herb Humulus scandens, in order to analyze the differences in physiological response and regeneration strategies between male and female plants, while over-wintering. Various physiological data, including soluble sugar (SS), starch (ST), and pyruvic acid (PA) contents and nitrate reductase (NR) activity of male and female plant parts (young leaves, mature leaves, mature stems, roots) were determined before winter (December 1), during over-wintering (January 15) and after winter (April 15). Survival rate and regeneration rate of plant parts biomass allocation ratio were also determined after wintering, to give insight into differential biomass allocation strategy of male and female plants. The results showed: 1) The ST content in the leaves of male plants before wintering was lower than that in female plants, and the content of SS and ST in mature stems and roots were lower than those in female plants (P<0.05). Male plants resisted cold by increasing SS in leaves, while female plants responded to cold by transferring sugar to the stems and roots. 2) The PA content of male plant leaves and stems was significantly higher than that in female plants before wintering, but PA content in male plant roots was significantly lower than that in female plants (P<0.05). There was no gender difference in NR activity of plant modules (P>0.05). Male plants resisted cold by enhancing the respiration of stems and leaves, while female plants responded to the cold through utilization of substrate reserves in the roots. 3) The content of SS and ST in the regenerated leaves of female plants was higher than in male plants (P<0.05), and the PA content and NR activity in leaves were both lower than in male plants. The PA content increased over winter in the female mature stems yet decreased in male plants (P<0.05). The metabolic activity involved in female plant regeneration was higher than that of male plants. 4) The survival rate of over-wintering male plants was 26.67%, while survival rate of female plants was 76.7%. The survival rate of stems in male plants was only 32.24% of that in female plants (12.50% and 38.77%, respectively). The regeneration rates of plant parts were, for male and female plants, respectively: leaves 5.85% and 1.23%, stems 13.10% and 3.12%, while inflorescence regeneration in female plants was 74.40%. 5) The number of regenerated leaves, the leaf area, and the length of the regenerated stems of female plants were all lower than those of male plants (P<0.05). The total biomass proportion contributed by regenerated stems and leaves was only 0.59% and 1.31%, respectively, while the contribution to total biomass of regenerated inflorescences was 98.09%. The regenerated inflorescence stalk and axis length and floret number of regenerated inflorescences were larger than those of inflorescences observed before winter. Sepals exhibited increased area and greenness, and accounted for 31.26% of total biomass in regenerated plants, and their total area was as much as 625 cm²·plant^-1, compared with a total area of regenerated leaves of 25.51 cm²·plant^-1. During overwintering, male plants resisted cold through physiological response, in which the stored substrates of male stems and roots were lower than those of female plants. Thus the survival rate and regeneration rate of male plants were lower than those of female plants. After wintering, the biomass of regenerated male plants was only 1.57 g·plant^-1 and all of this was allocated to vegetative organs. By contrast, the average biomass of female plants was 32.05 g·plant^-1, and 98.09% of this was allocated to inflorescence formation with sepals instead of leaves being the main photosynthetic organs, providing nutrients for inflorescence formation and nearby flower development.

The impact of different soil moisture and sterilization treatments on root architecture and rhizosheath formation of Kengyilia hirsuta at the seedling stage

