Grade 12 | Ohio
Grade 12 | Ohio
Old-growth cliff-dwelling forests exist worldwide, but none have been definitively studied in Adams County, Ohio, where I live. Two species that survive on the dolomite cliffs near my house are northern white cedar (Thuja occidentalis) and eastern red cedar (Juniperus virginiana) (Figures 1 and 2). I became interested in these trees after reading an article by Dr. Douglas Larson from the University of Guelph in Ontario, Canada, who discovered old-growth white cedars growing on cliffs of the Niagara Escarpment in Canada. I wondered if the cliff-dwelling white and red cedars growing locally around my house were potentially as old as those documented by Dr. Larson, because they looked similar to the twisted trees in his study.
Then I found another article by Dr. Larson and learned that he documented old-growth cliff-dwelling forests on cliffs across the country and around the world, with white and red cedars being mentioned as species capable of obtaining old age on cliffs (Larson et al., 2000). I was even more intrigued. Could old-growth trees be present on cliffs in my own backyard? I hypothesized that the cedars in my area would follow this trend of old age and slow radial growth rates because they grow on cliffs with characteristics and associated plant genera similar to those found in Canada and around the world.
Eastern red cedar and northern white cedar both belong to the Cupressaceae family. Evidence shows that both of these species possess a radially sectored vascular system, resulting in a stem strip growth pattern (Figure 3) that allows them to reach more than 1,000 years of age when growing on calcareous cliffs on the Niagara Escarpment (Larson 2001).
The vascular system allows sections of the tree to be served by different roots (Larson et al., 1994). As roots die or are lost to rock fall, slumping of the soil and exfoliating bedrock, the sections of the tree supported physiologically by those specific roots die, leaving the rest of the tree to survive. This leads to a stem strip growth pattern in older trees (Matthes, 2002). This attribute can be essential to trees living in harsh cliff environments, where root or crown damage is prevalent. The loss of one root means only partial cambial mortality to the tree. White cedars on the Niagara Escarpment has been documented to survive with only 10 percent of their living cambium (Kelly et al., 1992).
Ancient forests in cliff ecosystems exist in Canada, the U.S., England, France, Germany, and New Zealand (Larson et al., 2000). In eastern North America sites, both northern white cedar and eastern red cedar on limestone cliffs have been documented of great age and with a slow radial growth rate (Larson et al., 2000). One of the oldest northern white cedars in the Niagara Escarpment was found to be 1,653 years of age (Larson 2001), while the oldest living eastern red cedar documented is more than 900 years old, growing along the Jacks Fork River in Missouri (Stahle, 1996).
Eastern red cedar and northern red cedar both inhabit the dolomite cliff systems of the Edge of Appalachia Preserve, where I live (Figure 4). My study was a two-year effort. First, in 2011 I investigated the radial growth rates and ages of the white cedar population, and in 2012 I investigated the ages and radial growth rates of eastern red cedar, which grow on the same dolomite cliffs as northern white cedars, at Cedar Falls (Figure 5) and Wilderness Preserves (Figure 6) in the Edge of Appalachia Preserve.
Two study sites within the Edge of Appalachia Preserve were selected in 2011 and 2012, based on the presence of dolomite cliffs with both northern white cedar and eastern red cedar inhabiting the cliff face. My study examined the age and radial growth rates of 38 red and 38 white cedars growing on dolomite cliffs at two sites. Cross-sections of downed cliff-grown trees were taken, and ring counts were conducted to obtain tree age. The sites selected and sampled were in Cedar Falls (Figure 7) and Wilderness Preserves (Figure 8).
The sites were searched for dead and downed red cedars that were attached, or had been attached, directly to exposed rock. A section of each tree was removed using a saw, at breast height (one meter) and labeled with a specimen identification number. Global Positioning System (GPS) coordinates were taken for each specimen and recorded.
In instances in which trees were sampled at other than breast height, due to excessive pith rot, a formula was utilized to account for missing inner tree rings (Kelly and Larson, 1996). In trees where the section height was greater than 5% of the total height of the tree, the following height-correction factor was derived to correct for tree rings lost: N = (C) (A) / (H-C) + A, where N is the new age of the tree, A is the age of the tree at section height (C), and H is the total height of the tree.
Rings were counted using a dissecting microscope along the longest radius from the tree’s center (Figures 9 and 10), if present.
In cases where centers were missing because of rot (Figure 11), I developed the following proportion for the variable to calculate the missing rings along the radius: r/p = e/x, where r is the radius present (cm.), p is the rings present, e is the estimated radius missing, and x is the missing rings. Radial growth rate was then determined for each sample by dividing the radius (mm) by the number of tree rings counted in that distance (Kelly et al., 1992).
Only specimens with 50% or more of the radius intact were used. The percent of radius present was found by using the following proportion: p/e = x/100, where p is the present radius (cm.), e is the total estimated radius, and x is the percent of radius present.
Comparisons of the data sets between northern white cedar and eastern red cedar were made. The first data set compared age, and the second compared the radial growth rate of both species sampled. Regressions were run analyzing whether a correlation existed between the age and the radial growth of the two tree species, meaning: Could one predict the age of a tree simply by measuring its diameter or, conversely, could one predict a tree’s radial growth rate simply by knowing its age? Collectively, these results were used to ascertain if northern white cedar and eastern red cedar growing on dolomite cliffs in Adams County share similar growth patterns due to synonymous habitat characteristics.
