City Creek Nature Notes – Salt Lake City

June 25, 2017

June 24th Revision 2

Filed under: Gambel's Oak, Uncategorized — canopus56 @ 10:57 pm

The Oak Forest Over Time

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Composite images of lower City Creek and Ensign Peak oak forest in 1912 and 2017 (Fisher 2017, Shipler 1912 taken near 9th Avenue and A Street).

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Composite images of Dry Fork Canyon mouth in 1958 and 2017 (Drobnick 1958, Fisher 2017 taken near North Campus Drive and Mario Capecchi Drive, west of Primary Children’s Medical Center; Drobnick image is modified).

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Composite images of George’s Hollow in 1958 and 2017 (Drobnick 1958; Fisher 2017, taken from This is the Place Park; Drobnick image is modified).

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Composite images of the mouth of Deaf Smith Hollow’s mouth taken by Fisher 2017 at 9155 South 3100 East) compared to Rogers’ 1977 image (Rogers 1982, Plate 45B) and Gilbert’s 1901 image (Rogers 1982, Plate 45A; taken near SE half, Sec. 2, T3S, R1E, SLBM, near 9788 Wasatch Boulevard).

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Composite images of Landsat Images, 1985 and 2017 (NASA, 1985 and 2017).

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Trend in Acres Burned in Utah Wildfires, 1960-2012. (Utah Dept. of Agriculture and Food 2013 at 8).

11:30 a.m. I am standing at the corner of 11th Avenue and Bonneville Drive where the road turns north above the lower canyon that leads to Guardhouse Gate. The Gambel’s oak forest is visible on the distant hillsides around Ensign Peak. Across the almost forty years that I have lived near the canyon, I have had the subconscious impression that the Gambel oak chaparral forest is expanding on the southern half of the Salt Lake salient hillsides that overlook the city and on the slopes that face the canyon. I take a photograph of the Gambel’s oak forest around the Ensign Peak area and begin looking for historical comparison photographs.

Trees are unique among modern urbanite relationships with nature because of their longevity (Jonnes 2016). Our dogs share our lives for at most fourteen years, elephants in our zoos live to be forty, our life-long friends begin to pass and disappear in our sixties, and only a few zoo animals, like a giant tortoise in my boyhood Cleveland zoo will outlive me at 100 years of age. In our ordinary daily lives, only trees share our longevity. Using modern internet based maps, I am able to view near real time images of homes that I have lived in the past, and I look at images of a home where, as a boy, I helped my father plant four sapling oak trees. The first summer, I used to a broom to save them from an infestation of Eastern tent caterpillar moths. Now they have grown to a strong maturity of fifty feet in height. I wonder how the Gambel’s oak chaparral forest that has surrounded me over the last forty years has changed.

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Per Thoreau’s “Journal” on June 24th, 1852, he observes clouds and describes the virtues of watching clouds. He smells fragrances blowing off a meadow, and notes that twin flower (Linnaea borealis) is past its peak bloom. On June 24th, 1853, he notes that birds use hair to line their nests. On June 24, 1856+, he notes that the surface of springs are covered with dust and insects. On June 24, 1857, he examines a screech owl nest. On June 24, 1860, he sees young bluebirds.

