Opportunistic plants: Some plants benefit wildlife, pose little threat to grazing land
When grass is grazed harder, resulting in moderate plant defoliation, the open plant cover left behind is ideal for allowing opportunistic plants to grow. Although producers may consider plants like annual sunflowers and wild ragweed a nuisance, these plants can offer several benefits to wildlife, according to Chris Helzer, director of the Science for Nebraska program with The Nature Conservancy.
“If we think about grassland and rangeland, we have dominant grasses, wildflowers and other plants,” he explained to producers during the Nebraska Grazing Conference. “In ungrazed grassland, the roots of these plants are big and dense. Above ground, the grasses will be really tall.”
“New plants don’t have a lot of opportunity to grow, because they don’t have access to any light or resources below ground. It is kind of a closed system,” he says.
With light to moderate defoliation, livestock take some of the leaves off these grasses.
“It doesn’t have a huge impact on the root system, which is what happens if we have a rotational grazing system where we move livestock through quickly,” he explained. “The idea is to leave those grasses with enough resources that they can heal and grow back quickly.”
Helzer cautioned producers about intensive defoliation. Over a long period of time, it can cause changes above and below ground.
“After running some numbers this year, by far, the largest number of pollinator plants we saw were in areas that were grazed hard the previous year,” he explains.
“Above ground, the soil now has light hitting its surface because the plant canopy is smaller,” he explained. “When the plant becomes defoliated and can’t photosynthesize, it basically shuts down the root system.”
When this happens, Helzer said some opportunistic plants, will take advantage of grass weaknesses.
“As managers, we worry about plants that compete with our grasses. We worry they will reduce forage and cause problems. Some of these plants will only push in when the grass is weak, but they don’t push the grass out,” he said.
Opportunistic plants are ones that often take advantage of this open space, but they are usually not favored by livestock, Helzer continued.
“That is why they get a bad name, because it looks like they are taking over the grasslands. Actually, the presence of these plants can be an indicator of what’s going on underground,” he said.
“If the opportunistic plants have flowers, they are useful as insect pollinators,” Helzer explained.
This spring, the Monarch butterfly came into Nebraska from Mexico.
“They usually don’t stop in Nebraska before they breed,” he said. “There wasn’t a lot of plants for them to lay eggs on this year or enough food for them to eat. What got them through was dandelions, which is not everyone’s favorite plant, but this year it made an important contribution to the Monarch butterfly population.”
Insects and wildlife
Any time there’s a recovery period after intensive grazing, the insect numbers are also higher.
“Insects, like amphibians and reptiles, have to thermo-regulate their temperature,” Helzer explained. “In a system where grasses are short and have tall wildflowers or weeds standing above them, it’s like walking in a park with short grass and tall trees.”
“Insects can very quickly find a shady spot where they can manage their temperature, which is very important,” he continues. “That includes grasshoppers and stink bugs, as well as the predators that help control them.”
High insect numbers are good for wildlife numbers.
“From a wildlife standpoint, the combination of short grass and tall wildflowers is very important for wildlife trying to move around,” he said. “For wildlife like young grouse, sandpipers and pheasants, the cover left after intensive grazing is ideal.”
Western ragweed and annual sunflowers are examples of opportunists that aren’t progressive plants.
“We shouldn’t have to worry about actively controlling these species because they aren’t competing with our grasses,” Heltzer said. “They are present because our grass is weak.”
“As the grass gets stronger, it will push them out. So, don’t spend money on a herbicide to kill them. If we kill those off, more of the same plants will grow back. There’s still an opening in the canopy, and something has to fill it,” he explained.
Nebraska has nine varieties of sunflowers, and other plants that look and act like sunflowers.
“There are bees that will only act on sunflowers, and they feed on them,” he stated. “It is important from an insect standpoint.
“Some predators, like spiders, hang out on the sunflowers to prey on bees,” he noted.
Sunflowers produce a sweet, syrupy substance that appeals to the bees. Sunflowers are one of the best and most nutritional feeds for wildlife, Helzer said, which is why it is an ingredient in bird seed mixtures.
“As someone who manages property for wildlife, the approach we take is to encourage a large variety of plant species from very short to very tall but especially the intermediate plants. Those may be the most important and yet the hardest to find. Our approach is to put all our grazing pastures through that progression,” he said.
To help monitor plant recovery, Helzer said the Nature Conservancy uses a camera with a timeline scanner that can photograph images of an area every hour. In one location, this camera has taken pictures since 2013. The photos are of an eight-by-10 foot area, which shows what the vegetation looks like and how it changes over time.
Helzer discussed one 12,000-acre single pasture where 500 head of bison graze. In 2012, a fire destroyed a large portion of the pasture, but the bison were not destocked.
“We watched the plant recovery occur with the buffalo present,” he explains.
Gayle Smith is a correspondent for the Wyoming Livestock Roundup. Send comments on this article to firstname.lastname@example.org.