Green party

Natural History, Nov, 2002 by Stephan Reebs

How's this for international scientific cooperation? Thirteen biologists from seven countries monitor 115 plant species at eleven mountain sites in North America, South America, and Europe. Aptly enough, the goal of this display of organizational virtuosity was to show that under some circumstances, plants, too, can help one another.

Cooperation among plants is only rarely appreciated. But, at least in principle, plants can provide protection for one another against wind, soil erosion, and (by creating microclimates) extreme temperatures. One might think that such cooperation would be more prevalent in tough places, whereas competition would reign under less rigorous conditions. The biologists, led by Ragan M. Callaway of the University of Montana in Missoula, tested that idea by removing all neighboring plants within four inches of every plant they were testing, at both harsh, alpine sites and gentler sites at lower elevations. At the lower elevations the loners generally ended up growing and surviving better than the controls, whose neighboring plants were left untouched. Hence when life is easy, neighbors are just stressful competition. But at high altitudes, the loners did worse than the controls. So when the going gets tough, the tough plants get going--together. ("Positive interactions among alpine plants increase with stress," Nature 417:844-48, June 20, 2002)

Stephan Reebs is a professor of biology at the University of Moncton in New Brunswick, Canada, and the author of Fish Behavior in the Aquarium and in the Wild (Cornell University Press).