北方常用草坪草的蒸散量差异及耗水性评价

对不同供水条件下,草地早熟禾、高羊茅、多年生黑麦草、野牛草、结缕草和狗牙根整个生长季的蒸散量差异进行研究。结果表明,草坪蒸散主要与草坪本身的生物学特性有关,同时与水分条件也密切相关。另外,根据测定结果估测了理论补水量,并通过计算坪草系数Kc,与北方常用作物的耗水量进行了比较。

北京地区几个造林树种耗水性比较研究

利用热扩散式边材液流探针于 2 0 0 0— 2 0 0 1年 ,在北京西山地区北京林业大学教学实习林场对油松、侧柏、刺槐、栾树、臭椿和君迁子等树种的蒸腾耗水性进行了对比研究 .结果发现 ,树种之间在耗水量、耗水节律、耗水生态对策 ,以及耗水的调节机制方面存在很大差异 .其中 ,树木的叶片蒸腾速率、树干木质部边材宽度、边材导管分布与形态特征、根系空间分布特征等因素对单木耗水量均有不同程度影响 .通过比较发现 ,油松液流通量显著大于侧柏 ;刺槐、栾树、臭椿和君迁子 4个树种中栾树单木耗水速率最高 ,其次是臭椿 ,刺槐和君迁子最低 .

水分胁迫对3个藤本树种蒸腾耗水性的影响

生长季节对水分胁迫条件下2年生盆栽常春藤、扶芳藤、小叶扶芳藤3个藤本树种的土壤水分状况、蒸腾速率及叶片水势等生理生态指标日变化进行了连续测定,以弄清水分胁迫对各树种蒸腾耗水特性的影响。研究表明,扶芳藤具有土壤水势、土壤容积、含水量最低,蒸腾速率却最大的特性,是最耗水的树种;小叶扶芳腾耗水特性表现为土壤水势和土壤容积含水量最高,蒸腾速率最低,是最不耗水的树种;常春藤介于这两者之间。相关性分析表明,这3个树种的蒸腾速率与气孔导度呈显著正相关,与土壤水势或土壤含水量、叶片水势有一定的相关性,与环境因子相关性不明显。

北京15种园林树木耗水性的比较研究

采用盆栽称重法对北京丁香等15种园林树木的蒸腾耗水量进行观测,结果表明,在相似的环境平台下：单位叶面积的年均日耗水量榆叶梅最大,为1990.5 g/m^2,黄栌最小,为291.4 g/m^2,榆叶梅、栾树、金丝柳、元宝枫、西府海棠为高耗水树种,年均日耗水量大于1000 g/m^2,黄栌、铺地柏、金叶女贞为低耗水树种,年均日耗水量低于500 g/m^2,北京丁香、大叶黄杨、棣棠、北京桧、油松、白皮松、侧柏为中等耗水树种,年均日耗水量500～1000 g/m^2;15种树木耗水的季节差异明显,元宝枫属于春季耗水型,金丝柳、大叶黄杨、金叶女贞、棣棠、白皮松、油松、铺地柏、侧柏属于夏季耗水型,北京丁香属于秋季耗水型,西府海棠属于夏秋耗水型,栾树、榆叶梅、黄栌、北京桧属于均衡耗水型.研究结果可为北京城市绿化低耗水树种选择、绿地结构合理配置提供依据.

林木耗水性研究述评

系统阐述了林木耗水研究的意义 ,介绍了林木耗水的概念 ,辨析了现实耗水性与潜在耗水性的区别及其应用条件 ,探讨了林木耗水与水分利用的含义 ,综述了林木耗水研究的方法 。

