City Creek Nature Notes – Salt Lake City

December 21, 2016

December 20th

The Canyon at Rest

12:00 pm and 5:00 p.m. It is the last day of Fall, and tomorrow the tilt of the Earth keeps the canyon furthest from the life giving Sun for the longest part of the day. Nature in the canyon is in a deep sleep. The trees are still; all natural sounds are silent. The air is warmer today, but not enough that snow and ice on the trees melts. Sun warmed ice melded with tree branches expands slightly and then breaks away. Instead of raining droplets as with the last storm, today trees rain tiny chunks of ice. There are two places in the lower shaded canyon where the stream freezes over. The first is the perpetually shaded bend between picnic sites 7 and 8. There the stream is completely frozen over for several hundred feet; the stream is milky white and stone-like. The second is between the up canyon end of Pleasant Valley at mile 1.8 to milepost 2.0. There the stream is eighty percent frozen over. At Bonneville Drive, about twenty percent of the surface of the flood retention ponds is frozen. At mile 1.3, where animal tracks make impressions that are kept partially in shadow, half-inch hoarfrost crystals sublimate, but then evaporate in the warmer late afternoon air. Although the canyon looks dead, the irrepressible force of life continues.

Lichens and mosses respond to the wet cold and grow both on the trees and on rocks in the stream. Digging some leaves up from underneath the snow, some show signs of the beginning of bacterial decay, but mostly the leaf litter and the microbes are dormant, waiting for spring’s explosion. At the surface, data by Whitman, Coleman and Wiebe at the University of Georgia suggests that there are about 3.5 x 10^15 microbes per square meter in woodlands and shrublands and about microbes 5.7 x 10^13 in each square meter of deciduous forests (Whitman 1998, Table 2). In 1995, Richter and Markewitz estimated that there were about 1.1 x 10^12 bacteria and fungal microbes in each gram of soil at the surface (Fig. 3a), and their density decreases to about 4.1 x 10^7 at 8 meters beneath the surface. In 2014, Raynaud and Nunan found an average of 8.9 x 10^9 microbes in the top 0.6 meters of each gram of agricultural field soil (Table 1).

But life does not stop there. Whitman et al also estimated that between 10 meters to 3,000 meters below the surface, there were on the order of 10^6 prokaryotes per cubic centimeter. They made an order of magnitude estimate that in a cubic centimeter column going from the surface down to 4 kilometers, there are a total of about 2.2 x 10^30 prokaryotes (id., 6579). But life exists even further down in the subsurface column beneath the canyon’s surface. In 2006, Li-Hung Lin, et al. discovered Archean microbes living at 2.8 kilometers beneath the Earth’s surface in a South African gold mile, and those microbes were genetically related to Archean microbes living the Yellowstone Hot Springs a few hundred miles north of the canyon. These subsurface microbes may comprise a substantial fraction of biomass in the canyon. Whitman et al estimated a wide first-order ratio of the mass of subsurface prokaryote carbon to plant surface carbon at 60% to 100% (id., at 6580).

I stand at the surface in the canyon, I and am part of this scene. In 2013, Bianconi et al estimated the number of cells in the human body at 37 trillion. In a 2016, Sender, Fuchs and Milo at the Weiztmann Institute for Science in Israel, revised estimates of the total number of cells in the human body and the number of microbes that inhabit each of us. They found that along with the approximately 3.8 x 10^13 (38 trillion) human cells in a 70 kilogram person, another 3.0 x 10^13 foreign microbes live (cooperatively but sometimes uncooperatively) within us or about 44% of the total (3.0/(3.0+3.8)). Because of the exponential power of these estimates, the 10^13 cells, both human and parasitic cell in me, are a minuscule portion of of 10^30 prokaryotes that are in just one 4 kilometer deep column of soil that is one centimeter square. Subtracting my 10^13 cells, there are still 9.999999…. x 10^29 prokaryotes under each square centimeter of subsurface. I measure the bottom of one of my shoes and find conservatively guess there are about 450 square centimeters in the soles of my feet.

Around and above me, even the air above the road contains some levels of bacteria, fungi, and pollen as part of the daily PM10 daily air particle count. In 2009, Wiedinmyer and colleagues counted on average 3.5 particles of DNA containing material per cubic centimeter of air collected from a mountain summit in the Rocky Mountains (Table 1) or about 3.5 million particles per cubic meter of air. Whitman et al estimated that there were about 1.8 x 10^21 microbes in each cubic meter of air from the surface up to 3 kilometers (id., 6580 reporting 5 x 10^19 per cfu). This continues into the high upper atmosphere. In 2013, DeLeon-Rodriguez and her colleagues at the University of Georgia and NASA found 5,100 cells per cubic meter in samples taken from air 10 kilometers above the surface of the Caribbean ocean.

Microbes also dominate the stream’s bedrock. In that aquatic environment, deep blue-green algae grows in thick mats, and at the stream’s edges, large mats of watercress thrive in the freezing water. Although no trout are seen in the lower canyon stream; they move upstream and a group of about fifteen congregate just below an old water head gate at mile 2.8. At the stream’s edge, horsetails are still green, and this indicates that photosynthesis is still occurring despite the cold.

At the retention ponds, a male-female pair of mallards (Anas platyrhynchos) rest. The female is in the sleep position with her head laying on her back. The males feeds on the algae on the pond’s bottom. At picnic site 2, there is a small unidentified sparrow that is not a European sparrow. Further up the canyon, near picnic site 3, there is a Belted kingfisher (Megaceryle alcyon)! No avid birder will probably believe this, since this kingfisher is far out of its winter range, and I am unable to take a photograph of it. I first had a fleeting view of this bird on December 7th at the south end of the circle where the Pleasant Valley reservoir once stood. Then it was too far away to see clearly. Today, I am able to watch it for several minutes at the top of a snag about 100 feet away. Then the bird sees me, spooks, and flies down canyon to another snag, and again I am able to catch up and watch it closely for another few minutes. At picnic site 4, I am greeted by a flock of mountain chickadees, and they sit in several trees calling back to each other. Below picnic site 5, a flock of six Black-hooded juncos feed and preen themselves on a red osier dogwood bush. The coldest winter makes some birds more tolerant of humans, and I am able to stand directly next to the bush and about four feet from juncos. They grab a piece of snow-ice from clumps of shriveled white berries that still cling to the tree. They eat part of the ice and then dip the rest into their feathers to clean themselves. Then they try to eat the sour fruit of the dogwood (see Nov. 6th), but most of the fruit seems to drop to the ground and not into their beaks. I again see an unidentified raptor that patrols the lower canyon just before twilight. At mile 1.3, a magpie can be heard in the distance. A series of tracks in the snow tell of two birds that had landed on two adjacent rocks that stick up out of the snow. They then hopped across the snow for about 20 feet.

At mile 1.0, high on the western ridgeline, a single anterless elk digs through the snow to green grass underneath. And, in the early morning hours as I am returning home on other business, two mule deer that are refugees from the canyon are grazing a few hundred feet from my urban front door. As for humans in the canyon, there is myself and about twenty other walkers, runners, and bicyclists.

In short, the canyon is asleep, but life cannot be stopped. Life can be attenuated from its peak productivity (August 31st), and today, like sunlight, life in the canyon is at its nadir.

In Thoreau’s “Journal” on December 20th, 1851, he observes a high-flying hawk that is patrolling for prey. He lists the colors of the winter landscape: red, white, green, and brown. On December 20, 1854, he feels that the winter sun has more relative warmth on his skin than the summer sun.

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