黄土高原北部坡梁地微地形气候的温度变化特征研究

用多个热敏电阻温度计对准格尔旗五道敖包坡梁地不同部位离地面30,80,150cm的气温进 行测定,结果表明,黄土高原的沟壑地形中,同海拔高度南坡的温度较北坡高,有的高出0．3-0．5℃。近 地面30cm的日平均气温一般高于150cm,有的位点白天温度平均高1．0℃,尤以光照条件好地方明 显;而夜间近地面的温度相对较低。地形影响到温度差异,同时影响到降水的重新分配,进而将影响 到作物的生长发育。     

Gender discrimination and its impact on income,productivity, and technical efficiency: evidence from Benin

This paper examines the occurrence and impact of gender discrimination in access to production resources on the income, productivity, and technical efficiency of farmers. Through an empirical investigation of farmers from Koussin-Lélé, a semi-collective irrigated rice scheme in central Benin, we find that female rice farmers are particularly discriminated against with regard to scheme membership and access to land and equipment, resulting in significant negative impacts on their productivity and income. Although women have lower productivity, they are as technically efficient as men. The findings suggest that there is considerable scope for improving the productivity of women through increasing their access to production resources.     

Construction of a plant expression vector of chalcone synthase gene of <Emphasis Type="Italic">Ginkgo biloba</Emphasis> L. and its genetic transformation into tobacco

The chalcone synthase gene (chs) from Ginkgo biloba L. was cloned by PCR procedure. For constructing a plant expression vector of Gbchs, the gene was digested with XbaI and BamHI and inserted into the pBI121 vector. Gbchs was transferred into tobacco mediated by Agrobacterium tumefaciens LBA4404. PCR and Southern blot were performed, and the results showed that chs had been transformed into the genomic DNA of tobacco. The total flavones in the transformed tobacco leaves was extracted by the methanol extraction method and tested by UV spectrophotometry. The results showed that, compared to the control tobacco, the content in the transgenic tobaccos, n = 6, was generally higher, and the difference reached a significant level (P < 0.05) and highly significant level (P < 0.01), except one sample. Moreover, the highest sample was nearly 7.7 times greater than that of the controls. All these results show that utilizing genetic manipulations to improve plants in order to regulate flavone content by gene engineering may be an effective and hopeful method.     

半干旱地区杨树新品种选育初报

通过青杨派的种间杂交,在半干旱地区的杨树新品种选育中,初选出四龄树的金科5号优良无性系。对金科5号在耐干旱、耐盐碱、速生等方面的特性进行了试验研究,发现其表现优良,适于在兰干旱地区推广。     

三维碎片拼合的轮廓提取和特征点检测

针对三维空间碎片的拼接,提出一种轮廓提取和特征点检测的方法。首先,采用一种简单、有效的方法来构建三维碎片数据的拓扑关系,并在此基础上提取碎片的轮廓曲线。对存在缺陷、拓扑关系难以建立的三维测量数据,中给出了相应的修改、调整方法。同时,提出了一种对轮廓进行重采样的方法来计算空间轮廓上每一点的曲率和挠率。将曲率和挠率相结合得出轮廓曲线上各点的全曲率,然后由全曲率值来检测碎片轮廓的特征点。轮廓曲线的描述就由其上每一点的曲率和挠率以及特征点来表征。实验表明了该算法的有效性和稳定性。     

Building the local food movement in Chiapas,Mexico: rationales,benefits, and limitations

Alternative food networks (AFNs) have become a common response to the socio-ecological injustices generated by the industrialized food system. Using a political ecology framework, this paper evaluates the emergence of an AFN in Chiapas, Mexico. While the Mexican context presents a particular set of challenges, the case study also reveals the strength the alternative food movement derives from a diverse network of actors committed to building a “community economy” that reasserts the multifunctional values of organic agriculture and local commodity chains. Nonetheless, just as the AFN functions as an important livelihood strategy for otherwise disenfranchised producers it simultaneously encounters similar limitations as those observed in other market-driven approaches to sustainable food governance.     

