Climate Change Affects Pacific Northwest Mountain Meadows
November 4, 2012

Impact Of Climate Change On Mountain Meadows Analyzed

redOrbit Staff & Wire Reports - Your Universe Online

Reduced amounts of snow cover, longer growing seasons, and other factors associated with climate change are adversely affecting a high mountain meadow in central Oregon. And experts believe that global warming is having a similar impact on such landscapes throughout the Pacific Northwest.

In research funded by the Pacific Northwest Research Station of the US Forest Service and published in the journal Landscape Ecology, researchers from Oregon State University (OSU) analyzed Jefferson Park, a subalpine meadow complex in the Oregon Cascade Range, and found the area that was occupied by trees increased from 8% in 1950 to 35% in 2007.

The area had previously been covered by grasses, shrubs, and wildflowers, and the changes that are occurring there "are representative of a larger force that is affecting not only this beautiful meadow at the base of Mount Jefferson, scientists say, but many areas of the American West," according to a university statement.

“We worry a lot about the loss of old-growth forests, but have overlooked declines in our meadows, which are also areas of conservation concern,” Harold Zald, a research associate in the OSU College of Forestry and lead author of the study, said in a statement. “The first awareness of declining meadows dates back to the 1970s, and we´ve seen meadow reduction at both high and low elevations."

"Between climate change, fire suppression and invasive species, these meadows and all of the plant, animal and insect life that depend on them are being threatened," he added. “Once trees become fully established, they tend to persist, and seed banks of native grass species disappear fairly quickly. The meadows form an important part of forest biodiversity, and when they are gone, they may be gone forever.”

Zald compared the decline of the meadow to the melting of a glacier, noting that both environmental changes occur over a period of several decades and, as such, are good ways to measure long-term climate change. The reason for this, he explained, is that the changes continue to occur from season to season and year to year, through both hotter and colder than average conditions, as well as wetter or drier than usual conditions.

"In this study, it appears that snowpack was a bigger factor than temperature in allowing mountain hemlock tree invasion of Jefferson Park, a 333-acre meadow which sits at the northern base of Mount Jefferson, a towering 10,497-foot volcano northwest of Bend, Ore.," the university said.

"Seedlings that can be buried by snow many months every year need only a few more weeks or months of growing season to hugely increase their chance of survival," the university added. "The study also found surprising variability of tree invasion even within the meadow, based on minor dips, debris flows or bumps in the terrain that caused changes in snowpack and also left some soils wetter or drier in ways that facilitated tree seedling survival."

Zald said the invasion of trees into the meadow typically tends to take a long period of time, but can occur rapidly under the right condition. While some experts have suggested that alpine meadows may just be moving upward on a mountain face in response to the warming global climate, Zald argues that slopes often become too steep and the soil quality becomes too poor to support such plant life.