排序方式： 共有6条查询结果，搜索用时 125 毫秒
1
1.
Minna-Liisa?RantalainenEmail author Hannu?Fritze Jari?Haimi Oili?Kiikkil? Taina?Pennanen Heikki?Set?l? 《Biology and Fertility of Soils》2004,39(3):200-208
Due to their high abundance and ubiquitous existence, microbes are considered to be efficient colonisers of newly established habitats. To shed light on the dispersal mechanisms of soil microbes, a controlled microcosm experiment was established. In these microcosms, the dispersal of microbes from a source humus patch to originally sterile humus patches (embedded in a mineral soil matrix) was followed for 16 months, applying 16S and 18S ribosomal DNA-based PCR-DGGE molecular methods. Specifically, the role of enchytraeid worms and habitat (humus) corridors as possible facilitators of microbe dispersal was studied. The results showed that enchytraeid worms function efficiently as vectors for horizontal dispersal of saprophytic fungi in soil. Some of the fungi also proved to disperse through the corridors by vegetative growth, although this dispersal was inefficient as compared to dispersal with the enchytraeids. Virtually no saprophytic fungi were able to disperse through the mineral soil matrix in the absence of both enchytraeid worms and corridors. Unlike soil fungi, the dispersal of soil bacteria was not affected by any of the studied factors. The results of the present experiment provide direct evidence of the crucial role of soil fauna in aiding the horizontal dispersal of soil fungi. The role of enchytraeids as a functionally important species in boreal forest soils is further emphasized, since bringing microbes into contact with new resources is likely to enhance the rate of decomposition in soils. 相似文献
2.
以三年生藤稔葡萄为试材,研究了双膜覆盖和早期阶段性加温对设施葡萄棚内温度、物候期及果实品质的影响。结果表明：与单膜对照相比,双膜和加温处理的日最高温度分别降低了34和48℃,40℃以上高温天气由6 d降到了3和1 d,日极端低温由08℃分别提高到42和77℃,活动积温分别提高了189和273℃。双膜及加温处理各物候期明显提前,成熟期提早至5月底;双膜和加温处理后虽然萌芽率略有降低,但坐果率提高,单性果率显著降低,果实硬度、色泽、可溶性固形物等品质指标都有不同程度提高。双膜覆盖和早期加温后种植效益显著提高,分别比单膜栽培提高了691%和1166%。 相似文献
3.
Alessandro?GrapputoEmail author Tomi?Kumpulainen Johanna?Mappes Silja?Parri 《BMC ecology》2005,5(1):5
Background
Despite the two-fold cost of sex, most of the higher animals reproduce sexually. The advantage of sex has been suggested to be its ability, through recombination, to generate greater genetic diversity than asexuality, thus enhancing adaptation in a changing environment. We studied the genetic diversity and the population structure of three closely related species of bag worm moths: two strictly sexual (Dahlica charlottae and Siederia rupicolella) and one strictly asexual (D. fennicella). These species compete for the same resources and share the same parasitoids. 相似文献4.
Markus?Soimasuo Seija?Sinkkonen Jaakko?PaasivirtaEmail author 《Journal of Soils and Sediments》2004,4(2):75-83
Background Adult sea lampreys, a delicate food species catch from Baltic Sea rivers, migrate from sea and spawn to sediments of still
river water areas. Their larva live there four years before return to sea. The few published studies of toxicity of the sediment
contaminants to the lamprey larva, however, do not include chlorinated persistent organic pollutants (POPs), thus far. Kymijoki
River in southeast Finland is known for high polychlorinated POP contamination which has been measured to accumulate in several
bottom fauna and fish species.
Goal of the Study To obtain the first screening results of the bioaccumulation power of POPs from sediment to lamprey larva during their life
stage in the contaminated sediment. The accumulated dioxin-type of toxic load (TEQ) was also studied as a possible human hazard.
