Table of Content

20 September 2021, Volume 30 Issue 9

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Dynamic monitoring of grassland resources and their responses to environmental factors in Qinghai Province based on analyses of daily MODIS NDVI data from the past 20 years

Xin YANG, Wen-xia CAO, Xiao-jun YU, Hai-bin WANG, Yuan-yuan HAO

2021, 30(9):  1-14.  DOI: 10.11686/cyxb2020398

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Dynamic monitoring using remote sensing technologies is an important means to clarify the spatio-temporal dynamic changes in grassland vegetation， and an effective basis to explore the responses of grassland vegetation to environmental factors. Using MOD09GA data， we explored the spatio-temporal dynamic changes in grassland vegetation NDVI （normalized difference vegetation index） in Qinghai Province from 2000 to 2019 on various time-scales （e.g.， daily， ten-day， monthly， annual） by conducting qualitative and quantitative analyses. The relationships between grassland vegetation and various environmental factors （elevation， slope， aspect， temperature and precipitation） were determined using the maximum value composite method， monadic regression trend analysis， and correlation analysis. The overall aim of this study was to provide a theoretical basis for ecological protection and the development of high-quality vegetation resources at the source of the Yellow River. The main results were as follows： 1） The daily change in the NDVI of grassland vegetation showed a stable trend. During the 20-year period， the 10-day fluctuation in NDVI increased， peaked in 2010， and then decreased， but the overall trend was an increase over time. In addition， the re-greening period became earlier and the peak date became concentrated and later， indicating that grassland grew better and its growth period was extended. The multi-year average NDVI gradually increased from northwest to southeast. 2） Grassland quality decreased from southeast to northwest. The area of high-quality grassland decreased at both sides of the study area， with the center at 4500-5000 m. The area of ordinary grassland decreased， then increased， then decreased with increasing elevation. The area of degraded grassland decreased with increasing elevation. The area of all types of grassland gradually decreased with increasing slope， and as the slope direction changed from shaded to sunny and to half-shaded and half-sunny. 3） From 2000 to 2015， both precipitation and temperature increased， with increases in temperature being more marked. Precipitation and temperature tended to decrease from southeast to northwest. Precipitation and temperature tended to be lower in the north and south and higher in the middle of the study area. The correlation between NDVI and precipitation was 6.76% higher than that between NDVI and temperature.

Remote sensing estimation of vegetation cover in alpine grassland in the growing and non-growing seasons

Jia-li LIU, Jian-rong FAN, Xi-yu ZHANG, Chao YANG, Fu-bao XU, Xiao-xue ZHANG, Bo LIANG

2021, 30(9):  15-26.  DOI: 10.11686/cyxb2020324

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Vegetation cover is an important ecological parameter for describing vegetation status of terrestrial ecosystems. Using Landsat-8OLI data for Dangxiong County as the data source， the most suitable vegetation index for estimation of vegetation cover in Alpine Grassland in the growing and non-growing seasons was selected from 10 commonly used vegetation indices. A three-pixel linear mixed model was used to estimate the end element values. The optimal vegetation index for inversion of vegetation cover in the growing and non-growing seasons was determined by comparison of results obtained using the different vegetation indices， based on the pixel bisection model. The selected model was then used to analyze the temporal and spatial distribution of vegetation cover in the growing and non-growing seasons. The results showed that： 1） A vegetation index constructed from the visible-near infrared band performed best for the inversion of vegetation cover in the growing season， and an index constructed from the shortwave infrared was suitable for the inversion of vegetation cover in the non-growing season. 2） The modified soil-adjusted corn residue index （MSACRI） pixel dichotomy model was the best model to invert the vegetation cover in the non-growing season， and the normalized difference vegetation index （NDVI） pixel dichotomy model was the best for inversion of the vegetation cover in the growing season. 3） Across a gradient of increasing altitude， the vegetation cover presented a single-peak pattern with the peak at mid-altitude. Grassland was mainly found at 4300-5100 m above sea level. The vegetation cover in the growing season typically ranged from 20% to 80%， while cover in the non-growing season was mostly less than 40%. This research results provides reference data for studies on grassland ecosystem carbon storage， vegetation productivity， soil erosion， and ecological hydrology.

