Grass Rules — Thank Fungi, But Be Wary of Climate Change


When it comes to climate change, here’s another thing to worry about: the continuing viability and stability of ancient fungi living deep inside your pasture grass, and the overall lack of attention they — and indeed the ecology of pasture grass in general — are receiving in these rapidly changing times.

If you pasture livestock, you may remember, or know about, the great Kentucky 31 fescue fiasco, back in the 1970s. It was introduced as a pasture grass, and producers planted it widely as part of good pasture management…or so they thought.

At first, Kentucky 31 had everything going for it – namely, it was hardy, prolific and drought resistant.

But the livestock grazing on it started having problems. They got sick, showing ill effects during pregnancy and at other times as well. In some cases, necrotic tissue was the unfortunate outcome of the exposure to this grass.

Researchers ultimately traced the situation to microscopic fungi living inside the grass, between plant cells.

In nature, these fungi help their host grasses compete against others. The fungi give their hosts superior survivability traits, so that they too may live on. Their role is to help the grass flourish, not to help livestock get fat.

Normally, this symbiotic evolutionary technique is good for both. And although the fungi were toxic to livestock — a defence mechanism, perhaps? — they, and the Kentucky 31 fescue they lived in, got along just fine. The fescue provided a home; the fungi helped it be a survivor.

This symbiosis has stood the test of time. In fact, plant ecologist Prof. Jonathan Newman, dean of the College of Biological Sciences at the University of Guelph, points out that this grass-fungi relationship has been going on successfully for about 30 million years.

But he also knows times have changed. And so does the country’s biggest scientific granting agency, the Natural Sciences and Engineering Research Council. It’s just funded a study for he and his lab to try to determine if this millennia-old relationship is likely to last, and if indeed it’s changing, how that will affect pasture. His findings will have implications for lawns, golf courses and everywhere else grass grows…which is just about everywhere.

“With major climatic change predicted for the remainder of this century, an open question is whether or not these symbioses will continue to provide economic benefit, or continue to invade and subsequently alter native ecosystems,” says Newman.

Jonathan Newman, dean of the College of Biological Sciences at the University of Guelph
Jonathan Newman, dean of the College of Biological Sciences at the University of Guelph

It’s a worthwhile question, given pasture’s economic importance to agriculture, and to the ecological palette of the global landscape. Around the world, pasture and fodder crops cover more than 70 per cent of agricultural land. In Canada, Newman’s lab is the only one looking at how the symbiotic relationship between grass and fungi could be altered with climate change.

This would all be so much easier to study, and manage, if grass wasn’t so competitive. But it is, and you can tell just by looking around. Think beyond pasture. Grass rules.

And it might not be obvious, but through the ages, native grass species have been continually outcompeted by invasive species. Mostly lately, humans have aided this phenomenon by cultivating imported grass seed with beneficial traits, such as hardiness and higher protein or vitamins, for their livestock pastures. They’ve made invasive species work for them. And after the Kentucky 31 problem, they came to figure out which fungi were beneficial — or at least not harmful — and plant breeders proceeded to develop grasses that wouldn’t cause livestock woes.

But grass is grass, and it’s still very competitive with other varieties around it. Kentucky 31 has persisted, and continues causing farmers problems. No wonder…despite its impact on agriculture, it’s still sold for lawns. However, grasses like this and others routinely “escape” from the pasture into which they were seeded or introduced.

Then what?

That’s a question that Newman says needs to be addressed now, with so much other climate-driven change occurring. For example, what if an invasive grass arrives on the scene in our new hotter and drier world, stands up well against drought…but like Kentucky 31, ends up being toxic to livestock, and spreads like wildfire?

Newman hopes to come up with some answers. For the past nine years he’s worked with 340 research plots near the university. His focus is on trying to determine if grasses used for pasture are becoming more aggressive, if they are affected by increasing levels of greenhouse gas, and which ones thrive under different soil conditions and management techniques.

In Newman’s words, he’s setting out “to address some of the serious gaps in the basic ecological understanding of the system.” He doesn’t know what he’ll find…but that’s why society supports research, to help him try to find out.

Otherwise, how will we know?

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