以δc分析有机粪肥养鱼池中鱼类生长能源的初步研究

本文介绍了通过对鱼体、饵料、粪肥的δc值的分析来追踪碳元素的流向,从而研究施肥鱼池中鱼类生长能源的动力学过程的结果。研究表明,滤食性鱼类的生长能源主要来自自养生产系统;杂食性鱼类中的白鲫和鲤鱼,分别有三分之一以上和二分之一左右是来自自养生产系统,而其他部分的生长能源,则来自异养生产系统。     

基于变化环境的地下水动态敏感性分析方法研究

【目的】探索、完善地下水动态敏感性分析方法。【方法】通过对地下水动态敏感性分析方法研究现状的分析,对地下水动态敏感性分析的概念进行了重新定义,并探索性地将正交试验与地下水动态建模相结合,用以进行地下水动态敏感性的分析。【结果】建立了基于改进正交试验法的地下水动态敏感性分析方法,将该方法用于宝鸡峡灌区,所得结果与现有其他方法所得结果相近,即均认为地表水灌溉量和蒸发量是影响灌区地下水动态的主要因素,并且该方法也在理论上克服了现有分析方法的一些局限性。【结论】基于改进正交试验法的地下水动态敏感性分析方法在实际中具有一定可行性,是对传统地下水动态敏感性分析方法的补充和完善。     

短角幽天牛成虫林间种群动态的监测研究

以安徽省黄山风景名胜区等为试验基地,应用蛀干类害虫引诱剂,系统地研究了短角幽天牛成虫林间种群分布和种群动态规律.研究结果表明:短角幽天牛种群最高可分布于海拔1 700 m高山,高密度的分布区为海拔300m以下的低山马尾松地区;林间活动期长达150 d以上,具两个明显的峰期,主峰期为6月上、中旬,次峰期为9月.林间诱获的短角幽天牛成虫种群个体雌、雄性比为1.0:1.4.     

鼎湖山和尖峰岭土壤及凋落物中微生物数量季节动态

研究海南岛尖峰岭和广东鼎湖山两样地采集的土壤样品及森林凋落物样品中细菌、放线菌和真菌三类微生物数量的季节动态变化。结果表明:两样地的土壤及凋落物中各类群微生物数量均有明显的季节变化;同一微生物类群在凋落物和土壤中的数量均有明显而相似的季节变化;凋落物中各类微生物的数量都较土壤中的多。     

微热管阵列平板太阳能集热器中空保温层厚度优化

为分析微热管阵列平板太阳能集热器的热性能,该文建立了集热器的CFD模型,对其进行数值模拟,将模拟结果与试验结果进行对比,验证了模型的可靠性。采用该CFD模型对集热器保温层厚度进行优化,结果表明,当实心保温层导热系数分别为0.02、0.03、0.04、0.05W/(m·K)时,优化的实心保温层厚度分别为4.5、5.0、5.5、5.5cm。合理设计的中空保温层(空气层与实心保温层相结合的保温层形式)集热器能够达到与实心保温层集热器相当的保温隔热效果,同时可使集热器保温层成本及质量降低25%~50%。最后,该文给出了保温层总厚度分别为4、5、6cm时的中空保温层厚度优化结果,为该类集热器保温层的设计提供了理论依据。     

气象因子对芒果园桔小实蝇种群动态的影响

桔小实蝇[Bactrocera dorsalis (Hendel)]是芒果的重要害虫之一。试验利用性引诱剂对芒果园桔小实蝇的全年种群动态进行监测,分析气象因子与其种群数量变动的相关性。结果表明,芒果园桔小实蝇雄虫种群数量一年有2个明显高峰,2月为短时高峰,3月种群活动有所下降;5月开始数量逐渐升高,至8月达到高峰,9月开始逐渐下降,到12月至1月为发生低谷。经逐步回归分析发现,气象因子显著影响桔小实蝇雄虫的数量,主要受月平均气温、月平均最低气温和月降水量综合影响。     

Lumbricus terrestris L. distribution within an experimental humus mosaic in a mountain spruce forest

