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As a measure to increase soil temperature, conserve soil moisture, and increase available nutrients, film mulching (FM) has been generally and successfully used for crop cultivation. In this paper, using a crop without FM as a control (CK), the effects of FM on soil physical properties in an alfalfa field were studied in the second, third, and fourth year of the crop. The annual means of soil pH in the second and fourth year in the 0 to 20 cm depth soil layer in FM treatment were significantly decreased, and were 2.7% and 2.6% lower than those in CK. The annual mean values of water-soluble salt and Na+ content in FM treatment increased at first and then decreased over time, as they did in each soil layer depths. Both of the values in FM treatment were inferior to those in CK. FM significantly decreased the water-soluble salt content in May of the second year in the 0 to 20 cm depth soil layer by 62.9% compared with CK. The Na+ content in August and October of the fourth year in the 0 to 20 cm depth soil layer and in August of the second year in the 20 to 40 cm depth soil layer in FM dropped by 36%, 37%, and 39.5%, respectively, compared with that in CK. To a certain but statistically insignificant degree, FM increased the available nitrogen, available phosphorus, available potassium, and organic matter content in different years and in different soil layer depths.
Applying Li-8100 soil respiration measurement system, we made field observations on the soil respiration rate of Nitraria tangutorum nebkhas, which is at the stable stage and is largely located in the oasis-desert ecotone at the southern fringe of the Badanjara Desert. The daily change and the spatial heterogeneity of soil respiration at different positions of the nebkhas in different growing periods were analysed and studied. The results showed: 1) The daily change of the soil respiration rate of N. tangutorum nebkhas at different positions and at different growing periods were different. It exhibited a “one-peak curve” at the beginning of the growing period and at the dormancy period; but the “one-peak curve” and “double-peak curve” were overlapped in the flourishing period. 2) The peaks of soil respiration in different growth periods were different: the peaks of each observed position occurred around 11:00 in the morning at the beginning of the growth period, the peaks of the flourishing period were concentrated around 09:00 and 17:00, and the peaks in the dormancy period occurred between 13:00-15:00 in the afternoon. 3) The soil respiration rate of N. tangutorum at different observation points showed a strong sensitivity to water content, the correlation between them was higher at lower water content (<1%) than at higher water content (>1%). 4) There was spatial heterogeneity of soil respiration rate at different positions on the nebkhas: there was a non-significant difference (P>0.05) between the soil respiration rate at the beginning of the growing period and in the dormancy period; whereas there was a significant difference (P<0.01) in the flourishing period. The average soil respiration rate at different growing periods varied significantly, which was ranked as follows: flourishing period [0.53 μmol·(m2·s)-1]>at the beginning of the growing period [0.24 μmol·(m2·s)-1]>dormancy period [0.12μmol·(m2·s)-1]. The regression analysis showed that the significant spatial heterogeneity in the soil respiration rate was the result of the interaction between the near-surface water condition at different positions, the temperature, and humidity at the depth of 5-20 cm of N. tangutorum.
The study and analyses of the structure of the topsoil aggregates is important to make informed decisions not only for the ecological restoration of the land, but also to prevent erosion of the topsoil. The aim of this study was to analyse the properties of the aggregates and their interdependencies at different depths of topsoil taken from the Mo Us region. The results illustrate that the diameter of the aggregates in the region measure between 0.25~0.50 mm. The contents of the aggregates differed with the depth and with biotope conditions. The maximum content of aggregates of size greater than 1 mm was seen in land covered with willow and Calamagrostis pigeios land constituted 4.27% and 3.55%, respectively. The analysis of the aggregate stability indicated that the soil in this region is not fully developed and is unstable. The soil structure appears to be gradually developing in the areas protected by vegetative cover or those that arerestoration areas, implying that organic matter is the most important factor influencing the occurrence and stability of aggregates in topsoil.
Analysing the relevance between variable soil physicochemical properties and soil organic carbon (SOC) content using soil data available from Xinjiang Uygur Autonomous Region will help us in farming using scientific fertilization and management of the Xinjiang soil. Significant and positive correlations were found between soil total nitrogen, cation exchange capacity, and the SOC content. Among them, the strongest correlation was between the quantity of SOC and total nitrogen (P<0.0001, the determination coefficient R2=0.936 7). Soil pH and the soil bulk density showed negative correlation with SOC content (P<0.05). The total phosphorus, total potassium, soil porosity, and soil organic carbon content was not significantly correlated (P>0.05). The results can help to scientifically analyse the contribution and ecological significance of the soil ecosystem in arid areas in the global climate change scenario.
