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61.
Monitoring the persistence of Laccaria bicolor as an ectomycorrhizal symbiont of nursery-grown Douglas fir by PCR of the rDNA intergenic spacer 总被引:2,自引:0,他引:2
B. HENRION C. DI BATTISTA D. BOUCHARD D. VAIRELLES B. D. THOMPSON † F. LE TACON F. MARTIN 《Molecular ecology》1994,3(6):571-580
The large-scale inoculation of selected beneficial ectomycorrhizal fungi in forest nurseries has generated renewed interest in the ecology of these symbiotic fungi. However, information on the dissemination and persistence of introduced symbionts is scarce due to the limitation of the current identification methods. To identify ectomycorrhizal fungi on single root tips, we investigated the polymorphism of the PCR-amplified ribosomal DNA intergenic spacer (IGS) from a wide range of ectomycorrhizal fungi. To investigate the reliability of this molecular approach in large-scale surveys, the dissemination and persistence on Douglas fir seedlings of the introduced Laccaria bicolor S238N were assessed in a forest nursery in the Massif Central (France). Several hundred ectomycorrhizas and fruiting bodies were sampled from plots where control and L. bicolor inoculated-Douglas fir seedlings were grown for 1.5 years. PCR typing of mycorrhizas indicated that trees inoculated with L. bicolor S238N remained exclusively colonized by that isolate (or sexually derived isolates) for the entire test period. In contrast, control seedlings were infected by indigenous isolates of Laccaria laccata and Thelephora terrestris. The molecular evidence for the persistence of the introduced mycobiont despite the competition from indigenous isolates of the same species provides further illustration of the potential of exotic species for large-scale microbial application. 相似文献
62.
红旗泡水生植物群落结构与功能的研究 总被引:6,自引:0,他引:6
红旗泡是松嫩平原上的水草型湖泊,1972年由引嫩干渠补入嫩江水,使其成为大庆市主要水源地和渔业基地。该湖水生植被分布面积大,覆盖近1/2的水面。本文分析了芦苇,狭叶香蒲和稗等单优群落的结构与分布,并统计了混合群落的数量特征。随着油田开发,大庆地区的水体均受到不同程度的污染;因红旗泡水生植物资源丰富且其具清除油污、吸附重金属和沉降悬浮物等净化功能,故使其成为大庆地区水质最好和鱼产量最高的湖泊。 相似文献
63.
Changes in the fish community structure and habitat use were followed after the introduction of pikeperch (Stizostedion lucioperca) to the roach-dominated Lake Gjersjøen. Quantitative echosounding showed that the density of juvenile roach (Rutilus rutilus) was dramatically reduced in pelagic areas, from 12 000–15 000 fish/ha to 250 fish/ha, while total fish density remained unchanged in littoral areas. At the same time, the habitat segregation between different size groups of roach was altered as larger roach utilized the pelagic zone after pikeperch introduction. The loss of the pelagic refuge for juvenile roach increased the availability of juvenile roach to littoral predators, notably perch. In littoral areas, the fish community changed from one dominated by roach (> 95%) to one dominated by perch (> 50%). 相似文献
64.
R. J. FENSHAM 《Austral ecology》1994,19(2):189-196
Abstract Sucking insects constituted 79% of all phytophagous insects collected from woody sprouts in the ground layer of a tropical eucalypt forest. Mobile insect groups such as non-psyllid Hemiptera and Orthoptera were relatively frequent in this environment compared to temperate, Eucalyptus-dominated vegetation. The high fire frequency of the tropical eucalypt forest may favour mobile insect groups. The capture of sucking insects and caterpillars peaked in dry season samples. Other patterns of abundance of phytophagous insect groups showed little consistency in their seasonal trends between host species or between vegetation types within host species. Disparities between chewing insect abundance in daytime samples and the damage chewing insects cause, may result from disproportionate consumption by large, mainly nocturnal insects, such as members of the Orthoptera. In this study, 21% of insect species were specialists on single plant species. This study suggested that insect abundance reflected the growth patterns of woody sprouts after regular burning, rather than that plant growth and development were tuned to the pressures of insect herbivory. 相似文献
65.