Effect of temperature changes on nitrogen mineralization in soils with different degradation gradients in Gahai Wetland

Liang-cui SONG, Wei-wei MA, Guang LI, Shuai-nan LIU, Gang LU

2021, 30(9):  27-37.  DOI: 10.11686/cyxb2020347

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Nitrogen （N） mineralization is a major component in the process of soil N cycling. To further understand soil N cycling in the context of global warming， it is important to explore the effect of temperature variation on soil net nitrogen mineralization rate in alpine Wetland soils with different degradation status. In this research， Gahai Wetland was selected as a model system for study， and a methodology involving indoor incubation of soil samples for 69 days and periodic rinsing was used to study the soil N mineralization characteristics in three soil layers （0-10 cm， 10-20 cm， 20-40 cm） of a four-step soil degradation gradient （non-degraded， mildly-degraded， moderately-degraded and severely-degraded） under the condition of different temperature cultivation. The results indicate that： 1） For the same degeneration level， with increasing temperature， soil net nitrogen mineralization rate and nitrification rate rose， however， ammoniation rate initially increased and then reduced. By fitting the results with a first-order kinetic equation， we found that the maximum value of soil nitrogen mineralization occurred at a culture temperature of 35 ℃. Under the same temperature level， soil nitrogen mineralization potential （N₀） showed significant differences depending on the extent of soil degradation， reflecting the potential for soil nitrogen mineralization. 2） Soil nitrogen mineralization and nitrification rates for a particular temperature， soil degradation status， and soil layer decreased with increasing duration of soil culture. Initially rates were high， and over time they slowed. 3） There was a significant difference in soil nitrogen mineralization along the degradation gradients， we ranked the net nitrogen mineralization over the 69 days of incubation for soils with different degradation status and temperature， results were： mineralization at 15 ℃<25 ℃<35 ℃. Our results indicate that temperature has a substantial influence on the process of soil nitrogen mineralization， and high temperature speeds up the process of soil nitrogen mineralization.

Responses of forage nutrient quality to grazing in the alpine grassland of Northern Tibet

Gang FU, Jun-hao WANG, Shao-wei LI, Ping HE

2021, 30(9):  38-50.  DOI: 10.11686/cyxb2021123

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In this study， we determined the responses of herbage nutrient quality to grazing in alpine grasslands in different seasons and different grassland types. Three fenced and free-grazing grassland sites in the alpine grassland in the Northern Tibetan Plateau were selected for this study. We found that winter grazing increased the nutritional quality of forbs by decreasing the acid detergent fiber content by 24.29% and the neutral detergent fiber content by 18.98%， and by increasing the crude ash content by 41.05%. However， winter grazing did not affect the nutritional quality of the plant community and high-quality forage in the alpine steppe meadow. Summer grazing increased the nutrient quality of the plant community by decreasing the acid detergent fiber content by 31.82% and the neutral detergent fiber content by 27.45%， and by increasing the crude ash content by 137.35% and the crude fat content by 24.73% in an alpine steppe meadow. Summer grazing increased the nutrient quality of high-quality forage by decreasing the acid detergent fiber by 22.04% and the neutral detergent fiber content by 22.50%， and by increasing the crude ash content by 202.19%. However， summer grazing did not change the nutrient quality of forbs in the alpine steppe meadow. Summer grazing increased the nutritional quality of forbs through decreasing the acid detergent fiber content by 37.18% and the neutral detergent fiber content by 25.10%， and tended to increase the nutritional quality of high-quality forage through increasing the crude protein content by 26.55%， but had no effect on the nutritional quality of plant community in an alpine meadow. The nutritional quality of the plant community was related to its α and β diversity. The nutritional quality of high-quality forage was mainly related to soil variables， and the nutritional quality of forbs was related to its α diversity and soil variables. Therefore， in alpine grasslands of Northern Tibet， the responses of forage nutrient quality to grazing differ depending on plant types and grazing seasons. Alpine grassland should be managed by different grazing patterns.

Effect of short-term fencing on the forage quality of plant communities in degraded grassland in Northwestern Liaoning

Jing-dong ZHAO, Wuyunna, Yan-tao SONG

2021, 30(9):  51-61.  DOI: 10.11686/cyxb2020330

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The impact of fencing on the forage quality of degraded grassland is an important aspect of evaluation of fencing effectiveness. This research studied the changes in community characteristics and forage quality indicators from 2017 to 2019 under fencing and free grazing treatments in degraded grassland in northwestern Liaoning Province. It was found that plant community height， vegetation cover， aboveground biomass， plant litter and the levels of crude protein （CP）， non-fibrous carbohydrate （NFC）， net energy for lactation， milk perton index （MT） in the fencing treatment were significantly higher than corresponding values for the grazing treatment （P<0.05）， thus it was deduced the forage in the fencing treatment had higher nutrient content and feeding value. The forage crude ash， ether extract， lignin， acid detergent fiber， in vitro dry matter digestibility， neutral detergent fiber digestibility， digestible neutral detergent fiber， and elemental calcium， magnesium and phosphorus contents in the grazing treatment were all significantly higher than those in the fencing treatment （P<0.01）， so the forage in the grazing treatment had high digestibility and was rich in mineral elements， but had poor palatability. In 2019， the levels of CP， NFC， elemental potassium， net energy for maintenance and total digestible nutrients in forage were significantly higher than those in the first year of fencing （2017） （P<0.05）， and the neutral detergent fiber concentration was the lowest among the three years （P<0.05）. Hence， the results show that the indexes describing community characteristics and forage quality of degraded grassland were improved after three years fencing. These results provide theoretical reference data for short-term fencing of degraded grassland and show the importance of fencing for grassland management and utilization.