In this study, we investigated the effects of grassland caterpillar on the vegetation (community cover, height, above-ground biomass, and plant diversity) of a Kobresia pygmaea alpine grassland under the interference of yak grazing using artificial grazed methods (grazed and ungrazed) and caterpillar field control methods (caterpillar presence and absence). The study included four treatments: yak alone (Y), grassland caterpillar alone (C), both yak and grassland caterpillar (YC), and without yak and grassland caterpillar (CK).The results showed that the density of grassland caterpillar increased during the first phase of the experiment and decreased thereafter. Density and growth trends of grassland caterpillar were higher in the grazed plots than ungrazed plots. There were no significant differences in community cover, height, and total above ground biomass between C and CK (P>0.05), but these values were significantly lower in YC. The important values of the main plant species were changed in YC. Plant diversity indices such as richness index, Simpson index, Shannon-Wiener index, and Pielou index were significantly lower in Y and YC compared to CK (P<0.05). However, these four diversity indices were not observed in the C plots. Based on our findings, we conclude that yaks significantly affected the influence of caterpillars on the vegetation of the Kobresia pygmaea alpine grassland.
Switchgrass (Panicum virgatum) is one of the important energy grasses, and the drought resistance of its seedling stage plays a key role in growth under arid and semi-arid conditions. Therefore, selecting switchgrass genotypes with good drought tolerance in the seedling stage is important. In greenhouse experiments, we tested eight physiological indicators related to drought resistance, including superoxide dismutase and peroxidase activity, free proline, soluble protein, soluble sugar and leaf water content, relative electrical conductivity, and malondialdehyde levels. In addition, we evaluated the drought resistance of eight switchgrass varieties chosen from American gene bank by subordinative function value analysis. The results showed that the eight accessions compared differed significantly in drought resistance at seeding stage. The drought resistance ranking was as follows: Shawnee>Cave-in-Rock>Blackwell>BN-309-69>Trailblazer>Carthage>TEM-SLC>Grenville. The results provided a theoretical basis for developing switchgrass breeding programmes aiming to improve drought resistance, and valuable information for planting switchgrass varieties in marginal lands.
Carex brunnescens is a pioneer plant that has an excellent ability to fix sand and plays an important role in maintaining the ecosystem stability of the Maqu desertified alpine grassland of the source area of the Yellow River. In this study, the biological characteristics (phenological characters, the above- and belowground growth processes, and the morphological characters of belowground organs) of C. brunnescens was studied in a field observation experiment. The results showed that C. brunnescens has the characteristics of turning green earlier than other plants, a long growth period, and two flowering and fruiting cycles. The leaf width, length, and count of individual plants, and the community plant density and leaf density showed significant increases from the leaf growth stage to the fruit maturity stage, and then tended to be stable in the withering stage, while the plant height, leaf areas of individual plants, and community leaf areas showed significant increases at first and then decreases. Underground stems (horizontal and vertical stems) and roots of C. brunnescens could survive in sand of depths 0-60 cm. There were more mid-sized roots (0.2~0.5 mm) than other root size classes in all soil layers (0-20, 20-40, and 40-60 cm). The total length of fine roots with <0.2 mm diameter was maximal in the 20-40 cm sand layer and, 0.2~0.5 mm diameter roots maximed in the 0-20 cm sand layer. The length and fresh and dry weights of the main root and horizontal and vertical stems was maximal in the 10-30 cm sand layer, and minimal in the 40-50 cm sand layer. These results showed that C. brunnescens has unique biological characteristics which could well adapt to the Maqu alpine sandy habitats, and is a species that has good potential for ecological restoration in Maqu desertified Alpine grassland.
