1. The Willowbrook Project Amira Hassan, Nick Gonzalez, Nuwan Panditaratne and Todd Stein PRESENT:
2. Introduction The Willowbrook Project focused on analyzing the sensitivities of the ring porous species of trees in Willowbrook Park, specifically their sensitivities to temperature, precipitation and drought severity. After measuring the widths of tree rings we ourselves cored and sampled in the park, and standardizing the data using various software tools meant to organize and analyze our findings, we were able to compare the information to data records of temperature, precipitation, and drought severity in the area dating back to 1895. Hoping to find a correlation between our discovered ring data and the climate data of and around Willowbrook Park, a series of statistical correlation tests were conducted to see how similar the data sets were, thus, identifying whether or not the correlations we were looking for existed at all. Our findings were rather interesting.
3. The following video depicts the general concepts and methodologies of the Willowbrook Project
4. Click on green screen to play mini video documentary of project
5. The following is a screen shot of the excel spreadsheet we worked with to make all of our graphs and statistics
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7. The following graphs represent the data we have collected over the course of this experiment.
9. After coring non-native species in Willowbrook Park (a process that is minimally invasive to a tree and produces a small cylindrical core of the tree which we can use to measure the growth of a tree per year) we were able to produce a timeline (in blue) of the raw tree width data over time (dating back to 1906). Trying to eliminate natural anomalies in average tree growth (like larger tree widths in the early years of a tree simply due to quicker growth during the youthful years of a tree) we standardized the tree width data to eliminate the natural growth of the trees from factorability when considering why external anomalies occur.
11. The timeline displays the correlation between the Average Temperature in July and the Standardized Tree Width plotted over a time interval from 1949-1950. When graphing the widths and the average temperature and fitting a trend line to the graph, you would notice that there is a negative trend; meaning that as temperature decreased, tree growth increased. With this supportable data, one could conclude that optimum tree growth in the summer months prefers cooler temperatures.
13. The above timeline displays the correlation between the Average Precipitation in July and the Standardized Tree Width plotted over a time interval from 1949-1950. When graphing the widths and the average precipitation and fitting a trend line to the graph, you would notice that there is a positive trend, meaning that as precipitation increased, tree growth increased. With this supportable data, one could conclude that optimum tree growth in the summer months prefers wetter climates.
14. PDSI vs. Standardized Tree Widths (Lagged Correlation of December PDSIs from 1949-2010) *Notice a positive correlation more significant than the previous graphs
15. The ring porous trees of Willowbrook Park appear to show signs of sensitivity to factors of temperature, precipitation and PDSI (Palmer Drought Severity Index). The graph above displays a distinct correlation between the standardized tree widths The Willowbrook Project group measured with the lagged PDSI from 1949-1950. The R2 value represents a measure of relation between the widths and the drought index; a value of one meaning they are exactly identical and a value of 0 meaning they are not relatable at all. Though .21 may seems like a small number, it is significant enough to allow us to state that tree growth during any given year is differentiable due to drought severity and the state of drought severity of previous years, supported by the lagged correlation.
16. Conclusions: After weeks and weeks of research and formulating conclusions supported by the data we collected in the beautiful Willowbrook Park, we have arrived at a point in our research where we could rather confidently state the following: Analyzing tree core samples is a useful tool in identifying the effects of external stimuli like temperature, precipitation and drought. During the summer months, tree growth increases in cooler temperatures and wetter climates. In the winter months, tree growth increase is inversely proportional to increase in the Palmer Drought Severity Index and is also affected by the drought index of the year’s prior. Tree sensitivity to a particular factor such as temperature, precipitation and drought index varies with the time of the year, conditions of years passed, and natural seasonal tree growth.
17. Final Note Upon conclusion of this experiment we statistically found correlations that identify sensitivities of the ring porous species in Willowbrook Park to temperature, precipitation and drought severity. We found a negative correlation between our ring data and the temperature in the areas, meaning tree growth of these particular species of trees is optimized in cooler weather. We also discovered that the trees are most sensitive to drought severity and the amount of water availability in the area; the correlation being greater tree widths with more precipitation. When testing the drought severity data specifically we found that tree growth of a particular year is also sensitive the drought severity of years passed. When reflecting upon the conclusions we made at the completion of this experiment, simply stating that trees in the area grow best in cooler and wetter climates doesn’t come off as most interesting and scientifically relevant end to months of labor on the Willowbrook Project. However, the significance these findings represent has the potential to be quite extraordinary. The discovery of these sensitivities backed by statistical data give us room to make assumptions about the growth of these trees in the future depending on future climate conditions. There is little denying that the Earth is warming, a fact that doesn’t seem promising for the ring porous species of Willowbrook Park, based on the findings we arrived at. What is to become of precipitation and drought in the area in the years to come is a mystery, but a project such as this with findings such as the ones we arrived at could prepare us to expect the inevitable.
