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81.
82.
应用热扩散式树干茎流计(TDP)对辽宁省章古台樟子松人工固沙林生长季期间树干液流速率进行了连续5年的测定,结合同步观测的降水、林冠截留量、林内蒸发散量和土壤水分含量,利用水量平衡的方法,推算了现阶段樟子松应有的合理密度。结果表明:4月上中旬沙地樟子松液流启动,10月中下旬液流基本结束,生长季(4-10月)各月平均液流速率分别为2.58、4.78、5.19、5.01、4.84、4.30、1.93 cm·h-1,以6月份的最高,其次依次为7、8、5、9月份,4、10两月平均液流速率较低。通过推算,径阶14、16、18、20 cm的樟子松纯林的合理密度分别应为688、531、422、344株·hm-2,现有同径阶的林分普遍存在密度过大的问题。研究结果对于现有林分的科学经营具有重要的指导意义。 相似文献
83.
气力输送技术可在很大程度对农业机械进行结构简化,降低成本和提高作业效率,越来越多地被用于播种、施肥和捡拾收获等物料输送装置中。了解气力输送技术的特性以及在农业机械中的应用现状,对于提高农机作业效率、促进先进农业机械化技术研发具有重要意义。为此,在农业物料气力输送特性、气力输送技术在农机领域的应用情况等方面进行大量文献调研分析和归纳总结。根据正负压输送的不同特点,对气力播种、施肥、收获捡拾机械装备的主要结构、工作原理和特点进行分析和阐述。在此基础上,指出农业领域气力输送应用和研究中存在的问题,包括:气力输送方式存在易堵塞、精度稍低的问题,能耗较大的问题以及相关基础研究不足的问题。针对以上存在的问题,提出针对性的建议:优化结构、配套监测系统,提高工作可靠性;改用效率较高的智能风机,降低能耗;加强基础研究,充分利用仿真等研究手段,进一步促进气力输送技术的应用。 相似文献
84.
Mao Mori Kohei Mizobata Taro Ichii Philippe Ziegler Takehiro Okuda 《Fisheries Oceanography》2022,31(1):19-39
The Antarctic toothfish (Dissostichus mawsoni) is an important fishery species widely distributed in the Southern Ocean, especially in areas covered by sea ice. Understanding fish distributions and life cycles, including the transport and survival of eggs and larvae, is essential for the assessment and sustainable management of the fishery. However, owing to difficulties with in situ winter observations, information on the early life stages of D. mawsoni is lacking. Here, we investigated the transport pathways of fish eggs and larvae through a particle tracking study, using satellite-derived ocean surface velocities in the East Antarctic region, which includes important D. mawsoni habitats and exploratory fisheries. Our results indicate that particles released from continental slopes are more likely to be successfully transported to suitable settlement grounds than those released from the BANZARE Bank (the southern region of the Kerguelen Plateau), which is situated further north and has been hypothesized to be a potential spawning ground for D. mawsoni. This study demonstrates successful source–settlement connections in relation to ocean recirculation and suggests important settlement regions for D. mawsoni larvae in the East Antarctic region. 相似文献
85.
王利盈 《甘肃农业大学学报》2014,(5)
为了解近几十年来云南省日照时数和风速的变化规律,利用云南省1960~2010年29个台站日照时数和风速的月值数据,采用线性倾向估计、Mann-Kendall突变检验等统计方法,分析了其年代际、年际、季和月的变化特征.结果表明:1960~2010年云南省日照时数和风速都分别以-16.8h/10a和-0.037(m·s-1)/10a的速率呈显著减少趋势;日照时数和风速年际和年代际变化幅度都较大,日照峰值(60年代)与谷值(90年代)相差92.0h,风速峰值(70年代)与谷值(90年代)相差0.32m/s;日照时数和风速各个季节都呈下降变化,但也有明显的季节差异,日照时数各季节变化幅度大小为冬季>春季>夏季>秋季,风速各季节变化幅度大小为春季>冬季>夏季>秋季.日照时数和风速各月变化以减少趋势为主,其中日照时数7月减少最多,风速3月下降最多.年日照时数在1981发生由多到少的明显突变,而风速突变不明显. 相似文献
86.
