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Yellow Bluestem in a field in Elgin.jpeg

INVASIVE GRASS

BRN employees harvest native seed for revegetation projects.jpeg
pelletized native seed ready for revegetation.jpeg

Grasslands are among the world’s most endangered ecosystems. Unfortunately, they are also among the most unappreciated, partially because of what we can’t see because up to 80% of the biomass of grasslands are underground! Grasses have deep fibrous roots that store carbon and help make these ecosystems resilient to fire and grazing

 

Here in the Sky Islands, our grasslands support endemic plants, migratory birds, and threatened mammals like pronghorn and black-tailed prairie dogs. However, invasive plants pose one of the largest threats to our grasslands and the species that call them home.

 

Invasive species are introduced nonnative species that can take over ecosystems reducing the diversity of native plant and animal species. A particularly aggressive species of invasive grass called Yellow bluestem, Bothriochloa ischaemum, has started spreading throughout southeastern Arizona along roadsides and across rangelands, converting diverse grasslands to invasive monocultures. This species has been documented in small populations in the Sonoita-Elgin grasslands.

 

With support from the Arizona Department of Forest and Fire Management, we are leading a collaborative effort with the Appleton-Whittell Research Ranch, the Babacomari Ranch, and the Tucson Audubon Society. This cooperative effort is aimed at controlling Yellow bluestem on 21,000 acres of mixed grassland habitat directly adjacent to the Las Cienegas National Conservation Area and Coronado National Forest.

 

While this species has been found in small, relatively controllable patches for over a decade, it has recently begun to spread to new places and can be seen along many roads and within the grasslands. With our partners, we are monitoring and mapping the extent of invasive grass species across the 21,000 acres, will repeatedly treat invaded areas, and facilitate the establishment of native species in treated areas.

 

Revegetating treated areas with native plants helps keep invasive species from returning and speeds the recovery of the grassland. To improve the success of the reseeding efforts we will use pelletized seeds, seeds added to a mixture of clay, compost, and water. Seed pellets are formed mechanically in a cement mixer and dried. Because seeds embedded in pellets have high soil contact and are protected from seed predation by insects and rodents, they require minimal soil disturbance. Also, these seeds remain on site until heavy rains arrive with the monsoon, which wets up the clay and allows seeds to germinate while the soil is moist. 

Contact horticulture@borderlandsrestoration.org with questions about this project. 

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