Grassland accounts for about 40% of the total land area in China,but the long-term excessive resource utilization by farmers and herdsmen results into large-scale grassland degradation,as output and input of grassland ecosystem in terms of energy flow and material circulation are out of balance. Since the 18th National Congress of the Communist Party of China,great efforts of grassland protection and restoration have been continuously made,and therefore the deterioration of grassland ecology has been preliminarily prevented. The construction of perennial mixed sowing artificial grassland is an important measure for animal husbandry development and ecological restoration of degraded grassland,and has great strategic significance for the sustainable development of grassland ecosystem and the construction of ecological civilization. In this paper,we reviewed the progress of the relevant researches in the recent 20 years,and put forward a theory of Quasi-stable state for the mixed sowing artificial grassland. We define the contents and significance of Quasi-stable state,and construct a technological system to maintain the Quasi-stable state in perennial mixed-sowing artificial grassland. This work provides guidance for the healthy and sustainable development of animal husbandry and ecological restoration in China.

Forage is of the indispensable importance to herbivores. The strategy of utmost spurring the development of the high-quality forage industry can be adopted by the measures of expansion of the forage sources,increment of the forage yields and extension of the animal products application in the line of the vital technical approaches such as,increasing grain production with the exploring of forage,saving grain supply with the exploring of forage,and replacing grain supply with the exploring of forage. In this way,we can achieve the conversion of forage into grain,and make an important contribution to enhance the level of national food security and comprehensively consolidating the foundation of food security.

Oat ( Avena sativa L.) is one of the main sources of roughage for ruminants,and it is beneficial to rumen health and production performance of cows because of it is rich in carbohydrates. Silage is one of the main forms of safe storage of oat,which has the advantages of good palatability and high digestibility. As for oat silage,predecessors have carried out a lot of researches,mainly focusing on the moisture,harvest period,additives,mixing and feeding of oat silage. Based on these,this paper summarized the researches on oat silage. The constraints affecting the fermentation and nutritional quality and the utilization value of oat silage were summarized,which would promote the concoction and utilization of high-quality oat silage.

Thesium chinense Turcz.,known as “plant antibiotic”,is an important Chinese herbal medicine plant for its purgative and detoxifying effects in China. Based on the characteristics of semi-parasitism,seed deep dormancy,short growth cycle,long dormancy period and low reproductive efficiency,this review summarized the research progress on the parasitic biology,growth of live plants,tissue culture and rapid propagation,cultivation of Thesium chinense Turcz. The main factors limiting the artificial cultivation of Thesium chinense Turcz. are climate,soil type,seed germination and the amount of nutrient accumulation in the roots of the plant,etc.,thus the corresponding cultivation methods are proposed. It would provide some valuable information for the future studies on the tissue culture reproduction,cultivation and utilization of Thesium chinense Turcz.

Melatonin is a small molecule indolamine hormone that widely exists in plants,and the studies have already clarified its synthetic pathway,catabolism and physiological functions. Melatonin can act as a signaling molecule to regulate plant circadian rhythms,seed germination,root and flower development,and also help to enhance the resistance of plants to various stresses. In this paper,the physiological functions of melatonin in regulating growth and development of herbaceous plants were summarized up,and its regulatory effects in response to abiotic and biotic stresses were particularly focused on. Additionally,functional study on melatonin in growth,development and stress resistance,as well as its application in stress resistance breeding in forage species were prospected. This review is expected to provide insight into improving the stress resistance,yield and quality enhancement of forage plants by using melatonin.