Preliminary evaluation of 48 alfalfa varieties for resistance to three diseases

Yan-zhong LI, Jun-qiang YU, Ming LI

2021, 30(9):  62-75.  DOI: 10.11686/cyxb2021043

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The aim of this field study was to compare the resistance of 48 alfalfa （Medicago sativa） varieties from China and abroad to three different diseases： common leaf spot （Pseudopeziza medicaginis）， downy mildew （Peronospora aestivalis）， and root rot （Fusarium acuminatum）. The study was conducted at Yuzhong Campus， Lanzhou University. The disease incidence rate was used as an indicator of susceptibility， and the internationally accepted alfalfa disease resistance evaluation grading standard was applied to compare resistance among the 48 alfalfa varieties. The results of our analyses showed that， in terms of resistance to common leaf spot disease， UC-1465 was a highly resistant variety， UC-1887 was a resistant variety， Siriver and Trifecta were medium-resistance varieties， Avora， Hunter River and Saranac AR were low-resistance varieties， and the remaining 41 varieties were susceptible varieties. In terms of resistance to downy mildew and root rot， all 48 alfalfa varieties were highly resistant varieties. The results of subordinate function analysis showed that Vertus， Zhonglan No.1 and Xinmu No.1 were strongly resistant to common leaf spot， downy mildew， and root rot， indicating that they are highly resistant varieties； while UC-1887， UC-1465 and Saranac AR had lower resistance to the three diseases， indicating that they are susceptible varieties.

Drought tolerance of wild Elymus nutans during germination and seedling establishment

Chuan-qi WANG, Wen-hui LIU, Yong-chao ZHANG, Qing-ping ZHOU

2021, 30(9):  76-85.  DOI: 10.11686/cyxb2020396

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Elymus nutans is a suitable forage grass for growing in the cold and semi-arid environment in the Three-River Headwaters region. In this study， we evaluated the drought tolerance and water demand threshold values of E. nutans during the germination and seedling establishment stages. For these analyses， seeds were germinated on paper under drought conditions simulated using the polymer polyethylene glycol （PEG-6000）. Solutions of PEG-6000 （-0.15， -0.30， -0.50， -0.75 and -1.00 MPa） were prepared to impose different levels of drought stress， with ultrapure water （0 MPa solution） as the control. The main findings were as follows： drought stress reduced the seed germination emergence percentage and germination emergence rate of E. nutans， delayed the peak period of seed germination and seedling emergence， and also delayed the peak period of seed germination and seedling emergence after re-watering. The seed germination percentage， seedling emergence percentage， germination index， vigor index， bud length， dry and fresh weight of buds， and dry matter accumulation of E. nutans decreased with increasing severity of drought stress. The root length and dry and fresh weight first increased and then decreased with increasing severity of drought stress. After re-watering， the seed germination percentage， seedling emergence percentage， germination index， and vigor index of E. nutans first increased and then decreased with increasing severity of drought stress， while the root length， bud length， and dry and fresh weight of root and buds decreased. Drought stress had little effect on the root elongation of E. nutans， but strongly affected bud elongation， and this effect became stronger with increasing severity of drought stress. Consequently， the root to shoot ratio of seedlings increased continuously with increasing severity of drought stress. The water demand threshold values of E. nutans varied during the period of germination and seedling emergence stages showed different requirements on environmental water potential. The germination stage had strong drought tolerance. Re-watering after drought stress positively affected seed germination and seedling emergence. Even under severe drought stress （-0.50 MPa）， seeds could still germinate and grow after re-watering. The results of this study have important theoretical value for further research on the drought adaptation mechanism of E. nutans， and also have practical significance for growing E.nutans to effectively control grassland degradation， desertification， soil erosion， and water loss in the Three-River Headwaters region.