The salt tolerance of six Lolium perenne varieties during seed germination, seedling growth, and the establishment stage under different temperatures was investigated. The results showed that temperature, variety, salt concentration, and their interaction affected plant response to salt stress. Moreover, plant salt tolerance varied with seedling growth stage, regardeless of variety and incubation conditions.The relative germination rate, germination index, root length, seedling length, biomass, and density decreased with increasing salt concentrations. Salt tolerance was highest at 15/25 ℃(12 h light/12 h dark), whereas 5/15 ℃ and 25/35 ℃ aggravated salt stress. Use of the subordinate function method for comprehensive evaluation and comparison indicated that the best variety is Gray star, and the worst is Neruda.
In order to reveal effects of SO2 wet deposition on growth and photosystem Ⅱ(PSⅡ)of mulberry seedlings, Na2SO3 and NaHSO3 mixture (molar concentration ratio of 3∶1) were used to simulate SO2 wet deposition for foliage spraying for 28 days. The results showed that significant burns spot appear in leaves in treatments of 50 and 100 mmol·L-1 simulation SO2 wet deposition, meanwhile, photosynthetic ability was significantly lower than control(P<0.05), in addition, the plant height, branch number and leaf number were reduced significantly. However, the photosynthetic capacity of leaves were increased, and then, the plant height, branch number and leaf number were increased significantly, promoted the growth of mulberry. Rapid chlorophyll fluorescence kinetics parameter analysis showed that the absorbed light reaction center (ABS/RC), reaction center of dissipated energy (DIo/RC) and capture reaction center for energy reduction QA (TRo/RC) in treatments of 50 and 100 mmol·L-1 were no significant difference with CK. While, the reaction center capture of the energy for the electron transfer (ETo/RC), active reaction center of the light at 2 ms, open degree of active reaction center (Ψo) and absorb the light energy used for electron transfer quantum yield after QA- (φEo) were decreased. Meanwhile, the maximum amount quantum yield of photochemical quenching (φDo) was rised, which indicated that the light energy absorption of the reaction center were not affect in treatments of 50 and 100 mmol·L-1, while, excess light energy was used in the non-photochemical quenching, photosynthetic performance index (PIABS) were dropped significantly(P<0.05), the reasons of the electron transport in the PSⅡ were suppressed. In this experiment, the PS Ⅱ function and activity of mulberry were improved under ≤20 mmol·L-1 SO2 wet deposition, which could promote the mulberry growth.
In this study, the ephemeral species Plantago minuta, wildly distributed in the Gurbantunggut Desert in central Junggar Basin, China, was selected as the target species, and its the modular morphology, biomass allocation and allometric scaling relationships were systematically analysed based on field investigation and sampling. The results showed that, the body size of P. minuta was small, and its total biomass was only 0.402 3 g. Inaddition, the root to shoot ratio was 0.157, reproductive biomass and leaf biomass accounted for 44.2% and 36.9%, respectively, and biomass allocation was independent of body size. Significant correlations and allometric scaling relationships were generally found between modular morphological indices, between modular biomasses, and between morphological indices and biomasses. Among these, modular biomass commonly exhibited isometric scaling relationships (allometric scaling exponent=1), modular morphological indices generally showed allometric scaling relationships with the exponent >1, while allometric scaling relationships with the exponent <1 were commonly found between morphological indices and modular biomass. The results partly confirmed the theoretical prediction. The differential allometric scaling relationships of P. minuta at the modular level demonstrated different response and adaptations to the external environment and development regularity of different modular components.
Planting annual forage crops in winter fallow fields is a main way to solve the problem of roughage shortage in southern China. In this study, the yields, nutritive value, and fermentation quality of barley (Hordeum vulgare) were determined. The main results were as follows: 1) Dry matter yield of barley increased with maturity. Relative feed value and dry matter digestibility of barley at the milk stage were 107.19 and 63.84%, respectively, and were significantly higher than those at other stages (P<0.05). 2) The fermentation quality of barley silage was increased with the maturity of barley. 3) Lactobacillus plantarum CCZZ1 inoculation significantly reduced pH values and ammonia-nitrogen content of barley silages at all stages of maturity, and markedly increased lactic acid content (P<0.05), but was apt to aerobic deterioration after silo was opened. Inoculating L. parafarraqinis ZH1 improved aerobic stability of silages at all maturity stages. From these results we can infer that barley grown in winter fallow fields should be harvested in the milk to early dough silage, which will be beneficial for the development of southern China.