利用热扩式边材液流探针(TDP)测定树木整株蒸腾耗水量的研究

介绍了热扩散式液流探针的工作原理及利用液流探针测定树木边材液流速率的方法。利用边材液流探针和多种气象因子传感器及数据采集系统组成的微型气象站 ,通过对北京西山地区油松 (Pinustabulaeformis)、栓皮栎 (Quercusvariabilis)混交林林分平均木树干边材液流速率及风速、有效辐射和空气温度、空气相对湿度的日变化和连日变化的测定和分析 ,揭示了 5月干旱季节两树种蒸腾耗水的日变化和连日变化规律 ,以及栓皮栎树干基部和树冠大枝边材液流的差异 ,并进行了理论推导 ,同时分析了液流速率的波动规律与主要气象因素波动的相关性。

巨桉与5种木本植物幼树的耗水特性及水分利用效率的比较

巨桉因生长迅速且经济效益高,在我国南方被广泛用于营造短周期工业原料林,但其蒸腾耗水状况与其他常见或乡土树种存在怎样的差异,大面积种植是否会改变栽培区原有的水分平衡,是一个尚未明确的问题。利用LI-6400光合作用仪测定了巨桉与其他5种木本植物在不同光强、温度、湿度下的净光合速率(Pn)、蒸腾速率(Tr)和水分利用效率(WUE),用称重法测定了参试植物载叶量、生物量和耗水量,并对这些树种的蒸腾耗水特性进行了评价。结果表明:(1)相同环境条件下,巨桉的Tr最大,WUE最低,单位质量耗水量最多,单株蒸腾耗水量远高于其他树种,其明显较大的叶面积可能是重要原因之一,虽然其Pn仅次于杨树,生物量积累最大,因此为高光合、高蒸腾、低水分利用效率植物。(2)阔叶树种的Pn和Tr明显高于针叶树种,而WUE低于针叶树种。(3)环境因子(光照强度、温度和湿度)对植物Pn、Tr和WUE的影响较大,其中Pn主要受光照强度影响,Tr对湿度最为敏感,一般情况下WUE随湿度的增大而升高。在试验设置的温度范围(24—32℃)内,光合作用变化幅度不大。光照强度800μmol.m-.2s-1和温度28℃最有利于参试植物的光合作用。(4)巨桉等速生树种较强的光合作用使其生长迅速,固碳潜力大,但其高蒸腾和低水分利用效率的特点意味着在栽培区替代原有植被进行大规模造林时,可能会消耗更多的水资源而对生态环境造成一定的不利影响,因此在发展巨桉人工林时应选择水分条件好的区域(尤其是年降雨量充沛且季节间分配相对均匀的地区),并进行科学的经营管理。

玉米的耗水特性及节水增产栽培措施

玉米是黑河地区的主要粮食作物,露地种植和覆膜种植是其主要栽培方式。由于受水资源及其时空差异的限制,玉米的“卡脖子”旱时有发生,加上不合理的灌溉,使水资源不足的矛盾更加突出,从而导致玉米产量降低和种植面积缩小。因此,研究玉米露地和覆膜条件下的节水增产栽培技术,实行科学灌溉,具有重要的意义。为此,本文在对黑河地区玉米耗水特性分析研究的基础上,选用灌溉定额及其各次分配量、灌水次数。

晋北黍子耗水特性及水分利用率的研究

在降雨多、中、少年份,研究黍子不同生育期耗水特性及不同深度土壤水分变化规律表明,黍子耗水高峰期在抽穗至灌浆期,整个生育期需耗水251.8～262.8毫米;在降雨多、中年份,黍子仅利用0～60厘米土层有效水的10～15％;在干旱年份,利用有效水深达180厘米,0～60厘米土层有效水利用率达50％以上;在降雨中等以上年份,亩产低于200公斤的情况下,肥是限制产量的主要因素;在干旱年份或要求进一步提高作物产量,水将成为限制因素。

