Effect of graded levels of dietary carbohydrate on growth,feed utilisation and intestinal microbial community structure in dusky kob Argyrosomus japonicus fed a pelleted diet

The ability to utilise carbohydrates is limited for many predatory marine fishes. Graded levels of dietary carbohydrate (4.1–24.6%) were formulated using pregelatinised maize starch, to determine optimal levels for dusky kob Argyrosomus japonicus, an emerging mariculture finfish for which pelleted feeds are being developed. Specific growth rate increased with an increase in the carbohydrate level up to 16.72%, after which it declined. Feed utilisation followed a similar trend, with the best feed conversion ratio (1.28) and protein efficiency ratio (1.76) recorded at 16.4% carbohydrate. Lipid vacuolisation of the hepatocytes was evident in all livers examined, with melano-macrophage aggregates in those of fish fed 24.6% carbohydrate suggesting starvation. Gut bacterial community profiles were variable but were not influenced by dietary carbohydrate level and differed mostly between fish fed trout feed prior to the trial and those fed experimental diets containing starch. The dusky kob were able to clear glucose from their blood when fed up to 16.4% carbohydrate, but glucose removal was not achieved at 24.6% carbohydrate. In conclusion, dusky kob has a limited ability to utilise cooked starch as a carbohydrate source, which may be included in pelleted feed at 16.4% without adverse effects. For this species, levels of dietary carbohydrate above this may result in symptoms consistent with physiological breakdown, including reduced growth, reduced feed intake and feed conversion efficiency, prolonged hyperglycaemia, liver pathology and altered microbial communities in the foregut.     

基于三维激光扫描技术的草方格沙障内蚀积形态监测

三维激光扫描技术是近年来发展起来的新型空间信息测量技术。本文将三维激光扫描技术引入治沙工程领域,通过实验对草方格沙障内的蚀积微形态变化过程进行了模拟,并应用三维激光扫描仪测定草方格沙障内蚀积变化状态,认为草方格沙障内的蚀积状态,蚀积深度以及由堆积转化为侵蚀的位置等由于坡度等条件的不同而有所差异,从而证明了应用三维激光扫描技术监测微地貌形态变化过程的可行性。同时认为该技术在沙丘移动监测、机械沙障合理设计及防沙治沙效益评估等方面具有独特的优势和广泛的应用前景。但其技术本身和应用方面仍有一些问题亟待解决。     

生物工程处理草浆造纸废水系统的特点

文章通过对许昌造纸厂废水处理系统的论述 ,介绍了以生化为主的碱法草浆造纸废水治理成套技术的概况、工艺流程、投资概算和运行成本等 ,并进一步阐明了这套技术的科学性、实用性和先进性     

草方格沙障尺寸分析的简单模型

针对草方格沙障防护区域内流场的特点,提出一个单排理想涡列模型,用以模拟实际风沙流场。在此基础上,利用流体力学的分析方法,给出了与目前工程实际所建议的尺寸比较吻合的草方格沙障间距(或草方格边长)与出露草头高度的对应关系。     

干旱胁迫下秸秆覆盖增强玉米耐旱性的研究

田间试验于1994- 2000年在吉林省西部半干旱地区洮南市幸福乡实施,试验田包括露地栽培和秸秆覆盖栽培两个处理,覆盖区于玉米植株5叶期用粉碎的长度为2~3的玉米和小麦秸秆全面覆盖,随机区阻设计,重复4次,试验区每年重新安排,以免上一年的覆盖物对试验结果产生影响。于5叶期在每个小区的中部连续标记10株,以后跟踪调查记录,子粒达生理成熟时收获。研究结果表明:秸秆覆盖前处理与对照的土壤含水量无差异,而5叶期实施秸秆覆盖处理的土壤含水量显著高于对照,这种效应一直持续到7月的第二周。6月10日、6月25日和7月15日秸秆覆盖处理的土壤含水量分别比对照高12.86%、7.17%和2.86%,这就保证了玉米植株的根系和地上部生长发育对水分的需求。在半干旱地区及干旱年份实施秸秆覆盖处理可提高田间土壤水分含量、促进玉米植株中后期的生长发育、提高单株叶面积和干物质重、有利于雌穗分化发育、改善穗部性状、增加单穗粒数和粒重、最终增加子粒产量。因此,可把秸秆覆盖作为玉米综合抗旱栽培措施中的一项措施加以实施。     