CHEN You-jun, DONG Quan-min, ZHOU Qing-ping

2020, 29(3):  60-69.  DOI: 10.11686/cyxb2019278

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In order to explore the influence of water content and the sterilized soil on the root architecture and rhizosheath formation of Kengyilia hirsuta at the seedling stage, five water supply levels (10%, 20%, 30%, 40% and 50% of field water capacity) were watered in sterilized and unsterilized soil to cultivate K. hirsuta. Several parameters for root architecture and rhizosheath weight were measured under different treatment conditions. The experimental results turn as follows. 1) The symbiotic relationship between K. hirsuta root system and soil microorganisms was found and the high water supply levels significantly increased root crossing numbers and branch numbers in the unsterilized soil (P<0.05). However, the symbiotic relationship was destroyed in the sterilization soil. The total root volume between levels of 40%-50%, the root average diameter under levels of 40%, the branch numbers under levels of 20% and 50%, the number of links and the number of root tips under the water levels of 20%-50%, the total root surface area under the water level of 50% were significantly higher than under 10% level in the sterilization soil (P<0.05). After soil sterilization the microbial community changed and the root morphology index significantly increased compared under the condition of unsterilized soil, such as the total root length and root branch in the 20% level, the number of links and the number of root tips in 20%, 30%, 40% and 50% levels, the total root surface area, the root diameter in the 40% level and the total root volume between in 40% and 50% levels, all differed. 2) Under the different water and soil treatment, the topological index of the root of K. hirsuta at the seedling stage was close to 1. The root branching pattern was close to fishtail branching, which is more suitable to grow in the poor soil. The root architecture of K. hirsuta was optimum in the 20% and 30% levels where the topological index (q_b) and fractal dimension (FD) were significantly higher than other water levels (P<0.05). The function of root system in soil was affected by the difference of biomass distribution between primary root and secondary root, and the elongation and extension ability of roots in the soil (total root length, total root surface area, number of links and number of branches) affected more root architecture than the fixed permeability (root average diameter). 3) There was no interaction effect on rhizosheath formation between the water supply and soil treatment (P>0.05), the factors with different influence degrees to the formation of rhizosheath of K. hirsuta at the seedling stage: water>soil>FD>q_b> fixed permeability. With the increase of water supply levels, the rhizosheath weight increased first and then decreased. The rhizosheath weight was maximum in the unsterilized soil of 20% and 30% field water capacity and in the sterilized soil of 30% field water capacity. q_b, FD and the fixed permeability have significantly positive effects on rhizosheath formation (P<0.05).

Effects of oregano oil and rumen-protected methionine on lactation performance and nitrogen excretion of dairy cows

DING Da-wei, TENG Le-bang, GAO Xu-lei, LV Yong-yan, SUN Guo-qiang

2020, 29(3):  70-77.  DOI: 10.11686/cyxb2019273

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This experiment was conducted to determine the effects of different combinations of oregano oil (Oo) and rumen-protected methionine (RPMet) on lactation performance and nitrogen excretion of dairy cows. Forty lactating holstein dairy cows of similar age, body weight, parity, milk yield, milk composition and lactation status [(90±15) days post-calving] were divided into 10 groups with 4 cows per group. A Control group was fed a basal diet, and experimental groups were supplemented with different levels of Oo [11.5 (L), 13 (M) or 14.5 (H) g·(d·head)^-1] and RPMet [22.5 (L), 25 (M) or 27.5 (H) g·(d·head)^-1] to make nine treatment combinations, which were designated LL, ML, HL, LM, MM, HM, LH, MH and HH (i.e. the first letter indicates Oo supplementation rate, and the second letter indicates RPMet supplementation rate). Following a pre-experiment adjustment period of 15 days, the experiment lasted for 60 days. It was found that: The milk yield of LL, HL, HM, MH and HH groups was significantly higher than in the Control group (P<0.01), with MH being the highest. In terms of milk components, the milk fat percentages of MH and HM groups were significantly higher than the Control group (P<0.01), and the milk protein percentages of HM and HH groups were significantly higher than the Control group (P<0.01). Milk somatic cell of the experimental groups were significantly lower than the Control group (P<0.01). Nitrogen excretion rate of LL, ML, LM, MM, HM, LH, MH and HH groups was significantly lower than the Control group (P<0.01), with the MH group being the lowest. Under the conditions of the experiment, the MH group [Oo 13 g·(d·head)^-1, RPMet 27.5 g·(d·head)^-1] was the best treatment combination.

An in vitro study of dietary concentrate∶forage ratio and small peptide supplementation effects on ruminal fermentation parameters of yaks

