Species Spotlight: Big Sagebrush

Dale Nibbe

Author: Rachel Renne  |  Published: February 13, 2023  | Category: Species Spotlight 

This article originally appeared in The Source on February 8, 2023.

In May 2021, I hiked the entire 750-mile-long Oregon Desert Trail, touring the high desert plant communities of central and eastern Oregon on foot. Throughout this otherwise lonely trek, one plant was my constant companion: the aromatic shrub, big sagebrush (Artemisia tridentata Nutt.).

There are 25 species of sagebrush in the western United States, and all but one are in the genus Artemisia (budsage has been renamed from Artemisia spinescens to Picrothamnus desertorum). Although I did occasionally encounter budsage during my walk through Oregon, it was unusual to pass a day without seeing big sagebrush (Artemisia tridentata Nutt.). As its common name suggests, this shrub is larger than many of the other species of sagebrush and it gets its scientific name from the three small lobes at the end of each of its wedge-shaped leaves, which resemble a trident. Native to 14 states, big sagebrush is the most widespread of the Artemisia shrubs and has been classified into several different subspecies that each prefer different habitats across the region.

Lower elevation sites with deeper soils support basin big sagebrush — which is easy to recognize by its long, thin leaves and tall, leggy growth form.

Wyoming big sagebrush is round and short-statured and is found at moderate elevations and where soils are shallower. This subspecies can extract water from soils too dry for many other plants — including the other big sagebrush subspecies.

Mountain big sagebrush is found at higher elevations where soils are deeper. This subspecies is often flat-topped but can resemble Wyoming big sagebrush. Connoisseurs can tell the two apart by smell, but even a novice can distinguish them by placing a few leaves in water under blacklight. Mountain big sagebrush leaves glow bright blue, thanks in part to the same chemicals that provide their characteristic sweeter smell.

“Sweeter” is perhaps a relative term. Although big sagebrush is an important food source for animals like the greater sage-grouse, pronghorn and mule deer, it is bitter and unpleasant to humans. Note that we often refer to these shrubs as “sage,” but this is not the sage used in savory dishes. Big sagebrush belongs to the family Asteraceae, along with sunflowers and daisies. Culinary sage is in the Lamiaceae family, with mint, rosemary and thyme as relatives.

Humans are not the only animals in Oregon to find this plant unpleasant to eat. Nearly all big sagebrush ecosystems support livestock grazing, and cattle prefer a diet that excludes this ubiquitous plant. As a consequence, many extraordinary and imaginative methods have been developed to remove sagebrush in an effort to promote grasses and cater to the bovine palate.

Today, big sagebrush is considered a valuable part of the landscape rather than a nuisance — and for good reason. These shrubs engineer their habitat in surprising ways that improve conditions for both animals and plants. Big sagebrush promotes water infiltration and helps maintain snowpack. Its robust root system reaches deep into the soil, allowing it to use water that is inaccessible to most other plants — and then share that water. At night, the big sagebrush’s roots transport water from wetter to drier parts of the soil. This phenomenon, common to many plants, was first discovered in big sagebrush. It’s called “hydraulic lift” because the primary direction of this redistribution is up in these ecosystems where sun and wind rapidly dry shallow soils. In addition to enhancing water resources, big sagebrush also concentrates nutrients in the soils directly beneath its canopy, and these “islands of fertility” can promote recovery after fire.

At first glance, landscapes defined by big sagebrush can appear as monotonous grey-green expanses of shrubs surging towards the horizon. Early descriptions suggested that these ecosystems support low plant diversity, but more recent accounts suggest otherwise. Although it is true that local plant diversity may be relatively low in dry areas, even moderately wet sites often support dozens of species. Even more impressive is the enormous assortment of plants that are found across big sagebrush ecosystems, so that the unique collection of species found at single sites can vary substantially from place to place. Stop and look closer and you will see that big sagebrush canopies can provide favorable microsites for grasses and wildflowers.

voices

Durlin Hicock, Alice Elshoff Award winner

Durlin Hicock, Alice Elshoff Award winner

“Protecting public land is part of my spiritual being. It’s central to my identity to be in wilderness and to see it protected.” Durlin is proud to protect public lands for future generations, saying, “The highlight of my childhood was our family’s weekend outdoor trips. I look forward to my grandchildren having similar experiences outside in their lifetimes, and it wouldn’t be possible without ONDA.”

fact

What defines Oregon’s high desert?

What defines Oregon’s high desert?

Bounded by the Cascade Mountains to the west and the Blue Mountains to the north, Oregon’s high desert covers approximately 24,000 square miles. Annual rainfall in the high desert varies from 5 to 14 inches. The average elevation is 4,000 feet; at 9,733 feet, the summit of Steens Mountain is the highest point in Oregon’s high desert. The terrain of the high desert was mostly formed by a series of lava flows that occurred between 30 and 10 million years ago.

Sources: The Oregon Encyclopedia; Wikipedia  

fact

Bobcat

Bobcat

Found only in North America, where it is the most common wildcat, the bobcat takes its common name from its stubby, or “bobbed,” tail. The cats range in length from two to four feet and weigh 14 to 29 pounds. Bobcats mainly hunt rabbits and hares, but they will also eat rodents, birds, bats, and even adult deer.

Latin name: Lynx rufus fasciatus

 

Wildflowers, like these paintbrush, balsamroot and phlox, thrive alongside big sagebrush

Rachel Renne

Big sagebrush is evergreen and able to photosynthesize during winter.

Rachel Renne

Strange, but true: mountain big sagebrush leaves glow bright blue under a blacklight.

Rachel Renne

The way big sagebrush marks the passing of each season is also subtle, with slight, but important changes that allow it to thrive in its harsh environment. In winter, its evergreen leaves usually remain partially uncovered by snow, allowing it to photosynthesize on warmer days. When water is abundant in the spring, this shrub grows both small, perennial leaves and big, ephemeral leaves to gather and store energy. When temperatures increase and water becomes scarce, big sagebrush sheds the larger leaves and assumes a more frugal affect to wait out the hot, dry summer. At the same time, it shifts its efforts to growing stems that will support hundreds of tiny yellow flowers in the fall. Although this happens when water is scarce, these stems efficiently photosynthesize and can contribute energy to their own growth.

Whenever you find yourself in the company of this stalwart western shrub, keep an eye out for wildflowers (and wildlife) and take note of its seasonal adaptation. As you hike stretches of the Oregon Desert Trail, try to imagine how big sagebrush is quietly engineering the water and nutrients beneath your feet.

About the Author: Rachel R. Renne is a PhD student studying big sagebrush ecosystems at the Yale School of the Environment, a long-distance hiker and a volunteer with Oregon Natural Desert Association.