The influences of reseeding date and mowing prior to reseeding on establishment of alfalfa in Leymus chinensis meadows北大核心CSCD

This research studied the effects of sowing date and cutting prior to sowing on establishment of the leguminous forage，alfalfa（Medicago sativa），in a lightly degraded Leymus chinensis meadow and investigated the sowing date×cutting interaction. The factorial experiment comprised four sowing dates（May 1，June 1，July 1，August 1）and cutting treatment（cut or uncut）prior to sowing，and evaluated the establishment performance of alfalfa and the ecological mechanisms related to establishment. It was found that soil moisture during emergence of alfalfa was the greatest when sowing occurred on July 1，and clipping prior to sowing significantly decreased the plant height of L. chinensis during emergence and seedling growth of alfalfa. There was a significant sowing date×cutting interaction effect on alfalfa establishment. Clipping prior to sowing significantly increased the emergence percentage of alfalfa through reducing the plant height of L. chinensis and associated above-and below-ground competition，and the seasonal soil moisture change resulted in a 20% higher（P<0. 05）alfalfa emergence rate when sowing occurred on July 1. With cutting，the number of surviving alfalfa seedlings and seedling survival rate were greatest（83 plants· m−2 and 53%，respectively）when sowing occurred on July 1. For later sowing，owing to the shortened growing time，the development and overwintering survival rates of alfalfa seedlings were significantly reduced. Cutting prior to sowing significantly increased the overwintering rate of alfalfa seedlings through improving their development. In the cutting treatment，the number of overwintered alfalfa seedlings（22 plants·m−2）when sowing was on July 1 was significantly higher than for other reseeding dates. In the second year，a botanical composition measurement showed that clipping prior to reseeding significantly increased the alfalfa biomass within the meadow，and the alfalfa biomass was significantly greater than in other treatments when sowing occurred on July 1 after cutting. Cutting prior to sowing also significantly increased the crude protein content of forage. Based on these research results，normal production practice should include cutting when alfalfa is sown into L. chinensis meadow. Combined with cutting，a sowing date around July 1 is the most favorable for the establishment of alfalfa. © 2022 Editorial Office of Acta Prataculturae Sinica. All rights reserved.     

Dynamic Characteristics of Soil Sucrase and Amylase Activities during Vegetation Degradation in Gahai Wetland北大核心CSCD

In order to study the activities and dynamic characteristics of soil invertase and amylase during the process of vegetation degradation (Non-degradation, Light degradation,Moderate degradation, and Heavy degradation),the filed experiments were conducted in marsh meadow of Gahai wetland in Gannan state,Gansu province. The main results were as following: the average activity values of invertase and amylase activities in 0~100 cm layers varied in different stages of vegetation degradation of marsh meadow, following the order of CK (Non-degradation) > SD (Light degradation) > MD (Moderate degradation) > HD (Heavy degradation). With the increasing of soil layers,the activity of invertase significantly decreased (P<0.05),while the activity of amylase decreased fluctuantly. The activities of enzymes in the surface soil (0~20 cm) accounted for more than 60% of the total activities of each enzyme. The activities of invertase and amylase showed the obvious dynamic characteristics with time in all stages of vegetation degradation. The average activity of invertase in different months was the highest in June (47.07 mg·g-1) and the lowest in August (22.69 mg·g-1). The average activity of amylase was the highest in July,85.18 mg·g-1,while the activity values in other months were low. Correlation analysis showed that soil organic carbon was significantly correlated with invertase and amylase (P<0.01),and soil water content was only significantly correlated with invertase (P<0.01). The results showed that the vegetation degradation in Gahai wetland significantly affects soil invertase and amylase activities,reduces the efficiency of enzymatic reaction,and leads to the deterioration of wetland soil environment. © 2019 Ｊｏｕｒｎａｌ ｏｆ Ｒｅｆｒｉｇｅｒａｔｉｏｎ. All rights reserved.     

Effects of Exogenous Glycine Betaine on the Physiological Characteristics in Medicago sativa Seedlings under Low-temperature Stress北大核心CSCD

