| |
| author |
Erica Cowper
| | title |
Climate change and the Asteraceae family: Changes in leaf length and area from 1886 to 2021 in Morris County, NJ
| | abstract |
Climate change, specifically human-caused climate change, has presented ecosystems, and
organisms within them, with unprecedented challenges. In this study, I investigated how leaf size
has changed over time in response to climate change, with the hope to better understand one of
climate change's impacts. I utilized herbarium specimens, ImageJ, and climate data to see how
leaf size has changed over time in the plant family Asteraceae from 1886 to 2021. I analyzed 151
specimens from Drew University's Herbarium, the Virtual Chrysler Herbarium at Rutgers
University, and my personal 2021 field collections. These 151 specimens were representative of
10 genera, Ambrosia, Artemisia, Bidens, Cirsium, Eurybia, Euthamia, Eutrochium, Helenium,
Solidago, and Symphyotrichum. To measure leaf length and leaf area, I used ImageJ, software
used in various fields of biology to collect precise size measurements. After collecting leaf size
measurements for these specimens, I collected climate data from Weather Underground, NOAA,
and the NJ State Climatologists Office, to analyze how the climate in New Jersey has changed
over time, and relate this to how leaf length and area have changed over this 135 year period. A
correlational analysis was performed to determine if leaf length or area varied as a function of
year and three climate variables: annual mean maximum temperature, mean minimum
temperature, and mean precipitation for all ten genera combined, for these genera individually,
and over 30 year time periods. The results were not statistically significant for leaf length and
leaf area when all genera were combined. One genus, Euthamia, showed a statistically
significant increase in leaf area by year, but not leaf length, and this was consistent across all
three climate variables. In contrast, from 1950 to 1980, Ambrosia and Symphyotrichum both
showed a statistically significant decrease in leaf length and area as a function of the year, with
Symphyotrichum showing a statistically significant decrease for both dependent variables as a
function of mean maximum temperature. Additional research is needed to further investigate
some genera, specifically those that had a small representative sample in this study. Additional
research is also needed to further examine all the ways plants are affected by anthropogenic
climate change, and how they respond. My hypothesis was not supported by some of these
findings, specifically an increase in Euthamia leaf area. On the other hand, my hypothesis was
supported by other results, specifically a decrease in Symphyotrichum leaf length and area. These
findings support the idea that different organisms, even those within the same family, are
responding to climate change in different ways.
| | school |
The College of Liberal Arts, Drew University
| | degree |
B.S. (2022)
|
| advisor |
Tammy Windfelder
|
| full text | ECowper.pdf |
| |