TU Rui, MIAO Jian-jun, PENG Zhong-li, GAO Yan-hua, BAI Xue, XIE Xin-ting

2020, 29(3):  78-88.  DOI: 10.11686/cyxb2019300

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This study investigated the effects of different combinations of dietary concentrate∶forage ratio and small peptide supplementation on in vitro gas production, nutrient digestibility and ruminal fermentation parameters of yaks. The experiment comprised a factorial combination of three different concentrate∶forage ratios (40∶60, 50∶50, 60∶40; CFRs) and five different small peptide supplementation levels (0, 0.75%, 1.50%, 2.25%, 3.00%), making a total of 15 treatments, with 3 replicates per treatment. Fermentation samples were collected after 48 hours of fermentation. It was found that: 1) CFR had no significant effect on the degradation rate of neutral detergent fibre and acid detergent fibre (P>0.05). Across the range of small peptide supplementation levels, the degradation rate of neutral detergent fibre and acid detergent fibre displayed a quadratic pattern (P<0.01). The optimal small peptide supplementation treatments were 1.50% and 2.25%. There were significant interactions between CFR and the level of small peptides for gas production and the degradation rates of dry matter and crude protein (P<0.01). 2) With increase in CFR from 40∶60 to 60∶40, rumen pH decreased (P<0.01), while microbial protein increased (P>0.05). However, no significant changes in digestive parameters between CFR 50∶50 and 60∶40 were observed. A quadratic response pattern (P<0.01) was also observed for pH and microbial protein across the range of small peptide supplementation rates tested, with the optimal supplementation rate being 2.25%. A significant interaction was observed between CFR and the level of small peptide supplementation, for the concentration of ammonia nitrogen (P<0.05). 3) There was a significant interaction between CFR and the level of small peptide supplementation for rumen volatile fatty acid concentrations (P<0.01). Across the three tested CFRs, acetate∶propionate and the proportion of acetate, isobutyrate and isovalerate presented quadratic variation (P<0.05). The lowest value of acetate∶propionate ratio and lowest proportion of acetate occurred with 1.50% small peptide supplementation, and the highest proportion of isoacids occurred at 2.25%. These results showed that CFR and the level of small peptides affected gas production, nutrient degradation and ruminal fermentation parameters. In this research, the better CFRs were 50∶50 and 60∶40, and the optimal peptide levels were 1.50% and 2.25%.

Effects of formic acid additives and ensiling time on the quality of alfalfa silage

YU Hao-ran, GE Gen-tu, WANG Zhi-jun, JIA Yu-shan, LIAN Zhi, JIA Peng-fei

2020, 29(3):  89-95.  DOI: 10.11686/cyxb2019290

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In this study a second cut alfalfa crop harvested at the early flowering stage (10% of plants flowering) was used as raw material for making bagged silage. The research comprised a two-factor evaluation of formic acid as an additive [concentration 3 (A₁), 6 (A₂) or 9 mL·kg^-1 (A₃)], with no addition as the control. Silage bags from the various formic acid treatments were opened for fermentation analysis after 30, 60 and 120 days. Both formic acid addition and ensiling time significantly influenced silage quality. Formic acid addition significantly reduced the pH value, ammonia nitrogen:total nitrogen ratio, and acid detergent fiber (ADF) value of the silage (P<0.05). Except for crude protein (CP), silage time had a significant effect on the silage nutritional quality (P<0.05). Among all the treatments, alfalfa silage with 6 mL·kg^-1 formic acid added (A₂) and 60 days fermentation time gave the best overall result. The interaction effect between formic acid addition and ensiling time was significant for dry matter (DM), neutral detergent fiber (NDF) and crude fat (EE) content (P<0.05), but was not significant for other silage quality parameters (P>0.05).

Response of biological characteristics of two color morphs of pea aphid (Acyrthosiphon pisum) to different soybean varieties

MA Ya-ling, LIU Hui, LIU Yang, LI Chun-jie

2020, 29(3):  96-102.  DOI: 10.11686/cyxb2019281

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The effect of four soybean varieties (‘Fendoumulü2’, ‘Nanxiadou25’, ‘Nanheidou20’ and ‘Nandou5’) on the biological characteristics of two color morphs of pea aphid (Acyrthosiphon pisum) were studied in order to provide a theoretical basis for evaluating resistance of soybean varieties and formulation of strategies for comprehensive control of pea aphid damage. The experiment was conducted in an artificial climate chamber with photoperiod 10 h light and 14 h dark, temperature (23±1) ℃, humidity of 60%±10% and light intensity of 212 μmol photons·m^-2·s^-1. Two color morphs of pea aphid (red and green) were established to feed on the different soybean varieties. Biological parameters of the pea aphids such as instars, developmental duration, weight difference, and mean relative growth rate (MRGR) were measured. It was found that: 1) There were significant differences in the development duration and MRGR of red pea aphid among different soybean varieties. The developmental duration of red pea aphid was longest (8.30 d) in ‘Nanxiadou25’ and shortest (7.29 d) in ‘Nanheidou20’. Compared with ‘Nanxiadou25’, the MRGR of aphids feeding on ‘Fendoumulü2’, ‘Nanheidou20’ and ‘Nandou5’ was MRGR decreased by 31.25%, 25.00% and 12.50%, respectively. The nymph survival rate was the highest on ‘Nanheidou20’; The red aphid feeding preference for the soybean varieties was ‘Nanheidou20’>‘Fendoumulü2’>‘Nandou5’>‘Nanxiadou25’. 2) The average growth rate, development duration and MRGR of green pea aphid differed significantly in different instars between soybean varieties, with the longest development duration (8.84 d) occurring in ‘Nandou5’ and the shortest development duration (7.81 d) in ‘Nanxiadou25’. Compared with ‘Nanxiadou25’ the MRGR of ‘Fendoumulü2’, ‘Nanheidou20’ and ‘Nandou5’ decreased by 6.25%, 25.00% and 12.50%, respectively. The highest nymph survival rate was for ‘Nanheidou20’. The green aphid feeding preference for the soybean varieties was ‘Nanxiadou25’>‘Nanheidou20’>‘Fendoumulü2’>‘Nandou5’. Therefore, the growth and development of red and green pea aphids was affected differently by different soybean varieties.

