Posts Tagged: Grazing management

Once perceived as a problem, conservation grazing by cattle a boon to vernal pools

Giving 1,200-pound cows access to one of California's most fragile and biologically rich ecosystems seems a strange way to protect its threatened and endangered species.

But a recently published study suggests that reintroducing low to moderate levels of cattle grazing around vernal pools – under certain conditions – leads to a greater number and greater variety of native plants.

“We found that after 40 years of rest from grazing, reintroducing conservation grazing had – across the board – positive impacts on vernal pool plant diversity,” said Julia Michaels, a visiting professor at Reed College who led a three-year study in a Sacramento-area reserve during her time as a UC Davis Ph.D. student.

Ecologists consider vernal pools – ephemeral ponds that form seasonally – “islands of native habitat” amid California's grasslands that are dominated by exotic grasses. These biodiversity hotspots harbor about 200 native species of animals and plants, such as the coyote thistle, which germinates under water and forms a snorkel-like straw to deliver oxygen to its roots – and then “fills in” its stem as the pool dries.

Specially adapted to survive in those stages of wet and dry, many of these species are found only in vernal pools scattered across California – making those pools an urgent priority for conservationists.

“It's estimated that more than 90% of the original vernal pools in California have been destroyed due to agriculture and urban development, so management of those remaining – including those that have been re-created – is of high concern,” said Valerie Eviner, a UC Davis plant sciences professor and UC Agriculture and Natural Resources affiliate. Eviner is a co-author of the study, along with UC Davis colleague Kenneth Tate, UC Cooperative Extension specialist.

During the 1970s and 1980s, vernal pools were fenced off in parts of the state, in the hopes of protecting the flora and fauna from grazing cattle. In the early 2000s, however, UC Davis researcher Jaymee Marty found that grazing was actually crucial to vernal pool biodiversity: once livestock were removed from areas that had been grazed historically, the diversity of plants plummeted.

“Her research was critical to rethinking the best ways to protect the diversity in California's vernal pool ecosystems,” Eviner said.

The Michaels-led study, published in the Journal of Applied Biology, builds on Marty's work, by looking at scenarios where cattle had been blocked from vernal pools for decades, and then observes the rate at which biodiversity returns after reintroduction of the animals. Michaels said she wanted to provide some initial answers to the practical questions that ranchers and land managers have in potentially reintroducing cattle.

“A lot of them had these areas that had been fenced off from grazing for the last 20–30 years, and they were very concerned about what happens if we let cattle back onto these vernal pool grasslands – are there going to be negative impacts because that land had been at rest for a few decades?” Michaels explained.

In their study within the Sacramento Valley, the researchers focused on transition zones – the “battlegrounds” between vernal pool native species and the encroaching invasive grasses, where they are able to detect most readily the effects of disturbances such as grazing.

They discovered that, after reintroducing cattle to areas that had been fenced off since the 1970s, there was a greater abundance of native flora (species like the vernal pool buttercup, bractless hedge-hyssop and bristled downingia), as well as increased diversity among the plants (both in number of species and in how evenly distributed they were).

“Encouragingly, diversity is rapidly restored,” Eviner said, “providing conservationists with strong data to show that rapid action can enhance plant diversity.”

And as for potential worries about cattle making a snack of vernal pool plants, Michaels and her colleagues observed that the cattle appear to be more interested in munching on grasses.

“Anecdotally, we saw very few signs of herbivory on the vernal pool species because the timing is such that [the plants] are underwater for a good part of the late winter and early spring, and then by the time they're blooming, there's plenty of good forage around for the cattle,” Michaels said.

In fact, the cattle seem to be performing a function filled for millennia by native grazers (namely, the once-abundant tule elk), helping to knock down vernal pool species' chief competitor in those transition zones: the grasses.

Although the researchers were concerned about a loss of biodiversity, excessive nutrients in the ponds due to defecation and harmful compaction of “fluffy” soil, none of their worries materialized on the test sites where grazing was reintroduced.

Instead, microdepressions created by the cattle appeared to encourage the proliferation of native plants. Each hoofprint became a miniature basin – “a vernal pool within a vernal pool.”

