and Yosemite's Meadows: Keeping the Balance
By Carol Blaney and Peggy Moore, research scientist, Yosemite National Park
Crouching on a 10,000-foot ridge above the Gaylor Lakes basin at dawn in September, I coaxed my frozen brush into painting the scene below: a frost-tipped yellow diamond of a meadow caressed a blue, blue alpine lake, and a coyote on the hunt trotted across golden, crusty sedges.
|So much grass, so little time: Yosemite mule goes to work, providing grazing data for NPS researchers.|
Coming upon a meadow in the Sierra Nevada always gives me a thrill. Such jewels appear suddenly after monotonous acres of lodgepole pines, and they soften the gray granite expanses that make up most of the high country.
Meadows not only provide visual relief for weary hikers, but they serve specific needs for animals and the rest of the ecosystem as well. An acre of meadow can produce up to two tons of forage per year, an excellent food source for wildlife. Meadows act as natural water purifiers, filtering sediment from runoff so nearby streams run clear. Sierra Nevada meadows harbor more than 110 species of plants, and even though such grasslands cover less than 10 percent of the "range of light," they have drawn travelers for centuries, and wandering wildlife for millennia before that.
Deer, bighorn sheep and other wildlife all use meadows as a stopping-and-munching point. Native Americans living in the Sierra hunted near meadows and may have maintained the grassy expanses by burning. Early white settlers in California used meadows for stock grazing, once they discovered the presence of moist summer forage in the mid-19th century, and the meadows have been used for stock feed ever since.
Allowing livestock to graze in meadows creates conflict for public land managers in the Sierra Nevada. Stock users state firmly that there is plenty of meadow to go around. But backpackers and other wilderness users complain that the animals damage resources and the wilderness experience. Caught in the middle, park managers have lacked hard data to show what levels of grazing cause what levels of impacts.
A study, to be completed this year, will give resource managers at Yosemite and other wilderness areas information on how grazing at different intensities affects meadows, and how to manage that effect.
"There are three important things animals can do to a meadow," said Dr. Jan van Wagtendonk, a Yosemite-based research scientist with the U.S. Geological Survey (USGS), and one of the study's authors. "They can change the plant species that grow there, they can change the meadow's productivity, and they can increase the amount of bare ground," all of which can affect a meadow's overall condition.
Livestock ranching was California's first major industry, booming along with the Gold Rush. Ranchers ran their cattle and sheep in the fertile Central Valley and Sierra foothills. But when the lowland grass shriveled in the drought years of the 1860s and 1870s, ranchers brought their animals to alpine meadows to keep them from starving.
John Muir came to California in 1868, and his early experiences in the Sierra were as a shepherd. But after years traversing the highlands, he turned determinedly against using them for livestock forage, referring to sheep as "hoofed locusts," and writing in The Yosemite that the park was "all one glorious flower garden before plows and scythes and trampling, biting horses came to make its wide open spaces look like farmers' pasture fields."
In 1890, Yosemite was made a national park, and the U.S. government brought in the cavalry to guard park boundaries, in part to be sure that ranchers weren't poaching grasses. But horses still provided the prime mode of transportation in the mountains, so the cavalry ran its own animals on park meadows, once even seeding the green expanses with introduced grasses to be sure they produced enough feed, according to Jim Snyder, a Park Service historian at Yosemite.
Horses were the most convenient way to travel in Yosemite until 1913, when cars were allowed into the Valley. Massive pack trips for park visitors, run by the Sierra Club, brought in hundreds of animals at a time. Horses needed feed, and meadows supplied it.
By the mid-20th century, some scientists worried that indiscriminate stock use could damage fragile meadow systems. During the 1930s and 1940s, park scientists and the Sierra Club performed grazing studies to see whether harm was being done. As a result, the Sierra Club cut back on the size of its trips, according to Snyder.
In these studies, and others done in the following decades, resource managers found that grazing was only one of the things that could affect the health of a meadow. Peggy Moore, a USGS ecologist based in Yosemite notes that invasion by lodgepole pines, erosion caused by livestock hooves and hikers' feet, burrowing by mice and pocket gophers, and fire suppression all affect whether and which plants survive. Sierra Nevada meadows also have lost ground to trees over the years, possibly because of grazing, fire suppression, climate and other factors.
Stock use in Yosemite has generally dropped off since its heyday in the first decades of this century. But the southern Sierra--including Sequoia and King's Canyon National Parks--is more heavily used by pack animals than other areas in the Sierra.
Yosemite managers have kept an eye on grazing, closing Wawona Meadow to it in 1972. Wilderness permits, instituted about the same time, and a reduction in the number of head of livestock allowed per pack trip have also provided protection against overgrazing.
The park's 357 meadows "are in pretty good shape," van Wagtendonk said. Still, wilderness managers want to track heavily used meadow areas, such as Upper Lyell Canyon, Benson Lake and Dorothy Lake, where private packstock companies bring trips regularly.
