Table of Content

20 March 2021, Volume 30 Issue 3

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Desert grassland dynamics in the last 20 years and its response to climate change in Xinjiang

Chen CHEN, Chang-qing JING, Wen-yuan XING, Xiao-jin DENG, Hao-yu FU, Wen-zhang GUO

2021, 30(3):  1-14.  DOI: 10.11686/cyxb2020143

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Desert grassland is a key type of land ecosystem in arid and semi-arid areas. Desert grassland has an important ecological role and is sensitive to human activities and global change. In this paper， we studied the dynamic changes in desert grassland in Xinjiang and the responses to different driving factors on different time scales and spatial scales for the period 1999-2018. We first extracted the coverage of desert grassland in Xinjiang and determined the desert grassland threshold values for normalized difference vegetation index （NDVI）. Then， we used a unitary linear regression model， correlation analysis and other methods to combine NDVI， net primary productivity （NPP）， meteorological factors and other data to study the changes in area of desert grassland and their driving mechanisms. The results showed that： 1） There were differences in the distribution of desert grasslands in the North and South of Xinjiang during the study period. Over all the area of desert grassland decreased significantly， while the average NDVI was relatively stable， and the NPP showed an upward trend. 2） Meteorological factors over the study period showed different trends at different times of the year. In July and August there were significant differences between North and South Xinjiang. Temperature and precipitation in most regions of Xinjiang increased between 1999 and 2018. 3） In terms of interannual changes， precipitation， high evaporation events， and average wind speed are the important factors affecting NDVI of desert grasslands in Xinjiang. The effect of water conditions on NDVI in the growing season is more obvious. There is a significant negative correlation between annual evaporation and desert grassland NPP， and average wind speed and precipitation have a correlation with desert grassland NPP. 4） In terms of spatial correlation， the area where temperature and precipitation are positively correlated with the NDVI and NPP of desert grassland is larger than that dominated by other factors， and the area where the precipitation effect dominates is larger than that driven by temperature. It was concluded that the dynamic changes of desert grassland in Xinjiang were the result of the combined effects of multiple meteorological factors. Temperature and precipitation were the main factors of influence， and of these the impact of precipitation was more obvious. Water status is the decisive factor driving dynamic vegetation change in desert grassland.

Analysis of features and influencing factors of alpine meadow surface temperature based on UAV thermal thermography

Wei ZHANG, Shu-hua YI, Yu QIN, Dong-hui SHANGGUAN, Yan QIN

2021, 30(3):  15-27.  DOI: 10.11686/cyxb2020154

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Land surface temperature is an important parameter in the study of the eco-hydrological processes of vegetation in cold regions. Land surface temperature directly affects the surface sensible heat， latent heat and radiative heat transfer. This research studied alpine meadow in the source region of Shule River Basin， and used an unmanned aerial vehicle mounted with RGB and thermal infrared cameras to obtain vegetation cover data and land surface temperature data of six plots. Thermal infrared images were corrected and evaluated using the measured data. The detailed characteristics of daily changes in the surface temperature of alpine meadow were analyzed， and the factors influencing the surface temperature were explored based on the meteorological and vegetation cover data. It was found that the surface temperature indicated by thermal infrared images was highly consistent with the measured value. The R² was about 0.75， and the average error was within 5 ℃. On sunny days， the surface temperature of the alpine meadow first increased and then decreased， reaching the peak at 13：00-15：00， and there was no significant change trend during the observation period （July 4th-August 17th）. Net solar radiation and air temperature were positively correlated with surface temperature， and these two factors played a role in increasing surface temperature， while the air humidity was negatively correlated with the surface temperature， playing a role in cooling the land surface. Continuous precipitation resulted in wet bare soil， therefore， the vegetation cover was positively correlated with the surface temperature. The UAV-based thermal infrared remote sensing technology can quickly and accurately acquire high-resolution surface temperature data， providing data support for drought monitoring， and evaluation of soil moisture and evapotranspiration of the alpine meadow.

Root dynamics of artificial grassland for swards of differing ages in the ‘Three-River Source’ region

Jie LI, Pan PAN, Chang-ting WANG, Lei HU, Ke-yu CHEN, Wen-gao YANG

2021, 30(3):  28-40.  DOI: 10.11686/cyxb2020161

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In artificial grassland， measurement of root dynamic traits can indicate the efficiency of the vegetation in using soil resources and the progress of plant community restoration and ecological succession. In this study， the root dynamics of artificial grassland established 5， 6， 9 and 13 years previously was investigated in the Three-River Source region. Data were collected for two consecutive growing seasons （May-September 2015 and May-September 2016）， utilizing minirhizotron in situ monitoring technology. The results showed that the aboveground biomass and species richness decreased from 5 to 9 years and increased from 9 to 13 years. The soil physiochemical properties similarly changed in a “N” shape over the time series and the differences between different sward establishment years was significant. The majority of root growth and death occurred in the 0-10 cm soil depth， and root longevity， cumulative production and cumulative mortality all fluctuated across the time series of establishment dates. The average root standing crop continued to increase with increase in years established， and numbers of deep roots observed increased between 6 and 9 years after establishment. There were obvious seasonal changes in root production， mortality and standing crop. The growth peak was in June， the standing crop peak was in July， and the death-rate peak was in August， while the seasonal root growth peak of artificial grassland established for 9 years was later than in grassland of other ages. The number of years established and the soil depth directly affected root longevity， and other environmental factors indirectly affected root standing crop by influencing soil available nutrients or aboveground biomass. In summary， planting artificial grassland can promote the soil quality and increase the aboveground biomass， richness and root standing crop. The secondary degradation of planted artificial grassland from 6 to 9 years after establishment is only a temporary transitional stage. Therefore， at this stage， the establishment of suitable artificial management measures can ensure the stability of the soil nutrient status and accelerate the process of plant community succession， thereby improving the vegetation community stability and resilience of artificial grassland.