In this study,the 'Ganong 5th' alfalfa (Medicago sativa L.) was used as experimental material,and two application methods (leaf application,root application) and six exogenous betaine concentrations (0,10,20,30,40 and 50 mmol·L-1) were used to treat the seedlings of alfalfa. Plant growth and related physiological indexes were measured after 7 days of low temperature (4?) stress,and the physiological mechanism of exogenous betaine to alleviate the low temperature stress of alfalfa was explored. The results showed that exogenous GB alleviated the loss of plant height,root length,leaf dry weight,root dry weight and chlorophyll content,and increase the content of soluble sugar (SS) and free proline (Pro),and reduced the increase in leaf relative membrane permeability and MDA content. Exogenous GB increased antioxidant enzyme activities and non-enzymatic antioxidant content. And also,exogenous GB enhanced the osmotic adjustment capacity of the plant by increasing endogenous GB accumulation and BADH activity. These results indicated that exogenous GB enhanced the resistance of Medicago sativa to low-temperature stress under low temperature adjustment. The membership function analysis indicated that spraying 30 mmol·L-1 GB on the leaves and spraying 40 mmol·L-1 GB on the roots had the best effect on alleviating the low-temperature stress of alfalfa seedlings. © 2019 Ｊｏｕｒｎａｌ ｏｆ Ｒｅｆｒｉｇｅｒａｔｉｏｎ. All rights reserved.     

Effects of Utilization Patterns on the Spectral Characteristics of Soil Dissolved Organic Matter in Alpine Meadow of Qinghai Province北大核心CSCD

Soil dissolved organic matter is the most active component of the global carbon cycle. It plays an important role in the terrestrial ecosystem. In order to explore the effects of utilization patterns to the content and structural characteristics of soil dissolved organic matter of alpine meadow in Qinghai province,the contents of soil dissolved organic carbon,ultraviolet-visible spectroscopy,SUVA254,SUVA280,f450/500,HIX and synchronous fluorescence spectroscopy in 0 to 10 cm and 10 to 20 cm soil layers under 4 different utilization patterns,including secondary seabuckthorn forest,returning farmland to forest,farmland and natural pasture,were measured. The results showed that the variation of soil dissolved organic carbon and organic carbon contents in 0 to 10 cm layers performed a similar pattern,i.e. natural pasture > secondary seabuckthorn forest > returning farmland to forest > farmland. However,soil of returning farmland to forest and secondary seabuckthorn forest in 10 to 20 cm layers had higher dissolved organic carbon and organic carbon contents. The contents of organic carbon and dissolved organic carbon decreased with the depth of the soil layer. The same as the complexity of soil dissolved organic matter. The soil dissolved organic matter in the soil of natural grazing land had a higher degree of aromatization and humification,and had more polycyclic aromatic hydrocarbons. The results indicated that the structure of soil dissolved organic matter of natural pasture was more complicated and more stable. It could give a positive effect on maintaining the balance and ecological stability of the carbon pool in the alpine region of Qinghai province. The structure of soil dissolved organic matter in 0 to 10 cm layers was more complicated. © 2020 Ｊｏｕｒｎａｌ ｏｆ Ｒｅｆｒｉｇｅｒａｔｉｏｎ. All rights reserved.     

The Effect of Irrigation Period and Amount on Production Performance of Alfalfa in Haihe Plain北大核心CSCD

To explore the suitable irrigation techniques for Alfalfa in Haihe Plain, six irrigation treatments were set up to study the effects of different irrigation treatments on the yield, agronomic traits and water use efficiency of one-year and two-year Alfalfa from 2015 to 2017. The results showed that alfalfa yield increased slightly with increasing irrigation amount in Haihe Plain, but had no significant difference among six treatments. Compared with the treatment without irrigation, the cumulative increment of alfalfa yield in three years was only 6. 13 t • hm~z. The water use efficiency of Alfalfa significantly decreased gradually with the increase of irrigation amount (P相似文献   

Comprehensive Analysis of Mixed Soda Saline-Alkali Resistance of Germplasm Resources of Longmu Alfalfa北大核心CSCD

The effects of mixed soda saline-alkali (NaHCO3:Na2CO3=9:1) at different concentrations (10,20,30,40 and 50 mmol·L-1) on the germination of five Longmu alfalfa seeds were studied. The results showed that the germination rate,germination potential,germination index,vigor index,dry weight,fresh weight,water content,embryo length,radicle length of alfalfa seeds showed different trends under different mixed soda saline-alkali concentrations. Through principal component analysis of nine indicators,GR,GP,GI,VI,FW,WC and EL indicators were screened out to be related to salt and alkali tolerance of Longmu alfalfa varieties. According to the analysis of membership function,weight coefficient and D value of comprehensive evaluation,the salt and alkali tolerance of five longmu alfalfa varieties were in the order of LM 807 > LM 808 > LM 806 > LM 803 > LM 801. © 2019 Ｊｏｕｒｎａｌ ｏｆ Ｒｅｆｒｉｇｅｒａｔｉｏｎ. All rights reserved.     