Effects of nitric oxide on nitrogen metabolism in alfalfa under drought stress

Ying ZHAO, Xia-qing XIN, Xiao-hong WEI

2021, 30(9):  86-96.  DOI: 10.11686/cyxb2020322

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This experiment investigated the regulatory effects of nitric oxide on nitrogen compounds and nitrogen metabolism in alfalfa （Medicago sativa） under osmotic stress. External applications of NO donor sodium nitroprusside （SNP） and an NO scavenger （c-PTIO） to alfalfa seeds and seedlings were used to manipulate and study the behavior of endogenous NO-regulated nitrogenous substances and enzymes involved in nitrogen metabolism in alfalfa under PEG-induced simulated drought stress. It was found that， compared with PEG treatment， exogenous application of 0.1 mmol·L^-1 SNP increased the concentration of soluble proteins in the germination and seedling stages by an average of 16.91% and 8.87%， respectively， and decreased free amino acid concentration by an average of 14.92% and 0.68%， respectively. The activities of nitrate reductase （NR）， glutamine synthetase （GS） and glutamate synthase （GOGAT） were increased by up to 23.85%， 47.87%， and 60.06%， respectively， during the germination period， and by up to 16.31%， 23.56%， 72.89%， respectively， in seedlings. The activity of glutamate dehydrogenase （GDH） was decreased by up to 35.89% during germination and up to 33.35% in seedlings. The addition of c-PTIO under PEG stress exacerbated the inhibition effect on nitrogenous substances. The NO scavenger c-PTIO effects on NR， GS and GOGAT activities were not significant， while the activity of GDH was increased by an average of 18.26% and 4.62% during germination and in seedlings， respectively. Hence， the data indicate that NO promotes alfalfa nitrogen metabolism under PEG stress by regulating the activity of key enzymes in nitrogen metabolism， thus promoting the transport and accumulation of nitrogen for protein synthesis.

Effects of reduced glutathione on the growth and photosynthesis of perennial ryegrass under lead stress

Li-qing ZHAO, Xiang-yong PENG, Jun-xiang LIU, Jin-mei MAO, Zhen-yuan SUN

2021, 30(9):  97-104.  DOI: 10.11686/cyxb2020338

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The aim of this study was to explore the mitigative effects of reduced glutathione （GSH） on the growth and photosynthesis of perennial ryegrass （Lolium perenne） under lead stress. Twelve-week old seedlings of the perennial ryegrass cultivar ‘cuttle’ were used as the experimental material. In the control （CK）， leaves were sprayed with 50 mL distilled water， and roots were supplied with 1/2-strength modified Hoagland’s nutrient solution. In the other three experimental treatments， the roots were supplied with 1/2-strength modified Hoagland’s nutrient solution containing 0.75 mmol·L^-1 Pb（NO₃）₂， and the leaves were sprayed with 50 mL distilled water （Pb treatment）； with 25 mL distilled water followed by 25 mL 10 mmol·L^-1 GSH （Pb+GSH treatment）； or with 25 mL distilled water followed by 25 mL 1 mmol·L^-1 L-buthionine-sulfoximine （BSO） （Pb+BSO treatment）. The results showed that shoot length， root length， tiller number， biomass， chlorophyll content， photosynthetic parameters， and the kinetic parameters of chlorophyll fluorescence were significantly higher in the Pb+GSH treatment than in Pb treatment. In contrast， the values for root length， tiller number， biomass， carotenoid content， and photosynthetic parameters were lower in the Pb+BSO treatment than in Pb treatment. Together， our results show that spraying ryegrass leaves with 10 mmol·L^-1 GSH can effectively alleviate the inhibitory effects of Pb stress and improve the Pb tolerance of perennial ryegrass， whereas spraying with BSO at 1 mmol·L^-1 exacerbates the inhibitory effects of Pb stress.

Effects of nitrogen and phosphorus addition on root characteristics of alpine meadow

