The community structure of Lake Kinneret (Israel) microorganism populations: size distribution and succession

2000 ◽  
Vol 42 (1-2) ◽  
pp. 49-54 ◽  
Author(s):  
T. Bergstein Ben-Dan ◽  
D. Wynne ◽  
B. Shteinman ◽  
Z. Hu ◽  
Y. Kamenir
Keyword(s):  
Size Distribution ◽  
Bacterial Population ◽  
Vertical Plane ◽  
Term Effect ◽  
Lake Kinneret ◽  
Bacterial Populations ◽  
Long Term Effect ◽  
Bacterial Succession ◽  
Total P

The abundance and succession of bacterial populations, and their biovolume has been studied in the deepest station of Lake Kinneret, Israel during spring–summer. These parameters were then related to the chemical, biological and physical/hydromechanical conditions in the lake. Medium sized cells (2–3 μm) dominated the bacterial population in the spring, then in mid-summer the smaller cell fraction (1 μm) took over. Relatively low numbers of large cells (10 μm) were counted, but the biovolume of this fraction was significant, especially in mid-summer. Both the abundance and biovolume of medium sized cells were positively correlated with NH4+ and O2 concentrations, but not with NO3–, inorganic orthophosphate (Pi) and Total-P. At water temperatures above 28°C, the biovolume of medium sized cells decreased, probably due to faster grazing of zooplankton. When water circulation in the vertical plane was dominant, large cells disappeared from the water column, due to sinking to the bottom. We conclude that chemical parameters, such as NH4+ and O2 concentrations, had a long-term effect on bacterial succession and size distribution, whereas hydromechanical mechanisms, such as turbulent mixing in the horizontal or vertical planes, had a short-term effect.

Long-term effect of fresh and composted cattle manure on the size and nutrient composition of dry-sieved soil aggregates

2012 ◽  
Vol 92 (4) ◽  
pp. 673-683 ◽  
Author(s):  
J. J. Miller ◽  
E. Bremer ◽  
B. W. Beasley ◽  
C. F. Drury ◽  
B. J. Zebarth ◽  
...  
Keyword(s):  
Size Distribution ◽  
Soil Aggregates ◽  
Wood Chip ◽  
Aggregate Size ◽  
Soil Samples ◽  
Term Effect ◽  
Cattle Manure ◽  
Wood Chips ◽  
Long Term Effect

Miller, J. J., Bremer, E., Beasley, B. W., Drury, C. F., Zebarth, B. J. and Larney, F. J. 2012. Long-term effect of fresh and composted cattle manure on the size and nutrient composition of dry-sieved soil aggregates. Can. J. Soil Sci. 92: 673–683. Application of feedlot manure to cropland may impact the size distribution and nutrient content of soil aggregates. The objective of this study was to determine the effects of fresh or composted feedlot manure containing straw or wood-chip bedding on dry-sieved aggregate size distribution and nutrient contents. Surface (0–15 cm) soil samples were obtained from a long-term field experiment where treatments were fresh (FM) or composted manure (CM) containing straw or wood-chips applied annually at 0 (control) or 77 Mg ha−1yr−1for 11 yr. Air-dried soil samples were separated using a rotary sieve into six aggregate size fractions ranging from <0.47 mm to >12.7 mm. Total C, total N, C:N ratio, soil mineralizable N (41-d incubation), total P, soil test P, and P saturation index were determined on the six aggregate fractions. The amendments significantly (P≤0.05) increased the proportion of smaller (<0.47 mm) aggregates and decreased the proportion of the larger (>12.7 mm) aggregates relative to the unamended control. The geometric mean diameter (GMD) was also lower and wind erodible fraction (WEF) was greater for the amended treatments than unamended control. We attributed this manure effect to increased organic matter content in the soil making the aggregates more friable and susceptible to breakdown by tillage. Carbon, N, and P concentrations were not shifted to smaller aggregate sizes where root growth and nutrient uptake are generally greater. The exception was mineralizable N, which tended to be greater in the finer<0.47 mm fraction. Mineralizable soil N in all aggregate sizes ≥0.47 mm was reduced for wood-chip compared with straw bedding, and resulted in net N immobilization in aggregate sizes ≥1.2 mm. Phosphorus sorption was lower in soil amended with wood-chips compared with straw bedding for aggregates ≥0.47 mm. Long-term manure application may shift soil aggregates from larger to finer fractions because of greater friability and suggests that these soils should be managed to avoid the greater risk of wind erosion.

A long-term effect of subliminally presented words

2010 ◽  
Author(s):  
Andreas T. Breuer ◽  
Michael E. J. Masson ◽  
Glen E. Bodner
Keyword(s):  
Term Effect ◽  
Long Term Effect
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