Seeding rate is an important factor to guarantee high yield and quality of forage grass. Besides the biological characteristics of the forage grass, the reasonable seeding rate may also be affected by external conditions. In order to determine the optimum seeding rate in northwest alpine pastoral regions of Sichuan, Avena sativa cv. LENA was chosen as the material to explore the effects of six seeding rates (A: 120 kg·ha-1, B: 165 kg·ha-1, C: 210 kg·ha-1, D: 255 kg·ha-1, E: 300 kg·ha-1, and F: 345 kg·ha-1) on production performance and photosynthetic characteristics. Phenophase of A. sativa cv. LENA decreased with increasing seeding rates, and at the seedling stage, there was no significant difference, but at other stages, the differences were obvious. For plant height, there were no significant differences among the six seeding rates. The thickness of stems decreased significantly with the increasing seeding rates, and the tendency was more obvious at the latter stages. The stem-to-leaf ratio showed no significant differences between different seeding rates (P>0.05), but the ratio decreased significantly with the growth stages (P<0.05). The fresh and dry hay yield increased significantly with the growth stages, and the largest dry hay yield was at E and F seeding rates. At the flowering stage, the stoma was more active at the A, B, and C seeding rates, and the intercellular CO2 concentration was lower at E and F seedling rate. Under the conditions of 30 cm row spacing and 300 kg·ha-1 or 345 kg·ha-1 seeding rate, A. sativa cv. LENA production performance and photosynthetic characteristics were ideal. These results provide theoretical support for A. sativa cv. LENA cultivation practices in northwest alpine pastoral regions of Sichuan to attain higher yields.
In order to select fodder species of leguminous shrubs that are suitable for planting in southern China, we conducted a comparison trial with four fodder species of leguminous shrubs in this region, using a completely random block design. All the four leguminous shrubs species could be planted in southern China. Among the four species, Codariocalyx gyroides showed remarkable resistance to cold stress, produced high fresh yield, showed good performance after cutting (3~4 cutting times a year), showed good regenerative capability, produced hay yield of 11.60 t·(ha·a)-1 (14.74%~37.78% higher than those of other speies) and had higher leaf yield and protein content. After comprehensive analysis and comparison, C. gyroides was identified as the high-quality fodder species of leguminous shrubs suitable for plantation in southern China.
Two leguminous forages (Medicago sativa and Astragalus adsurgens) and three graminaceous forages (Bromus inermis, Elymus dahuricus, and Agropyron cristatum) were sown separately and in six combinations in Ningxia central semi-arid belt under three water treatments, i.e. low irrigation (484 mm), intermediate irrigation (707 mm), and high irrigation (1 160 mm). Yield, the whole plant Δ13C, and photosynthetic exchange parameters were determined. The results showed that mixed sowing of graminaceous and leguminous forages could improve yield and water use efficiency (WUE) in central Ningxia when irrigated. Among the different combinations that were sowed, the highest Δ13C, yield, and WUE were recorded when Astragalus adsurgens was combined with Elymus dahuricus. There was a significant effect of water treatment on the plant height, photosynthetic physiological parameters, yield, and Δ13C of graminaceous and leguminous forages (P<0.05). The values of yield, WUE, and Δ13C were the highest in high irrigation treatmentand the lowest in low irrigation treatment. Yield and WUE were found to correlate significantly with Δ13C, leaf stomatal conductance (Gs), leaf temperature, and plant height in high irrigation treatment and in low irrigation treatment. The former can be used as an alternative selection indicator for screening high-yield combinations and the latter can be used as an alternative selection indicator for screening water-saving combinations.
To investigate the physiological mechanisms of drought adaptation and protective enzyme system of Pennisetum alopecuroides under drought stress, we took the new strain of P. alopecuroides, LS-1, as the test materials, and analysed the differences in the physiological characteristics, including relative water content in leaf, root/shoot ratios, superoxide dismutase (SOD) activities, peroxidase (POD) activities, free proline contents and soluble sugar contents under drought stress and rewatering conditions. The results showed that with increasing stress due to soil drought, the relative water content of leaf decreased, but the root/shoot ratios, SOD, and POD activities in 5% soil water content, free proline contents, and soluble sugar content all increased significantly (P<0.05). After rewatering, the physiological characteristics of P. alopecuroides leaf recovered to different levels. Physiological mechanisms and protective enzyme system of P. alopecuroides offers the plant protection when under increased stress from drought. This is beneficial for the development of this species in drought areas.