Allelopathic potential of Carex thunbergii against three Poaceae species

ZHANG Jin-yu, ZHOU Zhong-ze, YE Xiao-xin

2020, 29(3):  103-111.  DOI: 10.11686/cyxb2019294

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Vegetation communities of the Yangtze river-lake floodplain zone subject to water-level fluctuation have been observed to gradually evolve into a mono-specific stand of Carex thunbergii. This study aimed to determine if there is evidence for allelopathy as one of the mechanisms mediating the observed plant community transition. We studied the effects of C. thunbergii extracts on seed germination, seedling growth and antioxidant activity of three accompanying Poaceae species (Lolium perenne, Cynodon dactylon, Phalaris arundinacea). It was found that the extracts of C. thunbergii significantly inhibited the germination rate, germination potential, radicle length and germ length of the three tested grass species. Inhibition of seed germination rate was >95% at the highest extract concentration, for all three tested grasses. At the same concentration, a methanol extract of C. thunbergii had more inhibitory effect than an aqueous extract. The seedling growth was significantly affected by C. thunbergii extracts, and the root:leaf ratio was significantly lower than for control seedlings. Levels of malondialdehyde in L. perenne and P. arundinacea increased with the concentration of extract. The activities of superoxide dismutase and peroxidase in L. perenne initially rose, then fell, increasing concentration of C. thunbergii extract. Our results show that C. thunbergii has potential for allelopathic inhibition of seed germination of the three tested grasses and inhibition of seedling growth of L. perenne and P. arundinacea. Our findings indicate that allelopathy may play a role in the dominance of C. thunbergii in Shengjin Lake.

Effects of endophyte infection on growth and physiological characteristics of Melica transsilvanica under Pb stress

LI Ke, SHI Chong, HE Fei-yan, LI Hao-yu

2020, 29(3):  112-120.  DOI: 10.11686/cyxb2019285

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The growth and physiological characteristics of Epichloё endophyte infected (E+) and endophyte free (E-) Melica transsilvanica were observed under different Pb concentrations (0, 200, 500, 1000, 1500, 2000 mg·L^-1) in a pot experiment. It was found that with increase in Pb concentration, plant height initially increased and then decreased. At the Pb concentration of 500 mg·L^-1, the proline content of E+ plants was 35.2% higher (P<0.05) than in the Controls. At Pb concentrations of 1500 mg·L^-1 and above, plant height was significantly inhibited. The root fresh weight exhibited the largest decrease, being 82.5% lower than the control (P<0.05); meanwhile, the MDA concentration in leaves increased significantly. When the Pb concentration was 2000 mg·L^-1, the MDA content of E+ plants were significantly higher than the Control (P<0.05), and the content of proline in the plant increased initially, and then decreased. Compared with M. transsilvanica plants without Epichloё endophytic fungi, the aboveground and underground biomass of E+ plants were both higher than in E- plants; the proline content of E+ plants was significantly higher than in the E- plants at the 1500 mg·L^-1 Pb concentration (P<0.05); and the MDA content of E+ plants was 25% lower than in E- plants (P<0.05), especially at the 2000 mg·L^-1 Pb concentration. In conclusion, the growth and physiological adaptability to Pb stress of M. transsilvanica infected with endophyte fungi was enhanced.

