Compatibility of root growth and tuber production of potato cultivars with dynamic and static water‐saving irrigation managements

The important root characteristics of root length density (RLD) and root mass density (RMD) generally differ among irrigation managements and potato cultivars. The objective of this study was to investigate the RLD and RMD variations and their functional relationships with gross potato tuber yield for two commercial potato cultivars, Agria and Sante, under different irrigation strategies. Full irrigation and water‐saving irrigation strategies, deficit and partial root drying irrigations, were applied statically (S) and dynamically (D) based on daily crop evapotranspiration. Results showed that SPRD had significantly greater RLD (3.64 cm/cm³) and RMD (132.7 μg/cm³) than other irrigation treatments. Between the potato cultivars, Agria had significantly larger values of RLD (3.50 cm/cm³) and RMD (138.7 μg/cm³) than Sante. The functional relationship between the root growth characteristics and tuber yield showed that under water‐saving irrigations, Agria increased root mass at the expense of gross tuber yield but Sante increased root mass to maintain larger gross tuber yields. However, Agria produced more roots and gross tuber yield than Sante, and it is concluded that Agria is a more drought‐tolerant potato cultivar, which is recommended for tuber production in regions where water might be scarce. It was shown that larger root production in potatoes was associated with improved tolerance to water stress.     

Seasonal growth and diet of juvenile chinook salmon (Oncorhynchus tshawytscha) in demonstration channels and the main channel of the Waitaki River, New Zealand, 1982–1983

Abstract– Juvenile chinook salmon in the Waitaki River, New Zealand and demonstration channels, living at about 16°C, increased in length by 0.32 mm day⁻¹ between 4 November and 4 March. They gained weight quickly, accumulated large visceral fat deposits and had high conditions factors. At 1600 h, stomachs averaged half full. The number of prey tended to decline as the fish grew and consumed larger items. Initially the diet was based mainly on chironomid larvae, but by December it included a diversity of prey in more equal proportions. These included Deleatidium in the Waitaki; amphipods in the demonstration channels; various trichopterans, hemipterans, elmid beetles, zooplankton. terrestrial dipterans and a variety of other prey. There were significant differences between sites in numbers of prey consumed and these probably reflected differences in the benthos. Diets in the Waitaki differ from those in the Rakaia River and the food of juvenile salmon appears closely linked to the availability of a diverse range of possible prey.     

数量化理论Ⅲ在土地质量综合评价中的应用

木文对土地质量综合评价的方法进行了探讨,首次提出将数量化理论Ⅲ应用于土地质量分级。与目前使用的系统聚类、动态聚类方法相比,数量化理论Ⅲ更适合于变量类型为定性变量的土地资源调查资料的分类。它弥补了系统聚类方法和动态聚类方法在土地资源评价中应用的局限性,数量化理论Ⅲ是一种可用于土地质量分级的理想方法。     

西藏山南地区草地资源及其合理利用

由于对西藏山南地区草原状况缺乏全面认识，未能合理利用，出现了草原退化等一系列问题。为了合理开发利用草地资源，通过调查提出：调整畜群结构，推行草场有偿承包责任制，开展季节性畜牧业，建立草地农业生态系统等建议。     

潜江小城镇景观规划

潜江小城镇的水资源丰富但开发落后，绿系统不完善，街景缺乏工艺性。在对现状调查分析的基础上，提出了对过境公路、水体、街景进行动感空间、情感空间规划的建议，对乡土化设计、恢复性设计进行了探讨。     

永丰草地的类型及其生产力评估

本文描述了甘肃省天祝县永丰草地的主要草地类型、生产能力及利用模式。研究工作显示,草地改良措施,对不同植被的生物量分布,将产生显著的效果。灌溉和施肥,将促进河谷草甸的地下生物量向地上生物量的转化过程。灌溉可使河谷草甸中禾草组分的增加超过50％,使产草量增加50％～100％。上年秋天和当年春天土壤的含水量,是全年产草量的决定因素,其对产草量的重要性超过全年平均降水量的影响。除了植被组分、产草量的变化外,河谷草地在可消化粗蛋白、可消化能、代谢能等方面也有重大变化,9月份与4月份相比,这三项指标分别高出376％、86％和86％。不同年龄组的绵羊饲料消耗显示,7岁羊的饲料消耗是10月龄羊的17倍;但是7岁羊的胴体重量仅是10月龄羊的2倍。根据永丰滩草地、饲草、家畜的这些特点,当地的畜牧业,不应当在毫无经济意义的情况下,保持太多的牲畜头数,优化畜产品生产的最好方法,就是实行季节畜牧业。季节畜牧业(其中繁殖母羊数达67％)与其他草地改良措施相结合,将使该地区单位面积上的绵羊的产肉量提高4.9倍。     

CVT起步离合器模糊控制算法研究

探讨了汽车无级变速器控制的关键技术之一———汽车起步离合器的控制技术,并针对汽车起步时条件的多样性以及驾驶员意图的不确定性,研究了适用于复杂条件的模糊控制算法.在离合器的滑磨阶段,把动态跟踪发动机转速的油压作为控制目标,离合器结合的控制便转化为一闭环控制.结果表明汽车能在任意工况下平顺快速起步.因此,本研究为控制CVT(Continuously Variable Transmission)起步离合器这种时变、非线性系统提出了一种简单可行的解决方法.     

羊草＋杂类草群落生物量动态模式的研究

对黑龙江肇州县羊草＋杂类草群落地上生物量的季节动态、地下生物量的分布以及地上生物量与降雨量、温度之间的关系进行了分析．结果表明，在生长季内，群落地上生物量动态模式呈单峰型，符合四次多项式模型增长，最大地上生物量出现在８月５日，其值为１９７．３ｍ２而后下降；群落地下生物量分布由上至下呈负幂函数变化，其模型为：Ｂｕ＝Ｙ·（Ｄ＋１０）－ｘ．其中在０－３０ｃｍ土层中，群落地下生物量占总地下生物量的７７％～８２％．     

人工种植沙拐枣生长发育特性及营养动态的研究

沙拐枣属蓼科沙拐枣属多年生灌木，主要分布在我国的西北地区,本文就沙拐枣人工种植后的出苗状况，生长发育特性及不同生育期营养成分变化动态等进行了研究，为我国西部大开发生态治理工程中沙拐枣的大面积推广种植提供了指导。     

具粘弹性支承的柔轴弹性盘转子系统的动力学分析

讨论了柔轴弹性圆盘转子系统在粘弹性支承下的临界转速和动力稳定性问题，轴和支承具有不对称的阻尼系数和刚度系数，利用能量法和耗散系统的Lagrange方程推导了系统的运动微分主程，阐述了求解方法，大多数的不稳定区出现在不平衡共振附近，通常可以通过调整轴、支承的阻尼和刚度系数的恰当组合来减小不稳定区域。