茶树氮素吸收利用机制研究进展

铵态氮(NH4~+)和硝态氮(NO_3~-)是茶树吸收利用的两种主要氮素形态,且茶树具有对NH4~+偏性利用的特点,其对NH4~+的吸收利用效率明显高于NO_3~-,造成这种差异的原因可能在于茶树对NH4~+、NO_3~-吸收、同化机制的差异。从代谢途径来看,茶树对NH4~+、NO_3~-的吸收利用均首先需要通过对氮素的转运,然后再参与谷氨酰胺合成酶/谷酰胺–α–酮戊二酸氨基转移酶(GS/GOGAT)同化过程。系统地综述了茶树氮素利用的营养特性及对参与氮素吸收、同化过程所涉及关键基因的研究现状;同时重点关注氮素同化中限速酶——谷氨酰胺合成酶(GS)编码基因家族成员的相关研究,为解析茶树氮素偏性利用机制提供新的研究点。     

城市消费者对碳标签牛奶的偏好及其异质性来源——基于选择实验法的分析

分析城市消费者对低碳农产品的偏好、支付意愿及其偏好的异质性来源对减少碳排放、促进农业可持续发展意义重大。基于选择实验法,以牛奶为例,利用上海、南京和杭州786名城市消费者的调查数据,采用混合Logit模型,分析了习惯性购买常温奶或鲜牛奶两类消费群体对碳标签牛奶的偏好和支付意愿,探讨其偏好的异质性来源。结果表明,在消费者了解碳标签基本含义的前提下,两类消费群体对牛奶低碳和中碳标签均有显著正向偏好,并且牛奶低碳与全脂标签存在互补关系;常温奶和鲜牛奶消费群体对牛奶低碳标签的平均支付意愿分别为4.13元/盒和5.63元/盒。两类消费群体对牛奶碳标签的偏好具有异质性,且异质性来源不同。对常温奶消费群体而言,年龄越小、个人月收入越高、牛奶购买频率越高和对碳标签较熟识的消费者更倾向于购买低碳足迹牛奶;对鲜牛奶消费群体而言,男性、年龄越小、受教育程度越高和较为关注低碳信息的消费者购买碳足迹较低的牛奶的可能性更高。另外,消费者对低碳农产品作用的认知在两类消费群体中均正向影响其低碳偏好。因此,提出政府及相关机构应完善低碳产品认证制度、加强宣传推广碳标签的力度、向消费者普及低碳农产品相关知识、企业要注重低碳...     

Spatial preference heterogeneity in policies for improving urban green spaces

Urban green spaces (UGSs) enhance the quality of urban dwellers’ lives. Thus, efficient policies for improving UGSs—which should reflect urban residents’ needs—are necessary. Additionally, it is crucial to manage the spatial distribution of residents’ preferences to find regions that can produce greater utility within limited budgets. Using online surveys conducted in 2015, which obtained 414 valid responses, this study analyzed urban residents’ preferences for UGS improvement policies and investigated spatial preference heterogeneity for such policies in the planned city of Seongnam, South Korea. A mixed logit model was applied to analyze policy preferences, and the preference heterogeneity level was assessed by coefficient of variation. Additionally, hot spot analysis was performed to examine spatial heterogeneity. The Getis-ord Gi* was computed to identify the spatial clusters of the estimated coefficients and the marginal willingness to pay (WTP). The results indicated a high preference for enhancing quality and connectivity. While the results showed that preference heterogeneity existed in each UGS improvement policy, heterogeneity levels differed per attribute. Statistically significant local spatial clusters of estimated coefficients and marginal WTP were observed for each UGS improvement policy despite global autocorrelation being insignificant. It was observed that estimate coefficients with low coefficient of variation can make extensive spatial clusters; otherwise, the opposite trend might occur. Additionally, marginal WTP hot spots did not change according to attribute but appeared in similar locations. Therefore, spatial heterogeneity analysis is necessary to manage UGSs with higher net utilities given limited budgets. These findings will ensure the satisfaction of all urban residents by identifying their preferences for UGS policies. They will also help prioritize cost-effective implementation of policy considering spatial preference heterogeneity.     

翠湖公园环境偏好、恢复性评价与健康效益评估关系研究

以昆明市翠湖公园为例,验证环境偏好、恢复性评价与健康效益评估三者间现有结构关系模型,为未来建设具有健康效益的公园景观提供理论依据。结果表明:环境的易识别性和景观的复杂性是城市公园游览者对公园环境产生偏好的重要影响因素,兼容性对于城市公园的环境恢复性效果影响最显著,镇定情绪项更能反应游览者的健康效益评估;环境偏好、恢复性评价与健康效益评估三者间为显著正向影响关系,即游览者的环境偏好对恢复性评价有显著正影响,游览者的恢复性评价对健康效益评估有显著正影响;游览者的环境偏好对健康效益评估既有显著正影响,且两者之间也存在恢复性评价作为中介产生的间接效应。     