Temporal and spatial variation in grassland ground surface soil heat flux on the Qinghai-Tibetan Plateau from 2003 to 2018北大核心CSCD

Based on measured data from 7 stations on the Qinghai-Tibetan Plateau,the ground surface soil heat flux （G0） was calculated,and the diurnal and seasonal variations were analyzed. Combining this data with a MODIS,1 km resolution all-weather surface temperature data set for Western China and a China regional surface meteorological element driven data set,the Ma model was used to retrieve the ground surface soil heat flux of Qinghai-Tibetan Plateau from 2003 to 2018,and the differences in surface soil heat fluxes of different grassland types were analyzed. It was found that：1） The soil heat flux G0 in the surface layer was greater than that in the subsurface layers. The diurnal curve of G0 showed an inverted“U”shape,and the flux was relatively gentle at night compared with that during the day. 2） The seasonal amplitude of soil heat flux,G0 in the surface layer ranked summer>spring> autumn>winter. The average value of G0 in spring and summer was typically positive,while the average value of G0 in autumn and winter was basically negative. The ground surface soil heat flux in the northwest of the plateau in summer is higher than that in the southeast,while the opposite occurs in winter. 3） The soil heat flux of plateau grassland ranged between 40 and 80 W·m−2. The highest average value of G0 among all categories of grassland in the 16 years surveyed was 76. 557 W·m−2 for the‘desertification’category of temperate grassland,and the lowest was 46. 118 W·m−2 for the alpine meadow category. 4） The G0 of plateau grassland increased and then decreased through any one calendar year and seasonally was ranked summer>spring>autumn>winter. The lowest G0 in spring and summer occurred in alpine meadow,while the highest in spring was in‘desertification’temperate grassland and the highest in summer was in the temperate grassland category; The highest G0 in autumn and winter was in the warm shrub grassland,while the lowest was in the alpine deserts steppe. The above results can provide reference data for the study of surface energy balance of plateau grassland. © 2022 Editorial Office of Acta Prataculturae Sinica. All rights reserved.     

Effects of slope on soil properties and post construction desertification of highway embankments in an Alpine Meadow region北大核心CSCD

This research investigated effect of slope on the performance of highway embankment soil properties post construction, as there is a demand for technical data of this nature to underpin the design of highway revetment work in alpine meadow regions of China. A section of national road G248 in Northwest Sichuan Alpine Grassland, built 10 years ago, was identified as a study site and plots were marked out for sampling on five slope classes: gentle slope, 6°-15° (GS); moderate slope, 16°-25° (MS); steep slope, 26°-35° (SS); very steep slope, 36°-45° (VS); extreme slope, >45° (ES). Undisturbed flat natural grassland >10 m distant from the roadbed was used as the control (CK). Measurements conducted included determination of particle size composition, physical and chemical parameters of the soils, vegetation cover and the proportion of the plot area exhibiting degradation or desertification. The relative reduction rate of organic matter and total nitrogen was also determined, and differences in soil water content and fertilizer retention capacity were assessed. It was anticipated these data would provide a basis for the construction of ecologically sound slope protection structures in alpine regions. It was found that: 1) Increased slope significantly decreased the proportion of clay and silt particles and increased the proportion of coarse sand and small stones (P<0.05). The greater the slope, the greater the soil bulk density and pH value, and the lower the soil water content. 2) Slope facilitated leaching of soil carbon fractions with the leaching intensity of the fractions ranking soil organic matter (SOM)>total carbon (TC)>inorganic carbon (IC)>dissolved organic carbon (DOC). For example, SOM levels were, respectively, 115, 92, 72, 30, 9 and 3 mg·kg−1 for CK, GS, MS, SS, VS, and ES slope classes while DOC levels ranged from 35.4 mg·kg−1 in CK to 9.2 mg·kg−1 in ES. 3) The ranking for the effects of slope on various soil fertility measures was: effective N>alkali-hydrolysable N>total N>available K> available P>total K>total P. Thus, available N was more easily lost than total N and alkali-hydrolysable N. Available N levels declined progressively across slope classes from 236 mg·kg−1 in CK to 6.3 mg·kg−1 in ES, while total N and alkali-hydrolysable N showed marked loss between GS and VS slope classes. A slope threshold for sharp increase in loss of total P and available P was observed between GS and MS slope classes. With increase in slope gradient, the total K increased, while the available K content decreased. 4) With respect to the influence of slope on the degree of desertification: for CK and GS >90% of the plot area was classed as non-desertified; for GS 79% of the plot area was moderately or severely desertified; for SS, VS and ES, 79, 86 and 94%, respectively, of the plot area was severely or extremely severely desertified. The proportion of severe desertification increased markedly at > 15° slope (i. e. MS) and the proportion of extremely severe desertification increased markedly at >25° slope (i. e. SS). 5) When the slope effects were expressed in relative terms, the relative increase in desertification was high and changed little at slopes >15°, while the relative decreases in organic matter and total nitrogen were high and changed little once slope exceeded 25°. As slope angle increased, relatively low rate of total coverage percentage and powder particles <0.02 mm and the relative increase rate of sand particles >0.05 mm increase significantly. In summary, as slope of the study plots increased, fine sand, silt and clay particles were progressively lost, soil fertility progressively declined, and the degree of desertification increased markedly. Therefore, the technical plan for ecologically sound slope protection in highway construction should be formulated according to the steepness of the slope. © 2022 Editorial Office of Acta Prataculturae Sinica. All rights reserved.     

