Fall Frost

Frost on a Hairy Leaf
Copyright © 2012 Andrea Liberatore

Frost on a Leaf
Copyright © 2012 Andrea Liberatore

Frost Damage on a Tomato
Copyright © 2012 Andrea Liberatore

Evergreens take hardiness
to the Extreme
Two-needle Pinion Pine
Copyright © 2009 Linda Kervin

Fall has descended in earnest across Utah. Leaves have flashed their colors and dropped to the ground. Juncos have replaced the flycatchers on my backyard’s best perches, and my garden has been cleaned up and tilled under. As I watched the fall weather affect plants in my vegetable garden, I began to wonder about the different reactions they had to the changing temperatures. My tomatoes and squash turned brown and wilted at the merest suggestion of cold temperatures. Other plants, like kale, carrots and onions are still bright and fresh, even after an early snowfall. What is it about some plants that allow them to withstand frost, while others succumb right away?

Frost occurs when the temperature of an object – in this case a plant leaf – falls below the dew point of the air. Moisture from the atmosphere collects on the surface of the leaf and freezes when temperatures drop below 32 degrees. Just seeing frost on a plant doesn’t necessarily mean it will die – it’s the internal tissue temperature that counts. Like humans, plants are made mostly of water – upwards of 80-90% in an herbaceous plant like lettuce. When temperatures drop, the water inside plant cells expands as it freezes, tearing cell walls and causing irreparable damage.

The amount of harm done to a plant depends on many different factors and is generally referred to as a plant’s hardiness. Species or individuals that are more compact will incur damage at a lower temperature than others due to their reduced surface area. Those growing close to the ground are more protected by their proximity to the warm earth. Plants with darker colored leaves such as the deep greens of spinach and chard may be hardier because their leaves absorb and retain heat better than lighter-colored leaves. Fuzzy or hairy leaves also fend off cold temperatures better than their smooth counterparts.

Perhaps the best defense of all is found in plants that protect themselves with natural antifreeze. When frost hits these plants, the relatively pure water in the space between leaf cells freezes first, which in turn draws more water out of the surrounding cells. The remaining cellular fluid contains a high concentration of sugars and other molecules, which reduces the fluid’s freezing point and protects the cell’s contents from ice.

Evergreens, of course, take hardiness to the extreme, utilizing a number of different tactics to remain alive and photosynthesizing throughout the winter. These tactics include compact leaf size, a thick leathery consistency, and a waxy coating that both insulates and prevents water from escaping into the dry winter air.

Frost damage to less hardy plants can be postponed by human interventions such as covering with blankets, but as the cold spells get longer and more frequent, damage is inevitable. Everything has its season, and now is the time to harvest the last of those hardy fall greens and tuck the garden in for the coming winter.

For the Stokes Nature Center and Wild About Utah, this is Andrea Liberatore.

Credits:
Images: Courtesy &
            Copyright 2012 Andrea Liberatore
            Copyright 2009 Jim Cane
Text:     Andrea Liberatore,
            Stokes Nature Center in Logan Canyon.

Additional Reading:


Savonen, Carol (2012) Some plants make natural antifreeze to cope with winter’s wrath. Oregon State University Extension Service. Available online at: https://extension.oregonstate.edu/gardening/node/847


Frost And Your Plants: What You Need To Know, Farmer’s Almanac, November 17, 2021, https://www.farmersalmanac.com/frost-temperature-outdoor-plants-9788

Huber, Kathy (Feb 16, 2002) What Happens When a Plant Freezes. The Houston Chronicle. Available online at: https://www.chron.com/life/gardening/article/What-happens-when-a-plant-freezes-1635570.php

Tales of the Packrat: The Legacy of Early Grazing on Utah’s Rangelands

Legacy of Early Grazing on Utah's Rangelands: Pack Rat Midden,  Photo Courtesy and Copyright 2009 Ken Cole - All Rights Reserved
Pack Rat Midden
Copyright © 2009 Ken Cole

Reaching for a Pack Rat Midden, Click to Zoom, Photo Courtesy and Copyright 2009 Ken Cole - All Rights Reserved Reaching for a Pack Rat Midden
Copyright © 2009 Ken Cole

One of the best storytellers in Utah’s national parks is not a ranger, but the lowly packrat.The Legacy of Early Grazing on Utah’s Rangelands
Their stories of past plant communities are written in their middens. The midden is a heap of leaves, twigs, seeds and fruits the packrat discards outside its nest. Protected in a desert cave or rock crevice and preserved by a rat’s own urine, this heap is a detailed and accurate time capsule of the past local flora.