 An experiment was designed at a mountain site to study the distribution of adult Lumbricus terrestris in relation to a small-scale mosaic of humus forms representative of different stages of a spruce forest ecosystem. Good agreement was found between distribution in the mosaic and that in the field. ANOVA tests demonstrated the strong influence of humus form on earthworm abundance when comparing a vermimull (high earthworm burrowing activity) taken from a spruce regeneration site (61.8 individuals m^–2) with a leptomoder (no earthworm burrowing activity) taken from a 60-year-old spruce stand (6.2 individuals m^–2). Other humus forms were intermediate (mean density 34.6 individuals m^–2). The same pattern was found with individual biomass, but with lower significance. Main differences observed in the experimental design were attributed to the immediate carrying density of the humus forms. A distinction was made between humus profiles built up with or without spruce cover. In the latter case (regeneration site and bilberry heath), the immediate carrying capacity indicated by the experimental approach overestimated the field density by a factor of 4. Under spruce this overestimate was even higher (approximately 10 times too high in an adult spruce stand (160 years old) and 30 times too high under moss cover). The increase in density due to experimental conditions was not determined for leptomoder humus accumulated under the actively growing spruce stand (60 years old) since the earthworm density was near zero in both cases. Relationships between humus form and earthworm populations are discussed. Received: 9 June 1997     

浙江衢州毛竹林低改后害虫种群变动分析

自20世纪80年代始,衢州市各县(市、区)逐渐推广毛竹低产林改造技术,为竹林增产增效打下了基础。但是,由于改制后的毛竹林地被挖锄,天敌资源锐减,竹林中年年有笋,立竹上终年披叶,使竹子害虫食物条件改善,致使竹子害虫种类、数量增加,危害逐年加重。通过害虫种群变动分析,可以为开展竹林病虫害综合防治提供有效的应对措施。     

一种流动体泄漏自动检测新方法

流动体泄漏自动检测系统是基于通信传输理论，根据流动体泄漏的特点，提出了一种全新的泄漏检测方法。该方法采用在流动体发送端加入测试物质或测试信号，在接收端检测该物质或信号，依据其变化确定是否有泄漏。     

Rehabilitation of degraded dry heather [Calluna vulgaris (L.) Hull] moorland by controlled sheep grazing

Many areas of heathland in Europe have seen a decline in the area and condition of Calluna vulgaris (heather)-dominated vegetation, with subsequent declines in the associated faunal interest. Grazing, alongside burning, is still the predominant means of managing heathland vegetation, and, therefore, it is by manipulating this management that cost-effective improvements in vegetation condition can be made. This paper investigates the suitability of different grazing treatments for rehabilitating degraded ‘dry heath’. Treatments varied in the intensity (0-1.9 sheep ha⁻¹ year⁻¹) and timing (summer vs. winter) of sheep grazing. These treatments were compared with the behaviour of vegetation outside the fenced area kept under the previous management (open access all year round). As rabbits were common on the site, fences were erected to prevent access to the sheep grazed plots. Vegetation composition remained stable outside the fenced area, whilst all the fenced treatments showed a decrease in heather utilisation and an increase in the relative frequency of heather over the 5 years of the experiment. The increase was in proportion to the reduction in stocking rate, with only slow increases in relative frequency observed in the high grazing treatments (winter and summer). Other species that benefited from reducing grazing included Empetrum nigrum and Vaccinium myrtillus, whilst declines were observed for Agrostis capillaris and total monocotyledonous species. Only small overall differences were observed between the winter low, summer low and no sheep grazing treatments. However, a difference in response was present between the sheep exclosures and the sheep+rabbit exclosures, indicating that rabbits were having a noticeable effect on heather recovery at this site. On this degraded ‘dry heath’ system, imposing a reduction in stocking density improved the condition of the dwarf shrubs present and reduced the grass component of the vegetation. There was little effect of the timing of grazing, such that a reduction in sheep numbers to 0.8/0.9 sheep ha⁻¹ year⁻¹, to give utilisation levels of below 20%, can achieve the desired result of improving vegetation condition whilst still achieving some economic return from grazing. However, the wide range of ‘sustainable’ stocking densities for different heathland systems highlights the need to base effective management on measured utilisation rather than on stock numbers.