Effects of Nitrogen Deposition on Soil fungi Community Structure in Stipa Baicalensis Steppe北大核心CSCD

Effects of six continuous years nitrogen deposition on soil fungi community structure in Stipa Baicalensis steppe were investigated by using high-throughput sequencing technology. The experiment included eight manipulative treatments:(0,15,30,50,100,150,200 and 300 kg N·hm-2·a-1). Soil samples were separately collected from the 0~10 cm and 10~20 cm soil layer. The results showed that nitrogen deposition significantly affected the structure of fungi community. the relative abundance of fungi in the phyla,class and genus level were significantly different at the 0~10 cm and 10~20 cm soil layer of nitrogen deposition treatment. The response of soil fungal community to nitrogen deposition at the 0~10 cm soil layer and 10~20 cm soil layer was significantly different,and there was obvious soil gradient effect. Canonical correspondence analysis (CCA) showed that soil pH,soil total organic C,NO3-N and available P were key environmental factors leading to the shift in the soil fungal community composition. In conclusion,nitrogen deposition changed the soil chemical properties,which drove the change of soil microbial communities and soil fungal communities. © 2019 China Agricultural University. All rights reserved.     

Effects of plateau pika on the relationship between plant species diversity and functional diversity in alpine meadow北大核心CSCD

The relationship between plant species diversity and functional diversity in grassland will change with environmental changes. The plateau pika （Ochotona curzoniae） has an effect on the hydrothermal process of alpine meadow in its nesting area. However,it is not clear whether the disturbance of plateau pika effects the relationship between plant species diversity and functional diversity in alpine meadow. A random stratified and paired design was used to select plots in Luqu county in Gansu Province,and Qilian and Gonghe Counties in Qinghai Province and a field survey was conducted to investigate the effects of plateau pika disturbance on the relationship between plant species diversity and functional diversity of the alpine meadow. It was found that plateau pika disturbance significantly increased the plant species richness index and the species diversity index but did not significantly affect the species evenness index. Plateau pika disturbance significantly increased plant functional richness index （P< 0.05） but had no significant effect on the plant functional evenness index or the functional divergence index. With plateau pika disturbance effects,the relationship between plant functional richness index and species richness index changed from a logarithmic function to a quadratic function,and the relationship between plant functional evenness index and species evenness index changed from non-significant to significantly positive. In addition, positive correlations between functional richness index and species richness index,and functional richness index and species diversity index were significantly decreased,as were negative correlations between functional divergence index and species richness index,and functional divergence index and species diversity index were significantly decreased. The findings of this study provide basic information for understanding the mechanism of species coexistence of plant communities under plateau pika disturbance and help understanding of how plant diversity effects in an alpine meadow ecosystem function under plateau pika disturbance. © 2022 Editorial Office of Acta Prataculturae Sinica. All rights reserved.     

Diurnal changes in photosynthesis and photosynthetic product partitioning in alfalfa in response to phosphorus application北大核心CSCD