A comparative study of root characteristics of three gramineous herbage species in the Northwest Sichuan Plateau

Si-li LIU, Chang-ting WANG, Chang-bing ZHANG, Lei HU, Li-tao TANG, Pan PAN

2021, 30(3):  41-53.  DOI: 10.11686/cyxb2020415

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In order to restore degraded alpine grassland in the Northwest Sichuan to sustainability， it is essential to have an understanding of the structure and function of the underground ecosystem and knowledge of the root characteristics of three cultivated herbage species. This study investigated the root characteristics and soil environment of cultivated herbage of Festuca rubra， Elymus nutans and Elymus sibiricus， using minirhizotron in situ monitoring technology and laboratory experiments. The results showed that： 1） There were obvious seasonal rhythms in the root growth of the three cultivated herbage species. The growth peak was from May to July， the peak of root standing crop was from July to August， and the death peak was from August to September. 2） The root standing crop of the three cultivated herbage species decreased significantly with soil depth （P<0.05）. E. sibiricus had significantly higher root standing crop than F. rubra and E. nutans （P<0.05）； the root production and mortality of F. rubra were the highest， and it’s root net growth rate was the lowest. 3） The root turnover of F. rubra was significantly higher than that of E. sibiricus and E. nutans， and turnover of F. rubra increased significantly with soil depth （P<0.05）. 4） Structural equation modeling revealed that herbage species and soil depth not only directly affected root characteristics， but also had indirect effects on root tips and root dynamic characteristics by changing soil stoichiometric ratios and soil physicochemical properties， thus affecting root turnover. In conclusion， there were significant differences in root growth and resource acquisition among the three cultivated herbage species. The strategy of shortening root longevity and accelerating root turnover was used by F. rubra to ensure nutrient absorption efficiency， while E. sibiricus and E. nutans used the strategy of increasing root production and prolonging root longevity to slow down root turnover， and thereby reduced carbon consumption of the root system while simultaneously increasing carbon sink function so as to adapt to the alpine environment.

Distribution characteristics and ecological function predictions of soil bacterial communities in rainfed alfalfa fields on the Loess Plateau

Xin MA, Zhu-zhu LUO, Yao-quan ZHANG, Jia-he LIU, Yi-ning NIU, Li-qun CAI

2021, 30(3):  54-67.  DOI: 10.11686/cyxb2020381

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A field study was conducted to investigate crop land and alfalfa land established for different lenghths of time ment years （L₂₀₀₃， L₂₀₀₅ and L₂₀₁₂） on soil bacterial communities and ecological function prediction. Soil bacterial communities were identified by high-throughput sequencing 16S rRNA gene amplicons. The Illumina MiSeq high-throughput sequencing technology was used to explore the structure and diversity of bacterial communities under three treatments， and statistical methods （such as redundancy analysis） were used to explore the relationship between soil physical and chemical properties and bacterial community structure and diversity. PICRUSt software was applied to predict the ecological function of soil bacterial communities present in different treatments. The results indicated that the predominant taxa at the phylum level are Actinobacteria， Proteobacteria， Acidobacteria and Chloroflexi of bacteria in loess soil， comprising 20.34%-32.40%， 18.99%-23.14%， 12.50%-13.39%， and 11.41%-12.55% of the microbial population， respectively. The relative abundance of Actinobacteria， Proteobacteria and Chloroflexi was higher in farmland soil than in alfalfa soil. The relative abundance of Actinobacteria showed a decreasing trend with increase in the stand age， and the relative abundance ofProteobacteria and Chlorophyta initially increased and then decreased with increasing stand age. The relative abundance of Acidobacteria did not differ significantly between farmland and alfalfa soil. The dominant bacterial genera of this loess soil were Gaiella， Nitrospira， Pseudarthrobacter and Solirubrobacter， which comprised 0.65%-3.33%， 1.52%-2.34%， 1.36%-2.61% and 1.03%-2.24%， respectively， of the microbial population. Compared with farmland， the relative abundance of the Solirubrobacter genus was significantly increased in alfalfa land. Redundancy analysis showed that soil total phosphorus is the main factor affecting the soil bacterial community structure. PICRUSt function prediction analysis indicates that the bacterial microbiota of the loessial soil has a total of 46 sub-functions， of which metabolism is the most important function， accounting for 69.20% to 70.22% of activity. Soil metabolism， genetic information processing， and biological system functional gene abundance of alfalfa soils were significantly higher than those in farmland soil， and these characteristics were specifically reflected in carbohydrate metabolism， exogenous substance degradation and metabolism， terpenoid and ketone metabolism， endocrine system， nervous system and substance dependent functional genes. This study emphasizes the bacterial community structure and metabolic function in loessial soil and the findings provide a strategy to enhance the sustainability of alfalfa fields through soil microbial community management.

