City Creek Nature Notes – Salt Lake City

July 11, 2017

July 4th

Hybrid Gambel’s Oak – Part II

4:00 p.m. Determined to find a sample of the oak cross in the wild, I go behind the University Hospital, where in 1958 Professor’s Cottam’s graduate student, Rudy Drobnick, located a grove of F1 hybrid oak crosses (Drobnick 1958). It is located on a steep slope above the Bonneville Shoreline Trail. Climbing the slope in the 100 degree heat and under the afternoon sun, after two attempts and twenty minutes of climbing, I finally find a copse of the cross. It was worth the climb. This F1 cross developed at the end of the last ice age about 7,500 years ago when in a wetter and warmer climate, both true Gambel’s oaks and the Arizona shrub oak existed at its northern limits around the Salt Lake Valley. (Ehleringer and Phillips suggest that the F1 cross may have occurred as little 750 years ago (Frates 2008).) As the post-glacial valley dried out, the true Gambel’s oaks and the Arizona shrub oak were forced further south. Now only four patches of the F1 hybrid remain.

I also want to verify if this F1 hybrid grove is the same dimensions as found by Drobnick in 1958. This requires climbing up a steeper slope and around of wall of oaks to the grove’s backside. This whole mis-adventure has been one comedic event after another. Today, I am under-geared. I am also jogging, so I am wearing sneakers and not my usual bushwhacking hiking gear. For bushwhacking in the Wasatch Front Mountain Range, I usually have walking poles and my favorite now well-worn thirty-year old pair of calf high leather boots with industrial grade soles. You can walk up-hill and over any grade and any condition with those boots. The slope is forty-five degrees and covered in a combination of dry cheatgrass and Winter rye grass (Secale cereale L.). The stems of both invasives are biased pointing downhill. About fifty feet up, I lose my footing and begin a quick fifteen mile-per-hour slide downhill. But I am smiling. This is the summer version of a fall and back-side slide on dense spring snow while back-country skiing in the mountains. My feet go out in front and I am able to self-arrest as I reach the edge of the oak grove. Another try, and I am around to the back of the grove.

In 1958, Drobnick recorded is size at 25 x 15 x 8 feet, and this is similar to what I find today. At the back of the hybrid copse, is a small sapling, three feet high. The hybrid copse is continuing to reproduce.

Later in the evening after a nap to recover from the heat, I return to City Creek Canyon and the stream. Cool canyon and stream breezes make of a pleasing walk to milepost 1.0. Since it is a holiday weekend, the canyon is nearly empty except for a few hand-in-hand strolling couples and families. Tracks reveal a mule deer has come down a steep slope and rested on a clump of crushed horsetails. I count four Broad-tailed hummingbirds in the first mile. Why have they come now, since all of the nectar producing flowers have gone? They also eat insects, and evening air is now thick with Variegated Meadowhawks (Sympetrum corruptum). For sugar, they drink the sap that the summer heat will shortly begin to boil from the Big tooth maple trees.

I have touched the canyon’s living past; I have touched the canyon’s living future; and this evening, I stroll in its present.

* * * *

Per Thoreau’s “Journal” on July 4th, 1852, he describes a summer sunrise. He hears a blackbird and sees a kingfisher. As the Sun reaches him, flies and mosquitoes rise. A humming bird passes by. He notes water lilies are damaged by insects. On July 4th, 1858 at night, he hears a loon, a screech-owl, and cuckoo.

* * * *

In 1954, University of Utah graduate botany student Rudy Drobnick noticed the existence of hybrid oaks along the Wasatch Front due to differences in the late fall foliage between the hybrid oaks and other Gambel’s oaks along the mountain range (Drobnick 1958, Cottam, Tucker and Santamour 1982 at 1). University of Utah botany professor Cottam dispatched Drobnick to locate all the patches of these hybrids in Utah (Drubnick 1958). There had been a long-standing debate in amongst botanists about what exactly Gambel’s oak (Quercus gambelii Nutt.) was. At the turn of the century, P. A. Rydberg had classified eleven types of Gambel’s oaks, including Quercus utahensis, Quercus submollis, Quercus gunnisonii, Quercus vereelandii, Quercus novo-mexicana, etc., but by 1942, it was generally recognized that Quercus gambelii Nutt. had an amazing variety of leaf shapes (Christensen 1949, Christensen was another of Cottam’s graduate students). Thus, all of Rydberg’s previous species were collapsed back into one species – Quercus gambelii Nutt. (id., Tucker 1961), and Rydberg’s former names were abandoned.