Physiological aspects of insect resistance of Achnatherum inebrians after spraying with methyl jasmonate or with Epichloё gansuensis infection

HE Ya-li, CHEN Zhen-jiang, WEI Xue-kai, ZHANG Hai-juan, LIU Yang, LIU Hui, LI Chun-jie

2020, 29(3):  121-129.  DOI: 10.11686/cyxb2019289

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The grass Achnatherum inebrians forms a symbiotic relationship with Epichloё gansuensis endophyte, which can promote plant growth and improve abiotic and biotic stress tolerance. The experiment was carried out in a greenhouse on the Yuzhong campus of Lanzhou University [Temperature (25±2) ℃; Humidity: 37.7%-48.3%], using endophyte-infected (E+) and nil-endophyte (E-) seedlings of A. inebrians from the Yuzhong region of Gansu province. After planting, seedings were exposed to exogenous methyl jasmonate (MJ) at concentrations of 200 or 400 mg·L^-1 to simulate herbivore feeding, and the physiological response assessed. It was found that, compared with the control, MJ treatments significantly decreased the soluble sugar content, and chlorophyll content (P<0.05) but significantly increased total phenol content (P<0.05). Effects of MJ treatment on herbivore resistance were different between E+ and E- plants. For E- plants, MJ treatment significantly increased polyphenoloxidase activity and phenylalanine ammonia-lyase activity. For E+ plants, the activity of trypsin inhibitors was significantly increased compared with the control group (P<0.05). In conclusion, MJ treatment strengthened the defensive ability of the host plant at the cost of reduced palatability, thus inhibiting the feeding of herbivorous insects. MJ treatment did enhance A. inebrians-mediated insect resistance.

Effects of nitrogen application on nitrogen accumulation and root nitrogenase activity in Medicago sativa at different soil water contents

GAO Li-min, SU Jing, TIAN Qian, SHEN Yi-xin

2020, 29(3):  130-136.  DOI: 10.11686/cyxb2019268

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The underlying mechanisms related to the impact of nitrogen fertilizer on alfalfa (Medicago sativa) growth at different soil water contents remain unclear. A pot experiment with three soil water levels (30%, 50% and 70% of the field water-holding capacity; W₁, W₂ and W₃), and four nitrogen application rates (0, 0.02, 0.04 and 0.06 g N·kg^-1; N₁, N₂, N₃ and N₄) was conducted to study the utilization of nitrogen fertilizer by alfalfa under different soil water regimes, and the relationships with nitrogen accumulation and root nitrogenase activity. The results indicated that: 1) for W₁, alfalfa biomass increased significantly with increase in nitrogen application rate, while for W₂ and W₃, the highest biomass values were observed in N₃ treatment; 2) for W₁ and W₂, the highest nitrogen accumulation was obtained in the N₄ treatment, while for W₃, the N₃ treatment had the highest nitrogen accumulation. A positive relationship between the amount of nitrogen applied and alfalfa biomass was therefore concluded; 3) the root nitrogenase activity was increased with increase in soil water availability, but decreased with increase in nitrogen rate. No significant difference in root nitrogenase activity was observed between W₃ and W₄ with N₄ application. Therefore, it was concluded from these results that under lower soil water content, nitrogen application was essential for meeting nitrogen demand and would promote alfalfa growth, and under higher soil water content, moderate nitrogen fertilizer application was advantageous for alfalfa growth, while higher rates of nitrogen fertilizer application inhibited root nitrogenase activity, and therefore no significant differences in nitrogen accumulation and biomass were found. The results of the present study provide a theoretical basis for determining water and nitrogen management in alfalfa production systems.

Effects of nitrogen and phosphate fertilizer application on yield and forage quality of forage triticale on the Haihe Plain

YOU Yong-liang, LI Yuan, ZHAO Hai-ming, WU Rui-xin, LIU Gui-bo

2020, 29(3):  137-146.  DOI: 10.11686/cyxb2019279

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The effects of nitrogen and phosphate fertilizer application on the yield and forage quality of forage triticale were studied to determine the ideal fertilization rate for forage triticale crops on the Haihe Plain. The experiment was conducted over two growing seasons (2014-2016) using the triticale variety ‘Zhongsi 1048’, grown under a range of nitrogen (N: 0, 60, 120, 180, 240, 300 kg·ha^-1) and phosphate (P₂O₅: 0, 45, 90, 135, 180, 225 kg·ha^-1) fertilizer treatments, to evaluate responses in forage yield, agronomic traits, forage quality and soil nutrient status in forage triticale under these different nitrogen and phosphate fertilizer treatments. No significant difference was found between CK (N₀P₀) and any of the fertiliser treatments for the two-year average hay yield (P>0.05). Crude protein content was significantly higher than CK in the various fertiliser treatments (P<0.05), while ADF and NDF levels did not differ significantly between CK and the various fertiliser treatments (P>0.05). The effect of increasing nitrogen and phosphorus fertilizer on the yield of triticale was not obvious, but fertilizer did improve the forage quality of triticale. Multivariate analysis of the data showed that on the Haihe Plain, forage triticale could be planted without fertilization or once every other year in areas with good soil fertility, and with fertiliser application at sites with poor soil fertility. Based on these results, recommended fertilizer application rates for triticale hay production on the Haihe plain are: N, 120-180 kg·ha^-1; P₂O₅, 90-135 kg·ha^-1.