Low temperature and drought are two abiotic stress factors that limit growth,development and yield of forage grass. Understanding the stress resistance mechanisms and breeding forage grass with strong cold and drought resistance is an important basis for the high-quality development of animal husbandry and the restoration of degraded grassland ecosystems in the cold and arid regions. At the morphological level,forage grass can form a variety of stress-resistant morphological structures under low temperature and drought stresses,and the changes of these morphological structures can reflect the response ability and adaptability of forage grass to adversity. At the physiological and biochemical level,forage grass can respond and adapt to low temperature and drought stresses by regulating superoxide dismutase,peroxidase,catalase,free proline,soluble sugar,soluble protein,abscisic acid,ethylene,gibberellin and cytokinin. At the molecular level,forage grasses adapt to cold and drought stresses through a combination of signaling transduction,response and resistance gene expression. In conclusion,this study reviewed the response and adaptive mechanisms of forage to low temperature and drought stresses from the levels of forage morphology,physiology and biochemistry and molecular level to provide an important reference for a comprehensive understanding of the stress resistant mechanisms of forage grass.

To investigate the characteristics of plant root pull-out resistance of alpine grassland in the source region of the Yellow River,six dominant grass species were selected from the alpine grassland in the source region of the Yellow River in Henan County,Qinghai Province. Through in-situ pull-out test,single root tensile test and root-soil composite system direct shear test,the root pull-out resistance characteristics of six grasses were analyzed. The comprehensive effects of root diameter,root number,root length,soil density,moisture content,compactness,root content,single root tensile strength and cohesion of root-soil composite system on pull-out resistance were investigated. The results showed that:the root pull-out resistance of Kobresia humilis K. was the highest (46.50 N),followed by Kobresia pygmaea C. B. Clarke. (37.50 N), Poa crymophila Keng. was the smallest (16.45 N). There was a significant positive correlation between root diameter,root number,root length and root pull-out resistance,with correlation coefficients ( R) of 0.881,0.727,and 0.969,respectively. There was a positive correlation between soil density,soil compactness,root content,cohesion of root-soil composite system and root pull-out resistance,and a negative correlation between moisture content and root pull-out resistance. The results of this study provide theoretical guidance for exploring the mechanical mechanism of alpine grassland degradation in the source region of the Yellow River,and provide theoretical basis and practical guidance for effectively preventing and controlling of grassland degradation,soil erosion and other shallow surface disasters in the region.

Facing the increasing risk of ecological degradation, it is urgent to establish a standardized framework of remote-sensing image interpretation to conduct grassland investigation and management. This study summarized the history of grassland resource investigation and analyzed the development of investigation technology in China through literature collection and historical data collation. Taking advantage of spectral endmember space, the correlation and scale effect among grassland resource typology, investigation, and management were established. We also proposed an interpretation framework of spectral endmember space based on a multiscale fusion strategy for grassland and made a suggestion of a sharing platform of grassland systematic knowledge, which would provide a support for the researches of management and other practices of grassland resources.

Nitrogen (N) addition experiment is one of the effective measures for assessing the effects of N deposition on terrestrial ecosystems. Though hundreds of N addition experiments have been conducted during the last decades,the differences of methods could cause large uncertainty for the comparison among the study results and global meta-analysis. Thus,we collected 302 N addition experiments in terrestrial ecosystems and performed a global analysis of their methods. Our results showed that only 8% of N addition experiments were conducted in tundra,wetland and desert ecosystems. Experiments implemented below the N rate of 2 g N·m ^-2·a ^-1 made up 4.4% and 17.5% for those solely using NH ⁺ ₄ or NO ^- ₃ form fertilizer. 13.6% for experimental duration above 20 years,and 5.1% for those with more than 4 levels of N addition. Based on these results,we presented some suggestions for the design and the methodoly of future N addition experiments.

The type and quantity of silage microbes play an important role in the whole fermentation of silage. Exploring and utilizing of silage beneficial microbes has become an important research direction to improve the fermentation quality. The microbial species in the different types of mixed silage are quite different,which makes the fermentation characteristics diverse. The succession process and community structure of fermenting microbes often determine the fermentation quality. Monitoring the dynamic changes of the composition of microbial flora can provide a theoretical basis for regulating the fermentation of silage. In this paper,the succession process of silage microbial community,the microbial diversity of different mixed silage types,and the factors affecting microbial diversity of mixed silage were reviewed. At the same time,the problems of antibacterial activity of lactic acid bacteria,the promotion of mixed silage and the performance of mixed silage on animal production are pointed out and the prospects were put forward,which could provide reference and new ideas for the practical application of silage microbes.

