Climate change impacts ‘medium’ meadows

IOWA STATE (US)—The effects of drought on the Greater Yellowstone Ecosystem of the Rocky Mountains provide a glimpse of how changing climate affects the diversity of meadow plants and animals.

As the Earth’s temperature rises, the area’s climate becomes drier, leading to changes in the types of plants and animals that live there, says Diane Debinski, professor of ecology, evolution, and organismal biology at Iowa State University.

To study the potential effects of climate change, Debinski has been conducting large-scale, long-term, observational studies of the plant and insect communities in 55 montane (mountainous) meadows in the ecosystem that ranged from dry (xeric) to wet (hydric).

The meadows get most of their water from the melting of winter snows—runoff provides water to the area into July and August.

“It was our aim to look at the same sites year after year,” explains Debinski. “We know that the world changes and ecological communities change over time, but not many people look at the same research sites for a decade or more. I wanted a data set to look at changes in the communities over the long term.”

Debinski measured changes in the plant community from 1997 to 2007, a time period that included an extended drought.

The research is published in the journal Ecology.

Shrubs that grow in the drier meadows (such as sagebrush) increased, while flowering plants decreased in number. Shrubs from drier meadows don’t provide as much food for animals as flowering plants that grow in wetter meadows.

This may result from the way the plants get water, Debinski explains. Shrubs generally have deeper roots and can obtain water from deeper in the soils. Flowering plants generally get water from nearer the surface. These types of changes could have important implications for wildlife in the montane meadows.

“In these meadows, as water became more scarce, that means less moisture for the plants,” she says. “The flowering plants don’t grow as well and therefore don’t provide as much food to the animals. These types of changes in the plants could affect populations of elk, bison, as well as many other smaller animals, including insects.”

Since there were fewer flowering plants in the drier years, pollinators such as butterflies were also becoming scarce in several of the plots studied. Two species of butterflies that live in the wetter meadows actually disappeared from her sampling sites for a year, but were observed again in later years.

Because there are six types of meadows, from wet to dry, Debinski was also able to examine which meadow type was most vulnerable to change. Medium-moisture meadows—neither wet nor dry—are in the biggest danger of change.

“If wet meadows get a little drier, they’re still wet,” she says. “If dry meadows get a little drier, they are still dry. But the meadows with a medium amount of wetness are the ones that may be changing most.”

The location of the study gives it added weight, Debinski says. “It is important to know what sorts of changes are happening in a place where people don’t have much of an impact. The results of other studies done in other places can blame changes on human impact. Not so much here.”

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