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How has the Gambel’s oak forest changed over the last one-hundred years along the eastern face of the Wasatch Front Mountain range that rings Salt Lake Valley? Is it advancing or retreating in response to the high snow years between 1900 and 1990? Is it retreating in response to the now nearly multi-decadal drought from 1997 to the present? In 1949, Christensen examined the distribution of Gambel’s oak forests along the Wasatch Front, and he concluded that the oak forests had in some local instances proliferated since the arrival of the Euro-American colonists (id. at 64). He found increases in maples on the Oquirrh Mountains on the west side of Salt Lake valley. In a 1957, he found that oaks on the BYU “Y” mountain were expanding downslope in a manner similar to that later seen by Rogers in the 1980s (Christensen 1957). Generally, Christensen concluded that most of the increases occurred after 1900 (Rogers, 19). In 1982, Rogers at Columbia University re-examined the question in light of the then developing question of climate change. He compared 49 historical images with some 400 contemporary matching photographs. Based on images hillsides near Tooele and west of Lone Peak, Rogers concluded that both Big Tooth maples and Gambel’s oaks were expanding at selected locations (Rogers, p. 136 and Plates 43, 45, and 46). The oak chaparral forest is expanding at a rate of about 4 inches per year and was also thickening in place (Rogers 1982 at 19 and 132; Christensen 1964, 1957 and 1949). 4 inches per year implies a potential oak forest advance of 33 feet every 100 years.

Working geographically from the north end of the Salt Lake valley to the south, I created some “then and now” images of Wasatch Mountain Front Range slopes covering a range of 116 years. In 1912, local commercial photograph Harry Shipler took an image of City Creek Canyon near the corner of 9th Avenue and A Street (Shipler 1912). A comparison of Shipler’s photograph with one taken by me in July 2017 shows fill-in in lower City Creek Canyon, in the gulch to the northeast of Ensign Peak, and in the gulch that contains Bonneville Shoreline trail (far upper right hand corner of the image).

In 1958, botany graduate student Rudy Drobnick surveyed locations of Gambel’s oaks in northern and central Utah (Drobnick 1958 at Plates 2 and 3). He took images of the mouth of Dry Fork Canyon behind and before the construction of the University Hospital and of George’s Hollow below Wire Mountain to the west of the current Natural History Museum and state arboretum at Red Butte Gardens. Comparison of Drobnick’s 1958 and my 2017 images of Dry Fork shows some thickening of the oak forest at the left center (see images North Campus Drive and Mario Capecchi Drive). An oak copse in the foreground of the 1958 image, that is obscured in the 2017 image, also thickened. In contrast, comparison of Drobnick’s 1958 and my 2017 image of George’s Hollow shows a retreat of the oak chaparral forest (see image taken from This is the Place Park, west of the main statuary monument). A local informant states that the retreat of the oak groves in George’s Hollow was the result of a fire sometime between 1980 and 2010. This was also my recollection, but I could not find a confirming newspaper account.

Moving further south to Deaf Smith Canyon between Big and Little Cottonwood Canyons, I updated some of the prior historical photographic matches done by University of Utah graduate student Gary Rogers (1982) (later at Columbia University), and I created some new “then and now” images. Rogers compared historical images taken by Grove Karl Gilbert during 1901 of many locations throughout Utah, including of Deaf Smith Canyon above the Kings Hill Subdivision and between Little and Big Cottonwood Canyons. Gilbert’s image was taken near the Grove Karl Gilbert Geologic Memorial Park south of Little Cottonwood Canyon’s mouth (9788 Wasatch Boulevard, Sandy). Gilbert authored a landmark geologic 1890 report on ancient Lake Bonneville, and he named Lake Bonneville after early Utah explorer B. L. E. de Bonneville (Gilbert 1890). Gilbert accompanied John Wesley Powell during his western surveys from 1874 to 1879, and worked for many years as a researcher under Powell, the second director of the United States Geological Survey. In 1982 by comparing his 1977 and Gilbert’s 1901 photographs, Roger’s concluded that there was some localized thickening of oak chaparral forest around the entrance Deaf Smith Canyon. This trend continues through a comparison image taken in July 2017 that combines my, Rogers’ and Gilbert’s images. Localized thickening is seen in the two areas marked with boxes in the Gilbert image.

On a larger scale, comparison of a 1985 and 2015 Landsat images of the Salt Lake Valley shows no definitive changes on the oak forest between Ensign Peak on the north and Parley’s Canyon on the south (image). Given the rate of potential growth of 4 inches per year, the resolution of Landsat images is insufficient to capture changes in the Gambel’s oak forest except for large wildfire burns.

