They pumped carbon dioxide into the enclosures, boosting CO2 concentration to double current levels in order to simulate the conditions that climatologists expect will prevail by the end of the century.
At the end of five years, there had been an explosion in the growth of a small woody shrub called Artemisia frigida. The plant's weight or biomass had increased 40-fold, and its coverage had increased 20-fold.
The results support the notion that rising atmospheric CO2, which is partly a function of burning fossil fuels, have contributed to shrubland expansions of the past 100 -200 years, the authors wrote.
"The increased proportion of woody plants has reduced significantly the available forage in many world grasslands and, without proactive management measures like burning, has rendered these lands less suitable for livestock grazing," they pointed out.
The paper appears in the most recent journal of the Proceedings of the National Academy of Sciences.