This research explored the effect of different levels of phosphorus application on diurnal variation in photosynthesis and partitioning of photosynthetic products in alfalfa under drip irrigation. In particular, the relationship between photosynthetic product levels in the plant and leaf photosynthetic parameters of alfalfa was clarified. Four phosphorus（P2O5）application levels of 0（CK）,50（P1）,100（P2）and 150 kg·ha-1（P3）were used as treatments in a field experiment. Leaf photosynthetic parameters were measured with a Li-6400 portable photosynthesis instrument on sunny days from 10：00-20：00 during the early flowering stage,together with environment factors and sugar and starch content in the leaves,stems and roots. A feature of the results was a ‘photosynthetic noon-break’phenomenon across all phosphorus application treatments,and stomatal limitation was the main factor responsible for the mid-day decline of net photosynthetic rate （Pn）. Photosynthetically active radiation had the greatest impact on the Pn of alfalfa leaves,while atmospheric CO2 concentration,atmospheric temperature,and atmospheric environmental factors such as relative humidity and vapor pressure deficit based on leaf temp also affected Pn. Principal component analysis showed that alfalfa photosynthetic efficiency in the four P-treatments ranked P2>P1>P3>CK. At the 100 kg·ha-1 phosphorus level（compared to CK）,the hay yield of alfalfa was increased significantly,the soluble sugar contents of leaves,stems,and roots were increased by 11. 6%,5. 0% and 4. 6%,respectively,and the starch contents were increased by 15. 2%,9. 6% and 5. 3%,respectively. Higher overall levels of soluble sugar and starch typically manifested as greater concentration increases in leaves,and relatively smaller increases in roots and stems. The diurnal troughs in Pn,transpiration rate,leaf internal CO2 concentration and water use efficiency（WUE）of alfalfa leaves were less marked in the P treatments,compared with the control treatment. Therefore,appropriate phosphorus application can increase the photosynthetic efficiency of alfalfa leaves,thereby significantly promoting crop growth and development. At the phosphorus（P2O5）application rate of 100 kg·ha-1（P2）,the alfalfa photosynthetic enhancement effect was the most pronounced. © 2022 Editorial Office of Acta Prataculturae Sinica. All rights reserved.     

Identification and biological characterization of the pathogens responsible for sclerotinia rot in Codonopsis pilosula北大核心CSCD

The aim of this study was to isolate and characterize the causal pathogen and study the biological characteristics of sclerotinia rot of Codonopsis pilosula. Pathogen material was obtained by tissue isolation. The isolated fungal species were comprehensively evaluated in terms of their morphology，rDNA-ITS sequence，RPB2 gene of RNA polymerase Ⅱ，and biological characteristics. The pathogens were identified as Sclerotinia nivalis and Sclerotinia sclerotiorum，and of the two，S. nivalis was the dominant species. The optimum temperatures for mycelium growth and sclerotia formation of S. nivalis were 20 and 15 ℃，respectively，while corresponding values for S. sclerotiorum were 25 and 25 ℃ . The optimum pH for mycelium growth was 6 for both species，while optimum pH for sclerotia formation was 6 for S. nivalis and 7 for S. sclerotiorum. The optimum culture medium was 100% potato dextrose agar（PDA）. The mycelial growth rate approach was applied to test the toxicity of adiacylamine， which exhibited inhibitory activity with EC50 on S. nivalis at 0. 2625 mg·L-1 and on and S. sclerotiorum at 0. 4165 mg·L-1. In summary，this is the first report of S. nivalis and S. sclerotiorum causing sclerotinia rot on C. pilosula in China，and the data presented provide a reliable scientific proof of the pathogen diagnosis and a theoretical basis for the development of prevention measures. © 2022 Editorial Office of Acta Prataculturae Sinica. All rights reserved.     

Seasonal Changes of Grazing Grassland Nutrition and Yields and Feeding Preferences of Tibetan Cashmere Goats in Nagqu Prefecture of Tibetan Plateau北大核心CSCD

This experiment was conducted in Nima County,Nagqu region,Tibet,to investigate the effects of seasonal changes on pasture nutrients and the feeding preferences of Tibetan cashmere goats,and estimate grassland yield and livestock carrying capacity. The results showed that the nutrient content in pasture showed regular changes with the seasons. The weight of crude protein (CP) and dry matter (DM) showed an inverted "V" shape with the increase of season,neutral,but the change in the content of detergent fiber (NDF) and acid detergent fiber (ADF) was in verse. Compared with autumn,there was a significant change in the eating degree of Tibetan cashmere goats on forages such as Stipa purpurea,Potentilla bifurca, Anaphalis xylorrhiza, Cirsium souliei and Leontopodium pusillum in summer (P<0.05),which was significantly correlated with the total coverage of forage (P< 0.05). The NDVI extracted from the TM remote sensing image of alpine meadow grassland showed linear and logarithmic relationship with fresh grass biomass and biomass,and the correlation coefficients were 0.8108 and 0.7970,respectively. At the same time,it found that there was overgrazed throughout the year. © 2019 Ｊｏｕｒｎａｌ ｏｆ Ｒｅｆｒｉｇｅｒａｔｉｏｎ. All rights reserved.     

