Productivity of hedgerow shrubs and maize under alleycropping and block planting systems in semiarid Kenya

A field experiment was conducted for eight cropping seasons from 1988 to 1991 in semiarid Machakos, Kenya, to compare the productivity of shrubs and crops in intercropping (alleycropping) versus block (sole) planting systems. The study, conducted in a split-plot experiment with three replications, consisted of two tree species (Leucaena leucocephala andSenna siamea syn.Cassia siamea) in the main-plots and combinations of two planting systems (alleycropping and block planting of the shrubs and maize) with five different ratios of land allocation for the shrub and crop (1000, 1585, 2080, 2575, and 0100) in sub-plots. Thus, a sole maize and a sole tree were included in the subplot treatments. The spacing between hedgerows of shrubs in intercropping was 6.7, 5, and 4 m, respectively, corresponding to 15, 20, and 25% land allocation to shrubs. The trees were pruned to 0.5 m height four times a year. Intercropped hedgerows of senna and leucaena produced 10% and 24% more biomass than their respective block planting systems. On average, leucaena produced more biomass than senna. Maize alleycropped with leucaena yielded 16% less grain than sole-crop maize, whereas senna intercropping caused hardly any maize-yield reduction. Compared with the respective sole-crop systems, leucaena intercropping did not affect land equivalent ratio (LER), whereas LER increased by 28% with senna intercropping. The different tree:crop land occupancy ratios did not affect the production of either the component species or of the total system, except that LER declined with incrreased spacing between hedgerows. It is concluded that in semiarid highlands of Kenya, leucaena and crops should better be grown in sole blocks, not in alleycropping. In the case of slow-growing species such as senna, intercropping is worthwhile to consider only if the additional labour needed does not pose a serious problem for management, and the species has fodder value.     

连续配筋水泥混凝土路面温缩应力简化公式研究

连续配筋水泥混凝土路面（CRCP）在铺筑完成一段时间后，会在路面纵向上断裂成一个个单独的板块.借助正交设计和多元统计回归方法，在有限元计算的基础上，提出了单独板的温缩应力简化公式.极差分析结果表明，CRCP温缩应力影响因素的重要程度从大到小依次为：温度变化、裂缝间距、板厚、粘结刚度系数、钢筋直径、配筋间距.单因素单变量的回归分析，确定了温缩应力与各单个因素之间的大致关系.通过对各变量的假设组合分析，以单变量多因素的多元统计回归方法获得了一定精度的并能通过假设检验的拟合公式.误差分析表明，此公式的最大误差范围能控制在8%以内.     

Design of ecoregional monitoring in conservation areas of high-latitude ecosystems under contemporary climate change

Land ownership in Alaska includes a mosaic of federally managed units. Within its agency’s context, each unit has its own management strategy, authority, and resources of conservation concern, many of which are migratory animals. Though some units are geographically isolated, many are nevertheless linked by paths of abiotic and biotic flows, such as rivers, air masses, flyways, and terrestrial and aquatic migration routes. Furthermore, individual land units exist within the context of a larger landscape pattern of shifting conditions, requiring managers to understand at larger spatial scales the status and trends in the synchrony and spatial concurrence of species and associated suitable habitats. Results of these changes will determine the ability of Alaska lands to continue to: provide habitat for local and migratory species; absorb species whose ranges are shifting northward; and experience mitigation or exacerbation of climate change through positive and negative atmospheric feedbacks. We discuss the geographic and statutory contexts that influence development of ecological monitoring; argue for the inclusion of significant amounts of broad-scale monitoring; discuss the importance of defining clear programmatic and monitoring objectives; and draw from lessons learned from existing long-term, broad-scale monitoring programs to apply to the specific contexts relevant to high-latitude protected areas such as those in Alaska. Such areas are distinguished by their: marked seasonality; relatively large magnitudes of contemporary change in climatic parameters; and relative inaccessibility due to broad spatial extent, very low (or zero) road density, and steep and glaciated areas. For ecological monitoring to effectively support management decisions in high-latitude areas such as Alaska, a monitoring program ideally would be structured to address the actual spatial and temporal scales of relevant processes, rather than the artificial boundaries of individual land-management units. Heuristic models provide a means by which to integrate understanding of ecosystem structure, composition, and function, in the midst of numerous ecosystem drivers.     