Cottam and Drobnick and University of California at Davis botany professor John Tucker sought some explanation of the bewildering array of leaf shapes of the Gambel’s oak throughout the west. Their provisional hypothesis was that in the post-glacial era about 7,500 years ago, Gambel’s oak and Arizona shrub oak co-existed in northern Utah (Drobnick 1958, Cottam, Tucker and Drobnick 1959, Tucker 1961, Tucker 1963, Tucker, Cottam and Drobnick 1961, Tucker 1963). As Utah’s climate became drier and in order to better adapt new conditions, Gambel’s oak and Arizona shrub oak hybridized into the F1 form, the hybrid copse that I viewed today. But the F1 hybridized form, with its spiked ends and shallow lobes did not explain multitude of forms of Gambel’s oak leaves seen today. Another of Cottam’s University of Utah botany graduate students, Robert R. Ream, could find no north-south pattern in the variation of Gambel’s oak leaves (Ream 1960).

Doctor Cottam retired from the University of Utah, but in his retirement he continued to work as an emeritus professor on a cross-breeding hybridization experiment of western “white” oaks in part to demonstrate that the current Gambel’s oak forest in northern Utah was a hybrid of other species (Cottam, Tucker and Santamour 1982). Using his grandchildren to nurture hundreds of seedlings, he undertook a massive block experiment to examine first (F1) and second (F2) generation of cross-breeds of western white oaks including Gambel’s oak (Quercus gambelii Nutt.), Arizona shrub oak (Quercus turbinnell Greene), Quercus douglasii, Quercus lobata, Quercus macrocarpa, Quercus robur, Quercus virginia, and six other lesser oak species. Two-hundred and forty-one cross-breeding experiments (id. at 61) and ten years later, Cottam, Drobnick and Tucker had their answer: only one F2 generation cross between Quercus gambelii Nutt. and Quercus turbinnell Greene was stable (Cottam, Tucker and Santamour 1982). This result supported, by brute force experimentation, the post-glacial hypothesis that the three investigators formulated in 1958.

Cottam’s F1 hybrid generation shows some remarkable adaptations that place it squarely between Quercus gambelii Nutt. and Quercus turbinnell Greene. Quercus gambelii has deep penetrating roots adapted to northern Utah’s snowmelt high-water season that is followed by drying summers. Quercus turbinnell is shallow rooted and adapted to the summer monsoons of northern Arizona. Quercus gambelii x Quercus turbinnell have roots of intermediate depth (Ehleringer and Phillips 1996). Electron microscopy of the leaves of the hybrid and of its parent plants confirm how the F1 hybrid has taken on the waxy upper surface and hairless underside of Quercus gambelii (Cottam, Tucker and Santamour 1982 at 62, 70 and 71), but the gross shape of the F1 hybrid follows Quercus turbinnell (id. at 72). Similarly, measurements of the F1 hybrid’s lobe ratio (the ratio of a lobe’s vein length to its lobe length), puts the hybrid statistically between Nuttal and turnbinnell (Tucker, Cottam, and Drobnick 1961).

* * * *

On July 4th, 2007, the City announces that City Creek Canyon will be closed for four days during July in order to host various road races (Salt Lake Tribune). On July 4th, 2006, legendary local endurance runner Heikki Ingstrom, who trained daily in City Creek Canyon, was reported to have passed away (Deseret News) On July 4th, 1999, City managers describe plans to update the City’s Watershed Management Plan, including for City Creek Canyon (Salt Lake Tribune). On July 4th, 1993, the City proposes a 100 mile bikeway system that will connect regional parks, including a bikelane from the University of Utah to City Creek Canyon (Salt Lake Tribune). On July 4th, 1908, Fisher Harris of the Commercial Club and Lon J. Haddock of the Manufacturers and Merchants’ Association urged that the Ensign Peak area should be turned in a large park (Salt Lake Herald). The Commercial Club provided $10,000 towards the expense of improving City Creek Road and along 11th Avenue to Fort Douglas (id). On July 4th, 1883, City Surveyor Jesse Fox and City Waterworks Superintendent G. M. Ottinger surveyed City Creek Canyon in order to determine possible locations of the construction of new higher water reservoir tanks (Salt Lake Herald).

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