In order to investigate the effects of Biological soli crusts (BSCs) on soil nutrients and enzyme activities in grassland and desert ecosystems, 11 characters from 30 Chinese and English literatures were selected for meta-analysis. Subgroup analysis was conducted to identify the effects of different types of the BSCs on soil nutrients and enzyme activities in grassland ecosystem and desert ecosystem separately, and soil nutrient recovery index (NRI) and random forest analysis were used to evaluate those effects. The results showed that the effect of BSCs on NRI in desert ecosystem was greater than that in grassland ecosystem, and the effect of the lichen crust >mixed crust >moss crust >algal crust in desert ecosystem. Moreover, through random forest analysis and fitting regression analysis on annual mean rainfall (MAP) and annual mean temperature (MAT), it was found out that the contribution of phosphatase, urease and invertase to NRI was significantly higher than that of other selected characters, further the phosphatase and MAP, and invertase and MAT were significantly positively correlated, while the urease and MAP, the phosphatase and MAT negatively correlated with each other. In the coming studies, it is possible to match desert ecosystem and grassland ecosystem with different types of the BSCs, so as to make more effective usage of BSCs to prevent the land degradation and desertification.

In this study,3 annual forage grasses ( Avena sativa L., Vicia sativa L., Zea mays L.) and 4 main crops ( Avena chinensis Metzg., Triticum aestivum L., Sesamum indicum L., Solanum tuberosum L.) were planted in Chabei Precinct of Hebei Province,the differences in water use efficiency between annual forage grasses and crops were compared through planting experiments. Conclusions were as follows:The yield of annual forage grass is higher than that of crops,and its average water use efficiency (52.93%) is 16.60% higher than that of crops (36.33%). The yield of maize (t·hm ^-2) is the highest,the water use efficiency (141.80%) is the highest,and the water use efficiency of potato (19.53%) is the lowest;Water use efficiency of annual forage grass was explained by plant phosphorus content,plant potassium content,temperature,intercellular CO ₂ concentration and fresh dry ratio;Crop water use efficiency is explained by stem leaf ratio,plant nitrogen content and intercellular CO ₂ concentration.

Grassland classification is the foundation for scientific grassland management. It can provide sound basis for the rational exploration of the grassland resources and the efficient protection of grassland ecosystems. The existing grassland classification system in China is rooted on the single dimension of grassland occurrence to define the connections and differentiations. However,it can not be properly used for grassland managements in the dimensions of grassland function,utilization direction and land tenure. In order to adapt to the transformation from productive orientation to ecological orientation in grassland management and from the contradiction to harmony between grassland management and support the systematic governing of mountain,water,forestry,farmland,lakes and grasslands in the new era of Ecological Civilization Construction,it is imperative to develop the multi-dimensional grassland classification systems,which are scientific,systematic and integrated. In this paper,we absorbed the advanced theories and technologies in the grassland classification in the world and referred to the multiple forestry classification systems to develop the principles,methods and indicators and to structure the frameworks for the multi-dimensional grassland classification from the perspectives of grassland occurrence,land tenure,functions and utilization degree. We also explored the integration and compensation of the multi-dimensional grassland classification systems forwarded in this study. The objectives were to provide the fundamental support for grassland research,protection,restoration,utilization,construction programs,and to serve as the scientific basis for the rational grassland resources and ecosystem management and the systematic governing of mountain,water,forestry,farmland,lakes and grasslands in the new era of Ecological Civilization Construction.