Effects of infiltration irrigation on growth characters and water use efficiency of alfalfa in the Ningxia Yellow River diversion irrigation area

QIAN Zhi-hao, HAN Bing-fang, LIU Zi-ting, CAI Wei, FU Bing-zhe, MA Hong-bin

2020, 29(3):  147-156.  DOI: 10.11686/cyxb2019254

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It is important to study the effects of infiltration irrigation on soil water content, production performance and water use efficiency of alfalfa for scientific evaluation of infiltration irrigation. This study evaluated the performance of alfalfa in the Ningxia Yellow River diversion irrigation area under a range of irrigation treatments. Specifically, infiltration irrigation application rates of 350 (S₃₅), 400 (S₄₀), 450 (S₄₅) and 500 (S₅₀) m³·667 m^-2 were compared with a flood irrigation allocation of 800 m³·667 m^-2 (CK). We measured soil moisture content, growth characters, feed quality and irrigation water use efficiency. The results can be summarized as follows: 1) Over the whole growth period, CK had the highest soil water content and water consumption, while S₄₅ had lower soil water content, and infiltration irrigation was used soil water more efficiently than traditional flooding irrigation. The coefficient of variation for soil water content of the CK treatment was the largest in the 0-20 cm soil layer, while the coefficient of variation for soil water content for each infiltration irrigation rate in the 0-40 cm soil layer was smaller. Under infiltration irrigation the soil water content decreased with the depth within the soil profile, and its coefficient of variation was lower than that of flood irrigation. 2) Infiltration irrigation resulted in an increase in leaf-stem ratio, branch number, leaf area index, root biomass and crude protein content, and a decrease the content of acid detergent fiber of alfalfa. This was more obvious under the S₄₅ and S₅₀ treatments. 3) Except for the S₃₅ treatment, the alfalfa herbage and crude protein yields under infiltration irrigation were higher than in the CK treatment. An appropriate irrigation rate improved the alfalfa herbage and crude protein yield, and irrigation water use efficiency, with a resulting economic benefit. Based on results from this study, the irrigation allocation of 450 m³·667 m^-2 is the suitable irrigation quantity of alfalfa infiltration irrigation in Ningxia Yellow River diversion irrigation area.

Mechanisms and factors affecting nitrogen transfer in mixed legume/grass swards: A review

XIE Kai-yun, WANG Yu-xiang, WAN Jiang-chun, ZHANG Shu-zhen, SUI Xiao-qing, ZHAO Yun, ZHANG Bo

2020, 29(3):  157-170.  DOI: 10.11686/cyxb2018184

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Nitrogen transfer between legumes and grasses in mixed grass-legume swards plays an important role in the nitrogen cycle of grassland agricultural systems. There is a nitrogen-sharing pathway in legume-cereal intercropping systems and in grass-legume mixed swards whereby the legume plant not only meets its own nitrogen requirements for growth by way of fixed nitrogen from the atmosphere, but also provides nitrogen for the associated grasses through various pathways. The pathways of nitrogen transfer in mixed grass-legume swards can be categorized as above-ground or below-ground. The above-ground pathway occurs when herbage of legume plants is eaten by grazing animals and returned to the soil via excreta, then absorbed by other plants (including grasses), or when herbage litter falls to the ground and is decomposed and mineralized by microorganisms in soil to release plant-available nitrogen. The below-ground pathway is relatively complex and involves three routes: 1) Decomposition: decomposition of legume root tissues followed by uptake of released N by neighboring plants. 2) Mycorrhizae: transfer of N mediated by plant-associated mycorrhizae. 3) Root exudation: the exudation of soluble N compounds by donors and uptake by receivers. Although the current study identifies the possible routes of nitrogen transfer, many questions remain. Which is the main transfer route? What is the contribution of each route? To what extent can particular transfer routes operate concurrently? Such questions still lack key evidence. This paper briefly describes the current research status of biological nitrogen fixation of legume forages and of legume-grass nitrogen transfer in mixed grass-legume swards. A number of possible nitrogen transfer routes are reviewed, and directions for future research are identified. Better understanding of these questions will pave the way to achieve sustainable development of agriculture and animal husbandry in China, through realization of the potential benefits offered by legumes.