Cloning and transformation of the CkCAD gene in Caragana korshinskii and analysis of its drought resistance function

Zhi-peng CHANG, Ying-ying SUN, Jia-yang LI, Chun-mei GONG

2021, 30(3):  68-80.  DOI: 10.11686/cyxb2020150

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Drought stress seriously affects the growth and development and even survival status of plants， which is one of the main abiotic stress factors restricting the restoration of desert vegetation in northwest China. Previous studies in our laboratory have found that phenylpropanoid biosynthesis of Caragana korshinskii was the most significant metabolic pathway for differential expression as precipitation decreases following the Loess Plateau from south to north. This study focused on the lignin synthase gene CkCAD in the phenylpropanoid biosynthesis pathwayof C. korshinskii. A bioinformatics analysis showed that open reading frame of the CkCAD gene is 1074 bp， encoding 357 amino acids. Protein sequence alignment showed that CkCAD is closely related to Abrus precatorius， Medicago truncatula， Glycine max and Arachis hypogaea， with a similarity of more than 80%. It is most similar to the A. precatorius ApCAD. The protein is acidic and hydrophilic， with no transmembrane domain， and its subcellular location is in the cytoplasm. C. korshinskiiCkCAD was transferred into wild-type Arabidopsis thaliana with overexpression vector pCAMBIA1302 by the Agrobacterium-mediated method to obtain positive plants. The drought resistance was analyzed after screening and obtaining T₃ generation homozygous positive plants. It was found by Real-time fluorescence quantitative PCR and Western blot methods that CkCAD and its enzyme protein were stably expressed in T₃ Arabidopsis plants overexpressing CkCAD. Compared with wild type A. thaliana， the A. thaliana T₃ generation overexpressing CkCAD has longer vein length and greater vein density， shorter vein island length and shorter diameter， greater vein island density， more developed veins and higher lignin content. Simultaneous drought treatment revealed that the degree of leaf wilting， malondialdehyde content， and electrolyte leakage of overexpressed plants were lower than those of the wild type plants， while the relative water content was higher than that of the wild type plants. This study confirmed that the lignin synthase gene CkCAD of C. korshinskii can promote lignin synthesis and improve drought resistance of overexpressed A. thaliana plants under drought stress.

Effects of different apple pomace levels on lactation performance， nutrient apparent digestibility， serum biochemical indices and the rumen pH of Guanzhong dairy goats

Mang-li XIONG, Xu-jin WU, Xiao-fu ZHU, Wen-juan ZHANG

2021, 30(3):  81-88.  DOI: 10.11686/cyxb2020162

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This experiment investigated the effects of different apple pomace levels on lactation performance， milk quality， serum biochemical indices and the rumen pH of Guanzhong dairy goats. Fifty healthy Guanzhong dairy goats with similar weight （50.81±1.53） kg， parities （3 parities）， days in milk ［（125.00±2.51） d］ and milk yield ［（2.15±0.05） kg·d^-1］ were assigned to 5 groups with 10 goats per group and one goat per replicate. Goats in the five groups were fed the experimental diets which were 0 （control）， 9%， 18%， 27% and 36% apple pomace. The pre-experiment diet adaptation period lasted for 10 days， and the formal experiment lasted for 60 days. It was found that： Milk yield and 4% fat corrected milk in the 18% and 27% groups were significantly higher than those of control group， 9% group and 36% group （P<0.01）. There were no significant differences in dry matter intake among groups （P>0.05）. No significant differences were observed in milk fat percentage， milk protein percentage and lactose percentage among groups （P>0.05）. The apparent digestibility of crude protein in the 18% group was significantly higher than in the control group and the 9% group （P<0.05）， while the apparent digestibility of neutral detergent fiber in the 18% group was significantly higher than in the control， 9% and 36% groups （P<0.05）. No significant differences were observed in serum total protein， serum glucose， serum triglyceride and serum urea nitrogen among groups （P>0.05）. The rumen pH was decreased with increase in the proportion of supplemental apple pomace， and 9%， 18%， 27% and 36% groups all had significantly lower （P<0.05） rumen pH than the control group. In conclusion， dietary supplementation of apple pomace improved milk yield， 4% fat corrected milk， apparent digestibility of crude protein and neutral detergent fiber， decrease the rumen pH， and improve milk quality and serum biochemical indices， which suggests that apple pomace can be used as a new type of feed resource for Guanzhong dairy goats， and the optimal supplemental level is 18%.

Effects of Broussonetia papyrifera silage on growth performance， serum biochemical indexes and meat quality of Dorper×Hu crossbred sheep

Sheng-wei ZHANG, Xiao-ping WANG, Zhan-hai ZHANG, You-ji MA, Shuang-bao GUN, Qiao-li YANG, Xiao-li GAO, Bao-jun ZHANG