To select suitable high quality green forage for winter season in Southern China, the cold resistance and nutritional qualities of six tropical and subtropical leguminous forage species including Desmodium intortum, D. laxiflorum, D. heterocarpum, D. reticulatum, D. heterocarpum var. strigosum and Stylosanthes guianensis grown in Guangzhou during the overwintering period were compared. The results showed that all species could maintain green leaves in winter except S. guianensis, and the chlorophyll contents of D. intortum and D. laxiflorum were significantly higher than those of the other four species (P<0.05). Further, D. intortum had the highest net photosynthetic rate (P<0.05), followed by D. laxiflorum. Hence, these two forages were considered to have a stronger cold resistance than others. During winter season, compared with the other species, D. intortum had a higher nutritional value because of its higher crude protein content (15.99%~20.26%) (P<0.05) and lower detergent fiber (neutral detergent fiber, NDF: 27.92%~30.89%, acid detergent fiber, ADF: 23.96%~27.06%) and condensed tannin content (6.05~11.95 mg·g-1) (P<0.05). Therefore, in Southern China, D. intortum can potentially be used as a preferred leguminous green fodder in winter.
Establishing perennial herbaceous vegetation buffer adjacent to a stream is considered to be an effective management to prevent nitrogen and phosphorus losses in croplands. In northern China, however, growth of herbaceous vegetation, such as herbal grasses, is affected by drought. In this study, a drought resistance experiment was conducted to evaluate nine grass materials (Pennisetum alopecuroides. Panicum virgatum, Miscanthus sinensis, Lolium perenne, Bromus inermis, Psathyrostachys juncea, Elymus dahuricus, and Elytrigia repens) under water stress during tillering stage. The results showed: 1) The growth characteristics of the nine grasses were significantly different. The tiller of L. perenne and P. juncea was the best, whereas the growth rate of E. repens was fast among these nine grasses. 2) The tillers and growth of all nine grasses were affected by drought, reducing their biomass. At the same time, under medium and heavy drought stresses the tiller number of P. alopecuroides and E. repens was significantly higher than that of other grasses. 3) The root length of Beijing No.1 (E. repens) was significantly greater relative to the control . The root length and surface area of P. virgatum also increased. 4) The drought-tolerance of the nine grasses was in the following order: P. alopecuroides>Beijing No.2 (E. repens)>P. virgatum>M. sinensis>B. inermis>Beijing No.1(E. repens)>E. dahuricus and L. perenne>P. juncea.
Potassium (K+) is one of the major nutrients, essential for plant growth and development. Inward rectifying K+ channel AKT1 belongs to Shaker-type K+ channels, and a K+ sensor in the plasma membrane has been shown to play an important role in mediating K+ uptake. AKT1 is also essential for normal growth and development, stomatal action and transpiration, and improving the drought and salt tolerance of plants. In this review, we consider recent advances in molecular structure, localization, expression, regulation and function of AKT1. Finally, research directions for the future are proposed, including the use of proteomics, gene engineering technology, and posttranscriptional gene silencing, in order to further investigate the role of AKT1 in plant physiological metabolism.
This study aimed to understand the relationships between panicle traits and the grain quality traits of hybrid sorghum. Using 58 hybrid combinations of sorghum, panicle traits (spike length, spike-stalk length, primary branch number, secondary branch number, grain number per spike, thousand seed weight, and single grain yield) and grain quality traits (crude protein, crude fat, starch, amylopectin, and tannins) were analysed by correlation and grey correlation analysis. Correlation and grey correlation analysis were based on the relationship between the main panicle traits and single grain yield showed similar results, and the sequence of the relationship was thousand seed weight>grain number per spike>secondary branch number>primary branch number>spike length>spike-stalk length. However, relationships between panicle traits and quality traits differed between the two methods of analysis. Grey correlation analysis showed a weak correlation between panicle character and tannin content, and that spike length, spike-stalk length or spike grain number and the three characters of grain quality traits had stronger correlation. Correlation analysis showed that crude fat content had strong significant negative correlation with spike length and spike-stalk length; Starch content had negative correlation with grain number per spike and was significantly positively related to thousand seed weight; Amylopectin had a significant negative correlation with grain number per spike and spike length; Tannins had strong significant negative correlation with primary branch number and secondary branch number, and was significantly negatively related to thousand seed weight. Correlation analysis results were more accurate than those of grey correlation degree analysis. As such, correlation analysis results can provide a theory basis for high yield and high quality sorghum hybrid breeding.