Biodiversity Characteristics and Biomass of Artificial Transplanting Leymus chinensis grassland in Soda Saline-Alkali land of Songnen Plain北大核心CSCD

In order to explore the effect of Leymus chinensis transplanting on the biodiversity and productivity of saline alkali grassland in Songnen Plain,a comparative experiment was conducted in the transplanting Leymus chinensis grassland. The results showed that the transplanting of Leymus chinensis enhanced plant species and the density of the grassland community. The total plant density under the transplanting of Leymus chinensis was 566.20 plant·m-2,6.85 times as much as that in the control (82.60 plant·m-2),and the difference between the treatments was significant (P<0.05),and the transplanting of Leymus chinensis increased the diversity index of Shannon-Wiener,the evenness index of Pielou and the richness of Margalf species. The total biomass of the community was higher than that in the control. In addition,the total biomass of the transplanting of Leymus chinensis was 357.77 g· m-2,2.14 times as much as that in the control (167.34 g·m-2),and the difference between the treatments was significant (P<0.05),which indicated that the transplanting Leymus chinensis increased the productivity of the plant community,and greatly increased the grassland output benefit, The total income was 3938.00 yuan·hm-2 for the transplanting of Leymus chinensis,7.37 times higher than that in the control (534.40 yuan·hm-2),and the difference between treatments was very significant (P<0.01).Transplanting technology of Leymus chinensis not only improved the biodiversity of the system,but also doubly increased the biomass and economic benefits,So it was a technical model which was worth of popularizing and applying in the saline alkali area of the Western Songnen Plain. © 2019 China Agricultural University. All rights reserved.     

Analysis of Differences and Influencing Factors of Plant δ13C in Leymus chinensis Grassland in Inner-Mongolia,China北大核心CSCD

In order to understand the distribution and change of stable carbon isotope13C in grassland plants and the effects of soil moisture and temperature on the stable carbon isotope13 C composition (δ13 C), w e measured the δ13 C of shoots and living roots which both had two treatments, 13 C pulse labeling treatment and control treatment, and analyzed the effect of soil moisture content, air temperature and ground temperature on the δ13 C of plants body during the fast-growing stage (July-September) of the Leymus chinensis grassland in Inner Mongolia. The results showed that the δ13C of the living roots was 1-2% higher than the δ13C of the shoots in control treatments, and the δ13C of the shoots in13C pulse labeling treatment was significantly greater than the δ13C of the living roots. The variation trends of the δ13C value of shoots and living roots in labeling and control treatments were both in good consistency with time, which showed that the value of13C in shoots and living roots decreased at first, then increased, and then decreased during the growing season of plants. The δ13 C of the shoots and living roots in control group and living roots in13 C pulse labeling treatment had a linear negative correlation with soil moisture content in the layer of 0-20 cm, but the δ13C of shoots in13C pulse labeling treatment had Quadratic function relation with the soil moisture content in the layer of 0-20 cm, which indicated that the δ13C increased with increasing soil moisture content when it had a low soil moisture content, and the δ13C decreased when there was a high soil moisture content. In13 C pulse labeling treatment and control treatment, there were significant positive correlation between temperature and the δ13C of the shoots and living roots, the δ13C of the shoots and living roots increased with increasing the temperature. © 2019 China Agricultural University. All rights reserved.     

Effect of Poly-β-hydroxybutyrate on Reproductive Performance and Larval Development of Fenneropenaeus chinensis

In the present study, Fenneropenaeus chinensis individuals were assigned into six groups, and fed with a diet supplemented with 0(Con-trol), 0.5%(Group E0.5), 1.0%(Group E1.0), 2.0%(Group E2.0), 3.0%(Group E3.0) or 5.0%(Group E5.0) of poly-β-hydroxybutyrate(PHB) during their growth and spawning periods, to explore the effect of PHB on the reproductive performance of parents and the development of larvae. The experi-ment was lasted for 192 d to measure the mortality rate, relative percentage of survival(RPS), weight gain rate(WGR), specific growth rate(SGR) and cycle of gonadal development of parental shrimps, number of eggs, number of nauplii, stages of larval development and metamorphosis. The results indicated that PHB had an obvious effect on the fecundity of parental shrimps and growth performance of larva. Compared with control group, the mortality rate of broodstock in experimental groups decreased initially and increased subsequently with the increase of PHB concentration, while RPS showed an opposite pattern. The mortality rate of group E2.0 was the lowest among all groups, showing significant difference from that of other groups(P﹤0.05) except group E1.0(P﹥0.05). WGR of all experimental groups was higher than that of the control group, among which, group E2.0 and group E5.0 had significantly higher WGR than the control(P0.05). However, there was no significant difference in the cycle of gonadal development between the experimental groups and the control group(P ﹥ 0.05). The numbers of eggs and nauplii in the experimental groups were higher than those of the control group. And the numbers of eggs and nauplii in group E2.0 were significantly higher than those of the control(P ﹤ 0.05), bud showed no significant difference from those of other groups(P﹥0.05). However, there was no significant difference in the duration of larval devel-opment and metamorphosis among all the groups. In summary, PHB is capable of improving the reproductive performance of parents and the survival and development of larva in F. chinensis, and 2.0% is the optimal concentration of PHB supplemented to the diet.     