2021, 30(3):  89-99.  DOI: 10.11686/cyxb2020167

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This study was conducted to explore the effects of Broussonetia papyrifera silage on growth performance， serum biochemical and immune indexes， meat quality and composition of amino acid and fatty acid in muscle of Dorper×Hu crossbred sheep. Healthy Dorper×Hu crossbred F₁ sheep （n=36） with similar body weight ［（24.2±0.65） kg］ were selected and randomly assigned to 4 treatment groups （Control group， CG； low， medium and high B. papyrifera silage dietary supplementation groups-LG， MG and HG， respectively）， with 3 replicates in each group and 3 sheep in each replicate. The sheep in the CG were fed a basal diet， and those in the test groups LG， MG and HG were fed experimental diets supplemented with 6%， 12% and 18%， respectively， of B. papyrifera silage added to the a basal diet. The trial period was 90 d， comprising a 10 d diet adaptation period and an 80 d formal evaluation period. The findings were as follows： 1） There were no significant differences in final weight and average daily gain of trial sheep after adding different proportion of B. papyrifera silage （P>0.05）. 2） The levels of serum immunoglobulin G， immunoglobulin A and immunoglobulin M of MG and HG were significantly higher than those of the CG （P<0.05）； the content of urea nitrogen in the serum of LG， MG and HG was significantly lower than that in CG （P<0.05）. 3） The level of crude protein and the cooked meat weight in the longissimus dorsi muscle of MG and HG were significantly higher than those in the CG （P<0.05）， while ether extract， cholesterol， shear force and water loss rate in MG and HG were significantly lower than in the CG （P<0.05）. There was no significant difference in pH， drip loss rate， meat color， marbling and fat color among groups （P>0.05）. 4） The levels of essential amino acids， umami amino acids， total amino acids and essential amino acids/total amino acids in the longissimus dorsi of MG were significantly higher than those in CG， LG and HG （P<0.05）. The delicious amino acids∶total amino acids ratio of MG was significantly higher than in the CG （P<0.05）. The contents of valine， leucine， phenylalanine， lysine and arginine in MG were significantly higher than those in the CG， LG and HG （P<0.05）. 5） The content of muscle saturated fatty acids in LG， MG and HG groups were significantly lower than those in the CG （P<0.05）， while the contents of polyunsaturated fatty acids were significantly higher than those in the CG（P<0.05）. Linoleic acid， α-linolenic acid， arachidonic acid， docosahexaenoic acid and eicosapentaenoic acid in MG group were significantly higher than that in CG group （P<0.05）. In conclusion， diet supplementation with B. papyrifera silage had no significant effect on the growth performance of Dorper×Hu crossbred sheep， however， it can promote the immunity of sheep， and improve the nutrient composition， amino acid and fatty acid levels in muscle， as well as the meat quality. Based on these results， the best supplemental level of B. papyrifera silage is 12% of the basal diet.

Effects of dietary concentrate∶roughage ratio on rumen morphology and microbial flora in fattening Tibetan sheep

Jiang-wei LI, Zhi-you WANG, Sheng-zhen HOU, Yun LEI, Jian-lei JIA, Li ZHOU, Lin-sheng GUI

2021, 30(3):  100-109.  DOI: 10.11686/cyxb2020385

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This experiment was conducted to study the effects of dietary concentrate∶roughage ratio on rumen tissue morphology and microbial flora in fattening Tibetan sheep. Early weaned Tibetan lambs （n=210） were randomly divided into seven groups with 30 lambs in each group. The seven groups were fed diets with concentrate∶forage ratios of 20∶80 （A）， 30∶70 （B）， 40∶60 （C）， 50∶50 （D）， 60∶40 （E）， 70∶30 （F） and 80∶20 （G）. The experiment comprised a feed adaptation period of 10 days and a measurement period of 90 days. After the experiment， 3 sheep in each group were slaughtered and rumen tissue and rumen fluid samples were collected. Frozen sections were used to observe the development of rumen tissues， the thickness of the rumen muscle layer and keratinized layer， and the length， width and density of ruminal papillae. 16S rDNA gene sequencing was used to determine the identity of rumen microorganisms present， and the abundance and diversity index of rumen bacteria were analyzed. The results showed that： 1） The morphology of rumen tissue was significantly affected （P<0.05） by the dietary concentrate∶forage ratio. When the concentrate∶forage ratio was 50∶50， the thickness of the rumen keratinization layer， the density and height of the ruminal papillae were significantly higher than that of the other groups （P<0.05）. When the dietary concentrate∶forage ratio 30∶70， the thickness of the rumen muscle layer was significantly higher than that of the other groups （P<0.05）. 2） In this study， 299 OTUs were detected across the seven treatment groups， including 259 OTUs （86.7%） and 40 unique OTUs， including 14 unique OTUs in group F and 8 unique OTUs in group G. The Shannon index， Ace index and Chao1 index of group F were significantly higher than those of other groups， while Simpson index of Group F was significantly lower than that of other groups （P<0.05）. There was a significant difference in bacterial diversity among groups. 3） At the phylum level， the relative abundance of Firmicutes decreased with increase in the concentrate∶forage ratio， and the relative abundance of group A was significantly higher than that of other groups （P<0.05）. At the family level， the relative abundance of Lachnospiraceae was negatively correlated with the concentrate∶forage ratio， and the relative abundance of Prevotellaceae in group E was higher （P<0.05）. According to the rumen tissue phenotype and bacterial flora diversity， the rumen tissue morphology changed with the increase of concentrate level in the diet， and the development of the ruminal papillae and keratinized layers was inhibited to a certain extent. However， increased concentrate∶forage ratio （70∶30） enriched the bacterial diversity of the rumen.

Effects of phenological period on the composition of fatty acids and conjugated linoleic acids in rumen fluid， forage and milk fat of grazing yak and their correlation analysis

Fa-ming PAN, Sheng-hua CHANG, Guo-dong WANG, Sheng-yan HAO, Jia LIU, Hui-yuan ZHANG, Yin-ping XU