Rapid economic development,increasing population, and decreasing arable land, are leadind to energy crisis, and food shortage problems, which are becoming serious concerns in the society. Sweet sorghum (Sorghum bicolor) is a crop with multiple uses: its stem can be used as pasture, hay, green fodder, and for silage production, which can alleviate the current shortage of animal forage; due to its high sugar content, its stalk can be used to produce ethanol, a new biofuel; and its residue can be used to the production of wine, sugar, paper, etc. It has great importance in the virtuous cycle of agro-ecosystems. In this paper, we present a preliminary review on sweet sorghum germplasm, cultivation and management, bioprocessing technology, storage technology, livestock feeding effect, and applications. This paper elucidates advances in sweet sorghum applications in China and overseas, and provides references for future production practices of sweet sorghum.
To find out the optimum harvest time of Caragana microphylla for forage, and to provide a theoretical basis for their scientific management and reasonable utilization, our study evaluated the changes in the nutrient contents in different periods of its life cycle and phenological periods of the yearly growth cycle. Growth and phenological stages of C. microphylla plants were recorded continuously over three years. The branches of 1~8 a and 3 a in different phenological stages, containing the leaves, flowers, and fruits, were collected to measure the nutrient contents, such as crude protein, crude fat, crude fiber, crude ash, nitrogen-free extract, calcium, phosphorus, and so on, and then to compare whether there exists significant differences between the branches. The optimum harvest time for forage was determined by the analytic hierarchy process (AHP) method to calculate the grey correlation degree of each branch age, phenological stages, and reference vector. Our study shows: 1) Based on nutritional value of branches in different growth ages, the equal relational grade sequence is 3 a>2 a>4 a>5 a>1 a>6 a>7 a>8 a, while the weighted grade is 3 a>1 a>5 a>2 a>4 a>6 a>7 a>8 a. 2) In order of phonological stages, the equal relational grade sequence is fruit forming stage>fruit maturity stage>postharvest growth stage>flowering stage>leaf expansion stage>seedling emergence stage>defoliation stage>dormancy stage, and the sequence of the weighted grade analysis was fruit forming stage>postharvest growth stage>fruit maturity stage>flowering period>leaf expansion stage>defoliation stage>seedling emergence stage>dormancy stage. In conclusion, the optimum harvest time of C. microphylla for forage is the fruit forming stage while branches are in 3 a, when it is also the best time for trunk cutting.
Medicago sativa cv. Caoyuan No.4 with anti-thrips was selected through three cycles using insect resistance identification, superior clones, and combination of insect resistant identification and cooperation equipped with basic groups (registration number: 477). Root of the variety was erect with horizontal growth root. Stem was erect with setae. Leaf was three compounds with surface setae. Flower was purple. Pod was spiral of 2 to 3 times. Thousand grain weight was 1.86~2.35 g. The variety was high insect resistance (hazard point coefficient: 0.26, and pest index: 0.33), drought resistance, cold resistance, and barren resistance. It can be cut three times, average hay yield was 12 000~16 000 kg·ha-1, and seed yield was 230.90 kg·ha-1 in Hohhot regions. The crude protein content was 19%. This alfalfa specie was suitable for the cultivation in serious thrips harm regions as southern provinces of the north China.
