Differences in phenotypic characteristics: Comparing the growth rate among sub-populations of eastern red cedar (Juniperus virginiana) to different growth treatments

Background/Question/Methods

Plants that have an extensive geographical range can slowly create different sub-populations that are more isolated from other individuals within the same species. This can lead to extended periods of isolation and potentially develop local adaptations within these sub-populations from the constant exposure to different environmental parameters. Eastern Red Cedar is one of the most extensive conifers in the eastern portion of North America and its vast range has the potential to isolate individuals from one another. My goal was to see if different Eastern Red Cedar sub-population saplings would display differences in key phenotypic characteristics such as relative growth rate of height (cm), diameter (mm), crown size (cm). Also, I am interested to see if the exposure to different treatments, such as Bromus inermis, and fire would affect the phenotypical traits and survivability. This experiment was conducted in a greenhouse using 40 saplings from six different Eastern Red Cedar populations (Michigan, New Jersey, Wisconsin, South Dakota, Oklahoma, and Nebraska) and four different treatment groups (control, grass, fire, and grass w/fire). There was a total of 240 saplings used for this experiment and lasted from May 9th-Septemeber 29th.

Results/Conclusions

There was a significant effect in the mean of height and crown size relative growth rate between the New Jersey and Nebraska, Michigan and Nebraska, and New Jersey and Wisconsin populations. I found a significant effect in the mean of relative growth rate for the height, diameter, and crown size of Eastern Red Cedar saplings between the control and Bromus inermis treatment groups. In addition, there was a significant effect in the survivability of Eastern Red Cedar saplings when exposed to the different treatments of grass and fire. These results could indicate that the local conditions of the origin from some of these populations have fixed onto certain phenotypical traits and where able to grow at different rates in height and crown size despite the same environment conditions from the control group. These results also suggest that the effect of Bromus inermis and fire treatment groups made it difficult for the Eastern Red Cedar saplings to grow in the same conditions and could not withstand the intensity of the three different treatment groups. Overall, the experiment shows that some populations grow at different rates in height and crown size, but have difficult time surviving from the effects of Bromus inermis and fire treatment.