2021, 30(3):  110-120.  DOI: 10.11686/cyxb2020340

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The purpose of this paper was to study the effect of seasonal changes in alpine meadow herbage maturity （i.e. forage phenology） on the fatty acid composition of the forage and rumen fluid and on levels of conjugated linoleic acid （CLA） in the milk of grazing yaks. In this study， 10 Gannan yaks with calves and with an average body weight of （234.9±10.5） kg were used as the experimental subjects. The 10 yaks were naturally grazed in Gannan Pastoral Area of Gansu Province. During herbage re-greening in May， the growth flush in September， and winter herbage death in December， forage， yak milk and rumen fluid samples were collected for analysis as outlined above. The correlation between fatty acids and the composition of conjugated linoleic acid in milk fat was studied in order to find out the influence of forage phenology on the composition of fatty acid contents of forage and rumen fluid and the content of conjugated linoleic acid in milk of grazing yaks. It was found that the phenological period significantly affected the levels of lauric acid， myristic acid， palmitic acid， stearic acid， linoleic acid， linolenic acid， total fatty acids， polyunsaturated fatty acid， and polyunsaturated fatty acids/total fatty acid （P<0.05）. For all except stearic acid， and for fatty acid levels in the forage， levels during the summer growth flush were significantly higher （P<0.05） than those in the re-greening and winter periods. The levels of conjugated linoleic acid isomer c9t11， conjugated linoleic acid isomer t10c12 and conjugated linoleic acid in grazing yak milk were also significantly higher （P<0.05） during the herbage growth flush than those in the re-greening and winter death periods. The pH， and contents of acetic acid， propionic acid， acetic∶propionic acid， isobutyric acid， butyric acid， isovaleric acid， valeric acid， total volatile acids and trans-11-oleic acid levels in the rumens of the yaks also differed significantly between phenological periods （P<0.05）. There was a significant positive correlation （P<0.05） between the pH value of forage crude protein， ether extract， nitrogen free extract， tannic acid， total fatty acid and rumen fluid and the CLA content in grazing yak milk， a significant negative correlation （P<0.05） between crude fiber and crude ash and the CLA content in grazing yak milk， and no significant correlation （P>0.05） between polyunsaturated fatty acid levels and total volatile fatty acids and the CLA content in grazing yak milk.

Effect of lactic acid bacteria and storage temperature on the quality of Moringa oleifera leaf silage

Hong-jian LV, Xiang GUO, De-kui CHEN, Xiao-yang CHEN, Qing ZHANG

2021, 30(3):  121-128.  DOI: 10.11686/cyxb2020152

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Four lactic acid bacterial strains， isolated and selected from Moringa oleifera leaf （MOL） silage， were identified as Lactobacillus plantarum （LP）， Lactobacillus farciminis （LF）， Weissella thailandensis （W）， and Lactococcus lactis （E）， respectively. Fermentation quality， nutrient contents and tannin contents of MOL ensiled without or with the four strains at 15 and 30 ℃ external temperature were investigated in the present study. A completely randomized two-factor （lactic acid bacterium×temperature） design was employed. After 60 days the silages were opened to determine and analysis. It was found that the contents of crude protein and water-soluble carbohydrates were 25.31% and 7.53%， respectively， on a dry matter basis. Adding lactic acid bacteria decreased pH， lactic acid bacteria number and ammonium nitrogen content （P<0.05）， while increasing the lactic acid and acetic acid contents （P<0.05）. Silage fermented at 15 ℃ showed higher lactic acid bacteria number and true protein content than when fermented at 30 ℃ （P<0.05）. Furthermore， silage fermented at 15 ℃ external temperature had lower contents of non-protein nitrogen， ammonium nitrogen and free amino acid than silage fermented at 30 ℃ external temperature （P<0.05）. Tannin contents in each treatment group decreased after ensiling without significant difference between treatments （P>0.05）. In conclusion， MOL contain high protein content and they are easy to ensile. Lactic acid bacteria inoculants and a relatively low fermentation temperature are effective to improve the quality of MOL silage.

Effects of fungicide and sowing treatments on seed survival of three plant species on the Loess Plateau

Jin-wei HOU, Tao CHEN, Zhi-biao NAN

2021, 30(3):  129-136.  DOI: 10.11686/cyxb2020465

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To explore how soil fungal pathogens influence seed survival in a typical grassland ecosystem on the Loess Plateau， we used a ‘seed bag burial and retrieval’ methodology， and treated seeds of three common plant species resident in the area （i.e. Lespedeza davurica， Stipa bungeana and Setaria viridis） with fungicide and then buried them in the field in seed bags， either with seeds of one plant species per bag or a mixture of the three species. We retrieved seed bags and evaluated seed survival in each bag after burial for 1 month and 3 months， and performed germination tests in the lab to determine seed viability. We found that， 1） S. bungeana had the highest field germination percentage， 51.9% on average， significantly higher （P<0.05） than that of L. davurica （14.6%） and S. viridis （26.1%）. Seed germination percentage in the field of the three species increased significantly with increasing burial time， but it was not affected by fungicide treatment and sowing treatment. 2） Seed mortality of L. davurica in the field was the lowest （about 1% on average）， while field mortality of seeds of S. bungeana and S. viridis was 5.1% and 4.4%， respectively. In the non-fungicide and monoculture treatments， field mortality of seeds of S. bungeana and S. viridis in the field was 12.5% and 11.0% after 1-month burial， significantly higher （P<0.05） than that of other treatment combinations. Field mortality of seeds of L. davurica was not affected by fungicide treatment， sowing treatment or the length of burial time. 3） Seed germination of S. bungeana in the lab test was the highest， 64.3% on average， significantly higher （P<0.05） than that of L. davurica （5.9%） and S. viridis （29.2%）. With the increase of burial time， seed germination percentage of L. davurica and S. viridis in the lab declined significantly， whereas germination of seeds of S. bungeana increased significantly. Our study suggests that the effects of fungal pathogens on seed survival varied among plant species， and seed mortality was decreased markedly in bags with a mixture of species compared to bags with a single seed species.

