渔药自动喷施机的改进设计

为了提高喷施精度、渔药原液利用率、行进速度及转向灵活性,针对渔药喷施机的混药装置及喷施装置做了改进设计,并对改进后的混药装置和喷施装置的结构及工作原理进行了说明。其中,混药装置应用了比例施肥器进行在线混药稀释,稀释后的渔药和经过导向管的水将再次混合并从导向管末端喷出,达到混药和提供动力的目的。而喷施装置则需要配合混药装置一起使用,利用从导向管末端喷出的稀释药液与尾管的左右摆动来转向。改进的渔药喷施机平均行驶速度比原来提高了82.5%,且还可以实现原地转向。     

乙草胺采用药砂法防除玉米地杂草的效果

[目的]探讨芽前土壤处理除草剂采用药砂法防除玉米地杂草的使用技术。[方法]通过小区试验研究芽前土壤处理除草剂乙草胺采用药砂法防除玉米地杂草的效果。[结果]芽前乙草胺采用药砂法防除玉米地杂草,不仅具有同常规药液喷雾封闭法相同的防除效果,而且还具有工作效率高、使用成本低、对玉米安全、操作劳动强度低等特点,药砂法选用的干燥粗砂直径为0.2~0.3 mm,粗砂使用量以30 kg/hm2为宜。[结论]该技术是适合农村留守老人操作的新技术。     

不同生态区域沙地建群种油蒿的钙组分特征

为探索同一物种在不同生态区域钙组分特征的差异,选择我国北方沙地重要建群种油蒿(Artemisia ordosica)为研究对象,采集了内蒙古杭锦旗、乌审旗、阿拉善左旗以及宁夏盐池县和陕西榆林市榆阳区不同沙地类型、不同生长阶段的油蒿样品,利用连续组分法测定分析了油蒿的钙组分特征.结果表明,在油蒿的不同器官中,叶水溶性钙和醋酸溶性钙均显著高于枝和根,叶与根盐酸溶性钙均显著高于枝.在不同生态区域,降水量较多的地区油蒿体内水溶性钙含量较多,降水量较少的地区油蒿体内盐酸溶性钙含量较高.分析得知,降水条件较好的地区较高的水溶性钙主要体现在油蒿的叶中,而降水条件较差的地区较高的盐酸溶性钙主要体现在油蒿的叶和根中.油蒿在不同生长阶段钙组分没有显著差异,但不同类型沙地上油蒿的钙组分却有显著差异.可见,不同生态区域的油蒿,生境条件越好体内水溶性钙含量越高,生境条件越差体内盐酸溶性钙含量越高.     

低覆盖度行带式固沙林对土壤及植被的修复效应

在我国干旱、半干旱地区由于水分条件的制约,经过漫长的自然演替过程,逐步发育形成了广泛分布的低覆盖度植被,这些低覆盖度植被类型中存在大量的天然乔木疏林或稀疏灌丛,地表处于半流动状态,而配置成行带式后,能够完全固定流沙,并且不同配置模式下行带式固沙林土壤与植被自然恢复程度不同.因此,通过对不同带宽的低覆盖度行带式固沙林对土壤及植被修复的影响研究,揭示了不同带宽行带式固沙林带间土壤因子与植被因子的变化过程,从而阐明行带式固沙林对带间植被自然恢复和土壤发育的促进作用.结果表明,行带式杨树固沙林能够明显的促进带间土壤与植被修复;带间距离的宽窄影响植被恢复及土壤发育效果;宽带间距固沙林带间植被多样性指数高,地上生物量大,根系生物量,总长度及表面积均高,土壤水分养分条件好,微生物数量大植物残体分解快,有利于植被的生长;模糊综合评估结果表明,不同带间距行带式固沙林土壤植被恢复程度不同,宽带间距20m的恢复效果＞带间距15m＞带间距10m.行带式固沙林通过带间宽度的变化可以调节植被与土壤之间的相互作用,窄带间距固沙林土壤与植被的相互作用则由于造林密度大而受到抑制.宽带间距可以明显加快土壤及植被修复的速度,进而缩短土壤及植被修复的时间.     