Both advancing and retreating changes are seen over the last one-hundred years in Gambel’s oak chaparral forest of the Wasatch Front Mountain Range around the Salt Lake Valley, but the changes are localized. An increase of 33 feet in one-hundred years is generally not seen, but it did occur in lower City Creek Canyon where increased ground water percolation from the lawns of new homes constructed above the canyon provided an opportunity for expansion. That expansion is also seen in one area at the mouth of Dry Fork (2017 image, marked with box).

How will the forest change in the future? Rogers noted that most changes occurred after the 1940s (Rogers, 136). Rogers speculated, while calling for further research, that the cause of the expansion of Big Tooth maples and Gambel’s oaks was increased precipitation (Rogers, 136-137). Although difficult to show with certainty, Rogers felt that improved fire suppression by modern Utahans was not the cause of the increase. The rate of fires after 1900 had been constant despite a ten-fold increase in fire suppression funding (id. at 140). In theory, the cycle of fire followed by rapid cheat grass invasion should slowly erode the boundaries of the existing oak forest. Rogers’ offered the tentative explanation that extreme cold weather in the late nineteenth century may have overwhelmed the negative effects of overgrazing and fire, and colder weather allowed the oak forest and maples to expand (Rogers, 138-139).

Rogers’ 1982 hypothesis is consistent with later, recent tree ring studies in the Intermountain West that reconstructed a 576 year precipitation record for Rocky Mountains, including Utah (Bekker et al 2014, DeRose et al, Wang et al; see January 30th and February 9th). From the tree rings, Bekker et al found that persistent, severe droughts were far more prevalent in the distant past than in the 150 years of Euro-American presence in northern Utah. The local advances of Big Tooth maples and Gambel’s oaks may have been a long-term, delayed response to more frequent rain and snow. However, in 1984 and shortly after Rogers published his results, the number of acres annually burning in Utah began an upward trend that continues to today (Utah Department of Agriculture and Food 2013 at 8).

If global warming is considered, available modeling studies suggest the Gambel’s oak forest will retreat. Shafer and Bartlein at the University of Oregon and Thompson at the United States Geological Survey used global climate models to estimate, among other factors, the mean temperature of the coldest month and soil moisture index for 2090 (Shafer, Bartlein and Thompson 2001). Those constraints were compared to requirements for many plants in the Intermountain west. In their extreme scenarios that looked forward almost ninety years, they concluded, for example, that sagebrush would disappear from most of Utah, Idaho and Wyoming and would migrate north to Canada. Given the extreme nature of their scenario and time horizon, in 2007 McKenney et al at the Canadian Forest Service prepared an updated, an more refined climate envelope analysis for 130 North American tree species through 2070 (McKenney et al 2007). Under the modeling assumptions that carbon dioxide would increase and trees migrate into newly created favorable climate zones to the north, they concluded that the 130 tree species would shift northward an average of 700 kilometers and their favorable climate areas would decrease in size by 12 percent (ranging from a 93 percent decrease to a 44 percent increase depending on the species). McKenney et al noted that limitations of their method did not mean that broad regions of the United States would become treeless. In his massive review of current research on the Holocene environment of the Great Basin region over the last 13,000 years, Quaternary environment researcher Grayson at the University of Washington concluded that climate predictions are highly uncertain whether one uses reconstruction of past Great Basin in the which the climate was warmer than today, as he did, or whether one uses climate models, as Shafer et al did (Grayson 2011, Chap. 10).

Ignoring global warming and the issue of whether climate change is human-induced, if the local Utah climate regresses the historical mean, will future generations see the oak forests of the local Salt Lake hillsides retreat back up canyon?

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On June 24th, 1994, in a historical piece for the Salt Lake Tribune, Jack Goodman concluded that the “Lone Cedar” tree at 300 South 500 East was probably a pinyon pine.


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