Published by Communications and Public Affairs (519) 824-4120, Ext. 56982 or 53338
May 02, 2002
Plants that 'get along' with their dirt do best, study shows
Survival of the fittest has long been believed to be the key to success in nature. But new research by a University of Guelph professor reveals that in the plant world, longevity is determined by how well a species competes with its own soil and not other flora. And the longer a plant has been around, the tougher the battle.
“It has always been assumed that plants were fighting it out for space and other resources in the wild,” said botany professor John Klironomos, whose study will appear in the May 2 issue of Nature. “But it turns out that plants may not even be aware of what other plants are growing up next to them. The battle for survival is really between the plant and its soil pathogens.”
Klironomos conducted a series of controlled and field experiments involving plants that are native and foreign to Canada. He grew them for equal durations in pots of “home” and “foreign” soil, monitoring their growth and interactions with soil pathogens. He then planted the same species in natural meadows. What he found is that for a plant, there is no such thing as a “home court advantage.” “Many native species have trouble growing in ‘home soil’ because the species-specific pathogens have had so much time to accumulate,” Klironomos said.
“The plants that are flourishing -- both in the experiments and in the wild -- are often the invaders. They have escaped their predators and come to foreign soil, where their predators have not had time to form.”
The rate at which a plant grows also determines how it will respond to soil pathogens, the study found. Species that grow slowly allow pathogens to accumulate at a faster rate, which limits plant abundance. This gives faster-growing plants a competitive advantage because their pathogens take longer to develop, giving the plant a chance to multiply.
This is the first time scientific evidence has shown that interactions between plants and soil microbes is what determines the relative abundance of plants within natural communities. It explains why some plants are so rare in nature and others so abundant, accounting for about 60 per cent of plant diversification, Klironomos said.
“This study addresses an age-old question in ecology: how is it that in plant communities, more than one species survives? In theory, the most competitive species should win out and we should be seeing monocultures out there. But plant communities are made up of different species with varying levels of abundance and we have never really known why.”
This same theory has been applied for years in agricultural systems, he said. “It’s the reason farmers do crop rotations. If you grow the same plant over and over again, it builds up pathogens, reducing its ability to grow. The same theory now applies to natural communities.”
Understanding the mechanisms responsible for a natural plant abundance may lead to new approaches for the management of ecosystems, Klironomos said. “Most importantly, it may result in new ways to conserve rare and endangered species, and protect plant ecosystems from species invasions.”
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