关键词： 体层摄影术,X线计算机   三维重建   气管   支气管   动物,实验  

摘要： 目的　探讨低剂量多层螺旋CT气管支气管树重建的可行性。方法　改变层厚 (6.5、3 .2mm )、mAs(15 0、10 0、5 0、2 0mAs)、管球电压 (12 0、90kVp)和螺距 (1.75、1.2 5 )中一项扫描参数 ,对 8只健康成犬分别进行 7个序列胸部扫描和MPR、SSD、VB重建 ;与标准剂量组比较 ,评估各序列气管重建图像质量及支气管显示率 ;测量重建图像 0～ 3级支气管管径 ,与解剖标本气管内径比较。结果　 10 0mAs、5 0mAs、90kVp及螺距 1.75组气管重建图像质量及 0～ 4级支气管显示率与标准组无差异 (P >0 .0 5 )。 10 0mAs、90kVp和螺距 1.75组支气管测量值与解剖标本无差异 (P >0 .0 5 ) ,5 0mAs组对 3级支气管有差异 (P <0 .0 5 ) ,2 0mAs组对 2、3级支气管有差异 (P <0 .0 1)。结论　低剂量MDCT (标准剂量的 2 0 %～3 3 % )的气道重建图像可提供足够的诊断信息 ,可用于小儿或无法配合扫描的患者。

关键词： 动物类药材市场   市场价格   三棵树药市   市场供求   哈尔滨市  

摘要： 动物(昆虫)类药材,在哈尔滨三棵树中药材专业市场上的走势是:'十年一贯制',即:自1994～2004年的10年间,动物类药材中的95%以上品种热销不衰,亮点品种频频登场,销售活跃,销量增加,逐年上升,价格稳定,连年上涨,货源短缺,后市看好.笔者对我国10多家中药材专业市场动物类药材的10年走势排序调查显示,三棵树药材市场无论在销售数量,还是销售金额上,都走在其它药市的前列,其销售量与销售额均居该药市其它品种之首.这一现象早已引起国内中药材市场人士的关注,许多动物类药材的产地经销商与药农纷纷将产品投交该药市.吉林、辽宁、内蒙古等几个省区的众多用户也都云集三棵树药市,采购自己所需的品种.可以说,三棵树药市是我国动物类药材较理想的投交集散地.

关键词： Alouatta seniculus   herbivory   Lago Guri   Venezuela   nutrient availability   red howler monkely   tree growth rates   tropical forest fragments  

摘要： The role of herbivores in nutrient cycling in tropical forest ecosystems remains poorly understood. This study investigates several aspects of nutrient cycling along a gradient in herbivore (Alouatta seniculus, red howler monkey) density among small landbridge islands in Lago Guri, Venezuela. Specifically, two contrasting hypotheses were addressed: (1) herbivores increase the availability of soil nutrients and subsequently primary productivity, and (2) herbivores decrease nutrient availability and primary productivity because they increase the dominance of non-preferred, nutrient-poor, tree species. Although C:N increased with herbivore density, the annual increase in basal area (an indicator of aboveground productivity) increased with herbivore density. According to an analysis of the tree communities on the study islands, herbivory may also be causing a shift in the tree community toward non-preferred species, and thus, over a longer time scale, both nutrient availability and productivity are expected to decline. The influence of herbivores on nutrient cycling and plant productivity has important implications for conservation and rates of carbon sequestration in tropical forests.

关键词： EPIRRITA-AUTUMNATA LEPIDOPTERA   MOUNTAIN BIRCH   GROWTH   INSECT   GEOMETRIDAE   PERFORMANCE   COEVOLUTION   PHENOLICS   MOTH  

摘要： Short-lived insect herbivores should be able to adapt to the resistance mechanisms of their long-lived woody hosts because the life span of a single host will encompass numerous generations of herbivores. However, adaptation may be slowed down if host genotypes can create, in a single genotype, such large phenotypic variation in traits relevant for the herbivore that it matches variance among host genotypes. We tested this hypothesis by measuring leaf consumption by, and growth of, half-sibs of the geometrid moth Epirrita autumnata on individual birch trees, during three instars. The instarxtree interaction, rather than tree identity alone, was a significant variance component for both consumption and growth, indicating that different larval instars ranked individual trees differently. Both consumption and growth varied most between the 3rd and the later (4th and 5th) instars, coinciding with rapid seasonal changes in numerous nutritive and phenolic traits of maturing leaves. Thus, developmental variance in the leaf quality of individual trees may reduce the likelihood of E. autumnata genotypes adapting to the defenses of their host trees. We did not find evidence of in the ability of different half-sibs to utilize individual trees or leaf stages, indicating that E. autumnata larvae are generalists over a wide variety of host traits.