Methods Surface sediment and lamprey larva were sampled from four localities of the lower Kymijoki River and analysed for MeO-PBDEs,
PBDEs, PCBs, PCDDs, PCDEs, PCDFs, and PCDTs by solvent extraction, column clean up and GC/MS procedures. The larva were sorted
to seven composites according to locality and (for one place) size of the specimens (to classes of small, medium and large
individuals). From the analysis results, TEQ values for composites and the bioaccumulation factors from dry sediment to fresh
larva (BSAF), from dry sediment to larva lipid (BSAFlw) and from sediment organic carbon to larva lipid (BSAFoc) were calculated.
Results and Discussion TEQ load was highest (about 500 pg g-1 ww) in large larva composite due to high bioaccumulation of PCB 118, 1,2,3,4,7,8-hexachlorodibenzo-p-dioxin (D66) and toxic
penta- to octa-CDFs. A high positive significant correlation was found between weight and length of larva. Instead, lipid
content had no significant correlations with weight and length of larva. Larva lipid or sediment organic carbon did not correlate
significantly with any of the calculated BSAF, BSAFlw and BSAFoc values. Therefore, statistical comparisons between substance
properties and bioaccumulation rate were possible for BSAF alone. These comparisons indicated a slightly significant increase
of PCBs, but very significant decrease of PCDF bioaccumulation from sediment to larva by increase of the number of chlorine
atoms (NCI) in the molecule. This property of highly chlorinated PCDFs indicates, as found earlier for local fish, a kinetic
control of bioaccumulation by slow release from sediment back to water and the food chain.
Recommendation and Outlook The results obtained point out that bioaccumulation of POPs in lamprey larva is a possible source of toxic hazard to human
food consumption and to development of lamprey species. Therefore, both larva and adult lampreys should be studied further
for significance of their POP contamination compared with other experiences on impact of POPs to human and wildlife. 相似文献
5.
Aim and Background
In order to identify potential risks of sediments contaminated by pulp and paper mill effluents, two boreal lake areas were investigated from core samples. Resin acids (RA) and their aromatized derivative retene were measured, suggesting that these aquatic toxicants can be long-lasting sources to expose benthic biota. On the other hand, dredging or other human actions can liberate toxicants, even from deep sediments, to an aqueous phase with harmful consequences to aquatic species. Since no historical sediment profiles were available, we investigated the toxic potential of sediment-water elutriates by way of the bioluminescent bacteria Vibrio fischeri. In this investigation, we therefore analyzed both the concentrations of toxic chemicals and the toxicity as profiles in two contaminated lake sediments in Finland. 相似文献6.
Anne?Siira-Pietik?inen Jari?HaimiEmail author Hannu?Fritze 《Biology and Fertility of Soils》2003,37(3):163-174
In an experiment with factorial design performed in a mature, mixed Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.) stand in central Finland, we studied the effects of sod cutting (exposing the mineral soil simulating mechanical site preparation) and trenching the study plot (excluding root-mycorrhizal connections) on soil organisms, decomposition rate and pine seedling performance. During two growing seasons after sod cutting, the growth of pine seedlings was significantly enhanced compared to plots with the organic layer left intact. Some epiedaphic soil animals, such as ants, spiders and certain entomobryid collembolan, were more active (pitfall sampling) on sod-cut plots. By the end of the second growing season numbers of enchytraeids were greater in the exposed mineral soil than in the mineral soil under the forest floor. Trenching induced changes in microbial phospholipid fatty acid (PLFA) pattern and collembolan community structure with decreased numbers of collembolans and biomass of fungi in organic soil of uncut plots. In addition, N content of pine seedlings increased after trenching. Overall, the effects of trenching on the measured variables were similar in sod-cut and uncut plots. We conclude that the effects of mechanical site preparation on decomposers and decomposition processes can be explained partly by exclusion of mycorrhizal-root connections and partly by a decrease in unfavourable conditions created by the organic soil layer and ground vegetation. 相似文献
1