Search results for "Community structure"
showing 10 items of 163 documents
Estimation of atrazine-degrading genetic potential and activity in three French agricultural soils
2004
The impact of organic amendment (sewage sludge or waste water) used to fertilize agricultural soils was estimated on the atrazine-degrading activity, the atrazine-degrading genetic potential and the bacterial community structure of soils continuously cropped with corn. Long-term application of organic amendment did not modify atrazine-mineralizing activity, which was found to essentially depend on the soil type. It also did not modify atrazine-degrading genetic potential estimated by quantitative PCR targeting atzA, B and C genes, which was shown to depend on soil type. The structure of soil bacterial community determined by RISA fingerprinting was significantly affected by organic amendmen…
Dactylogyrus (Monogenea) communities on the gills of roach in three lakes in Central Finland
1992
SUMMARYDactylogyrus (Monogenea) species were studied on the gills of roach (Rutilus rutilus) from a total of 293 fish in 3 interconnected lakes in Central Finland. One of the lakes is eutrophic and polluted by a paper and pulp mill, one is eutrophic and one is oligotrophic. Nine Dactylogyrus species were found. The structure of the monogenean communities was analysed at the component and infracommunity level and the Dactylogyrus fauna of the lakes was compared. Although it was found that the component communities tended to be very similar there were also differences. The abundance and diversity were highest in the polluted lake; the infracommunities of this lake were considerably more often…
Soil environmental conditions rather than denitrifier abundance and diversity drive potential denitrification after changes in land uses
2010
Land-use practices aiming at increasing agro-ecosystem sustainability, e.g. no-till systems and use of temporary grasslands, have been developed in cropping areas, but their environmental benefits could be counterbalanced by increased N2O emissions produced, in particular during denitrification. Modelling denitrification in this context is thus of major importance. However, to what extent can changes in denitrification be predicted by representing the denitrifying community as a black box, i.e. without an adequate representation of the biological characteristics (abundance and composition) of this community, remains unclear. We analysed the effect of changes in land uses on denitrifiers for…
Community composition of soil microarthropods of acid forest soils as affected by wood ash application
2002
Summary The responses of soil microarthropod communities of acid forest soils to wood ash-application was studied both in a sixty years old pine forest stand (wood ash dose: 3000kg ha —1 ) and in laboratory microcosms (wood ash dose: 5000kg ha —1 ). We also tested whether microarthropod communities stressed with wood ash were more sensitive to an additional disturbance, drought, than the microarthropod communities in the ash-free soil. Microarthropods were sampled five times during the field experiment and four times during the laboratory experiment. At each sampling the abundance and community structure of microarthropods were analysed. In the field the number of collembolans, and in the l…
The Effect of perturbations on phytoplankton assemblages in a deep reservoir (Vouglans, France)
2003
Disturbances, such as rainfall and hydrological management of Vouglans reservoir, seem to influence the establishment of the ecological system inside this man-made lake. In this paper, the main effect of these disturbances are changes in the z mix :z eu ratio, with a shift in the composition and phytoplankton dynamics, and consequently in the Shannon’s diversity. The seasonal changes found in the surface layers of Vouglans reservoir were typical for mesotrophic and temperate lakes, but some perturbations induced the ‘reversion’ to an earlier stage in the expected successional pattern during the stratification period. This early-state displayed an intensive proliferation of the filamentous u…
Community Structure of Gastropods in Seagrass Meadows at Coastal Area of Nusi and Gersen, Nabire Regency
2020
Gastropods plays an important role in the food chain on seagrass ecosystem and its existence are depend on the physical-chemical factors in the seagrass ecosystem. This study aims to determine the density and diversity of gastropods associated in seagrass habitat in Nusi and Gersen coastal waters. The measurement results of some physical-chemical waters variables, are still quite good for the life of gastropods. Species composition of gastropod in Nusi at higher than at the Gersen, but instead of individual density in Gersen more higher than Nusi. Diversity index of gastropods at Nusi station is higher (3,757) than Gersen (3.053), on the contrary the eveness and dominance index are higher a…
Effect of cobalt and silver nanoparticles and ions on Lumbricus rubellus health and on microbial community of earthworm faeces and soil
2016
The aim of this study was to investigate the impact of silver and cobalt, supplied both as ions and nanoparticles (Ag+, Co2+, AgNPs, CoNPs) through contaminated food to earthworms (Lumbricus rubellus), on their health as well as on microbial community of both soil and earthworm faeces. Earthworms and microbes were exposed to the contaminants in laboratory microcosms with artificial soil. Contaminants were supplied once a week for 5 weeks by spiking them on horse manure. The accumulation of CoNPs and Co2+ in earthworm tissues was two and three times greater than AgNPs and Ag+, respectively. Except for AgNPs, contaminants significantly affected microbial community structure of earthworm faece…
Soil decomposer animal community in heavy-metal contaminated coniferous forest with and without liming
2002
Abstract Responses of decomposer animals to heavy-metal contamination were studied near a Cu–Ni smelter in Finland. Samples were taken 0.5, 2 and 8 km from the smelter. In addition, plots fertilised with lime were sampled. Decomposer community in coniferous forest soil appeared to be quite resistant to heavy-metals. Only in the vicinity (0.5 km) of the smelter, were numbers of soil animals clearly decreased and their community structure strongly altered as compared to the control site (8 km). At the 2-km site, the community structure was only slightly changed. Most of the collembolan species were still found at the 0.5-km site. High metal sorption capacity of the humus, and heterogeneous di…
Nested assemblages resulting from host size variation: the case of endoparasite communities in fish hosts
2001
Nested species subsets are a common pattern in many types of communities found in insular or fragmented habitats. Nestedness occurs in some communities of ectoparasites of fish, as does the exact opposite departure from random assembly, anti-nestedness. Here, we looked for nested and anti-nested patterns in the species composition of communities of internal parasites of 23 fish populations from two localities in Finland. We also compared various community parameters of nested and anti-nested assemblages of parasites, and determined whether nestedness may result simply from a size-related accumulation of parasite species by feeding fish hosts. Nested parasite communities were characterised b…
Long-Term Effects of Climate Warming on Forest Soil Collembola
2005
Long-term changes in the collembolan community structure were studied in a Scots pine forest in northern Latvia over a period of 11 successive years (1992–2002). Soil Collembola were yearly sampled from three pine forest stands of different age – young (30 to 40 years old), middle-aged (50 to 70 years old) and old (150 to 200 years old). During the study period a statistically significant increase in sums of positive temperatures (>+4°C) was recorded and a gradual decrease in species richness of Collembola was observed in all forest stands. The study showed that sums of positive air temperatures produce statistically significant effects on collembolan populations. Community responses were s…