87.
研究了黄鳝在不同温度、不同体重下的摄食速度,得到在17~20℃范围内,3组不同体重的黄鳝关于摄食速度与温度关系的回归方程:V=e^aT^b。由此可看出:在一定温度范围内,摄食速度随温度的上升而增大.而相对摄食速度随体重的增大而减小。根据回归方程还可推测不同温度、不同体重下黄鳝的摄食量。 相似文献
88.
A Brett-type respirometer was used to measure the effect of water pH on swimming performance of rainbow trout (Salmo gairdneri). Variations in water pH between 6 and 9 had no measurable effect on maximum aerobic swimming speed. At water pH 4, 5, and 10, however, the critical velocity was only 55, 67, and 61% respectively of that recorded for fish in water of pH 7. Exposure to acid conditions increased coughing and breathing frequency. Acid exposure resulted in a decrease whereas alkaline exposure resulted in an increase in both whole blood and red blood cell pH. Blood gas and acid-base characteristics showed little change during swimming at 2.0 BL/second, but exhaustive swimming resulted in a marked and immediate drop in blood pH in fish in acid, alkaline and neutral water. The blood acid-base status was restored to resting levels after exercise in neutral and alkaline water, but the acidosis was maintained following exercise in acid water. Fatigue occurred earlier and blood lactate levels increased to a higher level in fish swum to exhaustion in acid or alkaline water, compared with fish in neutral water. 相似文献
89.
Characterization of acetylcholinesterase and its molecular forms in organs of five freshwater teleosts 总被引:1,自引:0,他引:1
J. Ferenczy T. Szegletes T. Bálint M. Ábrahám J. Nemcsók 《Fish physiology and biochemistry》1997,16(6):515-529
The activity and molecular forms of acetylcholinesterase (AChE, EC 3.1.1.7) were characterized in the brain, heart, white skeletal muscle and liver of the Siberian sturgeon (Acipenser baeri), European eel (Anguilla anguilla), wels (Silurus glanis), common carp (Cyprinus carpio) and silver carp (Hypophthalmichthys molitrix), belonging in four families. The brain had the highest (between 183.2±10.6 and 1361.2±189.7 mU mg-1 protein and between 4.7±0.4 and 23.5±2.7 U g-1 wet tissue) and the liver the lowest (between 25.3±1.9 and 126.5±22.7 mU mg-1 protein and between 1.0±0.1 and 4.5±0.5 U g-1 wet tissue) activity in all these fish, with the exception of the wels, where the heart contained the smallest amount of AChE (26.2±7.5 mU mg-1 protein and 1.2±0.3 U g-1 wet tissue). The highest tissue AChE activity was found in the carp and lowest in the sturgeon. The solubility properties and molecular forms of AChE in the four tissues were studied by extraction in high-salt medium (1.0 M NaCl) with and without the detergent Triton X-100 (0.5%, v/v). The proportions of detergent-soluble (DS) and salt-soluble (SS) forms of AChE varied considerably from one species to another, but a general tendency could be observed: the proportion of DS AChE was generally higher in the brain (between 70.4±4.1 and 82.5±1.2%) and lower in the heart (between 12.0±2.0 and 51.3±2.3%) and skeletal muscle (between 16.0±2.0 and 64.4±0.7%). Velocity sedimentation centrifugation revealed that most tissues contained the G4 or A4 form. Three tissues (brain, heart, and liver) of the Siberian sturgeon contained a relatively high proportion of the G1 form (between 24.3±2.4 and 28.6±4.9%), while the skeletal muscle of the wels contained only the most complex type of AChE, i.e., A12. Amongst the tissues studied, the brain and liver mostly contained amphiphilic globular forms of the G4 type, while the heart and skeletal muscle were rich in asymmetric forms (A4 and A12). It was concluded that the differences revealed in the activities of AChE and in the distribution of its molecular forms may be connected with the variation in behavioral habits (feeding and swimming patterns), and the developmental stage of the nervous system. 相似文献
90.