In order to investigate whether artificial grassland can be established in Nagqu area and what kind of forage species is suitable for planting,this experiment selected the cold and drought-resistant forage species to carry out an introduction and screening test artificial grassland in the area. Through the comparison and evaluation of the harvested forage yield with the yield of natural grassland in Nagqu and other artificial grassland in the four major grassland areas in China,it can be seen that the yield of the harvested forage in the experiment is exponentially higher than that of the natural grassland in Nagqu,and the average yield of the artificial grassland in the experimental area is not lower than that of the artificial grasslands in the other grassland areas in China,which indicate that high yielding artificial grassland can be established in Nagqu region under adequate water and fertiliser management conditions. At the same time,the screening of suitable pasture species was carried out based on the seedling emergence and growth of different pasture species in the year of sowing and the seedling emergence of perennial pasture species in the following year (i.e. overwintering ability). The results showed that Avena sativa, Triticum secale, Brassica rapa and Brassica napus were suitable for planting in the Nagqu area. Elymus sibiricus and Elymus nutans,which were able to overwinter successfully,can be used as screening species for perennial grassland,but their stability in the second and subsequent years after overwintering remains to be studied.

To understand the response of soil C,N,and P stoichiometric characteristics to N and P addition in alpine meadows on the Tibetan Plateau and improve nutrient management and nutrient balance of grassland ecosystems,21 articles (612 data items) were rigorously selected for Meta-analysis in this study,and the effects of different fertilization methods (N addition,P addition,N+P addition) and different fertilization intensities (light,moderate,and heavy) on soil C,N,and P stoichiometric characteristics of Qinghai-Tibet Plateau meadows were developed through subgroup analysis. The results showed that nutrient addition significantly increased soil C,N,and P contents in Tibetan plateau grassland;the effect of N addition on soil increased with fertilizer application intensity,and the best increase in soil C,N,and P stoichiometric characteristics was observed under light application of phosphorus alone (less than 20 g·m ^-2) and the combination of nitrogen and phosphorus. Overall,it reflected that N and P additions had positive effects on alpine meadow soils,and the results of the study provided a scientific basis for the conservation of grassland ecosystems in the Qinghai-Tibet Plateau.

Plant senescence has a great impact on agricultural production. Premature senescence of crops leads to a decrease in yield,and premature senescence of forages leads to a decrease in grassland productivity,which limits the development of the grass industry. Deeply revealing the characteristics and regulatory mechanisms of plant senescence is not only of great value to clarify the ecological adaptability and population stability of plants but also of great practical significance to the selection of anti-aging technologies and regulatory measures. Plant senescence is a relatively complex process,which is determined by internal genetic factors and the external environment. This study summarizes the concept,research history,and plant senescence theory of plant senescence,focuses on the telomere theory of plant senescence,and summarizes the research progress of telomere in plant senescence,so as to provide a theoretical reference for the follow-up analysis of plant senescence mechanism from the perspective of telomere system.

Phosphorus (P) is an essential nutrient that affects plant productivity and ecosystem function in grasslands. In this study,we investigated the responses of soil P fractions to different levels of nitrogen (N) addition (5,10 and 15 g·m ^-2 for N5,N10,and N15 respectively) and the mechanisms in an alpine meadow of Haibei,Qinghai-Tibet Plateau (3 100 m). We found that low N addition could improve the availability of soil P,as N5 treatment significantly increased the content of the labile P pool,as well as the content of NaHCO ₃-Pi. In contrast,high N addition increased the aboveground biomass and P content in plant shoots,but no significant changes of labile P pool in the soil. Actually,only soil residual-P was significantly decreased under N15 treatment. The further analysis revealed key factors which might affect soil P fractions under N addition,including soil pH,microbial biomass carbon (MBC),and microbial biomass nitrogen (MBN). In conclusion,N additions increased the soil P availability,due to decreased soil pH and increased microbial biomass content in alpine meadows.

