Restoring Ponderosa Pine Forests
NAU’s greenhouse staff creates seed bank to repopulate burned lands
Brad Blake and Philip Patterson are NAU’s own Johnny Appleseeds—but
instead of dispersing non-native apple seeds, they are collecting local
ponderosa pine seeds from communities that are at high risk from catastrophic
wild fires and banking them until they are needed to restore a pine tree or
forest. They are also using their considerable skill to grow ponderosa
seedlings for dispersing to landowners after a fire.
a time when wildfires have been a frequent threat in Arizona, the seed bank is
an environmental boon. The stored seeds can speed the return of lost trees and
forests, which might normally take several generations—under ideal
conditions—to regenerate. And the seed
bank’s finely honed collection, storage, growing, and distribution process can
model how other communities can mitigate their own environmental disasters by
planning ahead. “I think this is a program that can be used anywhere for
restoration,” says Blake, the greenhouse manager. “It can apply to other
One million trees ready to go
Blake and Patterson, who run NAU’s eight research greenhouses, started
the ponderosa pine seed bank in 2002. Since then, they have collected,
processed, and banked 100 pounds of seed—an amount that has the potential to
generate nearly one million trees if everything goes just right. They have also
grown and distributed an additional 300,000 tree and plant seedlings to
landowners affected by the 2002 Rodeo-Chediski fire, and they continue to
provide seedlings to individuals whose lands burned during the 2003 Aspen Fire
on Mount Lemmon. “Natural regeneration after a fire is not
easy,” says Blake. “A really hot fire
will confound these conditions even more.”
Banking source seeds (“provenance”)
is the secret to optimizing restoration.
It allows the greenhouse staff to react quickly and to plant seeds from
the very region affected by a fire.
Because these seeds came from trees that have adapted to local circumstances,
the replanted seedlings should be able to more easily withstand weather fluctuations,
poor soil conditions, insect infestations, and diseases they may encounter,
thus increasing their survival rate.
“We are the only institution (other than the USDA Forest service) with a ponderosa pine seed bank, but the forest service has no mechanism to get seeds and seedlings to landowners,” says Patterson, the greenhouse plant production manager. Blake and Patterson have fine-tuned their own system of seedling distribution. It has been a trial-and-error process that began when the NAU greenhouse team was commissioned to help the Trees for the Rim Project (TFRP) restore private lands scorched by the Rodeo-Chediski fire. “Having trees grown properly under the watchful eyes of the NAU Research Greenhouse staff and distributed at the optimum time for planting provided property owners with the key for success in the restoration process,” reported TFRP.
Educating landowners is an important step to assuring the successful growth of the seedlings. Patterson has developed a plant care guide that teaches seedling recipients how to plant and take care of their trees. He and Blake also recommend a fire-wise planting program that encourages people to plant ponderosa pines away from their homes and fruit tree and other deciduous trees closer in.
“I think this is a program that can be used anywhere for restoration. It can apply to other species.”
Stocking the seed bank
Seed collection is a labor-intensive process, one complicated by unpredictable seed availability. In October, during the harvesting season, it’s not uncommon for Blake or Patterson to travel hundreds of miles and only collect a few, seed-rich cones. One bushel of cones yields one pound of seeds if the cones are burgeoning with good seed, but most bushels yield only a quarter or half that amount. Sometimes the two foresters go harvesting with an arborist who climbs up a tree to capture cones that are beyond the reach of clippers that only go up 30 feet.
Back in the greenhouse, the seeds are dried, dewinged, cleaned, and vacuum packed in heavy duty, one-pound freezer bags to prevent moisture loss. (Each bag holds 11,000 seeds.) Then the bags are stored in a stainless steel freezer at minus 10 degrees Fahrenheit, where they can lay dormant for 20 years or more before planting.
When ponderosa seeds are needed, the greenhouse staff, work/study students, and volunteers follow a method that was inspired by the late Dr. Richard Tinus of the USDA Rocky Mountain Forest Experiment Station. The team mixes soil (2/3 vermiculite and 1/3 peat moss), fills ridged cells in book-style containers, and plants the seeds (minimum two per cell), toping them off with a half-inch of pearlite. It takes 120 days to nurture a seed to a seedling (watering, feeding, flushing, thinning, and weeding) and another 60 days to harden the bud nodes and acclimate a seedling to being outdoors. “Work/study students and volunteers are an essential part of this effort,” says Patterson. “We couldn’t complete our projects without them. They contribute hundreds of hours of labor a year.”