Dr. K. Greg Murray
Size or age distributions of trees often yield valuable clues about changing environmental conditions and the responses of populations to them. In a recent study, we measured the size distribution of Eastern Hemlocks in a forest near Lake Michigan (the Hope College Nature Preserve) to determine whether active recruitment into the population is taking place at a similar rate as in the past. Increment cores were collected from 37 of the trees across the entire size range to establish the relationship between trunk diameter and age. Further analysis found that the size distribution was strongly skewed toward the intermediate and larger tree size classes, suggesting a failure of recent recruitment relative to that in the past. Age data collected from increment cores suggests that Eastern Hemlocks on this site take approximately 41 years to reach just 10 cm dbh (diameter at breast height), and coupled with the size distribution these data suggest that recruitment into the population has been virtually zero since the early 1970’s. Potential reasons for this decline in recruitment include, but are not limited to, herbivory by deer and possibly climatic changes in the last few decades (increasing temperatures and decreasing precipitation). Regardless of the reason, Eastern Hemlock will decline in density in this forest over the long term if the observed trend continues into the future. Our group plans to extend data collection to similar forest sites in West Michigan, both north and south of the Hope College Nature Preserve.
Repository citation: Gomez-Seoane, Andrew, "Long Term Population Trends of Tsuga canadensis in a West Michigan Dune Forest" (2013). 12th Annual Celebration of Undergraduate Research and Creative Performance (2013). Paper 66.
April 12, 2013.