Ken Cole with the US Geological Survey is a fluent translator of the packrat’s stories. Ken and colleagues sampled old packrat nests around Glen Canyon National Recreation Area and Capitol Reef National Park. By carbon-14 dating, the nest ages are known to span the last 10,000 years. As controls, they also collected nests from mesa tops inaccessible to livestock. Ken and colleagues then carefully translated these packrats’ stories by identifying and counting the plant fragments in these fossil nests.

At both Capitol Reef and Glen Canyon, old packrat nests revealed pre-settlement plant communities that were rich in diverse grasses, wildflowers and shrubs. Then these floras changed. Beginning 150 years ago, vast herds of sheep and cattle tromped and chewed their way across the unfenced rangelands of Utah in numbers unimaginable today. We know that palatable plant species and those susceptible to trampling suffered declines, because they are absent from middens from that time period. Unpalatable shrubs multiplied. Despite curtailed grazing in subsequent decades at Capitol Reef and Glen Canyon, packrats show us that the flora still has not recovered. Like Aesop’s fables, this cautionary lesson of the packrat’s ecological tale remains clear and relevant today. We should all listen.

This is Linda Kervin for Bridgerland Audubon Society.
The Legacy of Early Grazing on Utah’s Rangelands
Credits:

Photos: Courtesy and Copyright Ken Cole
Text: Julio Betancourt USGS and Jim Cane, Bridgerland Audubon

Additional Reading:

Betancourt, Julio L., Thomas R. Van Devender, and Paul S. Martin, eds. Packrat Middens: The Last 40,000 Years of Biotic Change, University of Arizona Press, 1990 https://www.uapress.arizona.edu/books/BID40.htm

Pack Rat Middens, Colorado Plateau in Land Use History of North America, Ken Cole, USGS/Northern Arizona University, https://cpluhna.nau.edu/Tools/packrat_middens.htm

Introduction [to Carbon 14 Dating], Tom Higham, Radiocarbon Laboratory, University of Waikato, New Zealand https://www.c14dating.com/int.html [Sep 24, 2009]

Cheatgrass

Click to view an article about cheatgrass, Cheatgrass Photo Courtesy NPS, Photographer Tom Heutte, USDA Forest Service, Bugwood.org
Cheatgrass
Photo Courtesy NPS, Photographer:
Tom Heutte, USDA Forest Service,
Bugwood.org

Click to view an article about cheatgrass, Photo Courtesy NPS, Neal Herbert, PhotographerA grassland inundated by cheatgrass
Photo Courtesy NPS
Neal Herbert, Photographer

Hi, this is Mark Larese-Casanova from the Utah Master Naturalist Program at Utah State University Extension.

It’s difficult to visit a landscape in the West without encountering cheatgrass. While cheatgrass’ small stature might make it hard to notice, it’s impossible to forget its sharp, spiny seeds. One hike through a cheatgrass meadow can render a good pair of socks unsalvageable.

Although cheatgrass, a nonnative grass scientifically known as Bromus tectorum, is an annual grass- germinating, growing, producing seeds, and dying each year- it is particularly effective at colonizing disturbed areas because it grows and produces seeds much earlier in the spring than many perennial native grasses. Cheatgrass monopolizes water and nutrients by germinating and establishing itself during the previous fall and winter, when many native plants have become dormant. Over time, “cheat grass” has become the dominant ground cover in many of Utah’s sagebrush ecosystems.