Effects of complex saline-alkali stress on seed germination and seedling physiological characteristics of Achnatherum inebrians

Ya-qi CHEN, Kai-qi SU, Tai-xiang CHEN, Chun-jie LI

2021, 30(3):  137-157.  DOI: 10.11686/cyxb2020416

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Saline-alkali land currently has limited options for cultivation and development. This project investigated seed germination， physiological characteristics and antioxidant enzyme activities of Achnatherum inebrians in order to better understand the adaptation to saline soil environments exhibited by this species and provide information to aid future breeding selection and cultivation. A set of 20 different alkali-saline stress conditions were stimulated by mixing two neutral （NaCl and Na₂SO₄） and two alkaline （NaHCO₃ and Na₂CO₃） salts with soil in different proportions （A： NaCl∶Na₂SO₄=1∶1； B： NaCl∶Na₂SO₄∶NaHCO₃=1∶2∶1； C： NaCl∶Na₂SO₄∶NaHCO₃∶Na₂CO₃=1∶9∶9∶1； D： NaCl∶Na₂SO₄∶NaHCO₃∶Na₂CO₃=1∶1∶1∶1； E： NaCl∶Na₂SO₄∶NaHCO₃∶Na₂CO₃ = 9∶1∶1∶9） and at concentrations of 50， 100， 150， and 200 mmol·L^-1. These soil mixtures were used to grow seedlings of endophyte-infected （E+） and endophyte-free （E-） drunken horse grass， and analyze the general salt tolerance of drunken horse grass accessions at the germination and seedling growth stages were analyzed. The seed germination rate， germination vigor， germination index， energy index and shoot length， root length， root-shoot ratio， and shoot tissue antioxidant enzymes peroxidase （POD） and superoxide dismutase （SOD）， malondialdehyde （MDA） and proline were evaluated and analyzed data explored by subordinate function analysis. It was found that the germination rate， germination potential， germination index and vigor index of both E+ and E- drunken horse grass were decreased under the five different saline-alkali stresses. Germination was significantly inhibited with increase in saline-alkali stress concentration （P<0.05）. The radicle length and root-shoot ratio were also significantly decreased with increased salt concentration. Except for treatments C and E， physiological indexes （POD， SOD and CAT activities， MDA and proline levels in shoot tissue） of drunken horse grass were reduced at higher salt concentrations. Subordinate function analysis and the multivariate analysis of salt tolerance indicated that the order of salt tolerance across treatments was A>D>B>C>E. In conclusion， saline-alkali stress significantly inhibited seed germination and seedling growth of drunken horse grass （P<0.05）. Among the alkaline salts tested （NaHCO₃ and Na₂CO₃）， Na₂CO₃， especially， had a stronger inhibitory effect on seed germination and growth. Vigor index， root length， POD， SOD， and proline were found to be the most useful indicators to evaluate the salt tolerance of drunken horse grass. The salt tolerance of E+ drunken horse grass was found to be better than that of E-. Epichlo? endophytic fungi can improve the osmotic adjustment and scavenging of reactive oxygen species of drunken horse grass， thus reducing the membrane lipid peroxidation， and improving the salt tolerance of A. inebrians.

Comparative metabolite profiling of alfalfa seeds dried at different temperatures

Di ZHANG, Li-fei REN, Guang-bin LIU, Fu-qing LUO, Wen-hao ZHANG, Tian-zuo WANG

2021, 30(3):  158-166.  DOI: 10.11686/cyxb2020147

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The present study explored the effects of different drying methods on the seed germination rate of Medicago falcata ‘Zhongke No.1’. High performance liquid chromatography and tandem mass spectrometry were used to analyze the different metabolites produced during natural drying of alfalfa seeds at 39 and 65 ℃. It was found that 39 ℃ was the highest drying temperature which did not affect the seed germination rate and drying at 65 ℃ reduced the germination rate of alfalfa seeds by half. Drying at 39 ℃ and natural drying were similar in terms of the change in metabolites detected before and after drying. However， drying at 65 ℃ induced a larger change in the metabolite profile of seeds. Based on analysis of metabolome data， nucleosides， nucleotides， and their analogues was altered most significantly by high temperature， and lipids and lipid-like molecules followed. The purine?metabolism pathway in seeds was acutely affected by drying at high temperature. The findings of this study elucidate， in terms of different metabolites present， the reasons for low germination rate after high temperature drying， and provide a theoretical basis for improving the design of equipment for alfalfa seed drying.

Effects of biosolids on the growth and auxin metabolism of Poa pratensis under drought stress

Ning ZHANG, Yun-xin CAO, Wei XU, Zhi-hui CAHNG

2021, 30(3):  167-176.  DOI: 10.11686/cyxb2020098

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Biosolids can improve the physical and chemical properties of soil， and promote plant growth. The aim of this research was to study the effects of biosolids on the growth and auxin metabolism of Poa pratensis. A split-plot experiment under the same nitrogen supply level and different water regimes was used， with the main-plot treatments being drought stress and sufficient water supply. The split-plot treatments were biosolids and hormone treatments， namely： indole-3-butytric acid， biosolids， biosolids with added tryptophan， tryptophan and a blank control with no additions. The results showed that biosolids significantly reduced damage to turf quality and ameliorated reductions in chlorophyll and carotenoid content of leaves （P<0.05）. Under different water conditions， both the biosolids and tryptophan increased the content of tryptophan and indoleacetic acid in the roots， while the biosolids significantly increased indoleacetic acid and tryptophan levels in the root system and leaves， and biosolids mixed with tryptophan was more effective than biosolids alone （P<0.05）. In summary， the application of biosolids significantly promoted turfgrass growth， increased the chlorophyll and carotenoid content of Kentucky bluegrass leaves under drought stress. Application of biosolids can also increased the content of tryptophan and indoleacetic acid in the leaves and roots， and increased the photosynthetic rate of P. pratensis and enhanced its drought resistance.

