EVST Section 002
November 28th 2013
Forest Lab (Title)?
This Lab we were sent to the Whitewater Forest to perform an analysis on the toxicity of juglone found in black walnuts. We predicted that the nearby soil containing this toxin would cause there to be little to no herbaceous plant matter around. After we took all of our measurements we determined that our prediction was wrong and that as a whole the soil didn’t seem to be impacted all that much by the juglone. Our results came back as insignificant, yet we still have valuable data to discuss why it came out that way. Although we didn’t obtain the outcome we hypothesized the experiment was still in a way successful and important. Only one alfalfa didn’t germinate in the 1 meter soil and only 1 out of the 5 tomato didn’t germinate in the 5 meter soil so the juglone didn’t seem to impact the soil all that much.
For the Forest Lab our goal was to observe and investigate how an ecosystem is structured. The purpose of the lab is for us to gauge the trophic composition as well as the productivity of an ecosystem. In this case we went to the Benedict nature preserve to conduct our experiment. We first went over all the details of the lab with our TA’s before we jumped into it. We were given the proper materials to perform our measurements and then we were told a location to occupy and measure. We split up into our groups and sectioned out our quadrants initially. From there we proceeded to mark our biggest quadrant (25m x 25m) to ultimately record the amount of trees in that area. We recorded that data and then moved on to sectioning off a 10m x 10m square to measure all the trees with a DBH greater than 3cm. Once we finished that we sectioned off a 1m x 1m plot of land inside the 10m x 10m area to measure the insects in the small square. Lastly we sectioned off an additional 1m x 1m square to collect all the leaf litter. All of these plots and measurements went into the overall analysis of the trophic pyramids we later developed. The bottom layer represents the autotrophs, the second level represents the herbivores/detritivores and the top level represents the carnivores. We then used the biomass for each tree species to create the biomass pyramid. From there a energy pyramid could be constructed. We used the previous biomass values to be able to estimate the energy equivalent for each level of the pyramid. This led us to calculating the ecological efficiency which is the transfer of energy from one trophic level to the next.
The methods utilized for this lab were relatively simple. We mainly used a tape measure and a coat hanger to gather our data with. So to measure off each section we would go the distance required and mark the spot in four corners to mark our area plot. As for the smaller plots we used a 1m x 1m coat hanger and recorded everything within that area. We used the tape measurer to find out the DBH of the trees. All of the methods to calculate the numbers/values for the various biomass’s of the different trophic levels are contained in the lab manual pdf.
We performed a two tailed T-Test of the decomposition of the leaf litter weights before and after. Here are the results we got for that.
Comparing Means [ t-test assuming equal variances (homoscedastic) ]
Degrees Of Freedom
Hypothesized Mean Difference
t Critical Value (5%)
t Critical Value (5%)
Critical Value (5%)