Vertical Distribution of Xiphinemabakeri Nematodes in Soil in a Douglas-fir Nursery

1974 ◽  
Vol 4 (2) ◽  
pp. 175-178
Author(s):  
Jack R. Sutherland
Keyword(s):  
Moisture Content ◽  
Vertical Distribution ◽  
Distribution Pattern ◽  
Seasonal Changes ◽  
Root Distribution ◽  
Pore Space ◽  
Douglas Fir ◽  
Soil Samples ◽  
Nematode Control ◽  
The Vertical Distribution

Soil samples were collected throughout the year to determine the vertical distribution of Xiphinemabakeri nematodes in soil in a Douglas-fir [Pseudotsugamenziesii (Mirb.) Franco] nursery and to monitor seasonal changes in nematode distribution pattern. Root distribution, moisture content, available pore space, and osmotic pressure were also determined for soil samples taken at various depths to see if they were related to nematode distribution. More than 90% of the nematodes were present in the upper 20 cm of soil, especially from 0 to 10 cm, and this percentage did not change with season. Nematode distribution was related only to root distribution. The significance of the results for nematode control practices is discussed.

Vertical distribution of pelagial zooplankton in a middle-sized dimictic valley reservoir

Biologia ◽  
2006 ◽  
Vol 61 (2) ◽  
Author(s):  
Martina Hudcovicová ◽  
Marian Vranovsky
Keyword(s):  
Vertical Distribution ◽  
Water Column ◽  
Seasonal Changes ◽  
Thermal Gradient ◽  
Summer Temperature ◽  
Zooplankton Abundance ◽  
Invertebrate Predation ◽  
Chaoborus Flavicans ◽  
Daphnia Cucullata ◽  
The Vertical Distribution

AbstractOur observations indicate the vertical distribution of zooplankton and its seasonal changes in Dubník II reservoir (Slovakia) are determined mainly by the thermal regime of the reservoir, by transparency, and by fish and invertebrate predation. During periods of circulation, zooplankton vertical distribution in the whole water column was more homogeneous, whilst during summer temperature stratification zooplankton concentrated in the epilimnion — rotifers in higher layers than crustaceans. During summer stagnation a steep thermal gradient occurred at the boundary of the epi-and hypolimnion and low temperature and low dissolved oxygen in hypolimnion offered a refuge for Chaoborus flavicans larvae against fish, enabling coexistence of vertebrate and invertebrate predation. This evidence supports our previous findings concerning dominance of rotifers in zooplankton and representation of crustaceans by small-bodied species in the study reservoir. Steep thermal gradient and the presence of Chaoborus larvae caused very low zooplankton abundance in the lower part of the water column and a reduction of cladocerans refuges against fish to layers of thermocline or closely under thermocline where Daphnia cucullata and Daphnia parvula were found. Our previous assumptions about the high density of zooplanktivorous fish in Dubník II reservoir are supported by the fact that these small cladocerans are represented by smaller individuals in the upper layers and bigger individuals in deeper layers.

Vertical distribution pattern of naidids in granular activated carbon filters and potential technology to control their penetration risk

2018 ◽  
Vol 18 (6) ◽  
pp. 1976-1983
Author(s):  
Xiao-Bao Nie ◽  
Yun-Zi Tang ◽  
Chang-bo Jiang ◽  
Yuan-Nan Long ◽  
Pan-Pan He ◽  
...  
Keyword(s):  
Drinking Water ◽  
Activated Carbon ◽  
Vertical Distribution ◽  
Distribution Pattern ◽  
Granular Activated Carbon ◽  
Distribution Patterns ◽  
Distribution Data ◽  
Vertical Distribution Pattern ◽  
Filter Bed ◽  
The Vertical Distribution

Abstract Aquatic worms propagated in granular activated carbon (GAC) filter has become a troublesome problem for drinking water supply. This study investigated the vertical distribution patterns of naidids in GAC filter beds and assessed the effect of an additional sand bed, located below the GAC bed, in preventing naidids from being present in effluent. The results indicated that the vertical distribution data of naidids in the GAC filter bed were well fitted by a Gaussian distribution, and the location of peak population density was mainly affected by downward flow. Backwashing experiments revealed that additional pressure air scouring shifted the distribution pattern of naidids in the GAC filter bed, resulting in a significant enhancement in naidid removal efficiency. Additionally, the addition of a sand bed exhibited pronounced interception and inactivation effects on naidids, suggesting that it may be a very promising technology for preventing naidids propagated in GAC filters from being present in the effluent.