“Right in those transition zones, where they could be hosting either the vernal pool species or the upland grasses, just a couple centimeters of soil topography can make a big difference,” Michaels explained. “If a cow comes and steps in that transition zone, and that lowers the soil surface so it stays inundated a little longer, you end up seeing these pockets of vernal pool species that are able to persist.”

Michaels is currently conducting a follow-up study on the hoofprints to pinpoint their role in boosting native plant abundance and biodiversity. Because the prints can last for several years, they might be able to deliver some enduring benefits – and land managers might not have to bring cattle in to graze the pools as often.

“If it's really the hoofprints making the big difference, maybe we don't need to graze every year – only during certain times of year when we know the hoofprints will form well and harden, and then we're good for a few years,” Michaels said.

Match.Graze launches to reduce wildfire fuel, feed livestock

Matchmaking grazing animals with grass and rangelands

Professional grazing of overgrown rangelands, pastures and parcels is proven to reduce the spread of dangerous and costly wildfires.

Do you have land but no livestock and feel concerned about fire fuels on your property? Or are you a livestock owner that can provide a grazing service and/or need land and forage for your animals? Match.Graze can help.

Match.Graze is a free online platform connecting landowners statewide who want grazing animals to livestock owners with animals that can provide vegetation management services, created by UC Cooperative Extension. 

From small semi-rural communities to large open spaces, grazing can provide an affordable solution to the inevitable accumulation of fire fuels. Grazing can be more cost-effective for reducing fuels on landscapes that are too steep, rocky or remote for mowing or chemical treatment, or in the wildland-urban interface where burning is not an option.

“I've noticed on several fires, including extreme fires, the fence lines where the fire just stopped. And the one variable, the one difference, was grazing,” said Marshall Turbeville, CAL FIRE battalion chief.

Cattle, sheep, goats and other grazing animals all have different roles to play in grazing for fire fuel reduction. If you want to use livestock to help reduce fire risk in your area, visit MatchGraze.com.

“Every property is different and requires thoughtful consideration of how it should best be grazed,” said Stephanie Larson, director of UCCE in Sonoma County, UCCE livestock and range management advisor and co-creator of the livestock-land matchmaking service. “UC Cooperative Extension is here to serve, put Match.Graze to work and let's prevent catastrophic fire while helping landowners and agriculture.”

To find a local grazing partner, visit MatchGraze.com, set up a free account, create a pin on the map and make a match.

Low residual dry matter on rangeland a concern heading into wet season

Over the past few years, drought has negatively affected everyone in the state and ranchers are no exception. Due to the drought, most areas have seen a decline in forage production and water availability, and as a result many livestock producers reduced their herd sizes and grazing season.

With some recent forecasts bringing encouraging news about a potential El Niño, some ranchers have been asking about what they should expect in terms of forage production, if and when the rains come. What they want to know is how soon rangeland productivity will reach the pre-drought levels again. One issue that I always draw their attention to is the levels of residual dry matter (RDM) on the rangelands. Even with the reduction in herd sizes and shorter grazing seasons employed by most producers, more rangelands now have less than recommended RDM levels.

RDM is a measure of the old plant material (without counting summer annuals) that are left standing or on the ground before the fall precipitation comes. It is a great indicator of both forage production and grazing intensity. These leftover plant materials are critical on California rangelands to reduce erosion and nutrient loss, and to create a conducive environment for diverse plant communities to thrive. Optimum RDM levels are site specific, they range from 100-2,100 pounds per acre, and depend on precipitation zone, slope and tree canopy cover. Ideal RDM levels increases with precipitation and slope, and decreases with tree cover. Studies show that too low or too high RDM levels will reduce species composition and forage production, both factors critical to any livestock production system. The good news is that annual rangelands are resilient and will likely return to normal production within two years after bringing RDM level to recommended standards.

Knowing the RDM standards for one's rangeland and continuously monitoring is an important step towards achieving sustainable rangeland management and livestock production.

Details about RDM standards, data collection methods and more can be found in the free UC Agriculture and Natural Resources publication Guidelines for Residual Dry Matter on Coastal and Foothill Rangelands in California. 

Author: Fadzayi Mashiri, Ph.D.

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