Spatial distribution patterns and interspecific relationships of Agropyron mongolicum populations in different desert steppe communities in Ningxia

XU Ai-yun, XU Dong-mei, CAO Bing, LIU Jin-long, YU-Shuang, GUO Yan-ju, MA Xiao-jing

2020, 29(3):  171-178.  DOI: 10.11686/cyxb2019440

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Population characteristics and interspecies relationships are important in the study of population ecology. To investigate the environmental plasticity mechanisms of Agropyron mongolicum populations, three 10 m×10 m plots dominated by communities of Stipa breviflora+A. mongolicum, A. mongolicum+Lespedeza potaninii and A. mongolicum+Cynanchum komarovii were studied in desert steppe grassland in Yanchi County. The spatial coordinates and quantitative characteristics, including height and above ground biomass of A. mongolicum were measured in the study plots. The spatial distribution pattern of the A. mongolicum populations and the interspecific relationships between the A. mongolicum populations and other dominant species in the studied plant communities were analyzed by ‘point pattern analysis’ and ‘O-ring function statistic’ methods. It was found that the density, ground cover and above-ground biomass of A. mongolicum populations in A. mongolicum+L. potaninii communities were significantly higher than those in S. breviflora+A. mongolicum and A. mongolicum+C. komarovii communities (P<0.05), and the height did not differ significantly among the three communities (P<0.05). The spatial pattern of A. mongolicum populations mainly displayed an aggregated distribution, with an aggregation scale of less than 4 m. When spatial distribution was evaluated at larger scale, the aggregation degree decreased with increasing scale and gradually transformed to random and uniform distribution. The associations between A. mongolicum and S. breviflora populations, and A. mongolicum and L. potaninii populations showed a negative relationship at a scale of less than 4 m and tended to show no association with increase in the evaluation scale. No association between A. mongolicum and C. komarovii populations was detected at the 0-5 m evaluation scale.

Ruminal degradation characteristics of Broussonetia papyrifera in beef cattle

KONG Fan-lin, DIAO Qi-yu, QU Jian-jiang, TU Yan

2020, 29(3):  179-189.  DOI: 10.11686/cyxb2019260

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In order to evaluate the potential of Broussonetia papyrifera for use in ruminant production as an unconventional feed, three beef cattle aged 24 months, each with a permanent rumen fistula, were used to investigate the degradability characteristics and nutritive value of different plant parts of B. papyrifera. Leaves, leafless branches, and whole plants of B. papyrifera were evaluated with a nylon bag technique, to calculate ruminal energy and nitrogen balance using digestibility and degradation parameters. Tests were carried out for smaller (height 125-135 cm) and larger (height 145-155 cm) plants. It was found that: 1) Crude protein (CP) content of the leaves was 23.18%, which was significantly higher than branches or whole plants of B. papyrifera (P<0.05), while the CP contents of the whole plants were significantly higher than that of the leafless branches (P<0.05). As expected, the pattern of results for acid detergent fiber (ADF) was opposite to that for CP. The ADF content of 125-135 cm whole plants was lower than that of 145-155 cm whole plants (P>0.05). 2) For leaves, values for effective degradability (ED) of dry matter (DM), organic matter (OM), CP and ADF were significantly higher than for whole plants of either height range (P<0.05). Furthermore, leaves and whole plants of B. papyrifera had higher ED of DM, OM, CP and ADF than leafless branches (P<0.05). The ED of DM of all tested B. papyrifera materials was above 40%, and the ED of leaves was up to 66%. 3) The ratio of rumen degradable protein (RDP) to rumen undegradable protein (RUP) of leaves was significantly higher than that of branches or whole plants (P<0.05), indicating that RDP proportion was in leaves. For branches and whole plants, the RDP content was lower than RUP content. 4) Rumen energy nitrogen balance value (RENB) of leaves was negative (-22.27 g·kg^-1) while the RENB values of leafless branches (28.79 g·kg^-1), 125-135 cm whole plants (30.87 g·kg^-1) and 145-155 cm whole plants (27.74 g·kg^-1) were positive. In conclusion, the ranking for nutritive value of the tested B. papyrifera materials was: leaves>125-135 cm whole plants>145-155 cm whole plants>leafless branches. All of the tested materials have the potential for use in high-quality feeds. Leaves can be used as a dietary protein source, while branches or whole plants can be used as roughage. However, energy and nitrogen balance are practical details also needing to be considered.