Based on the adaptive management technology platform of the alpine grassland-livestock system, in order to reveal the response mechanism of Kobresia humilis population to the regulation of grazing mode, this research studied the traits of leaves, resource input and the potential relationship between reproductive branches and vegetative branches of K. humilis. The results showed that:the height, number, and weight of vegetative branches of K. humilis in Yak:Tibetan sheep as 1:6 grazing treatment were significantly higher than those in Yak:Tibetan sheep as 1:4 grazing treatment, single Yak or Tibetan sheep grazing treatment. The vegetative branch weight and reproductive branch weight per unit length of K. humilis were not affected by grazing, and there was a positive correlation between vegetative branch weight per unit length and reproductive branch weight per unit length. The characteristics of individual reproductive branches and vegetative branches showed a cooperative relationship, and the weight of vegetative branches significantly affected the number of vegetative branches, and the number of reproductive branches significantly affected the weight of reproductive branches. In summary, this study suggests that under grazing disturbance, there is no trade-off between the resource input of the reproductive branch and vegetative branch. Kobresia humilis improves the resource allocation by increasing the resource input of the reproductive branch and vegetative branch per unit length.

Grazing is one of the most important uses of grassland ecosystems,and different grassland types,grazing intensities,herbivore assemblages,grassland use types and climate change all influence the structure and function of grassland ecosystems. It is very important to understand the mechanisms of grazing and climate change on grassland ecosystems for their sustainable development. In order to provide a theoretical reference for the adaptive management and sustainable development of grassland ecosystems,this paper provided a systematic review of the mechanisms by which grazing affects the structure and function of grassland ecosystems,and provided an outlook on several important research directions in this theme,and future research issues as the following:(1) to improve spatial coupling analysis in grazing grassland ecosystems;(2) to focus on multifunctionality studies of grassland ecosystems;(3) to elaborate the multi-factorial nested experiments on grasslands in the context of global change;(4) to refine the mixed grazing experiments with different herbivore assemblages;(5) to standardize the methods of grassland ecological experiments.

Vegetation change caused by environmental change has a significant impact on ecosystem processes. However,the research on vegetation growth and its response to multiple related control factors is still insufficient. This paper explored spatial-temporal variation and driving factors of grassland Normalized Difference Vegetation Index (NDVI) using Theil-Sen median trend analysis,Mann-Kendall test,coefficient of variation,ridge regression analysis and structural equation model. The results showed that from 2001 to 2020,the spatial variation of grassland Normalized Difference Vegetation Index (NDVI) gradually decreased from southeast to northwest in the Qinghai-Tibet Plateau (QTP),the interannual variation showed an upward trend,the distribution of grassland was more concentrated in the area with smaller slope,and the growth of shady slope grassland was better. In the region,grassland growth improved due to the increase of water use efficiency (WUE) and temperature,and the grassland WUE was the main factor affecting the change of grassland NDVI on the QTP. This study improved our understanding on how multiple variables worked together to influence grassland growth and highlighted the importance of WUE for vegetation growth.

To explore the biomass inversion model and its influencing factors of desert grassland in Xinjiang,based on the remote sensing product data such as Terra/MODIS,NOAA CDR NDVI,SPOT/VGT,and the measured data of aboveground biomass of grassland,the aboveground biomass vegetation index inversion model of desert grassland in the study area was constructed,the temporal and spatial distribution law of aboveground biomass of desert grassland in Xinjiang was analyzed,and the trend analysis method and correlation method were used. The relationship between biomass evolution trend and temperature and precipitation was revealed. The results showed that:Among the biomass models established from different remote sensing data sources,the accuracy of the exponential function inversion model was the highest,and the determination coefficient and estimation accuracy were 0.66 and 70.93%,respectively;Based on the changing trend of NDVI from 2000 to 2019,it is found that the desert grassland in Xinjiang is mainly stable and improved;The spatial distribution pattern of aboveground biomass of desert grassland in the study area from 2000 to 2019 showed a trend of high in the north and low in the south. The average aboveground biomass of desert grassland in the past 20 years was 38.92 g·m ^-2;From 2000 to 2019,both temperature and precipitation increased,and the annual average temperature rise rate and precipitation rate reached 0.32℃·(10 a) ^-1 and 2.18 mm·(10 a) ^-1. More than 50% of desert grassland had a positive correlation with temperature and precipitation,and the correlation between biomass and precipitation was better than that of temperature. The results can provide scientific basis and technical support for grassland protection and improvement and ecological environment construction in Xinjiang.