关键词： Acacia mangium plantation   explosive increase in biomass   nutrient cycling   soil macro-invertebrates   sustainability of soil fertility   wet tropics  

摘要： Sustainable ecosystem management of Acacia mangium plantation, the area of which is rapidly increasing in the tropics, especially in Indonesia and Malaysia, becomes more and more important. In this context, abundance, biomass and vertical distribution of soil macro-invertebrates were investigated in a mature plantation of A. mangium . n Sarawak, Malaysia. In the present paper, in order to reveal the changes in soil macro-fauna caused by conversion of natural forests to A. mangium plantations, the results were compared with those from a nearby primary forest. White total abundance of soil macro-invertebrates was similar, total, biomass was much Larger in the plantation than in the primary forest. The prominent factor for such a Large total biomass in the plantation was the high abundance of earthworms, followed by isopods and harvestmen with much smaller contributions. The common feature of the communities of these three taxa in the plantation was the absolute dominance by single species. The dominant earthworm species was of the endogeic type that was absent from the primary forest and thought to be introduced with A. mangium seedlings from outside. The isopod flushed in the plantation was a pill bug that occurred in the primary forest, too, and might have been pre-adapted to the vegetation change. The dominant harvestman in the plantation was of the life form different from that of the other species found, and was thought to be supported by the explosive increase in biomass of earthworm and/or pill bug. On the other hand, communities of termites, ants, fly Larvae, click beetle Larvae and other beetle Larvae were depressed by the vegetation change. Thus the major consequence of the conversion of natural forest to A. mangium plantation was simplification of community structure in many taxonomic groups. The major points of the simplification in turn were the explosive increase in biomass of the soil processing earthworm and the titter processing pill bug which may acc

关键词： soil and litter arthropods   effects of forest management   soil ecology   silvicultural practices   mites   springtails  

摘要： Soil and litter arthropods are important in many forest ecosystem processes where they help to regulate nutrient dynamics and soil quality, and are useful bioindicators of ecosystem condition and change. This study was initiated in response to concerns about possible decline in site productivity due to intensive forestry practices. We investigated the effects of tree harvesting and site preparation treatments on soil and litter arthropod abundance in a loblolly pine plantation in eastern Texas, USA. Using soil and litter cores, we sampled abundance of selected arthropods over two years following tree harvesting. Response to treatments varied somewhat among arthropod taxa. Acari (mites) and Collembola (springtails), the numerically dominant taxa in core samples, were initially higher in abundance in less intensive harvesting and site preparation treatments. However, after 2 years, abundance of these arthropods was comparable in all harvesting and site preparation treatments. Fertilization with nitrogen and phosphorus had a strong positive effect on abundance of most arthropod groups in the second year of the study. The recovery of arthropod abundance through time suggests that the silvicultural practices used did not jeopardize the ecological integrity of the site. The results reported here contrast with other similar studies which suggests that soil and litter arthropod communities respond differently in different geographic locations and forest types. Further comparative and extensive studies of this nature are needed therefore for a deeper understanding of the impacts of forest management practices. (C) 2004 Elsevier B.V. All rights reserved.

关键词： Biopsyche thoracica   Combretaceae   Conocarpus erectus   Great Exuma Bahamas   herbivory   hurricane disturbance   leaf nitrogen content   plant-insect interactions   polymorphism   sprouting   trichomes  

摘要： We studied consequences of storm damage on buttonwood (Conocarpus erectus) shrubs and their herbivores in the Bahamian islands. Buttonwood is polymorphic, with green shrubs producing few leaf trichomes and silver shrubs covered in dense trichomes. We first characterize traits of green vs. silver shrubs relevant for herbivores, and then assay damage by two prominent insects. Next, on replicated islands, we experimentally address how different types of storm damage (simulated hurricane surge damage vs. simulated intense wind) affected phenotypic traits of both buttonwood morphs and subsequent herbivory over a one-year sampling period. Our results show that although leaves produced by green shrubs are 21% tougher than leaves produced by silver shrubs, green leaves have 16% higher nitrogen concentrations and greater levels of herbivory. Consistent with previous observational studies of a natural hurricane at our study site, we found stronger effects of simulated surge damage than simulated wind damage. Experimental pruning of shrubs resulted in reduced toughness, higher nitrogen concentration, fewer trichomes, and greater herbivory compared to controls and compared to shrubs with their leaves stripped. The results were stronger for the silver compared to the green morph. Morph differences in buttonwood have strong consequences for herbivores, and these effects are modified by disturbance.