Strontium-90 from fallout in the diet and milk of a dairy herd

1960 ◽  
Vol 27 (1) ◽  
pp. 47-57 ◽  
Author(s):  
G. W. Cox ◽  
A. Morgan ◽  
R. S. Tayler
Keyword(s):  
Vertical Distribution ◽  
Dairy Cows ◽  
Dairy Herd ◽  
Soil Samples ◽  
Strontium 90 ◽  
Different Depths ◽  
Stable Strontium ◽  
The Vertical Distribution

SummaryThe diet and milk from a herd of dairy cows were analysed regularly for 90Sr and calcium. The ‘observed ratio’ (the ratio of 90Sr to calcium in the milk divided by the ratio of 90Sr to calcium in the diet) was found to be 0·10 against 90Sr in favour of calcium, which corresponds well with the results of other workers. The amount of 90Sr secreted into the milk was 1·2% of the total ingested. Similar values were obtained using stable strontium data.Soil samples from different depths and herbage were taken from three areas with different cultivation histories and analysed for 90Sr and calcium. The effect of ploughing on the vertical distribution of 90Sr in soil and on the 90Sr levels in vegetation was examined.

Dispersion of 226Ra in a Contaminated Environment

1988 ◽  
Vol 24 (1-4) ◽  
pp. 101-108 ◽  
Author(s):  
A.O. de Bettencourt ◽  
M.M.G.R. Texeira ◽  
M.J. Madruga ◽  
M.C. Faisca (INVITED)
Keyword(s):  
Organic Matter ◽  
Vertical Distribution ◽  
Gamma Spectrometry ◽  
Laboratory Experiments ◽  
Agricultural Soils ◽  
Soil Characteristics ◽  
Soil Samples ◽  
Vertical Profiles ◽  
Concentration Factors ◽  
The Vertical Distribution

Abstract A radium salts extraction factory was established in Portugal in 1908 in the northeastern part of the country. It was abandoned in the forties and is now in ruins. Wastes (mainly sands) highly contaminated with 226Ra were left near these ruins. Measurements were performed to evaluate the extent of the contamination due to the dispersion of radium around this site, using portable Gieger tube equipment as well as by gamma spectrometry analyses of soil samples. Vertical profiles of soil were taken to a depth of about 40 cm, and 5 cm sections were analysed by gamma spectrometry to evaluate the vertical distribution of 226Ra and 210Pb. Some soil characteristics, such as pH, organic matter and exchangeable calcium and radium were also analysed. The dispersion of radium seems to be mostly due to the removal of contaminated wastes by mechanical means, although some leaching may have occurred. Laboratory experiments were also conducted on sandy and agricultural soils to study the leaching of 226Ra and 210Pb with rainwater and to help explain the results obtained in the field study. The observed influence of different parameters on this leaching are briefly discussed. Vegetables grown on these soils (mainly cabbage) were analysed for their content of 226Ra and 210Pb in order to calculate concentration factors. For 226Ra, these range from about 7 x 10-3 to 7 x 10-2. For 210Pb, they range from about 10-3 to 2 x 10-2.

scholarly journals The Vertical Distribution Pattern of Microbial- and Plant-Derived Carbon in the Rhizosphere in Alpine Coniferous Forests

2021 ◽  
Author(s):  
Wentong Gao ◽  
Qitong Wang ◽  
Xiaoming Zhu ◽  
Zhanfeng Liu ◽  
Na Li ◽  
...  
Keyword(s):  
Vertical Distribution ◽  
Distribution Pattern ◽  
Soil Depth ◽  
Dominant Role ◽  
Mineral Soil ◽  
Coniferous Forest ◽  
Organic C ◽  
Vertical Distribution Pattern ◽  
Picea Asperata ◽  
The Vertical Distribution

Abstract Background and aimsWhile the quantitative assessment of plant- and microbial-derived carbon (C) in the soil organic C (SOC) chemical composition in soil profiles has been initially explored, the vertical distribution pattern of these two C sources and their dominant role in SOC formation based on the insights related to the rhizosphere are still lacking.MethodsWe quantified the divergent accumulation of microbial-derived C (i.e., microbial residues), plant-derived C (i.e., lipids and lignin phenols) and SOC in the rhizosphere at various depths (0-10 cm, 10-20 cm and 20-30 cm) in the upper mineral soil and analyzed its control factors in an alpine coniferous forest (Picea asperata. Mast). We further revealed the relative contribution of plant- or microbial-derived C to rhizosphere SOC in the soil profile.ResultsThe contents of microbial- and plant-derived C and SOC in the rhizosphere decreased with soil depth and were mainly regulated by root and microbial biomass. Moreover, the contribution of microbial-derived C dominated by fungal residues to rhizosphere SOC at each soil depth (more than 62%) was much higher than that of plant-derived C (less than 6%), implying that the soil microbial C pump was intensely stimulated in the rhizosphere.ConclusionsThese results indicated that microbial-derived C was the main contributor of rhizosphere SOC at various depths in the upper mineral soil. Our findings provide direct experimental evidence for assessing the dominant contribution of microbial- or plant-derived C to SOC in the soil profile from the perspective of the rhizosphere.

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