塔克拉玛干沙漠公路中段两侧不同下垫面的小气候分析

塔里木沙漠公路位于塔里木盆地,纵贯塔克拉玛干大沙漠,集沙漠特征与温带大陆性气候于一体,不少地段曾因流沙较为严重,造成了工程施工的难度,通过对沙漠公路塔中段两侧不同下垫面进行小气候分析,比较其差异来说明自然沙面、草方格、低矮防护林带、沙石路面等的不同防沙能力。从几种防沙效果来看,沙石路面短期内有一定的压沙作用,但长期效果不好;草方格短期效果较好,但随着时间推移,防沙效果逐渐减弱;防护林带体系随着林带的逐渐长成,效果将会越来越好,属于生态型防沙,意义重大而且深远。     

Effects of rice straw on the cell viability,photosynthesis, and growth of Microcystis aeruginosa

Rice straw is supposed to be an environment-friendly biomaterial for inhibiting the growth of harmful blooms of the cyanobacterium Microcystis aeruginosa. However, its potential mechanism is not well known. To explore this mechanism, the growth, cell viability （esterase activity, membrane potential, and membrane integrity）, photosynthesis, and cell size ofM. aeruginosa were determined using flow cytometry and Phyto-PAM after exposure to rice straw extracts （RSE）. The results show that doses from 2.0 to 10.0 g/L of RSE efficiently inhibited the alga for 15 days, while the physiologic and morphologic responses of the cyanobacteria were time-dependent. RSE interfered with the cell membrane potential, cell size, and in vivo chlorophyll-a fluorescence on the first day. After 7 days of exposure, RSE was transported into the cytosol, which disrupted enzyme activity and photosynthesis. The cyanobacteria then started to repair its physiology （enzyme activity, photosynthesis） and remained viable, suggesting that rice straw act as an algistatic agent.     

STRATEGY OF MAIZE'S CONCENTRATING TO ADVANTAGE AREAS IN JILIN PROVINCE

Jilin Province is one of the main grain-producing provinces of China, which has dominant position in maize production, by the view of its advantages in policy, location, breed and market. And after entering WTO,some measures have been taken to enhance maize competitive ability. But there are some difficulties in concentrating production to maize advantaged areas. This paper expounds the basis that Jilin Province becomes the advantage area of maize, analyzes the problems and puts forward the supporting policy. Some strategic measures are proposed,as developing comparable advantages, carrying out the strategy of un-equilibrium development and cultivating advantaged product areas of maize to rapidly improve the international competitive ability and productivity of maize in Jilin Province, cast the agricultural predicament off and promote the agricultural development into a new stage.     

华北平原玉米播种期和品种变化对冠层温度的影响及地表生物物理机理

通过改变陆—气界面的地表水热交换,农田管理变化是气候变化的重要反馈过程之一。华北平原玉米的播种期和有效积温发生了规律性变化,改变了叶面积指数(LAI)、地表反照率(α)、净辐射(R_n)、潜热(LH)和冠层温度(T_c)等,成为区域气候变化的重要反馈过程。论文利用SiBcrop模型模拟3种玉米情景(春玉米、夏玉米、潜在玉米)下的LAI、α、R_n、LH和T_c的季节动态。结果表明,春玉米具有早播种、早收获、早LAI峰值的特征;夏玉米具有晚播种、晚收获、晚LAI峰值的特征;潜在玉米具有早播种、晚收获、高LAI的特征。模拟情景之间LAI差异为±2.5 m²·m^-2;T_c差异为±0.5 ℃。地表反照率(α)和地表能量分配是决定情景之间T_c差异的决定因素,播种期推迟,以α升高的降温效应为主;有效积温增加,以LH分配增多的降温效应为主。春玉米具有最高的冠层温度,夏玉米和潜在玉米的冠层温度较低且差异很小。研究结果对于促进农田土地管理变化适应和缓解区域气候变化具有一定意义。     

东北春玉米生长发育气象条件的适应性分析

统计分析１９８１－１９９０年东北地区３０个试站的气象资料，物候资料和春玉米产量资料。建立光，热，水等资源条件与产量变化之间的统计关系，从而确定出各地种植春玉米的适应性指数及等级。