论黄土丘陵区造林树种选择的原则

从黄土丘陵区自然和社会经济条件出发 ,提出该地区在实行退耕还林、实现生态环境重建的过程中 ,在造林树种选择上应遵循的抗旱性、低耗水性。

植被作用下的土壤干化及其发生机制探讨

通过分析黄土高原不同类型植被下的土壤水分状况,探讨了植被作用下土壤干化的特征和机制,以正确认识其实质,并提供可调控的依据。结果表明,植被作用下的土壤干化具有相对稳定性,其数量指标可采用田间稳定湿度值衡量。在黄土高原气候及地质条件下,土壤干化是植被作用下易于发生的现象,但它并不是植被建造的必然结果。人为营造大片耗水性强的植被类型,高密度以及追求高生产量,是其发生的关键因素。通过了解人工林草物种特点的二重性、合理配置群落结构的必要性以及人工与天然起源的植被在植物竞争效应方面的差异,可对其实施有效管理。植被下土壤干化的普遍发生,不应当妨碍黄土高原进一步开展林草植被建设。

Effects of Irrigation Quantity and Term on Waterconsumption and Yield of Winter Wheat by Wide Precision Sowing

[Objective] The aim was to research effects of irrigation quantity and term on winter wheat by wide precision sowing and to provide references and technical supports for water-saving agriculture in North China. [Methed] During 2013-2015, Jimai 22, a winter wheat cultivar, was taken as materials to explore effects of irrigation quantity and term on water consumption characters and yield of winter wheat by wide precision sowing. [Result] As irrigation water increased, water consumption and irrigation water＇s proportions were growing, but quantity and proportion of soil water consumption were both diminishing; seed yields all kept increasing upon irrigation, but water use efficiencies were decreasing. Given the same irrigation conditions, water consumption by wide precision sowing was more, but yield and water use efficiency were higher. [Conclusion] The practice of combining wide precision sowing and irrigation in jointing and flowering stages, based on yield, water use efficiency and economic profits, has the potential to create more yields and higher water use efficiency and suitable to be applied and promtoed in North China.

Effects of Planting and Irrigation Patterns on Water Consumption Characteristics and Dry Matter Production in Winter Wheat

[Objective] This study aimed to investigate the effects of different planting and irrigation patterns on water consumption characteristics and dry matter produc- tion and allocation of winter wheat. [Method] With high-yield winter wheat cultivar Jimai 22 as the experimental material, field experiment was conducted during 2008- 2010. A total of 3 planting patterns were designed, uniform row, wide-narrow row and furrow. Under each planting pattern, total four irrigation patterns were designed, no irrigation （Wo）, irrigation at jointing state （Wl）, irrigation at jointing and anthesis stages （W2） and irrigation at jointing, anthesis and milking stages （W3）, and the irri- gation amount per treatment was all 60 mm. [Result] Under the three planting pat- terns, with the increased irrigation amount, the total water consumption of the exper- imental field increased; the proportion of irrigation in the total water consumption in- creased, and that of soil water consumption in the total water consumption de- creased significantly. Compared with W0 treatment, various irrigation treatments sig- nificantly increased the post-anthesis dry matter accumulation in wheat plants; with the increased irrigation amount, the grain yield under the three planting patterns all increased, while the water use efficiency （WUE） decreased. Under the same irriga- tion conditions, compared with other two planting patterns, furrow planting increased the total water consumption of the experimental field, increased the proportion of soil water consumption in the total water consumption, and improved the WUE and wheat grain yield. [Conclusion] Under the experimental conditions, considering both wheat grain yield and WUE, furrow planting with moderately deficit irrigation at joint- ing and anthesis stages is more suitable for the winter wheat production in North China Plain.