Effects of nitrogen forms on growth and nitrogen assimilation and utilization of Buchloe dactyloides北大核心CSCD

This research explored the nitrogen (N) uptake preference of Buchloe dactyloides, in order to improve the management of this species over the whole growth cycle. The experiment included two cultivars of B. dactyloides (‘Sundancer’ and ‘Texoka’) and four different N regimes (N0: No N as the control, N1: Urea, N2: Nitrate N, N3: Ammonium N and N4: a 1:1 mixture of nitrate N and ammonium N). The rate of N applied was 500 mg N·kg soil–1 in each case. It was found that total N content, root nitrate reductase (NR) activity, glutamine synthetase (GS) activity and shoot glutamate synthase (GOGAT) activity of B. dactyloides were significantly improved by adding mixed N (P<0.05). Shoot nitrate N content of B. dactyloides was significantly improved by adding nitrate N (P<0.05). Root nitrate N and ammonium N contents of B. dactyloides were significantly improved by adding urea (P<0.05). The shoot ammonium N content and NR activity of B. dactyloides were significantly improved by adding ammonium N (P<0.05). Shoot GS activity of B. dactyloides was significantly reduced by adding ammonium N (P<0.05). Root GOGAT activity of B. dactyloides was significantly reduced by adding nitrate N (P<0.05). Mixed N can better improve the physiological activity and promote the growth of B. dactyloides, but single nitrogen source will inhibit some nitrogen assimilase activity. Based on these results, it is recommended that 1:1 mixed nitrogen should be used as the nitrogen source in the production of B. dactyloides. Where the ammonium:nitrate is not 1:1, urea should be used as the nitrogen source. © 2022 Editorial Office of Acta Prataculturae Sinica. All rights reserved.     

Short-term Effects of Nitrogen Deposition on Soil Enzyme Activities in Tibet Grasslands

[Objective] The paper was to study the effects of nitrogen deposition on enzyme activity in different layers of soil. [Method] With grassland located in Zhuqudeng Village, Bujiu Township, Linzhi City, the Tibet Autonomous Region, as the object, nitrogen deposition was simulated from July 2014 to August 2015. Four N addition treatments were established: control(0 kg·hm2/a), low N(LN, 25 kg·hm2/a), medium N(MN, 50 kg·hm2/a) and High N(HN, 150 kg·hm2/a), aiming at measuring enzyme activity(invertase, catalase, urease, amylase, cellulase, polyphenol oxidase and β-glucosidase) in different layers of grassland soil(0-20 cm and 20-40 cm). [Result](1) Different levels of simulated nitrogen deposition had significant impact on invertase and β-glucosidase at the soil depth of 0-20 cm(P0.05), but no significant impact on catalase, urease, amylase, cellulase and polyphenol oxidase(P0.05); invertase, polyphenol oxidase and β-glucosidase had significant response to nitrogen deposition at the soil depth of 20-40 cm(P0.05), while catalase, urease, amylase and cellulose had no significant response( P0.05).(2) The activities of invertase and polyphenol oxidase were enhanced at the soil depth of 0-20 cm, and that of β-glucosidase was inhibited.(3) With the deepening of nitrogen deposition, the ac-tivities of invertase and cellulose were enhanced at the soil depth of 20-40 cm; the activity of polyphenol oxidase was reduced in LN treatment, but increased in HN treatment; the activity of β-glucosidase was increased in LN treatment, but decreased in MN treatment.(4) With the deepening of soil layers, invertase and polyphenol oxidase responded similarly to simulated nitrogen deposition. [Conclusion] The results provide certain scientific basis and fundamental data for better understanding and evaluating the effects of nitrogen deposition on enzyme activity in grassland soil.     

Effects of Lactic Acid Bacteria and Fructooligosaccharides on Growth Performance,Nutrient Digestibility and Serum Biochemical Indices of Arctic Foxes (Alopex lagopus) during Early Growth Period北大核心CSCD