Autotetraploid plant induction and the genome size estimation in Lanzhou lily (Lilium davidii var. unicolor)

LI Shu-jie, ZHANG Jin-wen, PEI Huai-di, WANG Hong-mei, LUO Jun-jie, LIN Yu-hong

2020, 29(3):  190-196.  DOI: 10.11686/cyxb2019425

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Lanzhou lily (Lilium davidii var. unicolor, 2n=2x=24) is a well-known plant that is used both as food and for medicinal purposes. It is of great significance to breed elite germplasm and estimate its genome size. Autotetraploid induction in Lanzhou lily was accomplished in this study by soaking in different concentrations of colchicine, using seeds and tube-bulbs as the explants. Numbers of autotetraploids identified by flow cytometry assay among the plants derived from colchicine treated seeds and tube-bulbs were 10 and 4, respectively. The tetraploid induction rates were 21.11% for seeds and 33.27% for tube-bulbs. In order to estimate the genome size of Lanzhou lily, Triticum aestivum “Chinese spring” was used as an internal standard. The DNA content of both diploid and tetraploid Lanzhou lily plants was tested by flow cytometry. The genome size of Lanzhou lily was found to be 64.9 Gbp, four times greater than that of T. aestivum “Chinese spring”.

Effects of different additives and cutting dates on nutritional and silage fermentation quality of Triticale silage in an alpine pastoral area of Gansu Province

REN Yu-xin, DAI Han-ling, TIAN Xin-hui, DU Wen-hua

2020, 29(3):  197-206.  DOI: 10.11686/cyxb2019405

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Triticale is a highly versatile cereal forage for grazing, silage, hay or as a cover crop. In the current study, ×Triticosecale Wittmack ‘Gannong No.2’ was used to determine the best cutting period and silage additive for triticale silage in the Hezuo city of Gannan Prefecture, Gansu Province. The experiment comprised a factorial combination of silage additives [untreated control (CK) and two proprietary silage additives (Sila-Max and Sila-Mix released by Ralco Nutrition, USA)] and crop development stage when harvested [head emergence, HE; flowering, FL; grain filling, GF; ripening (milk stage), RM; ripening (wax stage), RW] derived from Lactobacillus and study was conducted during the 2016/2017 growing seasons, with planting in late September. A comprehensive evaluation of data on cutting date and additive effects on silage nutritive (crude protein, CP; neutral and acid detergent fibre, NDF and ADF; dry matter digestibility, DMD; water soluble carbohydrates, WSC) and silage quality parameters (lactic, acetic and propionic acid levels; NH₄-N∶total-N) was carried out by the Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) method to estimate the differences of nutritional value and silage quality between different cutting dates and silage additive treatments. Hay yield cut at HE was 7.76 t DM·hm^-2, rising gradually to 19.31 t DM·hm^-2 when cut at RW. With respect to crop growth stage at cutting and silage nutritive value: CP fell gradually from 14.25% cut at HE to 8.66% at RW; NDF was lowest cut at HE (48.34%) and highest at FL (54.74%) with later crop growth stages intermediate; ADF values were similar (-29%) for HE, RM and RW cuts, but rose to 37.09% at GF; WSC values ranged between 4.82%-6.93% at all growth stages except RM (14.27%); and DMD was highest (72.06%) cut at HE, falling to 63.11% cut at FL, then gradually rising to 69.28% at RW. With respect to crop growth stage at cutting and silage fermentation parameters: pH ranged from 3.98 cut at flowering to 4.42 at RW with other values intermediate; lactic acid was highest (48.27%) cut at GF and notably lower than other growth stages (28.05%) cut at RW; acetic acid was highest (13.61%) cut at HE and lowest (5.36%) at RM with other cutting dates intermediate; propionic acid was >5% for HE, FL and GF cuts, but <2% for RM and RW cuts; NH₄-N∶total-N gradually increased from 4.64% cut at HE to 5.97% at RW. Comparing silage additives; lactic acid contents averaged across cutting dates were 33.69%, 34.59% and 50.18% for CK, Sila-Mix and Sila-Max, respectively, with other parameters showing expected changes linked to the higher lactic acid content in silage with Sila-Max additive. In conclusion, in order to obtain the highest hay yield, triticale should be harvested at RW growth stage, while in order to obtain better nutritional value and silage quality without excessively compromising high hay yield, it should be cut earlier at RM.