Study on separation algorithm of convolutive mixing model and separation of mixing signals of multiple partial discharges

To identify individual partial discharges(PD)signals produced by multiple insulation defects in gas insolated switchgear (GIS),this paper analyses the mechanism of propagation and mixing of multiple PD electromagnetic wave signals in GIS cylinder and proposes the convolutive mixing model to describe it for a separation algorithm to acquire individual PD signals. With the non-stationary property,mixing PD signals are changed at time domain into a set consisting of short-time stationary PD signals and then the Molgedey-Schuster decorrelation approach is employed to separate these stationary PD signals at frequency domain. The correlation of the envelope of separated PD signals in this set is used to reconstruct PD signals to realize the separation of non-stationary UHF PD mixtures. The effective separation of actual UHF PD mixing signals validates the assumption of convolutive mixing process in GIS and also offers a new approach to the identification of mixing PD signals by external ultra-high frequency detection scheme from multiple insulation defects in GIS.     

Amending a loamy sand with three compost types: impact on soil quality

The objective of this study was to investigate the effects of the long‐term addition of three compost types (vegetable, fruit and yard waste compost – VFYW, garden waste compost – GW and spent mushroom compost – SM) on the physical properties of a sandy soil and to quantify any such effects using indicators of soil physical quality. Soil samples were taken from a field with annual compost applications of 30 m³/ha for 10 yr and various physico‐chemical analyses were undertaken. Results show a significant increase in soil organic carbon (21%) with the VFYW and GW compost types. With SM, soil organic carbon increased by 16%. Increased soil macroporosity and water content at saturation with a corresponding decrease in bulk density were observed for all compost types. However, quantification of these improvements using existing soil physical quality indicators such as the ‘S‐index’, soil air capacity and matrix porosity gave mixed results showing that these indices perform poorly when applied to sandy soils. It is concluded that the long‐term application of compost does not significantly improve the physical properties of sandy soils, but the absence of adverse effects suggests that these soils are a viable disposal option for these composts, but new indices of quality are needed for the proper characterization of sandy soils.     

外植体取样时间对沙子空心李诱导培养的影响

【目的】研究取样时间对沙子空心李诱导培养的影响,为沙子空心李组织培养技术提供理论依据。【方法】以不同时间段的沙子空心李半木质化茎段为外植体,经过2种消毒方式后进行诱导培养。【结果】结果表明,使用0.1%HgCl₂进行消毒时,污染率最低,随着外植体取样时间的推移,诱导死亡率逐渐降低,4月25日取外植体时,死亡率与死亡率最低,成活率最高,分别为4%、10%和86%,与2%NaClO消毒效果无明显差异,但其余3次取样时,2种消毒剂的消毒效果差异明显,且0.1%HgCl₂明显优于2%NaClO。【结论】沙子空心李的适宜消毒方式是D2：75%酒精消毒10 s+0.1%HgCl₂消毒5min；诱导组培的外植体适宜取样时间是4月下旬。     

Effects of temperature and light on seed germination of ephemeral plants in the Gurbantunggut Desert,China: implications for vegetation restoration

