Science Saturday: Researchers look to the forest ground for native urban turf

By Jan Busco
Published on Nov 3, 2018 in the Arizona Daily Sun

One beautiful day in early November, three women walk through the ponderosa pine forest near the Museum of Northern Arizona. Their attention is not on the trees or mountain views, but down on the grasses. They are collecting seeds from black dropseed (Sporobous interruptus Vasey), a native grass that serves as habitat for native moth larvae, and provides cover and forage for mammals and seed eating birds. The small seeds are edible and have been gathered and eaten by humans, but todays harvest is for research, not food. Because of the short stature and tendency to form dense flat clumps, black dropseed exhibits potential as a native turfgrass that can provide islands of biodiversity in our increasingly urbanized environment.

Long-time MNA members Dorothy and Ken Lamm offered the museum the opportunity to collect seeds from their property at an opportune time. This year MNA received an Arizona Native Plant Society State Research Grant to study this low-growing native and evaluate its horticultural potential. This research is in line with MNA’s goal to manage its land base via reconciliation ecology, the branch of ecology which studies ways to encourage biodiversity in human-dominated ecosystems. Nearly 250 types of native grasses grow within a 25 mile radius of Flagstaff (www.swbiodiversity.org). Growing in the midst of towering trees and alluring wildflowers, they are not always noticed or appreciated.

Not so long ago, it was common to hear foresters refer to native grasses and other non-woody plants growing beneath and between trees as “LGS” – “little green stuff.” But today, word on their ecosystem benefits and services is spreading. In addition to their beauty and the soft rustling motion they bring to our landscape, native grasses hold the soil, keep out invading weeds, and provide habitat for a myriad of creatures from elk, deer and antelope to tiny mammals, ground nesting birds and lizards. They sequester carbon dioxide in the soil, prevent flooding and soil erosion, and can slow and process rain to recharge the ground. Reduced runoff volume from native grass-covered areas even offers economic benefits - a healthy grass stand can decrease the scope of storm-water management requirements and costly structures used in urban development.

On this November day the seed collecting trio - Museum of Northern Arizona Research Botanist Jan Busco and Living Collections volunteers Sara Skinner and Diane Traylor - gathers seeds locally in Flagstaff ponderosa pine oak woodland. On other days they will visit populations in Coconino, Navajo, Yavapai and Gila Counties where this Arizona endemic species grows in sunny openings in pine and pinyon-juniper forests. The AZNPS grant provides for several travel days to reach black dropseed in diverse growing conditions throughout its range.

Busco first encountered black dropseed at McAllister Ranch in 1999, when she and a co-worker came upon a naturally –occurring patch that looked as neat and tidy as a carefully-tended lawn.

But the idea that black dropseed might make an excellent native lawn is not new. Long before, in 1923, R.R. Hill, United States Forest Service Assistant Chief of Range Management, wrote:

“Black sporobolus is the best grass that grows within its range; very resistant to drought and grazing and capable of spreading vegetatively. It greens up early and remains so continuously until late in the season. I believe it has possibility as a lawn grass. It richly deserves extensive experimentation.”

Non-descript black dropseed blends into its surroundings until autumn chill, when its low tufts of forest green leaves first turn to a bright yellow green and finish up burnished gold. At the seed collection site, Busco helps the group recognize its fall color and delicate open Christmas-tree-shaped seed stalks and learn by touch when its dark hard seeds are ripe and ready to collect. When Sara and Diane run their fingers from the bottom to the top of a seed stalk, each mature seed comes off easily and makes a satisfying click as it falls into their collection bag.

Sara, Jan, Dorothy and Diane chat and quickly gather seed in small paper lunch bags. Although total volume is small, only about ¼ cup, after just a short time, they have collected nearly 10,000 seeds.

Back at the Museum’s botany work room on the MNA Harold S. Colton Research campus, seed is left to dry, then frozen to kill insects and eggs that may lie within. Staff will determine how to best germinate seed. Next seedlings from diverse collection environments will be grown out in a common garden experiment at the Museum’s Colton Research Garden. Size, vigor, form, overall appearance and drought-tolerance will be compared to determine which seed sources produce plants with the strongest characteristics for success as low-water use Northern Arizona native lawns that that will provide islands of beauty, biodiversity and ecosystem services in our increasingly urbanized environment.