David Dohnel, the owner of Frontier Pack Trains, has run trips in the park for 17 years. "There's a lot of feed in Yosemite, and they regulate it pretty well on us," he said. On backcountry trips, he said, he steers horses and mules away from heavily grazed meadows, both for their sake and that of the park. Dohnel said he tries to teach his clients about low-impact camping and educate other packstock leaders on how to prevent meadow damage. "We're very careful," he said. "We need to take care of the resource. We've tried to take a lead in this because we don't want to have more regulations."
As part of an effort to develop a grazing monitoring plan, the park began a five-year study in 1994, under the direction of four scientists: van Wagtendonk and Moore of Yosemite, Dr. Mitchel McClaran of the University of Arizona and Dr. David Cole of the U.S. Forest Service's (USFS) Aldo Leopold Wilderness Research Institute. Neil McDougald, of the University of California Cooperative Extension, was also a member of the research team.
|After the mule, the researchers: NPS scientists clipping & weighing grass samples.|
By taking measurements over several years, the researchers knew they'dhave a broader idea of meadow response than after just one season; they'd also be able to take into account other factors that affect meadow plants, such as snowpack. A heavy snowpack and late melting, for example, can shorten the growing season and reduce plant productivity much more than heavy grazing the previous year.
The scientists chose to study three meadows, each of a different type. To the untrained eye, all meadows may look the same--expanses of grasses surrounded by trees and nestled between ridges.
But look carefully: meadows have many faces. Some are bone dry and golden most of the summer, while others are extremely wet and verdant. Their botanical inhabitants may be tiny, wiry sedges or lush grasses and wildflowers. They also occur at a variety of elevations, on different sites ranging from a couple of acres to 50 or more, and they can be stable or unstable over time. Scientists have used many combinations of these features to group meadows into several categories.
The Yosemite team chose one wet, one intermediate and one dry meadow, at varying elevations and with different characteristic plant species. The dry meadow, at 10,200 feet at Gaylor Lakes, blooms early and turns golden and crisp by mid-summer. A six-inch-tall sedge (Carex filifolia var. erostrata) dominates the meadow, joined by goldenrods and a few inconspicuous wildflowers able to handle the elevation and scarcity of water.
The second meadow, at 8,600 feet, is a middling wet site at Tuolumne Meadows, near Delaney Creek. Meadows like these are clothed in a purple haze created by the fine, long stems of the grass (Calamagrostis breweri) that covers the meadow. Bright yellow cinquefoil, deep blue penstemon, and a reddish paintbrush also color these meadowscapes.
The wet meadow, along Harden Lake at 7,600 feet, is lush. Tufted hairgrass (Deschampsia cespitosa) grows thigh-high across the site. "As you're walking through red fir, the landscapes just open up to these meadows, with wildflowers like lilies, camas and the tall, wispy grasses," Moore said. "They take your breath away."
During July and August of consecutive years, research teams braved plentiful mosquitoes and heat to spend days setting up plots in the meadow study, funded by the Yosemite Fund and USFS with support from USGS and the University of Arizona. Half a dozen people did the tedious work of clipping, drying and weighing plants in sections of each plot to determine the meadow's productivity, species composition and amount of bare ground. A second group of workers brought in horses and mules, and carefully watched them until they devoured one-quarter, one-half or three-quarters of the available forage. Some plots received no grazing for comparison.
After the animals finished eating, researchers once again clipped and weighed plants in the plots, and they repeated the process the next season to find out how each meadow responded to the different levels of grazing.
Recent analysis of this grazing data indicated that the amount of bare ground increased after two years of grazing in all three meadow types. The area of leafy material covering the ground decreased significantly only in the tall tufted hairgrass type. And, while there was a measurable shift in species composition after two years of grazing, the most pronounced and consistent change across all meadow types was in productivity. Productivity declined by the second year of grazing in all three types.
The meadow productivity results provide for estimates of how much grazing will cause specific reductions in meadow growth in subsequent years. This should allow park managers to anticipate the effect that observed levels of pack stock use will have in these three meadow types. They can then adapt their management strategies appropriately to protect park meadows for the long term.
While grazing three-quarters of the plants off a meadow year after year may not seem likely, the study provides a yardstick for wilderness rangers to use in monitoring meadow health. In 14 heavily used meadows around the park, rangers will measure remaining plant material close to the end of each season, and compare that with study findings to decide whether changes in the meadows are likely to occur and what to do about them.
"They can start to make decisions with their eyes wide open about what's going on in the meadows and what it means," Moore said. If monitoring shows the meadows are being grazed so heavily that their productivity drops or their species composition changes, resource managers can choose whether to reduce meadow use, for example. This monitoring plan should allow the park's meadows to remain healthy for years to come.
Freelance writer Carol Blaney became interested in meadow research on a visit to the park and interviewed those involved. Research Scientist Peggy Moore is based in Yosemite.
Books from the Yosemite Association Bookstore
Flowers of the Sierra Nevada - Sierra Nevada Field Card No. 3. Drawings by Elizabeth Morales
Sierra Nevada Natural History by Tracy I. Storer and Robert L. Usinger
World of Small, Nature Explorations with a Hand Lens by Michael E. Ross, Illustrated by Cary Michael Trout
Check out the Yosemite Association Seminars for courses in Yosemite National Park on botany and natural history
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