The dense, dry, fine stalks of cheatgrass, which sets seeds and dries out by June, are particularly flammable fuel for wildfires. Fire roars through the carpet-like cover of cheatgrass, and wildfires are now at least twice as frequent as they were in the 1800’s. This has caused a loss of sagebrush habitat that is particularly important to a wide diversity of wildlife. More frequent fires create an even greater challenge for rare species such as the black-footed ferret and desert tortoise to survive. Native grasses are slower to recover from fire, and cheatgrass is particularly effective at recolonizing burned areas. Utah State University researchers Dr. Peter Adler and Aldo Compagnoni have found that reduced snowpack and warmer temperatures promote the growth of cheatgrass, which could potentially increase its distribution and fire risk into previously colder areas of Utah.

Researchers and managers are continually working to find ways to control cheatgrass in Utah. Effective control usually involves a combination of mechanical pulling or tilling, grazing, burning, spraying with a chemical herbicide, and replanting with native grasses. USU researchers Dr Eugene Schupp and his former graduate student Jan Summerhays found that applying a pre-emergent herbicide to prevent the germination of cheatgrass seeds, as well as temporarily limiting Nitrogen in the soil, gave native grasses and perennials a better chance of establishing. When faced with such a large management problem in Utah and throughout the West, we can use all of the helpful tools we can get.

For Wild About Utah, I’m Mark Larese-Casanova.

Credits:

Images: Courtesy NPS, Neal Herbert Photographer, NPS,
and USDA Forest Service, Bugwood.org, Tom Heutte Photographer
Text: Mark Larese-Casanova, Utah Master Naturalist Program at Utah State University Extension.

Additional Reading:

Beck, George. Cheat grass and Wildfire. Fact Sheet No. 6.310. Colorado State University Extension. https://www.ext.colostate.edu/pubs/natres/06310.html

Range Plants of Utah. USU Extension, Utah State University, https://extension.usu.edu/rangeplants/grasses-and-grasslikes/cheatgrass

Fairchild, John. Cheat grass: threatening homes, stealing rangelands. Utah Division of Wildlife Resources. https://wildlife.utah.gov/watersheds/links/cheatgrass.php

Opsahl, Kevin. USU study: Climate shift could trigger Cheat Grass. Herald Journal . October 21, 2012. https://news.hjnews.com/allaccess/article_f1436aee-1a3c-11e2-935a-0019bb2963f4.html

Forero, Leslie, Plants Surviving Cheat Grass Invasion May Improve Restoration Chances, Study Shows, UPR Utah Public Radio, Feb 26, 2018 https://www.upr.org/post/plants-surviving-cheatgrass-invasion-may-improve-restoration-chances-study-shows

Cane, James, Reseeding the West After Fire, Wild About Utah, November 29,2012, https://wildaboututah.org/reseeding-the-west-after-fire/

Strand, Holly, American Invasion, Wild About Utah, September 18,2014, https://wildaboututah.org/american-invasion/

Grant, Val, Short-tailed Bird of Perdition-Starlings, Wild About Utah, June 05,2009, https://wildaboututah.org/short-tailed-bird-of-perdition-starlings/

Red leaves in autumn: What’s in it for the tree?

Extension.usu.edu, https://treebrowser.org/index.cfm?controller=final&action=details&key=469&sortby=CommonName” alt=”Red leaves in autumn: What’s in it for the tree?: Canyon or Big-Toothed Maple leaves in late summer, Acer grandidentatum, Courtesy Michael Kuhns, https://Extension.usu.edu”>Extension.usu.edu, https://treebrowser.org/index.cfm?controller=final&action=details&key=469&sortby=CommonName” width=”250″ height=”192″ border=”0″ /> Canyon or Big-Toothed Maple
leaves in late summer
Acer grandidentatum
Courtesy Michael Kuhns
Extension.usu.edu
Canyon or Big-Toothed Maple leaves in fall, Acer grandidentatum, Courtesy Michael Kuhns, Extension.usu.eduCanyon or Big-Toothed Maple
leaves in fall
Acer grandidentatum
Courtesy Michael Kuhns
Extension.usu.edu

Hi, I’m Holly Strand.