Taxonomist survey biases and the unveiling of biodiversity patterns

Basic and applied studies based on biodiversity data need accurate information on the distribution of species. However, several studies clearly show that this information is frequently biased, mainly as a consequence of aggregated survey patterns in which taxonomists repeatedly select localities with specific characteristics. In this study, we have constructed three different but simple virtual species richness scenarios to simulate the capacity of random, aggregated or regular survey designs to reveal the true biodiversity pattern. We are specifically interested in the effect of taxonomist insistence on surveying those localities that guarantee success in the collection of as many species as possible (species richness bias), and on the coordinated or uncoordinated character of the efforts carried out by the whole community of taxonomists. In all simulated species richness scenarios, a survey directed towards those localities that were previously recognized as having a higher species richness value is not recommended if the aim is to recover the true geographical pattern of species richness in a given territory. This aggregated process of allocating survey localities is probably caused by the primary aim of taxonomists, which is to acquire specimens of rare species and/or as many species as possible. However, an increase in taxonomist curiosity towards non-surveyed localities near those previously identified as the richest allows one to obtain better results, provided that the species richness pattern is not too patchy and the effort for discovering the true map is not too difficult. Our results suggest that planned survey designs are necessary when most of the data comes from studies not specifically designed to reveal the distribution of biodiversity. The capacity of this data to represent the real geographical pattern of biodiversity may depend on the capacity of the taxonomist community to be self-motivated.     

On the use of multiple lattice designs and α-designs in plant breeding trials

Plant breeders in Germany often use multiple lattice designs to test a large number of entries that are to be directly compared for selection. Comparison among entries from different lattices is accommodated by the use of checks. While this design has some practical merits, it is statistically expected to be less efficient than alternative designs for a large number of entries. In this note a study is made of the gain in efficiency by using a single large α‐design in place of multiple lattices. The comparison for a number of settings shows that the efficiency gain in terms of sample size or variance may be appreciable. It is concluded that plant breeders should seriously consider using α‐designs in place of multiple lattices. A simple method is described which allows breeders to study the potential gain for their particular design. Practical considerations leading to a preference of multiple lattices are critically discussed.     

高压水射流清洗技术的探讨

高压水射流清洗技术在高压清洗机基础上，配套进给机构和三维旋转喷头，其垂直进给、倾斜、旋转和曲臂功能使得清洗效果更为理想。对于小直径容器及各类管道的内壁清洗则采用二维旋转喷头，可实现对管道内外壁的同步清洗。     

发酵法产氢培养基的响应面分析优化

借助于MINITAB软件,采用Plackett-Burman试验设计法及响应面法分析,对影响高效产氢菌Clostridium sp.Fanp2发酵产氢的培养基成分进行优化研究.首先利用Plackett Burman试验设计筛选出影响产氢的三个主要因素,即葡萄糖浓度、磷酸缓冲液浓度、和维生素液添加量.在此基础上用最陡爬坡路径逼近最大响应区域,再利用Box-Behnken试验设计及响应面分析法进行回归分析.结果表明,葡萄糖浓度、磷酸缓冲液浓度、和维生素液添加量与氢气产量存在显著的相关性,通过求解回归方程得到优化发酵条件:当葡萄糖浓度23.75 g/L,磷酸缓冲液浓度0.159 M和维生素液添加量13.3 ml/L时,氢气产量达到理论最大值4187.7 ml/L.经五批培养验证,预测值与验证试验平均值接近,在优化条件下微生物制氢产量提高85.3%.     

关于杉木双列杂交试验若干问题的探讨

利用杉木9×9半双列和杉木6×6全双列试验材料,并综合我国杉木配合力育种中所有的文献资料,进一步探讨了杉木双列杂交试验和配合力测定中应注意的若干问题.结果表明:(1)生长发育阶段及试验环境对控制杉木性状的加性遗传方差和非加性遗传方差比值没有质的影响;(2)在I类材料中,杉木的母本细胞质效应作用不明显,在II类材料中,在选择性状(生长性状)上,检测到显著的母本细胞质效应,但这不影响非加性遗传方差份量的主导作用;(3)交配设计类型的变化对杉木II类材料的性状基因作用方式的试验结果有明显的影响;(4)在控制子代性状的表达方面,母本的加性效应显著,父本的花粉效应不明显,但父本与母本互作效应极其明显.因此在杉木杂交育种中,可以评选出具有突出表现的杂交组合.     

基于机器视觉的水稻秧盘育秧智能补种装置设计与试验

对于工厂化育秧作业的水稻、蔬菜、花卉等,尤其是超级杂交稻,其机械化秧盘育秧播种的理想目标为2~3粒/穴,且普遍存在空穴和单粒穴的情况,为了保证秧盘育秧成秧率,提高精密播种合格率就显得非常重要。该文基于机器视觉技术,提出了一种智能补种方法,设计并研制了智能补种装置,主要用于超级杂交稻钵体秧盘育秧播种质量检测与补种过程。首先利用CCD摄像头采集秧盘图像,对图像处理与分析后得到空穴和1粒穴位置坐标,再利用定位机构和补种机构实现从种槽取种和对秧盘指定位置动态补种等功能。应用LabVIEW图形化编程软件,针对空穴和单粒穴的补种方案,开发出秧盘播种质量在线检测与补种运动控制系统,实现了智能补种任务。由试验结果统计可知,当补种率小于2%时,双补种器能够满足450盘/h的生产需求。