地红蝽特殊取食行为及其偏好性

为探究地红蝽Pyrrhocoris tibialis St?l的特殊取食行为及其取食选择性，通过在室内外观测并全程记录地红蝽的取食行为，研究其对12种植物种子以及不同部位和不同成熟度苘麻种子的取食偏好性。结果表明，地红蝽室外取食行为包括寻水、吸水、清理、离开、搜寻、摩擦、刺探、插入、携带、攀爬、取食、静止和离开共13个过程；在室内有92%的地红蝽具先吸水后取食的行为，8%只进行吸水行为。地红蝽对苘麻种子的取食偏好性最高，选择率为41.71%，取食时长为77.30 min，刺探次数为3.44次，均显著高于其余植物种子；地红蝽对苘麻种子种皮厚度最薄（96.12μm）的左肩部位取食选择率最高，为28.93%，显著高于其他部位；对成熟度最高的深色苘麻种子取食偏好性最高，选择率为42.00%，取食时长为182.94 min，刺探次数为6.44次，高于次深色和浅色苘麻种子。表明地红蝽取食行为是吸水-携带种子攀爬-取食的特殊取食行为，且偏好取食苘麻种子并对种皮厚度最薄部位和成熟度最高苘麻种子的取食偏好性强。     

同位素异位体溯源土壤N2O的方法、技术和展望

土壤是N₂O的重要排放来源之一。土壤中N₂O产生途径众多、受多种因素调控，深入分析土壤N₂O产生途径才能采取针对性的减排策略。稳定同位素技术已广泛用于研究土壤N₂O排放，N₂O同位素异位体法是近年来新兴的研究方法。该研究方法通过测定土壤N₂O的同位素组成(δ¹⁵NSPN₂O、δ¹⁸ON₂O和δ¹⁵N^bulkN₂O)分析N₂O排放贡献，因无需添加标记物、对土壤系统干扰小、成本低，适合在野外田间研究N₂O排放，是15N标记方法的有力补充。本文详细介绍了N₂O同位素异位体法的原理、质谱测定方法、定量分析方法、影响该方法的因素及其应用前景。     

Bridging landscape preference and landscape design: A study on the preference and optimal combination of landscape elements based on conjoint analysis

Landscape preference is the focus of landscape research, in which the relationship between landscape elements and landscape preference is an important issue. Most previous studies have analysed correlation between the landscape preference scored by the public and scores on the quality of landscape elements by experts; some have compared the effects of individual landscape elements on landscape preference by photo simulation. In this study, landscape preference is regarded as the selection preference of landscape element combination. The conjoint analysis method is used to further explore the ranking and optimal combination of the significant degrees of impact of landscape elements on landscape preference when multiple landscape element combinations are used. The results show that the influence degrees of landscape elements on landscape preference in urban parks followed the order water, square, openness of the landscape, vegetation, road and seats. The optimal combination of landscape elements is the open landscape with flowing water, a shaded square, rich vegetation, a road and seats. This study demonstrates the advantages of the conjoint analysis method over the univariate method in controlling multiple variables, improving experimental efficiency and obtaining more meaningful results. A combination of urban park landscape elements based on landscape preference is helpful to inspire landscape architects to make choices among multiple landscape elements, provides evidence-based design methods for landscape design and offers basic parameters for the wide application of the parametric design or computational design of landscape architecture.     

稀释中的深化效应：城镇化对农村人力资本积累的影响

城镇化与农村人力资本积累之间的关系将会影响到乡村振兴战略和城乡融合发展的成败。基于理论分析和2005—2017年中国省级面板数据,采用固定效应、面板工具变量估计方法检验城镇化对农村人力资本积累的因果效应和内在机制。结果表明：（1）在控制其他变量的条件下,城镇化对农村人力资本积累具有显著的正向影响,城镇化率每提高一个百分点,农村人均人力资本大约增加1200~1300元;（2）城镇化强化了农村家庭人口质量偏好,农村人力资本投资持续增加,即城镇化对农村人力资本的深化效应是借助人口质量偏好机制而现实的。上述发现进一步澄清了城镇化与农村人力资本积累之间的逻辑关系,并为政府部门在设计和完善相关政策方面提供理论启发和经验证据。     

斑翅果蝇对寄主果实及其挥发物嗅觉趋性的研究

斑翅果蝇是一种主要为害软皮水果的害虫, 诱捕剂诱捕是防治该害虫的重要手段。为明确斑翅果蝇对寄主果实及其挥发性物质的趋性, 进而研发植物源引诱剂, 本研究利用四臂嗅觉仪测定了斑翅果蝇成虫对不同种类（葡萄、树莓、杨梅、蓝莓、樱桃和草莓）和不同成熟程度鲜果的趋性, 并分析了寄主果实挥发物成分。结果表明:1)斑翅果蝇成虫对过熟鲜果的趋性最强, 其次为成熟鲜果和未熟的鲜果; 2)成虫对葡萄的趋性最强, 其次分别为树莓、杨梅、蓝莓、樱桃和草莓; 3)葡萄挥发物中含量最高的成分为反式-2-己烯醛, 樱桃和树莓中为苯甲醇, 蓝莓中为乙醇。研究结果为进一步开发高效的斑翅果蝇植物源引诱剂奠定了基础。