In order to explore soil trace elements and vegetation characteristics and their relationships in alpine steppe under different degradation degrees in Sanjiangyuan region,the alpine steppe at different degradation degrees in Maduo County of Qinghai Province were selected as the research areas to investigate. The vegetation community characteristics,the contents of soil trace elements (Fe,Mn,Cu,Zn,B,Mo,Se),and the key soil trace elements affecting the degradation of alpine grassland vegetation community were analyzed. The results showed that with the aggravation of alpine steppe degradation,the grassland coverage gradually decreased,and the diversity,richness and aboveground biomass first increased and then decreased. The content of trace elements in soil showed a downward trend;the characteristics of vegetation community were positively correlated with contents of iron,manganese,copper,zinc,boron and selenium in soil,especially with the contents of iron,copper and boron.

Silage plays a very important role in the process of animal husbandry production,but the accumulation of nitrite during silage fermentation is seriously harmful to animal production performance,milk and meat quality. Nitrite poisoning is a common foodborne disease to livestock. Mild poisoning can affect the growth and development of livestock,severe poisoning can even lead to the death of livestock. To reduce the risk of nitrite in silage and improve the quality of silage and secure the safety of silage,this paper described the hazards,sources,transformation pathways,nitrite degradation pathways and control measures during the silage process,to provide an effective reference for nitrite degradation and regulation in silage feed.

Inner Mongolia grassland is an important livestock production base and northern ecological security barrier in China,and its economic development and ecological protection issues are the hot topics of research nowadays. Family ranch as a major typical form of livestock production organization has become an important element in the development of agriculture and animal husbandry in Inner Mongolia. In recent years,climate change and human disturbance have caused the degradation of grasslands. This not only brings about problems such as the decline of ecosystem function,but also has an important impact on the economic development of family ranches. This paper discussed the development and definition of family ranch,provided an overview of the roles produced and the impacts caused from the management strategies of family ranch under different grassland types in Inner Mongolia,and finally raised questions and outlooks on the business model,herders' business awareness,management system,financial system and social service system,and landscape remote sensing technology applications relevant to the family ranch in Inner Mongolia. It is expected to provide a scientific reference for achieving grass-livestock balance at the scale of farmer's household in Inner Mongolia,while improving the economic efficiency of farmers and herders.

Droughts have been frequent in recent years,severely limiting crop production and vegetation recovery. Therefore,it is important to identify natural drought-tolerant plant species. The physiological indicators of root growth under drought stress were analyzed by setting four drought gradients in Sophora davidii potted seedlings,and it was found that the root system was the first to sense the onset of drought,and its root length,surface area,and volume increased,and the contents of auxin (IAA),gibberellins (GA ₃),proline,soluble sugars and malondialdehyde (MDA) and hydrogen peroxide (H ₂O ₂) contents increased,superoxide dismutase (SOD),peroxidase (POD) and catalase (CAT) activities decreased,and ascorbate peroxidase (APX) activity increased. Under severe drought, S. davidii did not suffer from severe dehydration and seedling death,indicating that it has strong drought resistance and is suitable for application in ecological restoration and fodder development in semi-arid areas as well as karst areas. The experiment elucidates the adaptive mechanism of drought resistance of S. davidii,reveals the drought resistance of S. davidii,and provides a certain reference basis for the all-round and three-dimensional industrial development and utilization of S. davidii in the western karst region.

As one of the important industries in the field of agriculture,the grass seed industry is playing an increasingly important role in improving the efficiency of farming,increasing the income of farmers and herdsmen,and promoting high-quality economic and social development. The collection,preservation,identification,evaluation and innovative utilization of germplasm resources and the breeding of new varieties (lines) have become hot topics in the current research of grass seed industry. This paper mainly summarized and prospected the genetic diversity of grass germplasm resources from four aspects:morphology,biochemistry,cytology and molecular level,aiming to provide reference for the creation and breeding utilization of grass germplasm resources.

