City Creek Nature Notes – Salt Lake City

July 10, 2017

July 1st

Talking Plants – Part I – Hidden scents

2:00 p.m. In the heat of the afternoon, it is another butterfly day. Cabbage white and Western tiger swallowtail butterflies line the road. Families stroll through the heat on a holiday weekend.

It is also the time of mature trees. The giant trees of the canyon – those taller than seventy-feet – now dominate the canyon experience. Species include Box Elder trees, Rocky Mountain narrowleaf cottonwood trees and Freemont’s cottonwood trees (Populus fremontii). They now provide a partial canyon that protects the mid- to small-sized trees and the understory bushes from the harsh summer sun. Walking past one of these biological skyscrapers, one can feel the increase in humidity from their exhalations. In winter, their skeletons are ignored and when walking up-canyon during the cold season, one does not give them a passing thought.

At Guardhouse Gate, Black-headed grosbeaks and Lazuli buntings dominate. At picnic site 3, Song sparrows are prominent, and at third active zone of birds appears at milepost 1.1.

At seep below picnic site 6, the Starry solomon’s seal has, in seemingly a few days, been overrun by Western poison ivy (Toxicodendron rydbergii). It is now a deep green, and in the fall will turn a deep red (Sept. 23rd).

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Per Thoreau’s “Journal” on July 1st, 1852, he notes that rabbit’s foot clover is turning colorful, mulleins are turning yellow, wild roses are at their peak. He describes a white lily in depth. He hears a red-eye, oven-bird and a yellow-throat. On July 1st, 1854, he again notes that the edges of distant objects are distinct in clear air. He watches the shadows of clouds moving across the land. On July 1st, 1859, he notes white ranunculus is in bloom.

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Plants communicate with each other and with insects by volatile airborne chemical signals in order to coordinate defenses against herbivores (Hartley 2010, Hartley 2009, Alba 2012, Engelberth 2012, Heil and Karbon 2009, see Witzany and Baluska (ed) 2012). Experiments suggest that Box Elder trees, the Gambel’s oaks, the bushes of the understory, the Curly dock weeds, the Starry Solomon plants, the sagebrush, and the other plants currently active in the canyon are carrying on a conversation, unheard by human interlopers. Experiments have been done on plants outside species of the Gambel’s oak forest, but one example exists for communication between the sagebrush groves along east Bonneville Drive. In 2011, Shiojiri at Kyoto University, Karban at University of California at Davis and Ishizaki at Hokkaido University replicated and expanded Karban’s 2006 study on Great basin sagebrush (Artemisia tridentata) plant communication (Shiojiri, Karban and Ishizaki 2011). They found that the neighbors of sagebrush plants mechanically damaged with scissors but allowed to spread VOCs suffered less damage from grasshoppers than sagebrush plants not allowed to receive VOC emissions from the damage sagebrush. In short, sagebrush plants talk with their sagebrush neighbors and warn them to start producing insecticides to ward off grasshoppers. In 2008, Mäntylä et al at the University of Bristol demonstrated that birch trees issue volatile airborne chemicals, not detectable by humans, when attacked by caterpillars. To control scents, they contained some damaged branches in plastic bags, but left other branches exposed. Birds preferentially visited and attacked branches where trees’ VOC scent was present. In short, their Great Britain birches talk to birds. Although the specific species in investigated in Great Britain are not present in the canyon, the canyon hosts Birchleaf mountain mahogany (Cercocarpus montanus Raf.). In 2011, Mäntylä et al demonstrated a similar effect in Scottish pines (Mäntylä et al 2011). Engelberth notes that some plants use VOCs to signal predatory insects, e.g. predatory wasps, that they have been damaged by insect herbivores that are preferred foods of the predator insect (Engelberth 2012).

Plant species talking between themselves, with other species of plants, and with insects and birds may have arisen by conferring an evolutionary advantage (Heil and Karban 2010). By alerting its same-specie and inter-specie neighbors, sagebrush, for example, can create a herd-like resistance to grasshopper attacks. Similarly, by talking with insects and birds, plants create co-evolutionary relationships that benefit both the plant and associated insect eating birds (id., Engelberth 2012). Through 2010, Heil and Karban summarize known examples of plant “talking” with VOCs (id). In this Great Basin canyon, such communication has only been shown specifically for Great basin sagebrush, but Heil and Karban also list known plant VOC demonstrations for families of plants whose cousins are also present in the City Creek Canyon, including willow trees, sugar maples, poplar trees and alder trees. That the other trees and other plants present in City Creek Canyon are talking to a each other seems a reasonable extrapolation, but demonstration of their VOC communication remains to be shown by future researchers.

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On July 1st, 2001, City Planning Director Stephen Goldsmith notes that a gate has been added at Memory Grove to control traffic (Salt Lake Tribune). On July 1st, 1997, a small grass fire broke out near Memory Grove (Salt Lake Tribune). On July 1st, 1925, a Salt Lake Telegram editorial approved of the City’s use of “hoboes, drunkards and indolent men” on the prison road work crew then working in City Creek Canyon. On July 1st, 1920, twenty-five service men convalescing at St. Marks Hospital will be given a picnic outing in City Creek Canyon (Salt Lake Herald). On July 1st, 1919, a Salt Lake Telegram editorial reported that a large fire had been burning in City Creek for several days (Salt Lake Telegram). The Telegram reported rumors that the fire may have been started by I.W.W. members (id). (Famed I.W.W. organizer Joe Hill had been previously executed in Salt Lake City in November 1915.)

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