Li-tao TANG, Rui MAO, Chang-ting WANG, Jie LI, Lei HU, Hong-biao ZI

2021, 30(9):  105-116.  DOI: 10.11686/cyxb2020327

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This research studied root characteristics， including standing root biomass， root mortality， root production and root life span in alpine meadow in Northwest Sichuan. Our methodology combined ‘minirhizotron’ root viewing tubes and indoor analysis to evaluate effects of nitrogen and phosphorus （NP） addition. The fertilization gradients were 0 （CK）， 10 （NP₁₀）， 20 （NP₂₀） and 30 g·m^-2 （NP₃₀）， respectively. We also discuss the relationships between root characteristics and soil physical and chemical properties. It was found that nitrogen and phosphorus addition increased the levels of total phosphorus， available phosphorus and available nitrogen in the 0-10 cm soil layer， decreased the pH and C∶P， but had little effect on soil total nitrogen and organic carbon levels. Also， N and P addition prolonged root life. Compared to CK， standing root length increased by 8.79 and 13.21 mm·cm^-3 in NP₂₀ and NP₃₀ treatments， respectively and the production and mortality increased by 3.17 mm·cm^-3 and 2.92 mm·cm^-3， respectively， for NP₃₀. However， in the deep soil layer （10-20 cm）， the standing root length decreased by 8.85 mm·cm^-3 for NP₁₀ and 5.37 mm·cm^-3 for NP₃₀， the production decreased by 1.63 mm·cm^-3 for NP₁₀ and 1.43 mm·cm^-3 for NP₂₀， and the mortality decreased by 2.14 mm·cm^-3 for NP₁₀ and 1.78 mm·cm^-3 for NP₃₀. In addition， there was a significant correlation between standing root length， root production， root mortality and soil available nutrients （P<0.01）. In summary， NP addition made the distribution of plant roots shallower through change in the content of soil available nitrogen and phosphorus. Addition of NP slowed down root turnover by prolonging root life， reduced the carbon consumption of the root system and enhanced its carbon sink function， thus changing the carbon distribution pattern of the studied alpine meadow ecosystem.

Factors influencing the scale of herdsmen’s livestock farming in tundra alpine grassland-A case study from Qinghai Province

Ting-mei WU, Hui-long LIN, Di FAN, Chang-ting JI, Yu-ting ZHAO, Jing-qiong WEI

2021, 30(9):  117-126.  DOI: 10.11686/cyxb2020337

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The scale of herdsmen’s livestock farming activities plays a crucial role in determining equilibria in grassland ecosystems. It is therefore important to analyze the factors affecting the scale of livestock production activities， and thus guide pastoralists to adopt rational grazing practices， restore degraded grassland， and ensure the ecological safety of rangeland in China. Using data from a pastoral households survey in Qinghai Province， this study employs principal component analysis to identify the contributions of various factors to livestock production decisions. In addition， quantile regression was used to analyze the factors of influence and the characteristics of livestock production of different scales， exploring the different factors affecting livestock breeding practices of individual of herdsmen. The results indicated that： natural factors are the most dominant factors influencing livestock production， followed by policy factors， education factors， and non-grazing factors in that order； livestock production practice at medium and lower scale is significantly affected by the proportion of family labor and non-pastoral employment income； livestock production practice at medium and higher scale is affected by the per capita available grassland area and the grassland compensation policy significantly and a grazing ban policy can achieve the goal of protecting grassland ecology better than the forage-livestock balance policies. We make the following suggestions for improvement of grassland status： increasing non-pastoral employment opportunities in pastoral areas， actively guiding herdsmen with smaller operations to participate in non-pastoral employment； increasing the range of forage-livestock balance zones in tundra alpine grassland， and an appropriate raise in the compensation standard for medium and larger-scale herders. This study found that the factors influencing livestock production practices in tundra alpine grasslands differ depending on the scale of operations of herdsmen. This insight provides a scientific basis for the government to differentiate management of herders with different enterprise sizes.

An evaluation of the effects of the plant endophyte Enterobacter on the salt tolerance of bermudagrass

Xin-tong ZHAO, Xiao-dong CHEN, Zi-ji LI, Ju-ming ZHANG, Tian-zeng LIU

2021, 30(9):  127-136.  DOI: 10.11686/cyxb2020317

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Endogenous Enterobacter species were isolated from Paspalum vaginatum and were then used to study the influence of plant endophytic bacteria on the salt tolerance of bermudagrass in two methods of seed germination and pot experiment. In pot experiments germinating bermudagrass seeds and seedlings forming miniature turves in pots 10 cm×10 cm×9 cm were inoculated with a single species of endophytic bacterium （Enterobacter ludwigii） or with a mixture of two endophytic bacterial species （E. ludwigii+Enterobacter bugandensis）. The experiments also included blank controls （CK）. Seed germination rate， shoot length， root length and biomass growth indexes， chlorophyll content， relative water content， relative electrical conductivity and leaf contents of sodium and potassium ions were determined to provide a comprehensive evaluation of effects of endophytic bacteria on bermudagrass salt tolerance. It was found that when germinating bermudagrass seeds under 150 mmol·L^-1 NaCl stress were assessed after 14 days， germination， radicle length and plumule length each ranked B3014>B30>CK （P<0.05）. For potted plants subjected to 200 mmol·L^-1 NaCl stress that had formed turves， inoculation with endophytic bacteria enhanced turf quality， shoot length， root growth， shoot and root biomass， chlorophyll content and relative water content of leaves， and also reduced cell membrane electrolyte leakage and these effects were more pronounced for B3014 than for B30 （P<0.05）. In addition the endophytic bacteria facilitated reduction of Na⁺ and increase in K⁺ concentrations in tissues of inoculated plants， with these effects again more pronounced in the B3014 treatment than in the B30 treatment. In summary， inoculation with Enterobacter improved seed germination and salt tolerance of bermudagrass seedlings under salt stress， and B3014 was more effective than B30 alone. Enhancement of the salt tolerance of bermudagrass by inoculation with endophytic bacteria provides a new method for improving the performance of turfgrass in saline alkali environments.