关键词： Postdispersal seed predation   Old-fields   Tallgrass prairie   Bluestem   prairie   Dispersal   Forest   Vegetation   Rodents   Microhabitat   Communities  

摘要： Increased abundance and distribution of eastern red cedar (Juniperus virginianus), a native species in the Great Plains, has been associated with changes in ecosystem functioning and landscape cover. Knowledge of the main consumers and dispersal agents of eastern red cedar cones is essential to understanding the invasive spread of the species. We examined animal removal of cedar cones in three habitats (tallgrass prairie, eastern red cedar and woodland-prairie margins) in the Cross Timbers ecoregion using three exclosure treatments during autumn and winter. Exclosure treatments excluded study trees from ungulates, from terrestrial rodents and ungulates or from neither (control). Loss of cones from branches varied by a habitat-time interaction, but was not affected by exclosure type. Loss of cones from containers located under experimental trees varied by a habitat-treatment-time interaction. In December and January, Cone Consumption from containers in no-exclosure treatments was highest in margins, followed by tallgrass prairie and eastern red cedar habitats. We Conclude birds consumed the majority of cones from branches and small and medium-sized mammals Consumed cones on the ground. Both birds and mammals likely contribute to the spread of eastern red cedar but at different scales. Limiting invasion of eastern red cedar in forests may require early detection and selective removal of pioneer seedlings in cross timbers and other habitats that attract a high diversity or density of frugivores.

关键词： Tamarix   saltcedar   regulated river   integrated pest management   invasive species   dams   riparian  

摘要： Tamarisk (Tamarix ramosissima) is an introduced shrub or small tree associated with the loss of biological diversity in riparian habitat throughout much of western North America. Control measures are often expensive and ineffective, so land managers need site-specific information to guide cost-effective integrated management strategies. We sampled 12 randomly selected tamarisk-infested inlets on Fort Peck Reservoir on the C.M. Russell National Wildlife Refuge stratified by stream basin size. At each site we sampled 2-5 stands of riparian vegetation, recording plot elevation, canopy cover of vascular plants, density of woody species and age estimates for representative woody plants. Tamarisk plants 1-3 years old were abundant in the drawdown zone along the shore of Fort Peck Reservoir. The lack of plants older than three years indicates that tamarisk in the drawdown zone were destroyed during a recent two summers of inundation and suggests that three months of inundation will kill tamarisk plants. The oldest (17-22 years) and largest tamarisk plants in the study area were found in the full-pool zone and were recruited in periods of significant drawdown following high-water years. Tamarisk was uncommon in cottonwood and silver sagebrush stands on stream terraces above full pool. Only the largest streams in our study area appeared capable of supporting tamarisk and significant native riparian vegetation. Tamarisk plants at or above full pool level should be removed in these drainages to prevent upstream invasion and loss of native species. The level of the reservoir should be raised to the level of full pool for three consecutive months during the growing season every 3-5 years to prevent development of extensive stands of tamarisk in the drawdown zone capable of producing large quantities of seed. (C) 2004 Elsevier Ltd. All rights reserved.

关键词： anura   ecology   Hyperoliidae   Hyperolius   Nigeria   trophic niche   tropical africa  

摘要： The feeding relationships of four sympatric, ecologically nearly unknown, tree frogs of southern Nigeria (Hyperolius sylvaticus, H. guttulatus, H. fusciventris burtoni, and H. concolor) were studied during both the dry and the rainy seasons. Stomach contents were obtained by stomach flushing. The largest species were H. guttulatus and H. concolor, whereas the other two species were of smaller average size. A statistically significant sexual size dimorphism was observed in H. guttulatus, H. concolor, and H. sylvaticus (in all species the females were larger), but not in H. fusciventris. In all four species, the frequency of animals with empty stomachs was significantly lower during the rainy season than during the dry season. The four frog species were mainly arthropod-eating: Araneidae and Blattoidea were preyed upon mainly by the two largest species, Acarina and Lepidoptera were taken mainly by the two smaller species, and Diptera and Formicoidea were eaten frequently by all species. The diet composition was similar between seasons in three of the four species, and H. guttulatus was the only species showing considerable diet variation between seasons. We concluded that 1) the intensity of interspecific competition should be particularly high between the two larger species on the one hand, and between the two smaller species on the other hand;and 2) the intensity of the interspecific competition should be relatively constant throughout the year.