Seed germination is a key transitional stage in plant life cycle and is strongly regulated by temperature and light. Therefore, research on the effects of temperature and light on seed germination is extremely meaningful for vegetation restoration, especially in desert ecosystems. Seeds of 28 ephemeral plants collected from the Gurbantunggut Desert of China were incubated at different temperatures (5°C/1°C, 15°C/5°C, 20°C/5°C, 25°C/10°C and 30°C/15°C) in 12-h light/12-h darkness or continuous darkness regimes, and the responses of seed germination to temperature and light and the germination speed were studied in 2016. Results showed that seed germination percentage of the 28 ephemeral plants significantly differed to temperature and light. We classified the studied plants as the following groups based on their responses to temperature: 1 low temperature responsed plants, 12 moderate temperature responsed plants, 7 high temperature responsed plants, 4 non-responsed plants and 5 plants of no germination. It should be noted that Corispermum lehmannianum Bunge is sensitive to both moderate and high temperatures. There were 4 groups of plant in response to light, i.e., 7 light responsed plants, 10 dark responsed plants, 6 light non-responsed plants and 5 plants of no germination. Based on seed germination speed of the 28 ephemeral plants, we divided them into 4 patterns of germination, i.e., very rapid, moderately rapid, moderate and slow. Combining variations of temperature, precipitation and sand dune types in the study area, we suggested that very rapid and moderately rapid germinated plants could be used to moving sand dunes in early spring during vegetation restoration, moderate germinated plants could be used to semi-fixed sand dunes in late autumn, and slow germinated plants could be used to sand plain in summer. Thus, seedling establishment and vegetation restoration would be improved by considering seed germination characteristics of these ephemeral plants in the Gurbantunggut Desert, China.     

设施蔬菜固液混合水肥管理系统建设实践及思考

针对北京市设施蔬菜生产园区对水肥管理装备技术的需求,引进建设了固液混合水肥管理系统,实现了水肥管理调控的自动化、数据化和精准化,提高了园区劳动生产效率,实际应用中每年每667 m2设施蔬菜可提高经济效益2066元。并结合系统建设实践,从水源设计、防冻设计和系统维修维护服务等建设要点方面提供了建议。     

Stable oxygen-hydrogen isotopes reveal water use strategies of Tamarix taklamakanensis in the Taklimakan Desert,China

Tamarix taklamakanensis,a dominant species in the Taklimakan Desert of China,plays a crucial role in stabilizing sand dunes and maintaining regional ecosystem stability.This study aimed to determine the water use strategies of T.taklamakanensis in the Taklimakan Desert under a falling groundwater depth.Four typical T.taklamakanensis nabkha habitats(sandy desert of Tazhong site,saline desert-alluvial plain of Qiemo site,desert-oasis ecotone of Qira site and desert-oasis ecotone of Aral site)were selected with different climate,soil,groundwater and plant cover conditions.Stable isotope values of hydrogen and oxygen were measured for plant xylem water,soil water(soil depths within 0–500 cm),snowmelt water and groundwater in the different habitats.Four potential water sources for T.taklamakanensis,defined as shallow,middle and deep soil water,as well as groundwater,were investigated using a Bayesian isotope mixing model.It was found that groundwater in the Taklimakan Desert was not completely recharged by precipitation,but through the river runoff from snowmelt water in the nearby mountain ranges.The surface soil water content was quickly depleted by strong evaporation,groundwater depth was relatively shallow and the height of T.taklamakanensis nabkha was relatively low,thus T.taklamakanensis primarily utilized the middle(23%±1%)and deep(31%±5%)soil water and groundwater(36%±2%)within the sandy desert habitat.T.taklamakanensis mainly used the deep soil water(55%±4%)and a small amount of groundwater(25%±2%)within the saline desert-alluvial plain habitat,where the soil water content was relatively high and the groundwater depth was shallow.In contrast,within the desert-oasis ecotone in the Qira and Aral sites,T.taklamakanensis primarily utilized the deep soil water(35%±1%and 38%±2%,respectively)and may also use groundwater because the height of T.taklamakanensis nabkha was relatively high in these habitats and the soil water content was relatively low,which is associated with the reduced groundwater depth due to excessive water resource exploitation and utilization by surrounding cities.Consequently,T.taklamakanensis showed distinct water use strategies among the different habitats and primarily depended on the relatively stable water sources(deep soil water and groundwater),reflecting its adaptations to the different habitats in the arid desert environment.These findings improve our understanding on determining the water sources and water use strategies of T.taklamakanensis in the Taklimakan Desert.