Effects of drought stress on yield and dry matter accumulation and distribution of Avena sativa cv. Qingyan No.1

Kai-qiang LIU, Wen-hui LIU, Zhi-feng JIA, Guo-ling LIANG, Xiang MA

2021, 30(3):  177-188.  DOI: 10.11686/cyxb2020168

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This study aimed to clarify the response of Avena sativa cv. Qingyan No. 1 to different drought stress treatments during crop development. We set up a pot experiment comprising different drought stress intensities （75%， 60%， 45% and 30% field water capacity） and times （0， 1， 2 and 3 times） with respect to crop development， to understand the effects on dry matter accumulation and allocation to plant organs and the changes in yield and yield components. Our results indicated that the plant traits were significantly decreased were length of spikelets （Ls）， seed number per spikelet （SNs）， seed weight per inflorescence （SWi）， hundred kernel weight （HKW） and yield. Number of spikelets （Ns） and seed number per inflorescence （SNi） increased or decreased in different treatments， but empty floret number （Ef） did not show any significant difference between treatments. Dry matter accumulation was inhibited by drought stress， and the proportional allocation to stems and roots was higher than to spikelets under drought stress. The overall effects of differing severity of water deficit were as follows： Imposition of drought three times， moderate and severe stress intensity had the greatest influence. With respect to timing of drought， stress applied at seedling-joint stage， booting-heading stage and flowering-milk stage drought （SM） and seedling-joint stage， booting-heading stage （SH） had the greatest influence. Correlation analysis and path analysis of various indicators found that Ns， SNi， SNs， SWi， HKW， Ls， dry weight of spikelets， dry weight of stem， dry weight of root， dry weight of leaf， spikelet distribution index and yield as having significant positive correlations， with correlation coefficients ranging from 0.368 to 0.922. The stem distribution index， root distribution index and leaf distribution index were negatively correlated with yield， with correlation coefficients ranging from -0.673 to -0.299. Ef displayed a small non-significant negative correlation with yield （-0.021）. Path analysis found that SWi， HKW and SNi had important effects on increase of oat yield.

Effect of organic fertilizer application on the medicinal character， yield and disease resistance of Angelica sinensis

Wan-jun XIAO, Feng-xia GUO, Yuan CHEN, Lan-lan LIU, Yong-zhong CHEN, Xu-sheng JIAO, Bi-quan ZHANG, Gang BAI, Jian-qin JIN

2021, 30(3):  189-199.  DOI: 10.11686/cyxb2020166

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In order to explore effect of organic fertilizer on medicinal cultivationof Angelica sinensis， various fertilization regimes including pure organic fertilizer （O，2000 kg·hm^-2）， pure chemical fertilizer （C， diammonium phosphate， 420 kg·hm^-2）， and half of organic and chemical fertilizers ［1/2（O+C）］ were applied under black film mulching in Min County， using no fertilization as the control （CK）. During cultivation， early bolting， incidence， yield and root character indicators were measured. The results showed that organic fertilizer could reduce the early bolting rateto 8.0%， which was 19.4%， 15.2% and 7.1% lower， respectively， than in the CK， 1/2（O+C） and C treatments. The angelica yield was increased by fertilizer. The fresh yields in O， C and 1/2（O+C） treatments were increased by 105.9%， 84.6% and 78.2%， respectively， compared with the CK treatment. In the O treatment， the medicinal plant had the longest roots， the most lateral roots， the heaviest single root and the highest yield. Fertilization treatment C resulted in a significant increase in root thickening， but the roots had a high water content， and a higher incidence of root disease. Among the different fertilization treatments the angelica fresh yields ranked： O（9220.6 kg·hm^-2）>C（9038.5 kg·hm^-2）>1/2（O+C） （8728.4 kg·hm^-2）>CK （4897.4 kg·hm^-2）. Values for a multivariate evaluative index ranked in the same order： O（0.926）>C（0.610）>1/2（O+C）（0.481）>CK（0.190）. Ranks for the angelica dry yield （which decided economic profit） were O （3149.2 kg·hm^-2）>1/2（O+C） （3098.7 kg·hm^-2）>C （2909.2 kg·hm^-2）>CK （1707.0 kg·hm^-2）. In summary， under black film mulching without pollution in Min County， pure organic fertilizer can significantly increase A. sinensis productivity， efficiently reduce early bolting rate， disease incidence and severity and improve medicinal root characters. Its application should be recommended as part of the standard cultivation method for A. sinensis so as to reduce the dependence on chemical fertilizer and promote green organic cultivation.

Characteristics of soil nutrients under different land types in the loess hill region based on ecological chemometrics

Shuai-nan LIU, Guang LI, Jiang-qi WU, Wei-wei MA, Chuan-jie YANG, Shi-kang ZHANG, Yao YAO, Yan-hua LU, Xing-xing WEI, Juan ZHANG

