陕西关中灌区冬小麦土壤养分丰缺指标体系的建立

为给陕西关中地区小麦合理施肥提供科学依据,2006-2008年在陕西关中灌区进行了多点冬小麦"3414"田间试验,分析了不同土壤肥力水平下冬小麦土壤有效养分含量与相对产量的相关性,并依此确定土壤养分等级和推荐施肥量.结果表明,关中灌区小麦田土壤碱解氮含量等级可划分为低(<60 mg/kg)、中(60～100 mg/kg)、高(100～120 mg/kg)和极高(>120 mg/kg);速效磷含量可划分为低(<10 mg/kg)、中(10～30 mg/kg)、高(30～45 mg/kg)和极高(>45 mg/kg);速效钾含量分为高(100～165 mg/kg)和极高(>165 mg/kg).当土壤碱解氮含量处于低、中、高等级时,氮肥推荐用量分别为155～175、135～155、125～135 kg/ha,极高等级的推荐施氮量未能确定;当土壤速效磷含量处于低、中、高和极高等级时,磷肥(P2O5)推荐用量分别为120～140、90～115、70～90和60～70 kg/ha;当土壤速效钾含量处于高和极高时,钾肥(K2O)推荐用量为50～80和15～35 kg/ha.     

Dynamics and stratification of Enchytraeidae in the organic layer of a Scots pine forest

In a Dutch Scots pine forest an experiment was conducted to quantify the role of soil biota in the functioning of the soil ecosystem, and the effects of enhanced nitrogen deposition. For this, the site was sampled at 8-week intervals during 2.5 years. This paper reports on the population dynamics of enchytraeids in the field and in stratified litterbags. Mean yearly abundance of the enchytraeid community in the field was 47 600 m^–2, or 0.70 g (dry weight) m^–2. The community consisted mainly of three species: Cognettia sphagnetorum, Marionina clavata and Achaeta eiseni, of which C. sphagnetorum was dominant. The enchytraeid populations showed a marked stratification in the same sequence. Freshly fallen pine needles were colonized by C. sphagnetorum, while other species followed much later. It was found that data from the litterbags were reasonably comparable with field data, when expressed per gram of dry substrate, but less so when expressed per square metre. Multiple regression analysis of the data showed that the population dynamics in the litter layer could largely be explained by temperature and moisture fluctuations; in deeper layers other factors, such as the stage of decomposition, were probably more important. Received: 26 June 1997     

鳀鱼的生物量、渔业及其生物学特征

IntroductionThe Yellow Sea is characterized by a shallow continental shelf. High tides and seasonally varying mon-soons,freshwater discharge from surrounding landmasses and large amounts of sediments transported intothe sea as well as the effect of the Kuroshio current have strong effects on the environment in these areas.Productivity of an ecosystem may be measured in terms of abundance of the adult population and recruitmentof new year classes.Japanese anchovy(Engraulis jap onicus) is cons…     

珍稀植物南方红豆杉群落物种-多度关系

采用Weibull分布模型、对数正态分布模型、对数级数模型、分割线段模型、几何级数分布模型来拟合珍稀植物南方红豆杉群落物种-多度分布格局,并用卡方临界值检验模型的拟合效果。结果表明:Weibull分布、对数正态分布、对数级数分布可用于描述南方红豆杉群落乔木层种-多度分布格局;而Weibull分布和对数正态分布适合于灌木层种-多度关系的描述。     

天然甜槠林物种多样性的研究

本文运用物种多样性、物种丰富度、物种均匀度等分析方法对福建省周宁县天然甜槠林的群落组成进行研究。结果表明:甜槠群落物种多样性指数和均匀度值均较大,群落结构复杂、物种丰富。研究结果为保护该地域森林植被提供了理论依据。     

Thirty-year recovery trend in the once depleted Hawaiian green sea turtle stock

The green sea turtle is one of the long-lived species that comprise the charismatic marine megafauna. The green turtle has a long history of human exploitation with some stocks extinct. Here we report on a 30-year study of the nesting abundance of the green turtle stock endemic to the Hawaiian Archipelago. We show that there has been a substantial long-term increase in abundance of this once seriously depleted stock following cessation of harvesting since the 1970s. This population increase has occurred in a far shorter period of time than previously thought possible. There was also a distinct 3-4 year periodicity in annual nesting abundance that might be a function of regional environmental stochasticity that synchronises breeding behaviour throughout the Archipelago. This is one of the few reliable long-term population abundance time series for a large long-lived marine species, which are needed for gaining insights into the recovery process of long-lived marine species and long-term ecological processes.     

白令海阿留申海盆区狭鳕当年生幼鱼数量分布的调查研究

１９９３年夏季白令海狭鳕资源调查期间，作者等应用声学／拖网评估调查方法，首次发现阿留申海盆区有大量当年生狭鳕幼鱼分布。研究结果表明：（１）当年生幼鱼主要分布在海盆区东北部，密集区位于东白令海陆架斜坡与公海区之间，呈西北东南走向；（２）鱼群主要栖息于中上层８０—１２０米处，有明显的昼夜垂直移动现象；（３）７月份海盆区东北部幼鱼鱼体长度为２９—４７毫米，而南部波哥斯洛夫岛附近的鱼体长度仅为１１—１７毫米，系两个不同产卵期鱼群的子代；（４）幼鱼主要栖息层的水温为３—５℃，盐度为３２．９—３３．１，其分布与陆架斜坡地理环境和饵料生物关系较密切。     

喀什市主要河流微生物生态分布研究

该研究采用稀释平板法分离培养喀什市克孜勒河、盖孜河、吐曼河、东湖、南湖5个水体中的微生物,初步揭示了喀什市主要河流中微生物的生态分布情况。结果表明,各类水体中的细菌数量、类型显著高于真菌和放线菌,尤以吐曼河细菌丰度最高,污染最严重。喀什水体微生物季节变动明显,夏季微生物丰度显著高于冬季,且3条河流不同河段微生物分布情况不一,中下游受污加剧,微生物数量高于上游。     

合肥地区草履虫丰度与水质关系的研究

[目的]研究合肥地区部分湖泊中草履虫丰度与水质的关系。[方法]对4个采样点的草履虫丰度和水质综合评价指数进行了相关分析和回归分析。[结果]草履虫丰度和水质综合评价指数之间呈正相关,即草履虫丰度越小,水质越好。[结论]草履虫丰度可以反映水质情况。     

褐家鼠体表蚤类流行分布预测（摘要）

[目的]预测褐家鼠体表蚤的感染率。[方法]在云南省的23个县（市）进行现场抽样,采集褐家鼠体表蚤,运用包涵平均感染度及方差的流行性模型。[结果]蚤感染率与感染度的对数值成线性相关,蚤感染率的预测值与实际值成线性相关。[结论]褐家鼠体表蚤的平均感染度可以预测其感染率。