Effect of Irrigation and Rainfall on Water Consumption Characteristics and Yield of High Yield Highland Barley in Tibet River Valley

This paper was to study the effect of irrigation and rainfall on water consumption characteristics and yield of high yield highland barley in Tibet river valley.In pots, highland barley-25 of Tibet was used as the test material to provide eight water stress treatments： normal water, slight water stress, middle water stress, and severe water stress in two environmental conditions（the whole growth period water stress and the rainwater irrigation after filling stage）. Test results indicated that water consumption increased with soil water rise. The maximum consumption of water was at the joining stage and filling stage. And then, the results showed that under rainwater irrigation treatment, the more the soil moisture was, the more the water consumption was. The water stress in whole highland barely growth period reduced biomass and yield. Compared with that of normal water treatment, biomass of slight water stress, middle water stress and severe water stress treatment was decreased by 29.9%, 41.7% and 47.6%, respectively, and yield of the three treatments was decreased by 15.8%, 43.7% and 57.2%, respectively. But rainfall after filling stage was beneficial to biomass and yield of highland barely. Compared with water stress on whole growth period, the biomass and yield of rainfall treatments after the filling stage were increased by 13%, 75.8%, 128.1%, 157.8% and 42.8%, 84%, 201.6%,and 269.5%. The results indicated that biomass and yield of rainwater irrigation after the filling stage had compensatory effect for highland barley growth under water stress, and could improve the water use efficiency. Therefore, properly rainwater usage is beneficial to the increase of yield and water use efficiency of Tibet highland barley-25 under water stress.

Validation of the Monte Carlo Model Designed to Simulate the Neutronic Characteristics of Advanced Boiling Water Reactor Assembly

In the last few years, interest in burnup calculations using Monte Carlo methods has increased. Previous burnup codes have used diffusion theory for the neutronic portion of the codes. Diffusion theory works well for most reactors. However, diffusion theory does not produce accurate results in burnup problems that include strong absorbers or large voids. MCNPX code based on Mont Carlo Method, is used to design a three dimensional model for a BWR fuel assembly in a typical operating temperature and pressure conditions. A test case was compared with a benchmark problem and good agreement was found. The model is used to calculate the distribution of pin by pin power and flux inside the assembly. The effect of axial variation of water （coolant） density, and of control rods motion on the neutron flux and power distribution is analyzed. The effect of addition of Gd2O3 to natural uranium （0.711%） on both the thermal neutron flux and normalized power are analyzed. The concentration of U^235, U^238, Pu^239, and its isotopes is also calculated at burn-up 50 GWD/T.

Parameter Test and Analysis for Dynamic Compensation Devices in Wind Power Farms

The dynamic reactive power compensation equipment in Jiuquan Wind Power Base of above 10 GW consists of three different types of compensation devices, including： static var generator （SVG）, thyristor controlled compensator （TGR） and magnetically controlled reactor （MGR）. The lack of experimental verification of performance is not conducive to voltage/var management or full utilization of device capaci- ties. In order to solve the above problems, the compensation device performance test was performed. The test items and procedures were selected based on related national standards with the consideration for different grid structures and wind farm operation modes. The testing contents included dynamic regulating range, active power loss, dynamic response time, and harmonic voltage level. Three types of compensation devices installed in different wind farms, namely SVG, TCR and MCR, were chosen and tested. The performances were compared and analyzed according to the field test results.

Distribution optimization of circulating water in air-cooled heat exchangers for a typical indirect dry cooling system on the basis of entransy dissipation

The flow and heat transfer of air-cooled heat exchangers play important roles in the performance of indirect dry cooling systems in power plants,so it is of benefit to the design and operation of a typical indirect dry cooling system to optimize the thermo-flow characteristics of air-cooled heat exchangers.The entransy dissipation method is applied to the performance optimization of air-cooled heat exchangers in this paper.Two irreversible heat transfer processes in air-cooled heat exchangers,the heat transfer between circulating water and cooling air and the mixing of circulating water,are taken into account and analyzed by means of the entransy dissipation method.The total entransy dissipation rate,which connects the geometrical parameters of air-cooled heat exchanger sectors and the heat capacity rates of the fluids to the heat flow rate in every sector,is obtained.Based on the mathematical relation and the conditional extremum method,an optimization equation group is derived,by which the air-cooled heat exchanger with known air-side parameters is optimized,showing that the entransy dissipation based optimization approach can contribute to the distribution optimization of circulating water in air-cooled heat exchangers of a typical indirect dry cooling system.