As early as 4th grade, children learn that leaves are green because of the high concentration of chlorophyll relative to other pigments. And that autumn leaves turn color because the breakdown of chorophyll molecules unmasks the yellow, orange and red pigments that remain.

This simple and satisfying explanation has existed for awhile. However, research in the past 15 years has uncovered a much more complicated story. Leaf physiologists jumped from the question, “What makes autumn leaves so colorful?” And started to ask the evolutionary question: “What’s the purpose behind this autumn color fest?” “What’s in it for the tree itself?”

The group of pigments that produce yellow or orange are called carotenoids. The carotenoids are in the leaf throughout the growing season but only become apparent with the breakdown of chlorophyll into colorless metabolites. However, the red pigments—or anthocyanins– are produced in the leaf AFTER much of the chlorophyll is lost. This active production of new anthocyanins led scientists to believe that the pigment must be performing a critical function.

Just what function is still not known but many hypotheses exist. One is that anthocyanins act as a sunscreen shielding leaf tissues against the harmful effects of sunlight. The risk of sun damage is particularly high in fall because of the lack of chlorophyll protection and because there is increased light due to a thinning canopy. Without sun damage, the leaves can continue to absorb nutrients right up to the end.

Another possibility is that anthocyanins function as an antioxidant shield. Plant chloroplasts produce fewer free radicals when shielded from green wavelengths of light. Anthocyanins absorb the green wavelengths. Without anthocyanin, a surplus of superoxides could cause damage to the plant cell structure.

Lastly, there is the coevolution hypotheses. Aphids and other insects feed, carry viruses and bacteria. So red coloration was an adaptation developed by trees designed to lighten their insect load. The red leaves signal to insects that the tree is not a suitable host. The coevolution theory is supported in part because trees with autumn colors tend to be the ones with a history of interaction with aphids. Also, experiments have shown that most aphids strongly prefer green leaves over red leaves. In some cases anthocyanin may be positively correlated with a form of chemical defense.

However, when considering this last theory, remember that species perceive color differently. To the human eye, a tree may be a brilliant autumn shade of red. To the aphid, that same tree might be an indistinguishable gray. Further the insect may be avoiding red leaves because of differences in texture, taste, scent, texture or something else that is important to an aphid.

Whatever the reason is, I hope you are enjoying Utah’s colorful reds and yellows.

For links to current research and a Forest Service update on fall color around the state, go to www.wildaboututah.org.

For Wild About Utah, I’m Holly Strand.

Credits:


Images: Courtesy and Copyright 2003 Michael Kuhns, Extension.usu.edu
Text: Holly Strand

Sources & Additional Reading


USDA Forest Service Fall Colors web site for the Intermountain Region https://www.fs.usda.gov/detail/r4/recreation/?cid=FSBDEV3_016189

Archetti, M., Doring, T. F., Hagen, S. B., Hughes, N. M., Leather, S.
R., Lee, D. W., Lev-Yadun, S., Manetas, Y., Ougham, H. J., Schaberg,
P. G., Thomas, Howard (2009). Unravelling the evolution of autumn
colours: an interdisciplinary approach. Trends in Ecology and
Evolution, 24, (3), 166-173. https://digitalcommons.fiu.edu/cas_bio/38/

Chittka L, Döring TF (2007) Are Autumn Foliage Colors Red Signals to
Aphids? PLoS Biol 5(8): 187. https://www.plosbiology.org/article/info%3Adoi%2F10.1371%2Fjournal.pbio.0050187

Lee, David and Kevin S. Gould Why Leaves Turn Red. American
Scientist, Volume 90. 524-531 https://harvardforest.fas.harvard.edu/sites/harvardforest.fas.harvard.edu/files/leaves/2002_11_leaf_article.pdf

Gunnell, JayDee, Reese, Julene, Ask a Specialist: What Causes the Fall Leaves to Change Color?, USU Cooperative Extension, https://extension.usu.edu/htm/news-multimedia/articleID=18662