本文应用DCA二维散点非等级制分类和TWINSPAN等级制分类的方法进行了四川西北部和甘肃南部云冷杉林的数量分类,共划分出15个群丛,分属于云杉、冷杉、高山栎和桦木四个群系,并分别讨论了各群丛的特征。用DCA二维散点的非等级制分类与TWINSPAN的等级制分类的方法对于云冷杉植物群落都产生了较好且一致的分类效果。通过TWINSPAN分类的研究,发现了对生境有指示意义的特征种和指示种,主要的植物种类有:圆叶菝契、网状小壁等(冷湿,指示藓类冷杉林和杜鹃冷杉林);小花拂子茅、箭炉樱等(冷旱,指示草类云杉林和箭竹云冷杉林);槭树、铁杉、沛阳花等(暖湿,指示落阔冷杉林和灌木云杉林等);罗氏异燕麦、华西矮卫茅、糙野青茅和狭叶柳兰等(暖旱,指示灌木云杉林和云冷杉疏林)。 相似文献
66.
In Feldberg Haussee, an anthropogenic eutrophicated lake, biomanipulation was executed for restoration. To increase the biomass of crustaceans, fish grazing on zooplankton was reduced by catching small fishes and introducing pike-perch. After biomanipulation rotifer biomass from a wide range of species decreased to a small spring maximum with three dominant species. The development of food in spring and food competition between crustaceans probably controlled the rotifer development. 相似文献
67.
Helminth community composition and richness were studied in brown trout, Salmo trutta , in 10 reservoirs of broadly similar age and characteristics situated close to each other in a well-defined region of south-west England. Communities were compared using cluster and ordination analyses, and possible correlations between helminth richness and a number of environmental variables were investigated. The hypothesis that the helminth communities should show high degrees of similarity and that large differences between reservoirs and a high degree of clustering would be unrecognizable was refuted. Levels of community similarity were low and comparable to those determined for helminths in salmonids in natural lakes. Trout in some reservoirs exhibited very distinctive helminth faunas and clustering of reservoirs was apparent. No single factor, including reservoir size and presence of piscivorous birds, had a predominant influence on community richness or composition but rather a multiplicity of local factors was believed to influence these parameters. The results indicate that local factors promoting distinctiveness have a greater influence on the composition and richness of fish helminth communities in lakes and reservoirs than do regional factors promoting similarity. 相似文献
68.
Seasonal fluctuations in the diversity and compositional stability of phytoplankton communities in small lakes in upper Bavaria 总被引:2,自引:2,他引:0
Roswitha Holzmann 《Hydrobiologia》1993,249(1-3):101-109
A study of diversity and compositional stability of phytoplankton communities during one vegetation period was carried out in small lakes in upper Bavaria. Shannon-Weaver diversity index was calculated on the base of number of individuals and on the base of biomass. On average, the diversity (annual mean) was highest in mesotrophic lakes. A comparison of three morphologically different (esp. exposure to wind, surface area and mean depth) lakes (Pelhamer See, Thalersee and Kautsee) sought to find out how the phytoplankton community structure reacts to events of intermediate disturbance, in terms of diversity- or biomass changes. Principal Component Analysis was used to measure the persistence of the phytoplankton association. The examples given in this paper led to these conclusions: High diversity or increase in diversity occur in compositionally instable communities, in high wind-stress events, with small algae and with high grazing. Low diversity or decrease in diversity occur in compositionally stable periods, when conditions select few species, as large forms dominate and as grazing by zooplankton takes effect. Gradual seasonal changes are observed in structurally stable lakes. In lakes exposed to frequent disturbances, seasonal changes may be dominated by intermediate responses. 相似文献
69.
70.
Gisela M. Figueiredo Hermógenes F. Leitão-Filho Alpina Begossi 《Human ecology: an interdisciplinary journal》1993,21(4):419-430
Local plants are a very important resource for the community of Gamboa, located at Itacuruçá Island, Sepetiba Bay, State of Rio de Janeiro, Brazil Ninety species of plants, belonging to 40 families, are used for a variety of purposes, such as food, construction, handicraft, and medicine. In a survey medicinal uses for plants were the most quoted by the community. Uses of medicinal plants within Gamboa and with other coastal communities are analyzed using diversity indices. Use by different categories of people based on sex, age, and economic activity was compared and significant differences were found among the groups compared, except for economic categories (fishermen and non-fishermen). The theory of island biogeography is shown to be useful for analyzing different levels of resource uses on different islands. 相似文献