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Plant Communities Beat Monocultures

Plant communities.tifAlthough monocultures can be cultivated efficiently, they are anything but sustainable: environmental damage to soil and water caused by monoculture cultivation is becoming increasingly evident, even beyond in-the-know sustainable farming circles. Despite their disadvantages, however, monocultures remain the principal crop form and are often regarded as the sole possibility for achieving higher yields in plant production — quite wrongfully, finds Bernhard

Schmid, an ecology professor at the University of Zurich. Schmid sees “an opportunity for the future of nutrition for humankind in the untapped potential of biodiversity” — a promising prospect as the OECD and the United Nations’ Food and Agriculture Organization (FAO) are giving off worrying signals: Both organizations predict that agricultural productivity will rise less steeply in the future than has been the case thus far.

In a 10-year study, a team of researchers from Switzerland, Germany and the Netherlands examined the yields from grassland plants which they had cultivated in monocultures or mixed plant communities. The latter proved to be more productive than the monocultures.

“Due to their diversity, plant species in communities occupy all the niches available in an ecosystem,” said researcher Dan Flynn. “This enables them to use soil nutrients, light and water far more effectively than monocultures, which ultimately leads to greater yields.”

Another advantage: There is less pressure from parasites on plants in diverse communities than on those in monocultures. In other words, a parasite can spread less effectively as it is unable to find its special host plant as easily in a biodiverse plant world. The different plant species thus act as protective shields for each other. This mutual protection within the group enables individual plants to invest the resources available into growth and the production of offspring instead of pest control.

“Diversity offers protection against pests and is a prerequisite for higher yields in plant communities,” says Schmid.

The researchers also discovered that species adapt to their plant communities in the time of a few generations. This so-called short-term evolution leads to a continued increase of crop yield in mixtures — a possibility that, according to Schmid, was unexpected in both basic research and plant cultivation. In this adaptation process, the various species specialize in their strengths and thus improve the complementary utilization of resources throughout the plant community by a process called character displacement. Grasses, for instance, develop thicker leaves, which are able to utilize the direct sunlight in the upper layer of a meadow while clover species sprout larger but thinner leaves to absorb the weaker light close to the ground more effectively

This article appears in the December 2014 issue of Acres U.S.A.

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