MicroRNA (miRNA), a class of endogenous noncoding RNAs, plays a role in regulation of the body’s physiological function by affecting target gene expression. miRNAs can regulate the development of gonads (testicles and ovaries), promote maturation and differentiation of sperm and oocytes, and affect the growth of oosperm. miRNAs can be used as an important index in diagnosis of ovarian cancer. This paper summarizes miRNAs’ biogenesis and its regulation in mammal gonadal development and the progress of ovarian cancer; research has mainly focused on these functions in vivo. The regulation mechanisms and signalling pathways of miRNAs in gonadal development of mammals and ovarian cancer is revealed through molecules, systems, and other aspects of biology through molecular biology and bioinformatics. We provide new thoughts and approaches for reproductive disease research and high-quality animal breeding.
The trace element selenium has various biological functions and is essential for animal health. There is considerable transference of substances in the grassland grazing system and, therefore, selenium circulates through the soil into plants and animals. This review summarized the recent research studies on various aspects of the circulation of selenium including its content, distribution, and functions in soil, plants, and animals. In addition, we analyzed the cyclic characteristics of selenium in the grassland grazing system. The results showed that the content of selenium in soil, plants, and animals was 0.1~2.0, 0.05~1.50, and 0.02~0.05 mg·kg-1, respectively. The circulation of selenium in the soil, plants, and animals is affected by numerous factors and has exhibited considerable differences and instability, which has led to consistent deficiencies in its intake by grazing animals. The implementation of a reasonable grazing system would efficiently increase the circular flow of selenium by initiating appropriate fertilization methods and reseeding selenium-enriched forage. We believe these strategies would relieve or resolve the current situation where grazing livestock consistently show deficient selenium levels.
Based on the geographical and environmental particularities of the Qinghai-Tibet Plateau and the importance of yak grassland grazing systems in this area, we wanted to know how management factors influence each other. This review focuses on primary and secondary productivity under different grazing intensities. We explore approaches to system optimization by contrasting the performance of different management systems. By reviewing existing studies, we summarize the differences in yak productivity and the reaction of vegetation under different management systems, and describe how management influences the interrelationship between livestock and vegetation. On this foundation, we analyse the problems in existing management systems and propose solutions to these problemsin yak grassland grazing systems.
Overgrazing has become a major inducing factor of grassland degradation, and the motivation of pastoralists seeking to maximize the economic benefits was the root cause of overgrazing. This study found that Single-Households, Small-Joint Households, and Large-Joint Households were the main contributors to grassland overgrazing, especially in terms of the overgrazing rate and degree. In order to maintain the family balance of income and expenditure and cope with the future unknown risks, the actual minimum number of livestock was higher than the theoretical minimum number. Thus, the pasture-overgrazing rate and degree of the Single-Households were significantly higher than the Joint Households, and the Medium-Joint Households were the main contributors while large-scale herders were the least. The households or herders were presented with the Forge-Livestock Balance Incentives of Rangeland Ecological Compensation Policy. The policy did not consider the differences, in scale, of the herdsmen and ignored their heterogeneity and the losses incurred due to reducing livestock. Moreover, the compensation standard was only linked with the area under grassland, owing to which the compensation received by small and medium-scale herders did not pay off the opportunity loss caused by reducing livestock. Therefore, the relationship between reducing livestock and compensation was unequal. As such, the policy could not promote the income of small and medium-scale herders, and widened the income gap with large-scale herders and triggered low efficiency of Rangeland Ecological Compensation Policy. In response to this phenomenon, the government should develop differentiated Rangeland Ecological Compensation Standards, and recognize the peering relationships of reducing livestock and compensation.
Based on the survey data of farmers who planted forages and grain crops, we calculated cost-benefit information of major forages and grain crops from the period of 2010-2014. Further, we comparatively analysed the variation. The results indicated that the net income and return rate of alfalfa declined in 2014, whereas that of ryegrass and silage corn showed an increasing trend. A comprehensive comparison showed that the average net income and return rate of alfalfa was higher than that of ryegrass and silage corn, from 2010 to 2014. The cultivation of potato and alfalfa had an economic advantage than other forages and grain crops, whereas wheat cultivation had a relatively lower economic benefit. Moreover, ryegrass and silage corn cultivation involved more labour and land cost, whereas alfalfa cultivation involved higher water and electricity costs. Finally, this study puts forth some valuable suggestions such as making amendments to the agriculture industrial structure, including the grain, economy, feed and forage crops, which would support the development of the forage industry, and establishment of a subsidy system for forages’ production factors.