2021, 30(3):  200-207.  DOI: 10.11686/cyxb2020146

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This research aimed to explore the characteristics of soil organic carbon （SOC）， total nitrogen （TN）， and total phosphorus （TP） under different land types in the loess hill region. Sites classed as typical wheat land， spruce woodland， and alfalfa land in the loess hill region were identified and SOC， TN， and TP levels and their stoichiometric ratio for the different land types and soil depths （0-10 cm， 10-20 cm， 20-40 cm， 40-60 cm， 60-80 cm， 80-100 cm） were evaluated. Based on the measured data， variance and relevant statistical analysis were conducted. It was found that SOC， TN， and TP concentrations in all three land types decreased with increasing soil depth， and their average contents were 12.19， 0.33， and 0.48 g·kg^-1， respectively. The spatial variability of SOC， TN， and TP at wheat and alfalfa land sites was larger than that in spruce forest. The ranking for SOC and TN was spruce woodland>wheat field>alfalfa field， and the TP concentration ranked spruce woodland>alfalfa field>wheat field. A significant positive correlation was found between SOC， TN， and TP. The wheat field C∶P ratio was higher than that of the alfalfa field by 41.96% （P<0.05）， while the N∶P ratio of wheat land was significantly higher than that of spruce woodland and alfalfa fields by 28.57% and 36.19%， respectively. Averaged over the three different land types， the values of the soil stoichiometric ratios （C∶N， C∶P， and N∶P） were 39.61， 31.53， and 0.83， respectively. The value for C∶N is greater than the average for greater China （12.3）， while values for C∶P and N∶P are significantly smaller than the national average （61.0， 5.2， respectively）. The C∶N value in the loess hill region is relatively stable. Land use types have distinctive C， N， and P content signatures and stoichiometric ratios. Appropriate adjustment of land use structure is conducive to the retention of soil nutrients and can potentially improve soil ecological status.

Effects of grazing on total nitrogen and stable nitrogen isotopes of plants and soil in different types of grasslands in Inner Mongolia

Guang-yi LV, Xue-bao XU, Cui-ping GAO, Zhi-hui YU, Xin-ya WANG, Cheng-jie WANG

2021, 30(3):  208-214.  DOI: 10.11686/cyxb2020149

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In order to explore the effect of overgrazing on nitrogen （N） cycling in different grassland ecosystems， we selected three main types of grassland （meadow grassland， typical grassland and desert grassland） in Inner Mongolia， northern China， and analyzed the effects of long-term overgrazing on plant biomass， total nitrogen （TN） and stable nitrogen isotope （δ¹⁵N） values in plant leaves， roots and soil. The results showed that overgrazing significantly reduced the aboveground and underground biomass of grassland vegetation （P<0.05）. Under zero grazing conditions， the TN and δ¹⁵N values of leaves， roots and soil samples from the three main types of grassland showed a downward trend from east to west， and the TN and δ¹⁵N of plant leaves （R²=0.73， P<0.001） and roots （R²=0.86， P<0.001） showed significant positive correlation in all cases. Overgrazing reduced the values of TN and δ¹⁵N in the plant leaves， roots and soil of the three grassland types. In summary， overgrazing has caused substantive impact on N cycling in all three grassland types studied， so we recommend adoption of diversified management methods to ensure sustainable grassland ecosystem development.

Effects of chemical fertilizer reduction and co-application with a JUNCAO nitrogen-fixing biofertilizer on growth and nutritional quality of Pennisetum giganteum and soil nutrient status

Yu-lei JIA, Zhen LIAO, Li-fang WANG, Jian-chao BU, Biao-sheng LIN, Hui LIN, De-wei SU, Guo-dong LU, Zhan-xi LIN

2021, 30(3):  215-223.  DOI: 10.11686/cyxb2020047

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Biological N-fixation offers potential for a significant role in plant cultivation and reduction in chemical fertilizer use. The aim of this research was to study the effect of JUNCAO nitrogen-fixing bacterial isolates on the growth， nutrient quality and soil nutrient of Pennisetum giganteum. JUNCAO nitrogen-fixing biofertilizer was produced using endogenous nitrogen-fixing bacterial strains isolated from the roots of P. giganteum. A field trial was carried out with a randomised complete block design and five treatments： no fertilizer （blank control， CK₀）， sterilized JUNCAO nitrogen-fixation biofertilizer （substrate control， CK₁）， a full rate of chemical fertilizer （FHF）， JUNCAO nitrogen-fixation biofertilizer （T₁）， JUNCAO nitrogen-fixation biofertilizer together with a 75% rate of chemical fertilizer （T₂）. Our results showed that compared with no fertilizer， the application of JUNCAO nitrogen-fixing biofertilizer alone and JUNCAO nitrogen-fixing biofertilizer with a 75% rate of chemical fertilizer treatment significantly boosted plant growth and yield， and improved the forage quality and soil physical and chemical properties in stands of P. giganteum. Compared with the full-rate chemical fertilizer application， application of JUNCAO nitrogen-fixing biofertilizer alone reduced the yield， the herbage crude fiber， lignin， and crude ash contents and soil alkaline hydrolysable nitrogen， available phosphorus， available potassium， and the soil organic matter levels of P. giganteum to different degrees. However， for the treatment of JUNCAO nitrogen-fixing biofertilizer with a 75% rate of chemical fertilizer the number of leaves， the tiller number， herbage crude protein， crude fiber， acid detergent fiber， lignin and crude ash content of P. giganteum were significantly higher than that of single application of chemical fertilizer， while the yield， plant height， crude fat content and soil alkaline hydrolysable nitrogen， available phosphorus， available potassium， and organic matter content of P. giganteum were higher than those at the full rate of chemical fertilizer but the differences were not significant. The neutral detergent fiber level was significantly lower than that of the full rate of chemical fertilizer. In summary， tactically reducing the application rate of chemical fertilizer combined with application JUNCAO nitrogen-fixing biofertilizer （a 75% rate of chemical fertilizer+JUNCAO nitrogen-fixing biofertilizer） showed indications of improved crop vigor in P. giganteum， and also significantly improved the herbage nutritional quality and soil nutrient status of P. giganteum to a moderate degree.