Controlling Invasives to Support Natives at NCOS
CCBER staff and volunteers from the Isla Vista Surfrider Foundation recently hand weeded a mound of burr clover (Medicago polymorpha) at NCOS.
It is spring time, and despite only 10 inches of rain falling this winter (about 60% of average), invasive weeds still grow and propagate. The late rains in March that followed a completely dry February delayed their onset, but the drying winds have accelerated the rate of maturity. Mature plants drop seeds and, as restoration practitioners, one of our goals is to minimize invasive plants at a restoration site.
One of CCBER’s goals is to restore diverse native habitats and plant communities with locally sourced seeds, and give them a weed-free window to get established on the landscape. If invasive weeds are not controlled, they can create monocultures of non-local species that limit or completely block out or change natural ecological and evolutionary processes. To date, CCBER has hand collected over 2 million milliliters, or 500 gallons of seeds from 115 different species, for the NCOS restoration project. All of these seeds have been collected within the immediate watershed of the project site. When you consider that some seeds are so small that a pinch could equal hundreds of plants, this represents enough seed for millions of plants. The seeds of some delicate wildflower species are being saved until the weed challenges have been addressed and there is an adequate window for establishment. Other species are so unique in their niche that we’ve already spread more than 200 gallons of their seeds: Pickleweed (Salicornia pacifica) grows at the lowest elevation of the salt marsh, where conditions are harsh enough to exclude most competitors.
Left: CCBER staff hand spreading seeds of Pickleweed (Salicornia pacifica) on the NCOS salt marsh this winter. Right: Mature Pickleweed.
While 100,000 seedlings have been planted over 26 acres, and another 4 acres of purple needle bunch grassland has been drill seeded, there are still 29 acres to plant and 13 acres to drill seed. We estimate that we will plant another 300,000 seedlings in the coming year and use more than 100 pounds of purple needle grass seed to restore the backbone of a native perennial grassland. The native bunch grass seed is being grown by Victor Schaaf at his S&S Seeds farm in Los Alamos. This production field will transform 4 pounds of locally sourced, hand collected seed into as much as 150 pounds, so that we can restore a grassland in as efficient a manner as possible. The 4 acres drill-seeded in October last year are showing promising results.
Left: Purple needle grass seed in the drill seeder before planting. Right: the sprouts of that seed on the NCOS Mesa.
But this story is about invasive weeds, which is the first challenge every restoration ecologist faces, even in recently graded sites. A weed plant grows where it is not desired; and an invasive weed is so aggressive that it can take over and dominate a site, leaving little room for the natives to become established. Newly disturbed sites can be particularly vulnerable, as can areas that have been ignored, where weeds have dominated for years. Both of these challenges are present at NCOS, and CCBER is using a number of tools and methods to address the weed challenge posed by this large site. The goal is to prevent the weeds from dropping seeds using the most ecologically sensitive tools available. Where possible, CCBER uses techniques such as solarization with black plastic, mowing, and hand-weeding, but in some situations, herbicide can be a highly effective weed control tool because it is fast-acting and does not disturb the soil. In the 4-acre drill seeded area, a specialized, non-toxic, broad-leaf-specific herbicide was used because it could be applied over the newly germinating native grass seeds and would target the burr and sweet clovers that surrounded the seedlings. Hand weeding in this area would have been slow and inefficient, and would have led to trampling of the grass seedlings and disturbance to the soil that could trigger new weed germination. Burr clover (Medicago polymorpha)
Left: Burr clover is controlled in the drill seeded area using broad-leaf-specific herbicide. Right: California Conservation Corps weeding clovers.
Mowing (or weed whacking) is a stop-gap effort to eliminate weed seed heads before they ripen, and primarily buys time over such a large landscape so that we can focus efforts on the more time consuming, delicate hand-weeding required around newly planted native seedlings.
CCBER staff weed whacking invasive plants at NCOS.
Solarization is conducted by laying black plastic over newly germinating seedlings of non-rhizomotous plants in order to cut off light and overheat them. It usually takes 2 to 4 weeks for each round of plastic to eliminate a portion of the seedbank. The extent of the weedy seed bank in the soil can be further reduced through multiple cycles of irrigation and subsequent solarization of new rounds of germinating weeds. NCOS is currently using about 80,000 square feet of black plastic in a range of zones where native seedlings haven’t been planted yet. Placing a layer of wood chips, or mulch, is another strategy for creating a window of weed-free growing opportunities for native plants and will be used in areas with larger shrubs.
Large sheets of black plastic are used to kill weeds by solarization where native seedlings haven't been planted yet.
There are more than 60 students working on the NCOS restoration project with CCBER, and they obtain extensive training in plant identification associated with this work. By paying attention to detail, this project can be successful in both restoring our native natural history and engaging students in the stewardship of our natural world.
At NCOS, UCSB students are gaining hands-on experience with native plant and ecosystem restoration and stewardship.
As the core native plants get established in each habitat zone and the weeds are abated, we will gradually be adding more native wildflowers and other more delicate native plant species. In addition, a grant from the California Natural Resources agency and CalTrans, offered through the enhancement and environmental mitigation program (EEM), is providing funding to remove particularly invasive plants from the 25-acre area adjacent to the west side of NCOS that was not graded. Invasive weed plants in that area include pampas grass, fennel, mustard and harding grass, which not only degrade that site, but also pose a risk of their seeds being blown into the NCOS project with the prevailing winds. These plants are being dug out (Pampas grass, Harding grass), cut at the root and painted with herbicide (fennel), and solarized (mustard and annual grasses). This area is currently being used as a training ground for the ROTC, and will become an area of the project where children can play in the willow trees and explore more freely. Removing the weeds will make this a more pleasant and sustainable site for generations to come.
Image of the 25-acre area adjacent to NCOS, where grants are funding the removal of weeds such as Pampas grass and Fennel.