为全面掌握"生产-生活-生态"空间的研究现状,完善"三生"空间的相关概念与基础理论,以"三生"空间与"生产-生活-生态"空间为关键词检索CNKI数据库与Web of science核心合集2012-2022年发表的相关文献,在对其中403篇文献进行查阅、分析的基础上,结合人地关系理论与土地利用多功能性理论系统总结、归纳"三生"空间的概念、演化机制、分类体系、相互作用关系与发展目标.研究发现:"三生"空间是人类活动与地理环境相互作用形成的具有一定结构和功能的空间实体,并以可持续、碳中和、协调为整体的发展目标;生产、生活与生态空间也分别具有不同的发展目标,并分别包含不同子空间;"三生"空间及其子空间之间存在明显的正向与负向作用.未来应加强"三生"空间形成机制、内涵、相互作用、发展目标等基础理论的研究,深入分析"三生"空间内部各类子空间的布局特征与演化机制,建立定量测度"三生"空间相互作用强度的理论与方法体系,丰富完善"三生"空间发展目标和优化研究的理论、方法与内容,推动"三生"空间与"三生"功能研究的并行发展.
Aiming at the problem of uneven distribution of solid inoculants directly added to the seedling substrate in the current production process of functional seedling substrates, based on a two-step compounding method, the mixing of γ-polyglutamic acid as inoculant carrier with traditional substrates was carried out. Single factor test and response surface analysis test were used to investigate the effects of carrier addition, seedling substrate moisture content, mixing speed and mixing time on the uniformity of Bacillus velezensis in seedling matrix. The results showed that the optimal mixing process parameters for the preparation of functional seedling substrates were as follows: The addition amount of γ-polyglutamic acid was 5.6 g/L, the seedling substrate moisture content was 35%, the mixing speed was 42 r/min, and the mixing time was 333 s. Under the above conditions, the coefficient of variation of B. velezensis was 4.59%. The optimized functional seedling matrix had no significant difference in bulk density and porosity with the traditional matrix, and the water-holding pore and maximum water-holding capacity of the matrix were increased by 5.68% and 7.92%, respectively.
Understanding how effective protective memory responses are produced in coccidiosis and how to design a successful anticoccidial vaccine are long goals in the coccidiosis research area. This study summarizes research progresses in the last 50 years and pinpoints possible directions to guide novel anticoccidial vaccine design. The assumption and new strategy are based on the three key points of generating efficient protective memory immune response, namly, threshold, effect site and time of generating protective immune level. The results show that: 1) Differences should be noted between the immune responses induced by infections and antigens delivered either as recombinant proteins, DNA or live vectors. Live oocysts vaccine can induce protective memory immune responses, rendering the infected hosts to a ‘Primed’ immune state（that is, the immune system can quickly and efficiently recognize hundreds of coccidian antigen and have higher resistance to reinfection by coccidia）; Non-live oocyst vaccine may fail to develop protective memory responses, and the vaccinated hosts are in immune ‘Naive’ state（that is, the immune system can only recognize one or several specific coccidian antigens, and its ability ro resist reinfection by coccidia is not effective to resist pathogen infection）. This also explains the limited success achieved in developing new anticoccidial vaccines. 2) The primed immune state originated from multiple players, including tissue resident memory cells(T RM ), circulating effector memory T cells(T EM ), central memory T cells(T CM ), etc., which can inhibit the infection at an early stage. How to develop vaccines inducing effective memory cells, especially T RM cells which populate the front line of coccidia infection, is key to achieve primed immune states for vaccinated hosts. Targeting antigen-experienced DCs to the gut offers a tremendous potential. 3) Inhibiting early schizogenesis of coccidian is an important feature of a ‘primed’ host to resist coccidiosis, which provides a new idea for evaluating high-efficient coccidian vaccine. In summary, only when we fully understand how to achieve the ‘primed’ immune state after infection or vaccination, can the scientific prevention and control of coccidiosis be realized.
In order to investigate the effect of agricultural product labeling cognition and consumption habit on consumers’ willingness to pay premium of green agricultural products, based on the theory of planned behavior, an analytical framework that affects the willingness to pay premium for green agricultural products was constructed. Taking green fresh-potatoes as an example, based on the survey data of 402 consumers in three cities of Beijing, Zhengzhou and Chengdu, the contingent valuation method is used to evaluate the willingness to pay premium of urban consumers. On this basis, the ordered logit model was used to analyze the influence of behavioral attitude variables, subjective norm variables and perceived behavioral control variables on the willingness to pay premium of green fresh-potatoes. The results show that: 1) The average willingness of consumers to pay premium of green fresh-potatoes is between 10% and 30%, and the overall willingness level is relatively low. 2) The attitude of behavior variables have a significant impact on the willingness to pay premium of green fresh-potatoes. The higher the convenience of the place of purchase, the higher the willingness to pay premium. The better the consumers’ perception of the quality of ordinary potatoes, the higher the willingness to pay premium. 3) The subjective norm variables also significantly affect urban consumers’ willingness to pay premium for green fresh-potatoes. Among them, compared with QS product labeling and organic product labeling, the consumers’ cognition of green product labeling has the greatest impact on their willingness to pay premium. 4) The effect of perceived behavior control variables on consumers’ willingness to pay premium for the green fresh-potato is also significant. Male consumers who are older and in better health are more willing to pay a higher premium for green fresh potatoes. Therefore, green agricultural product market should be cultivated and the green development of agriculture should be promoted from the aspects of strengthening the publicity of the value of green agricultural products, improving consumers’ cognition of green product labels, and promoting the convenience of consumers to purchase green agricultural products.
In order to explore the effects of the extensive use of direct seeding in southern China, based on the input—output data of 574 rice production cycles of 420 farmers in four southern provinces, this study investigated the impact of direct seeding technology on rice production efficiency from three perspectives including labor productivity, land productivity and technical efficiency. The results showed that: 1) Direct seeding technology significantly improved the labor productivity of rice; 2) Direct seeding technology had no significant effect on the land productivity of rice; 3) The adoption of direct seeding technology reduced the technical efficiency of rice. However, in the case of distinguishing farmers’ planting scale, with the increase of rice planting scale the impact became insignificant when the planting scale reached a certain critical value. In conclusion, the adoption of rice direct seeding technology is an important coping strategy against the background of rising labor costs, and this technological change is an important embodiment of China’s induced technological change theory. In addition, in order to save labor, farmers can bear a certain degree of output loss, indicating that the rice production mode has completely changed from intensive to extensive management. In order to give full play to the positive impact of direct seeding on rice production efficiency, we should tap the advantages and potential of direct seeding technology, focus on improving the supporting facilities and conditions of direct seeding technology, such as land leveling and land exchange, and further promote the popularization of direct seeding technology among farmers who have reached a certain rice planting scale.
