排序方式: 共有43条查询结果,搜索用时 355 毫秒
21.
22.
Cervical teratoma is a neoplasm composed of embryonic tissues with representation of all three germ layers. We report an extremely rare case of fetal cervical teratoma presenting at 24 weeks of gestation. A submaxillary mass and agenesis of corpus callosum were identified on ultrasonography, associated with agenesis of corpus callosum and a subarachnoid cyst. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
23.
24.
Contrasting influence of soil nutrients and microbial community on differently sized basal consumers
There is increasing evidence of the coexistence of trophic and environmental constraints belowground. While too often ignored in current literature, the extent to which phosphorus is relevant for soil biota was demonstrated in this study by positive correlations of soil C/P and N/P ratios with all the measured microbial parameters (biomass, density and activity), with the numerical abundance of roundworms (Nematoda) and potworms (Enchytraeidae) from lower trophic levels and with the roundworm biomass. Total worm biomass seems dependent on land use, being in rangelands about twice as high as in croplands, although the relative contribution of potworms remains comparable for both land use types (49?±?20 % SD versus 45?±?27 % SD). Besides soil [P], soil type plays an important role in the relative biomass of potworms compared to roundworms. Soil parameters (here pH, C/P and N/P ratios) are better predictors for the abundance and biomass of roundworms than microbial parameters. We also propose a graphical way to visualize the major responses of basal consumers to their microbial drivers. 相似文献
25.
26.
Christian Mulder Henri A. Den Hollander J. Arie Vonk Axel G. Rossberg Gerard A. J. M. Jagers op Akkerhuis Gregor W. Yeates 《Die Naturwissenschaften》2009,96(7):813-826
The large range of body-mass values of soil organisms provides a tool to assess the ecological organization of soil communities.
The goal of this paper is to identify graphical and quantitative indicators of soil community composition and ecosystem functioning,
and to illustrate their application to real soil food webs. The relationships between log-transformed mass and abundance of
soil organisms in 20 Dutch meadows and heathlands were investigated. Using principles of allometry, maximal use can be made
of ecological theory to build and explain food webs. The aggregate contribution of small invertebrates such as nematodes to
the entire community is high under low soil phosphorus content and causes shifts in the mass–abundance relationships and in
the trophic structures. We show for the first time that the average of the trophic link lengths is a reliable predictor for
assessing soil fertility responses. Ordered trophic link pairs suggest a self-organizing structure of food webs according
to resource availability and can predict environmental shifts in ecologically meaningful ways.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to all users. 相似文献
27.
28.
29.
30.