A preliminary study of the antifungal activity and antagonism mechanisms of Trichoderma spp. against turfgrass pathogens

Wu ZHANG, Jin-yu YANG, Xiang LU, Jin-mei LIN, Xue-li NIU

2021, 30(9):  137-149.  DOI: 10.11686/cyxb2020333

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Trichoderma spp.， is an antagonistic group of microorganisms widely found in nature and many species have important biocontrol value for use against plant pathogens. In order to evaluate Trichoderma spp. as a potential biocontrol agent for turfgrass disease， the antagonistic effects of four Trichoderma strains against 14 turfgrass pathogens were determined by agar confrontation culture and the mechanism of inhibition was studied by microscopic observation， the ‘cellophane method’ and bacteriostatic testing of crude extract. The results showed that tested Trichoderma spp. isolates had antagonism against all tested pathogens. Among the tested Trichoderma spp. isolates， an isolate designated SQ-1Q-18 had the greatest antibacterial efficacy. The antagonistic activity against Rhizoctonia zeae and Laetisaria fuciformis was scored as level I， with 100% inhibition rate； for Botrytis cinerea， Colletotrichum hainanese and Rhizoctonia solani the antagonistic activity was scored as level Ⅱ， with over 80% inhibition rate for the most potent Trichoderma isolate， and an average inhibition rate against these three pathogens of up to 72.8%. Further study of the inhibitory mechanism of the SQ-1Q-18 isolate on 14 pathogens was that Trichoderma surrounded the growth space of pathogens by generating a bacteriostatic circle， and covered and inserted into the pathogen colony and entwined with it to make the pathogen mycelium become thin， constricted and even broken. Trichoderma could also penetrate directly into a pathogen mycelium to absorb nutrients and cause mycelium cytolysis. In addition， the SQ-1Q-18 isolate could produce antagonistic compounds with inhibitory activity against the turfgrass pathogens. The antagonistic substances produced by the cellophane culture method had strong antagonistic effects against Sclerotinia homoeocarpa， Nigrospora sphaerica and L. fuciformis， and the relative inhibitory rate was as high as 91.77%， 89.80% and 79.59%， respectively. The inhibition rate of Trichoderma crude extract against S. homoeocarpa and Bipolaris peregianensis was 43.60% and 42.91%， respectively. Furthermore， the SQ-1Q-18 isolate was identified as Trichoderma harzianum by morphological characteristics and ITS-rDNA sequence. This study provides scientific data for the research and development of a biocontrol agent for efficient control of turfgrass fungal diseases.

Effect of Epichloë endophyte on the litter decomposition of Stipa purpurea in alpine grassland

Mei-ling SONG, Yu-qin WANG, Hong-sheng WANG, Gen-sheng Bao

2021, 30(9):  150-158.  DOI: 10.11686/cyxb2020462

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Grass fungal endophytes can positively improve the tolerance of their host plant to biotic and abiotic stress. However， the effect of the symbiotic fungal endophyte on grass host litter decomposition on the nutrient cycling of grassland ecosystem is not clear. In this research a detailed comparison was made between litter of Stipa purpurea with endophyte （E+） and without endophyte （E-）. Analyses performed included weight of litter shed， contents of total nitrogen， lignin and cellulose， change in lignin∶N and cellulose∶N ratios and residual concentrations of total N， lignin and cellulose in E+ and E- litter samples. The results were as follows： E+ S. purpurea litter had a higher decomposition rate and a shorter decomposition cycle than E- litter. With increase in the decomposition time， the content of lignin and the ratio of lignin∶N in S. purpurea litter changed gradually from higher in E+ than E-， to there being no significant difference between E+ and E- litter. The cellulose content， cellulose∶N ratio and cellulose residual concentration in E+ S. purpurea litter were significantly lower than E- litter in the latter part of the decomposition cycle. In contrast， the total N content of S. purpurea litter displayed a rising trend， and the elemental N residual concentration displayed a declining-rising-declining trend as decomposition progressed. E+ S. purpurea litter had a lower residual N content than E- litter in the later stages of decomposition. Hence， the presence of fungal endophyte enhanced， to different degrees， the rate of degradation of leaf mass， total N， lignin and cellulose in S. purpurea litter.