Grazing is one of the main utilization methods in desert grasslands. Biomass is the main manifestation of the energy acquisition capacity of the ecosystem. At present,there is a relative lack of research on biomass allocation and trade-offs of dominant plants in desert grasslands. In this study,three different grazing gradients (light grazing,medium grazing,and heavy grazing) were set up in Inner Mongolia desert grassland,and no grazing was used as the control. The above-ground and below-ground biomass of four dominant plants ( Stipa breviflora, Cleistogenes songorica, Artemisia frigida, Convolvulus ammannii) were analyzed to investigate the biomass distribution characteristics and biomass trade-off of dominant plants under different grazing gradients. The results showed that with the increase of grazing intensity,the above-ground and below-ground biomass,litter,cover,and above and below-ground biomass of the four dominant plants tended to decrease;All four dominant plant biomasses showed a trade-off to the belowground,and the trade-off value became larger as the grazing intensity increased;The above and below-ground biomass of the four dominant plants showed significant positive correlations with community cover and litter content,while the root/shoot ratio of Artemisia frigida and Convolvulus ammannii showed significant negative correlations with community cover and litter content. This study provides a new perspective and method for understanding above- and below-ground biomass distribution.

Arbuscular mycorrhizal fungi (AMF) are a kind of important soil microorganisms which can form mycorrhizal symbiosis within plant roots and have the function of promoting plant growth and development. Alfalfa,known as "the king of forage",is a high-quality leguminous forage crop,which is characterized by high protein content,rich nutrition,strong palatability,and a wide range of adaptation. In this paper,the progress of effects of AMF on promoting the growth and development of alfalfa,boosting the resistance of stress and disease,and improving soil was reviewed,and the existing problems and application prospects were discussed. It provided a reference basis for the application of AMF in the cultivation of alfalfa.

The nutritional quality of silage is largely determined by its microbial composition,and aerobic exposure will cause changes in microbial community diversity. To investigate the distribution of bacterial diversity in silage maize after aerobic exposure and its impact on silage quality,the nutritional quality and bacterial community structure of silage maize at 0,1,8,24,36,48,72,96 and 120 hours after aerobic exposure were determined and analyzed.The results showed that the contents of soluble sugar,crude protein and dry matter of silage maize decreased during aerobic exposure. The content of neutral detergent fiber and acid detergent fiber increased,and the content of calcium and phosphorus did not change significantly. During aerobic exposure,bacterial diversity increased first and then decreased,and the bacterial diversity was the highest at 36 hours of aerobic exposure. At different times of aerobic exposure,the dominant bacteriophyta are Firmicutes and Actinobacteria,and the dominant bacteria genus is Lactobacillus. During aerobic exposure,Firmicutes was significantly positively correlated with soluble sugars and proteins,and negatively correlated with neutral detergent fibers and acid detergent fibers. Proteobacteria and Acidobacteria were negatively correlated with soluble sugars. To sum up,silage corn should be fed within 8 hours of aerobic exposure in combination with production practice.

Grasslands take an important role in the construction of ecological civilization and the development of grassland husbandry in China. The grassland survey and monitoring is one of the main practices in grassland management. Overviewing the development courses of grassland survey and monitoring in China and the major grass-pastoral developed countries,it could be revealed that the grassland survey and monitoring domestic and abroad underwent the processes from focus on the production indicators to the ecological indicators,while the methods used in the grassland survey and monitoring domestic and abroad were the combination of the long-term and the short-term survey and monitoring approaches,with the long-term survey and monitoring approach dominant. All the countries analyzed in this study has developed a relatively complete system for the grassland survey and monitoring in the course of technology development in the light of the type,utilization and other characteristics of the grasslands in their country. We suggest the survey and monitoring of grasslands in China should set the grassland monitoring sites with the scientific layout, improve the long-term monitoring network of grasslands,establish a systematic space-ground-air integrated grassland monitoring technology system,strengthen the indicator system of multifunctional grassland monitoring;and reinforce the investment of grassland monitors and science and technology,in order to promote the sustainable development of grassland monitoring in China.