Restoring Ecosystem Services

A primary mandate of the Foundation is researching ways to improve what ecologists call “ecosystem services”soil formation, water-holding capacity, filtration of pollutants, and nutrient cycling, among others. Since the arrival of Europeans more than 200 years ago, California’s grasslands have undergone a complete phase change, from a landscape dominated by native perennial bunchgrasses to one dominated by annual grasses introduced here by European settlers. Perennial grasses coevolved with the habitat, and are much better at providing the ecosystem services described above, but they don’t compete well with the alien annuals. On the Mitsui Ranch, the Foundation has set out to attempt to re-establish a perennial grass–dominated rangeland through a multiphase experimental trial.

In collaboration with Dr. Andrew Rayburn, of River Partners, we first set out to measure and record what species of grasses are here on the ranch, and how those species are distributed on the landscape. We made limited random measurements (using quadrats) across pastures and used the results to project what is here and in what proportion. We found that very few native perennial grasses remain in the open pastures, and that a few species of introduced annual grasses dominate them. We also surveyed much of the ranch property and composed a list of native perennial grasses that are still present. Thus equipped with the data, we had to decide how to achieve our goals. We decided to exploit some differences in life history between perennial and annual grasses, in order to give an advantage to the native perennials.

Annual grasses invest most of their energy into producing a massive seed crop and invest very little in their root systems. (The shallow roots are what cause the annual brown-up of California’s rangelands in late spring.) When the rains stop and soil moisture recedes into the depths, annual grasses dry up. In contrast, perennial grasses invest heavily in their root systems. Often, the height of the growing plant on the surface has a root system that measures the same distance into the soil below…almost a mirror image.

This life-history difference between the two plant types profoundly affects each grass’s vulnerability to fire. Perennial grasses can start new growth from energy stored in their extensive root systems, so they recover from fire easily. Annual plants depend on energy invested in seeds that drop to the soil. Most of those seeds will survive on the soil surface and sprout when winter rains return—but if a fire occurs before the annuals’ seeds drop, the grasses will not recover from the fire . Many annuals are poor-quality forage species for cattle, so capitalizing on fire’s effect of these aliens drastically reduces the annual grass presence in a pasture.

Last June, we enlisted the aid of CalFire and several local fire departments to help us burn a ten-acre test field using prescribed (controlled) fire. We timed the burn for the period when the introduced annual grasses were almost dead but still held most of their seeds on their stalks. Our goal was to kill the vast majority of one particular species of invasive grass, an alien annual called Medusahead (Taeniatherum caput-medusae). On rangeland, cattle avoid Medusahead—so it continues to grow, unabated, until it’s crowded out native perennials and taken over vast portions of pasture, leaving little food for the cows. Medusahead is usually the last grass to die out each spring, making it easy to identify and isolate with a fire line. Our prescribed burn killed approximately 99 percent of the Medusahead, along with several other undesired annuals.

Prescribed fire

Prescribed fire

The burned-off pasture provided an opportunity to plant with native seeds. In consultation with Dr. Rayburn, and with the staff at Hedgerow Farms, we developed a nine-species seed mix to restore the burned area. The species mix was chosen based on our knowledge of which perennial grasses were native to the Mitsui property, and on their quality as cattle forage. Using a no-till seed drill rented from the Gold Ridge Resource Conservation District in Sebastopol, we seeded 4.5 acres last January. After a 10-day period, fine, hair-like shoots are appearing in the pasture… the promise of things to come.

Native perennial grass seed

Native perennial grass seed in the hopper.

As the new perennial grasses grow, they’ll provide many opportunities for research. How long will it take the perennial grasses to colonize beyond the planted area? How will they compete with annuals still present in the area, and which of the nine species restored to the pasture will flourish? These kinds of question will drive our research for the next few years on the Mitsui Ranch.

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