Effects of different doses of sodium nitrate on fatty acid composition and microbial population in in vitro simulation of buffalo rumen fermentation with added linoleic acid

Yan-xia GUO, Meng-wei LI, Zhen-hua TANG, Li-juan PENG, Kai-ping PENG, Fang XIE, Hua-de XIE, Cheng-jian YANG

2021, 30(9):  159-167.  DOI: 10.11686/cyxb2020320

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This research explored the effects of different doses of sodium nitrate on the composition of fatty acids and the numbers of microorganisms in in vitro simulation of buffalo rumen fermentation with added linoleic acid. Three female buffaloes with permanent rumen fistula were used. The ratio of dietary concentrate to roughage was 40∶60. The experiment comprised five replicates of four experimental treatments： a blank control （CK） and addition of sodium nitrate at rates of 1， 2 or 3 mg·mL^-1， with 0.25 mg·mL^-1 linoleic acid added in each case. Gas and methane production were measured after 3， 6， 9， 12 and 24 h anaerobic incubation in vitro， and the fermentation parameters， fatty acid concentrations and numbers of rumen microorganisms were determined after 24 h incubation. It was found that adding sodium nitrate significantly reduced the total gas production and methane production （P<0.05）. Adding sodium nitrate also significantly increased the simulated rumen pH value and ammonia nitrogen （NH₃-N） concentration （P<0.05）， significantly reduced the contents of isobutyrate and isovaleriate （P<0.05）， but had no significant effects on the concentrations of total volatile fatty acids （TVFA） （P>0.05）. With the addition of 1 mg·mL^-1 sodium nitrate， the contents of C18：2cis-9， trans-11， C18：2trans-10， cis-12 and unsaturated/saturated fatty acid ratios were significantly higher than those in other groups （P<0.05）. The concentration of C20：5n3 （eicosapentaenoic acid） in the 1 mg·mL^-1 sodium nitrate group was significantly higher than that in the 3 mg·mL^-1 sodium nitrate group （P<0.05）， and the concentration of C22：6n3 （docosahexaenoic acid） with 2 mg·mL^-1 sodium nitrate added was significantly higher than that of other groups （P<0.05）. The number of protozoa in treatments with added sodium nitrate was significantly lower than for CK （P<0.05）. The number of methanogens in treatments with 2 and 3 mg·mL^-1 added sodium nitrate was significantly lower than in the 1 mg·mL^-1 sodium nitrate treatment （P<0.05）， and the numbers of bacteria， fungi， Butyrivibrio fibrisolvens， Butyrivibrio proteoclasticus， Atypical butyrivibrio， and Butyrivibrio hungatei in the 1 mg·mL^-1 sodium nitrate treatment were significantly higher than in other treatments （P<0.05）. In summary， the addition of 1-3 mg·mL^-1 sodium nitrate and 0.25 mg·mL^-1 linoleic acid in vitro significantly reduced methane generation while maintaining the TVFA concentration. Moreover， 1 mg·mL^-1 sodium nitrate promoted the formation of conjugated linoleic acid （CLA）， optimized fatty acid composition， and increased the numbers of most rumen microorganisms.

Sustainable development of family ranches in the Inner Mongolian grassland

Qing ZHANG, Lu-yao LIU, Xue XU, Peng HAN, Yan-yun ZHAO, Jian-ming NIU, Yong DING

2021, 30(9):  168-181.  DOI: 10.11686/cyxb2021058

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The Inner Mongolian grasslands are an integral part of the arid and semi-arid steppes of central and eastern Asia， and are currently attracting topical research in a number of fields. The family ranch is the primary production and management unit of the area. It is helpful to provide the scientific basis for regional sustainability by exploring the requirements for sustainable development of the family ranch. Firstly， this article expounds the formation process and definition of the family ranch in the Inner Mongolian grasslands. Next， recent research progress relating to family ranch sustainability from the perspectives of the natural ecosystem， the socio-economic system， and the natural-economic-social system， is summarized. Finally， six current research thrusts for further enhancing the sustainability of the family ranch are discussed. These include： Adherence to the concept of grass-based livestock husbandry， reliance on the guidance of the landscape sustainability considerations， strengthening coupling of research across three interfaces， expanding sandy grasslands， focusing on future development models and recognition of the importance of technical support. It is hoped that this article will elicit more targeted suggestions for the sustainable development of the family ranch in the Inner Mongolian grasslands and provide reference information for developing the sustainability of arid and semi-arid grassland systems worldwide.