Investor ownership or social investment? Changing farmland ownership in Saskatchewan,Canada

There is growing recognition that land grabbing is a global phenomenon. In Canada, investors are particularly interested in Saskatchewan farmland, the province where 40 % of country’s agricultural land is situated. This article examines how the changing political, economic, and legal context under neoliberalism has shaped patterns of farmland ownership in Saskatchewan, between 2002 and 2014. Our research indicates that over this time, the amount of farmland owned by investors increased 16-fold. Also, the concentration of farmland ownership is on the rise, with the share of farmland owned by the largest four private owners increasing six-fold. Our methodology addresses some of the criticisms raised in the land grabbing literature. By using land titles data, we identified farmland investors and determined very precisely their landholdings thus allowing us to provide a fine-grained analysis of the actual patterns of farmland ownership. Although the article analyzes changes to farmland ownership in a specific historical, cultural and legislative context, it serves as the basis for a broader discussion of the values and priorities that land ownership policies reflect. Namely, we contrast an ‘open for business’ approach that prioritizes financial investment to one based on a land sovereignty approach that prioritizes social investment. The latter has greater potential if the aim is ecological sustainability and food sovereignty.     

Socio-economic and environmental changes related to maize richness in Mexico’s central highlands

The occurrence of genetic erosion in local maize varieties in Mexico is intensely debated. Recent publications from Mexico show contradicting results about the loss of local varieties. Genetic erosion is a complex process, and well-documented examples of actual genetic erosion are not common in the literature. We worked in a region in which adoption of improved varieties was negligible, but other factors affecting maize agriculture were at play. The objectives of the study were to describe changes in maize diversity in the last 10 years and to associate them with socio-economic and environmental changes in a region in Mexico’s Central Highlands. We used richness and abundance of local varieties and diversity indices of races as indicators of maize diversity changes over time. We analyzed statistics and based on interviews we evaluated maize diversity changes between 2005 and 2015. We interviewed 113 farmers on two occasions with intervals from 5 to 10 years. According to climate statistics, rain has declined and temperature has increased. We also found a decrease in the lake level during the past 35 years. The total population in the region has doubled since the 1960s. The indigenous population has not changed significantly. Number of people working in agriculture has decreased since the 1960s. Rain fed agriculture decreased 8.1 % from 1990 to 2007. In four villages studied, farmed land area had decreased between 1995 and 2015. This reduction varies between 22 and 39 % depending on the village. Maize planted area decreased from 9675 to 8115 ha from 2003 to 2014. In the same period, avocado plantations grew from 34 to 786 ha. In despite of these changes, we did not find significant changes in average landraces per farmer (2.13 ± 0.28 in 2015) nor per village (4.15 ± 1.26 in 2015). Significant changes in maize races were not found either (1.91 ± 0.26 per farmer, 2.85 ± 0.86 per village in 2015). These results show that maize landrace diversity in the region is resilient but dynamic.     

红点唇瓢虫对杨圆蚧的捕食功能

杨圆蚧是我国东北林区杨树的主要害虫，对它的防治已经由化学防治向生物防治转化，红点唇瓢虫作为杨圆蚧的主要捕食性天敌，对杨圆蚧有较好的控制作用。在前人研究的基础上，经在黑龙江省大庆市观察，越冬后的成瓢和冬龄幼瓢。     

“生物统计方法”课程题库建设与测试评价

以统编教材《田间试验和统计方法》中“生物统计方法”课程内容为主,根据经典测试理论建成“生物统计方法”课程题库,适用于农业高等院校农学类不同专业、不同对象、不同内容、不同时期及不同长度的测试.本科生测试 A,B,C 及研究生入学测试 D 的测试平均区分度、信度、效度分别为0.35,0.77,0.32,低区分度(D<0.1)题目占测试分数比例均在16%以下,自学测试 E 区分度为0.49.实例分析表明,题库组卷可控性强、难度适宜、区分度及信度较高。但是判断题目难度(0.14)及区分度(0.17)平均值偏低且平均变异系数(CV%)偏高(90.8%及135.3%).在题库定期更新中应注意改善判断及选择题目的参数估计及命题质量.