Results and Data
The radial growth rate and age averages of red and white cedars growing on dolomite cliffs on the Edge of Appalachia Preserve were extremely similar (Figures 12 and 13).
The mean radial growth rate of red cedar was 0.698 millimeters per year, 0.070 millimeters lesser than the mean radial growth rate of white cedar, which was 0.768 millimeters per year. Some very low radial growth rates were found in white and red cedar, respectively, at 0.2 and 0.4 mm per year. The mean age of the red cedars was 189.846 years, while the mean age of the white cedars was 211.358 years. This represented a 21.512-year difference in the average ages. Some very old individual trees were recorded, with 401- and 646-year-old white cedars and 304- and 319-year-old red cedars found.
Statistical analysis in the form of a linear regression proved that no correlation existed between the age and the radial growth rate of either species (Figures 14 and 15).
The linear correlation coefficients were -0.002329823 for red cedar and -0.00137004 for white cedar, respectively. These illustrate that the variable of radial growth rate is not predictable from the variable of age. For example, one cannot predict the radial growth of an individual tree based solely on its age.
Analysis & Interpretation
The data illustrate that my hypothesis was supported. Red cedar and white cedar growing on dolomite cliffs in Adams County do possess characteristics similar to other cliff-dwelling forests growing around the world (Larson et al., 2000), with low radial growth rates and old age. Age and growth rate distributions were similar for both red and white cedar at the study sites. This showed that these species were exposed to the same cliff-face growing conditions and responded with similar growth rates. A radially sectored vascular system is present in both tree species and is the major factor driving these results. The trees’ ability to survive with only 10 percent of their living cambium allows both species to reach old age and possess nearly identical radial growth rates.
The lack of correlation between age and radial growth rate in both species is likely owing to microsite variability on the sampled cliffs (Matthes-Sears and Larson, 1995). Due to the lack of studies focusing on cliff-dwelling eastern red cedar and northern white cedars, the potential for these species as old-growth trees is often overlooked, and opportunities to protect old-growth cliff communities are not being realized by conservation organizations. I hope to continue my study of old-growth trees on cliffs at other sites in hopes of documenting and protecting these rare ancient forests. Are there older trees to be documented at the Edge of Appalachia Preserve?
The author would like to thank Chris Bedel (preserve director, Cincinnati Museum Center, Edge of Appalachia Preserve) for project advising and fieldwork assistance; Mark Zloba (ecological manager, Cincinnati Museum Center, Edge of Appalachia Preserve) for his assistance with GPS software; Aaron McCann (mathematics instructor at West Union High School) for statistical analysis assistance; and Ryan O’Connor (master’s candidate at Eastern Kentucky University) for his manuscript review.
Kelly, P.E., E.R. Cook, and Douglas Larson. “Constrained growth, cambial mortality, and dendrochronology of ancient Thuja occidentalis on cliffs of the Niagara Escarpment: An eastern version of bristlecone pine.” International Journal of Plant Sciences 153.1 (1992): 117-127.
Kelly, P.E. and Douglas Larson. “Effects of rock climbing on populations of pre-settlement eastern white cedar (Thuja occidentalis) on cliffs of the Niagara Escarpment, Canada.” Conservation Biology 11.5 (1996): 1125-1132.
Larson, Douglas, J. Doubt, and U. Matthes-Sears. “Radially sectored hydraulic pathways in the xylem of Thuja occidentalis as revealed by the use of dyes.” International Journal of Plant Sciences, 155.5 (1994): 569-582.
Larson, Douglas, et al. “Evidence for the widespread occurrence of ancient forests on cliffs.” Journal of Biogeography 2 (2000): 319-331.
Larson, Douglas. “The paradox of great longevity in a short-lived tree species.” Experimental Gerontology 36 (2001): 651-673.
Matthes, U., P.E. Kelly, C.E. Ryan, and Douglas Larson. “The formation and possible ecological function of stem strips in Thuja occidentalis.” International Journal of Plant Sciences 163.6 (2002): 949-958.
Matthes-Sears, U., and Douglas Larson. “Rooting characteristics of trees in rock: A study of Thuja occidentalis on cliff faces.” International Journal of Plant Sciences 156.5 (1995): 679-686.
Stahle, D.W. “Tree rings and ancient forest relics.” Arnoldia, Winter 1996-1997.
This winning essay from the Museum’s Young Naturalist Awards 2014 is from a twelfth grader. Red and white cedars grow on the dolomite cliffs near this student’s home. An article on ancient cedars inspired him to investigate whether these cedars were hundreds of years old. His essay presents:
Have students explore the process of science with a discussion based on this essay.
Tell students that in the essay they are about to read a student, inspired by an article on ancient cedars, investigates whether cedars near his home are also ancient cedars. As students read the essay have them focus on the procedure that the student followed.
When students have finished have them discuss the essay. Ask:
Allow students time to explore other aspect of the essay that they found interesting.