Though it’s disappearing, California’s official state weed has the ability to live 100 years or more. New research shows that sheep and cattle can help achieve this longevity.
Purple needle grass once dominated the state’s grasslands, providing food for Native Americans and more than 330 land creatures. Today, California has lost most of its grassland, and coniferous grass occupies only a tenth of what remains.
It is drought tolerant, promotes the health of native wildflowers by attracting beneficial root fungi, burns slower than non-native grasses, and speeds recovery of burnt land after a fire. For these reasons and others, many in the field of habitat restoration hope to conserve the coniferous grass.
“Where she grows, those tall, slender clusters become focal points that are both beautiful and environmentally friendly,” said Loralee Larios, UC Riverside plant ecologist. “However, it is challenging to identify successful management strategies for a species that can live a few hundred years.”
To address this challenge, Larios teamed up with plant ecologist Lauren Hallett of the University of Oregon and the East Bay Regional Park District in Northern California. They tracked the health of nearly 5,000 individual clumps of coniferous grass over six years, including an El Niño rainy year and historic droughts.
Researchers took measurements of plant health, including growth and seed production. They placed small bags over many of the clumps of grass to capture the seeds and quantify the number of seeds produced.
Their results, now published in the Journal of Applied Ecology, where the purple pinegrass thrived better where sheep were allowed to graze. The positive effects of grazing increased during periods of wetter weather.
Previously, the park district spent a decade evaluating the success of its grassland maintenance techniques. However, the district’s method of using a strategy such as grazing and then measuring the percentage of coniferous clumps in a given area resulted in data that followed no discernible pattern from year to year.
“By tracking each plant over time, rather than scanning an area wide, we gained much more clarity on how the grass is responding to grazing,” explained Larios. “Perhaps counterintuitively, we saw that coniferous grass generally died back when sheep were not allowed to graze on it.”
When the sheep were removed from the study sites, the needle grass became less healthy at all but two of the sites. Researchers want to know if the two sites that have remained healthy have coniferous grasses that are genetically different.
Grazing is a controversial grassland restoration strategy. Some conservationists believe that sheep eating the target grass, especially during already stressful drought years, does not improve their survival. As early as the 18th century, some researchers hypothesized that the combination of grazing and drought led to the loss of perennial grasses.
Although drought was not beneficial for any of the plants in this study, the researchers believe grazing helped the coniferous grass survive in at least two ways. First, by trampling on leaves and other organic debris, sheep made room for new coniferous grass.
“Sometimes you get litter as deep as a pencil — so much dead, non-native grass piles up. It’s hard for a small seed to get enough light through all of this,” Larios said.
Second, sheep eat non-native grasses that produce growth-inhibiting debris and compete with purple needlegrass for resources.
When the Spanish colonized California, they brought with them forage grasses like wild oats, which they thought would benefit livestock. These introduced grasses are spreading and now dominating the state’s grasslands.
“Our grasslands are known for having one of the largest biological invasions in the world,” Larios said.
California has up to 25 million acres of grasslands, which is the combined area of Massachusetts, Connecticut, and Rhode Island. Although Larios doesn’t believe it’s possible to rid the state of all non-native grasses, she said it’s possible to conserve or even increase the amount of purple conifer grass.
“It’s great for carbon storage, which mitigates climate change, it doesn’t fuel wildfires, and it cultivates a space for wildflowers that pollinators can then use,” Larios said. “We want to keep all these advantages.”