6. Methods
• Study site is located by the northwest side of University Arboretum
• Mediterranean climate
• This study was conducted between February and April in 2012.
7. Methods
Treatment vs. control
• 20 x 10 feet slope
• Treatment site was added ammonium sulfate ;(NH4)2SO4 ,prior to the first
sampling.
• Control site was untreated.
• A slope is divided into four sections; a top, 1/3 from a top, 2/3 from a top, a
bottom, and our group was
responsible for the 1/3 from a top and
a bottom.
8. Methods
Vegetation coverage sampling
• 2 x 2 feet quadrat
• we estimated percentages of vegetation coverage
for each species within a quadrat.
• 2 replicas were made from each 1/3 from top and
a bottom of a slope.
Soil sampling
• Soil samples were taken at the 1/3 from a top and a bottom of a slope.
• 3 replicas were made from each sections.
• First sampling was done in end of February and
the second sample was carried out in beginning of April.
10. Methods
Tullgren funnel system
• Sampled soils were processed in the Tullgren funnel system at a lab for the
extraction of arthropods.
• Intense heat from the excess of light on the soils, leads arthropods into a flask
set below a funnel.
• For the identification and counting process, we used a microscope.
11. Results
Mite and Springtail populations were predicted to increase in the presence of
added nitrogen and down the gradient; this was statistically analyzed by a two-
way ANOVA. Sample #2 for Mites and #1 for Springtails were statistically
insignificant and the null hypotheses were accepted. The following null
hypotheses showed significance.
12. Results
Variable: Ammonium Sulfate (NH4)2SO4
The chemical equation that converts ammonium to useable nitrite ions is as
follows:
NH4+ + 1/2 O2 ↔ NO2- + 2H+ + H2O (Wright 2004)
Since this reaction is able to go both ways, the chemical equilibrium of the
substances takes affect, so that when one reactant is added in excess it shifts to
the product side and vice versa. When an excess of ammonium and oxygen are
present, the chemical equilibrium then will shift over to the product side
producing the beneficial Nitrite ions, Hydrogen ions and Water. The nitrite ion
is then changed by bacteria in the following equation:
NO2-+ 1/2 O2 ↔ NO3- (Wright 2004)
The produced nitrate is then used then for plant growth.
13. Results
The chemical synthesis of the nitrite and nitrate ions inspired a hypothesis. We
predicted that the nitrogen rich plot would contain greater percent moisture
than the control plot.
This proved to be accurate however, a greater sample size is needed to draw any
solid conclusions from the data.
14. Results
Species diversity was also predicted to increase with the soil moisture. By
conducting a simple graphical representation of the soil moisture and the
calculated species diversity trends, the control plot and treatment plot graphs
were compared.
When comparing the trend lines, a direct correlation between both species
diversity and soil moisture was observed.
15. Results
Hypothesis: “Plant productivity in the fertilized plot will increase with the added
ammonium sulfate.”
These results indicated that there was a significant positive relationship between
the wild radish growth and the addition of nitrogen (R2=.5995). In contrast the
control soil showed a much less significant increase in plant growth over the
same time period (R2=.1142).
17. Results
The control plot however didn’t correlate at all. Both nitrogen and water are
needed to support a successful arthropod community population (Henze 1997).
A successful arthropod community population is identified as a population with a
stable species diversity. Species diversity correlates with the community’s
success because when a community is diverse, each niche is filled, and
symbiotic relationships effectively occur.
Symbiotic relationships stabilize the environment and only occur when diversity is
abundant. The control plot lacked stable species diversity because it was
lacking in nitrogen compared to the treatment plot.
18. Possible Error
• Soil moisture didn’t follow an expected trend like it should have. Perhaps
there was more clay content in specific areas of the soil, which prevented the
rainfall from draining properly down the gradient. This may have provided
some false positive or false negative hypotheses; more samples would need to
be taken to solidify the drainage pattern for the treatment plot and the control
plot.
• Major source of error was that one half of the experiment was conducted by a
group that I had no contact with. This communication wall added much
variability to our samples.
– False Arthropod classification
– Lack of diligence in correct counting
• The core samples that were taken were also very high in variability. Some
samples were very large, while other samples were very small. This would
greatly affect the amount of arthropods counted and throw off statistical tests,
especially the ANOVA, where replication data was key.
19. Fixing Error
• There are clear routes for reducing the percent error if this experiment
were to be repeated.
– Greatly increasing the amount of samples taken is a necessity for greater
accuracy for the analysis for the data.
– Extracting and counting all the samples in a small communicative group
– Single-handedly extracting data would also increase the accuracy of the
results.
20. Literature Cited
1. Belser L. 1979. Population Ecology on Nitrifying Bacteria. Annual Review of
Microbiology 33:309-333.
2. Bradford, J. 2004. The Soil Nitrogen Cycle. Anderson Farms Centers.
http://www.andersonsfarmcenters.com/PDF/FC_Jeff_Bradford_April06.pdf
3. Henze, Mogens, Paul Harremo ︽ , Jes la Cour Jansen, and Erik
Arvin. Wastewater Treatment, Biological and Chemical Processes. Berlin,
Germany: Springer, 1997
4. Mihelcic, James R. Fundamentals of Envionromental Engineering. New
York: John Wiley & Sons, Inc., 1999.
5. Moiser, A. 2004. Agriculture And The nitrogen Cycle: Assessing the Impacts
of Fertilizer Use. Scientific Committee on Problems of the Environment 1:234.
6. Sawyer J. 2008. Surface Waters: Ammonium is not Ammonia. Iowa State
University <
http://www.extension.iastate.edu/CropNews/2008/0421JohnSawyer.htm>
7. Verhoef, H. 1983. Releaser and primer pheromones in Collembola. Journal of
Insect Physiology 30:665-670.
8. Wright, S. 2004. Nitrification: the Basics.< http://www.wrights-
trainingsite.com/Nitrif1onb.html>
