Warming may cause rapid plant species loss on Qinghai-Tibet Plateau

HOHHOT, July 6 (Xinhua) -- Global warming could cause a dramatic decline in
plant species diversity on the rangelands of the Qinghai-Tibet Plateau in
southwest China, say Chinese and U.S. scientists.

Research into climate change and grazing conducted in the northeastern
Qinghai-Tibet Plateau from 1998 to 2001 showed a 26 percent to 36 percent
decrease of plant species, said Julia Klein, a U.S. Colorado State University
assistant professor who led the research.

Global warming specifically had led to losses of 21 percent of medicinal
plants and 25 percent of pasture plants, said experts at the joint meeting of
the International Rangeland Congress and the International Grassland Congress.
The weeklong event ended on Saturday in Hohhot, capital of Inner Mongolia
Autonomous Region.

The research was carried out at four sites at the Haibei Alpine Research
Station, a facility in Qinghai Province run by the Northwest Plateau Institute
of Biology, of the Chinese Academy of Sciences, where the annual temperature is
minus 2 degrees Celsius and the elevation is 3,200 meters.

Two sites were in grasslands and two in the shrub land habitats. The two
types represent around 35 percent of the area of the plateau. Researchers fenced
each 900-square-meter site and laid out 16 plots, where they simulated warming
by using open top greenhouses and grazing through selective clipping.

The greenhouses, each 1.5 meters in diameter and 40 centimeters high, were
left on the plots year-round, elevating the average daily temperature by 0.6 to
2 degrees Celsius in the growing season. There were around 30 plant species in
each.

The study showed medicinal plants had an average annual loss of4.9 species
from 1999 to 2001, while edible plants had an annual average decline of 5.3
species, according to the researchers, who included John Harte, of the
University of California, and Zhao Xinquan, of the Northwest Plateau Institute
of Biology.

The researchers said the plants' individual characteristics, such as their
history and root depths, influenced their reactions to the warming.

For example, they found deep-rooted species, which lost an average of 20
percent, were less affected than shallow-rooted species, which had an average
loss of 39 percent.

The warming caused soil to dry, which was harmful to plants with shallow
rooting systems.

The researchers also found warming lowered rangeland quality by decreasing
the plants' productivity while grazing could maintain or improve rangeland
quality, by extending the plants growing season, for example.

"Our findings suggest the rangelands on the Qinghai-Tibet Plateau, and the
pastoralists who depend on them, may be vulnerable to future climate changes,"
said Klein.

Grazing could mitigate the negative effects of warming on the rangelands.
For example, grazing management may be an important tool to keep warming-induced
shrub expansion in check, she said.

Global warming, caused by greenhouse gas emissions, is the increase in the
average measured temperature of the earth's near-surface air and oceans since
the mid-20th century and its projected continuation. The average global air
temperature near the earth's surface increased about 0.66 to 0.92 degrees
Celsius during the hundred years ending in 2005, according to studies.

More extreme weather-related disasters such as flood and drought, the
melting of glaciers and the expansion of desert and rangeland degradation, are
believed to be related to the warming trend.