Research progress on rumen microorganisms in the utilization of lignocellulose as an energy resource

Juan-shan ZHENG, KAO Ren-qing DING, Xin-pu LI, Ze-yi LIANG, Jian-bo ZHANG, Mei DU, Xue-zhi DING

2021, 30(9):  182-192.  DOI: 10.11686/cyxb2020316

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The rumen is the first compartment of the digestive tract of ruminants， it functions as a pre-gastric anaerobic fermentation chamber， where are ingested plant material is degraded by various microorganisms （bacteria， fungi and protozoa） and converted into low-molecular-weight chemical compounds which are subsequently absorbed and digested by the animal. The rumen is currently recognized as a natural reactor， where a variety of lignocellulosic degrading enzymes are secreted by fungi and bacteria and the lignocellulose is degraded and utilized efficiently. Replication of rumen processes in vitro has potential value in the production of biofuels and chemical compounds from lignocellulose. Therefore， from the perspective of reviewing which rumen microorganisms degrade lignocellulose and related compounds， this paper focuses on the research progress of rumen microorganisms and organic acid biochemistry in the conversion of lignocellulose to ethanol and biogas. In compiling this overview， we aim to provide new methods and ideas for the research and application of rumen microorganisms in the utilization of lignocellulose as an energy or chemical synthesis resource.

Research advances in heat resistance of cool-season turfgrasses

Zhen-zhen TAN, Xia-xiang ZHANG, Zhi-min YANG

2021, 30(9):  193-202.  DOI: 10.11686/cyxb2020331

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Cool-season turfgrasses are widely used on parks， sports fields and lawn in climate transition zones， due to their strong cold resistance， long green period and good ornamental effect. However， cool-season turfgrasses are sensitive to heat stress. High temperature in summer causes a series of physiological and metabolic disorders of turfgrasses， resulting in a decline in turf quality， increased occurrence of disease， dormancy， withering and even plant death， further affecting the performance of lawns or sports fields. This review describes the physiological and molecular mechanisms of high temperature stress tolerance in cool-season turfgrasses， especially with respect to carbon metabolism， antioxidant metabolism， hormone metabolism， heat-related genes and transcription factors. Current issues and future prospects pertaining to heat resistance mechanisms of cool-season turfgrasses are discussed， in order to provide a theoretical reference for use in further studies.

Diurnal change in chlorophyll fluorescence parameters in three desert plants

Lu-yao WU, Jian-guo ZHANG, Wen-qian CHANG, Shao-lei ZHANG, Qing CHANG

2021, 30(9):  203-213.  DOI: 10.11686/cyxb2020345

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This research evaluated the relationship between chlorophyll fluorescence parameters and environmental factors in three common species of shelterbelt plants （Calligonum caput-medusae， Tamarix ramosissima， and Haloxylon ammodendron） found in the hinterland of Taklimakan Desert in order to elucidate the adaptation strategies of the three species in an extreme environment， and to provide theoretical data to assist with the management and protection of the highway shelterbelt. Diurnal changes in chlorophyll fluorescence were measured using a Photosynq MultiseQ multi-function plant-measuring instrument. There were four main conclusions. 1） All three soils were alkaline， and electrical conductivity （EC） values of the 0-30 cm soil layer were significantly higher than in soil below 30 cm depth. The water content in the upper 1 m of the soil profile ranked： H. ammodendron>T. ramosissima>C. caput-medusae. 2） The diurnal variation in photosynthetically active radiation （PAR）， atmospheric temperature， leaf temperature， and linear electron flux （LEF） increased through the morning to peak values at approximately 14：00 h and then declined， while values for atmospheric humidity and actual photochemical efficiency Y_（II） showed a ‘V’ shape. 3） For all the three plant species， PAR data had significant positive correlations with LEF， non-photochemical quenching coefficient （NPQ）， adjusting energy dissipation quantum yield ［Y_（NPQ）］， and non-adjusting energy dissipation quantum yield ［Y_（NO）］， however， they showed a significant negative correlation with actual photochemical efficiency ［Y _（II）］. In addition， Y_（II） had an extremely significant negative correlation with Y_（NPQ） and Y_（NO）. 4） Among the chlorophyll fluorescence parameters of the three plant species， LEF， NPQ， and Y_（II） of both H. ammodendron and C. caput-medusae were higher than those of T. ramosissima， while Y_（NO） of T. ramosissima was significantly higher than that of C. caput-medusae and H. ammodendron. Therefore， high temperature and high light intensity exerted different effects on the three species， and the stress resistance of the three species indicated by principal component analysis ranked H. ammodendron>C. caput-medusae>T. ramosissima.