This experiment was conducted to study the effects of dietary lactic acid bacteria (LAB) and fructooligosaccharides (FOS) on growth performance, nutrient digestibility and serum biochemical indices of Arctic foxes (Alopex lagopus) during early growth period. Sixty male post-litter Arctic foxes with the average body weight of (1.16±0.15) kg and at the age of (45±3) days were randomly assigned to 4 groups with 3 replicates per group and 5 foxes per replicate. The foxes were fed the following diets, respectively: basal diet (control group), basal diet+3×109 CFU / kg LAB (LAB group), basal diet+5 g / kg FOS (FOS group) and basal diet+3×109 CFU / kg LAB+5 g / kg FOS (LAB+FOS group). The experiment lasted for 30 days. The results showed as follows: 1) on the days 1 to 15, the diarrhea rate of foxes in the LAB group and LAB+FOS group was significantly lower than that in the control group and FOS group (P<0.05). On the days 16 to 30, the average daily gain of foxes in the LAB+FOS group was significantly higher than that in the control group and FOS group (P<0.05), but had no significant difference with LAB group (P>0.05); the diarrhea rate of foxes in the LAB+FOS group was significantly lower than that in the control group and FOS group (P<0.05), but had no significant difference with LAB group (P>0.05); compared with the FOS group, the feed to gain ratio of foxes in the LAB+FOS group was significantly decreased (P<0.05). 2) The dry matter digestibility of foxes in the LAB + FOS group was significantly higher than that in the control group and FOS group (P < 0.05), but had no significant difference with LAB group (P>0.05). There were no significant differences in nitrogen intake, fecal nitrogen, urine nitrogen, nitrogen deposition, net protein utilization and protein biological value among all groups (P>0.05). 3) Serum total protein (TP) content of foxes in the LAB+FOS group was significantly higher than that in the FOS group (P<0.05), but had no significant difference with control group and LAB group (P>0.05). Serum albumin (ALB) content of foxes in the LAB group was significantly higher than that in the control group and FOS group (P<0.05), but had no significant difference with LAB+ FOS group (P>0.05). Serum urea nitrogen (UN) content of foxes in the LAB+FOS group was significantly decreased compared with the control group (P < 0. 05). In conclusion, the combined supplementation of 3 × 109 CFU / kg LAB and 5 g / kg FOS in the diet is beneficial to reduce diarrhea rate, improve dry matter digestibility, improve body immune level, and promote the growth of Arctic foxes during early growth period. © 2023 Chinese Journal of Urology. All rights reserved.     

Effects of Dietary Quercetin on Growth Performance,Digestive Enzyme Activities,Immune and Antioxidant Functions of Cyprinus carpio北大核心CSCD

This experiment was conducted to investigate the effects of different dietary levels of quercetin on growth performance, digestive enzyme activities, immune and antioxidant functions of juvenile Cyprinus carpio. Three hundred juvenile Cyprinus carpio with an initial body weight of (26.00±0.50) g were randomly divided into 5 groups with 3 replicates per group and 20 fish per replicate. The control group (T1 group) was fed a basal diet, and the experimental groups were fed the basal diets supplemented with 50 (T2 group), 100 (T3 group), 200 (T4 group) and 400 mg/ kg (T5 group) quercetin, respectively. The experiment lasted for 8 weeks. The results showed as follows: 1) compared with T1 group, the final body weight of juvenile Cypri⁃ nus carpio in T3 and T4 groups was significantly increased (P < 0. 05), the weight gain rate and specific growth rate in T3 group were significantly increased (P<0.05), and the feed coefficient in all experimental groups was significantly decreased (P<0.05), which in T3 group was the lowest. With the specific growth rate as the evaluation index, according to the cubic regression model analysis, the optimal supplemental level of quercetin in the diet for Cyprinus carpio was 124.02 mg/ kg. 2) The activities of intestinal protease, lipase and amylase in T3 group were significantly higher than those in the other groups (P<0.05). 3) Compared with T1 group, the serum acid phosphatase (ACP) activity and complement 3 (C3) content in T3 group were signifi⁃ cantly increased (P<0.05); the serum complement 4 (C4) content in T3 group was the highest, and signifi⁃ cantly higher than that in the other groups (P<0.05); the serum lysozyme (LZM) activity and immunoglobu⁃ lin M (IgM) content in T3 and T4 groups were significantly increased (P<0.05), and the serum LZM activity in T3 group was significantly higher than that in T4 group (P<0.05). 4) Compared with T1 group, the activi⁃ ties of liver superoxide dismutase (SOD) and catalase (CAT) in T3 group were significantly increased (P< 0.05); the liver glutathione peroxidase (GPX) activity in T3 group was the highest, and significantly higher than that in the other groups (P<0.05); the liver total antioxidant capacity (T⁃AOC) in T3 and T4 groups was significantly increased (P<0.05); the liver malondialdehyde (MDA) content in T2, T3 and T4 groups was significantly decreased (P<0.05). In conclusion, the optimal supplemental level of quercetin can improve the growth performance, digestive enzyme activities, immune and antioxidant functions of juvenile Cyprinus carpio, and the optimal supplemental level is 100 mg / kg. © 2023 Chinese Journal of Clinical Research. All rights reserved.