Penstemon peckii Soil Seed Bank Study at 25 Years

Ed Guerrant, Rae Selling Berry Seed Bank

Penstemon peckii (G3-S3 Federal SOC) is an Oregon endemic with a relatively compact range in the semi-arid Ponderosa pine forest east of the Cascade Mountains. The vast majority of known populations (ca 93%) are almost entirely within the Sisters Ranger District of the Deschutes National Forest. A 1992 Species Conservation Strategy by Cindi O’Neil found that it is “Best adapted to open full sun habitats, low vegetative competition and natural fire.” The natural fire frequency was 7 to 15 years, but active fire suppression for many decades had diminished and degraded habitat. Number one in the “What we do not know” list is “How long does Peck’s penstemon seed remain viable in the soil seed bank?” To address that question, in 1992 we gathered seeds from multiple populations across the species’ range. We mixed seeds from 11 populations into a single, large bulk sample in order to compare their survivorship in the soil seed bank and in an ex situ seed bank. In addition to initial trials of fresh and dried and frozen seeds, samples have been removed from the field and ex situ seed bank after 6, 12, 18 months, and then at 4, 15 and now 25 years. The current round of germination trials of 25-year old seeds is still underway, but to date, approximately 26% of those stored in the soil and 51% in the freezer have germinated. The species clearly has the capacity to form a long-lived soil seed bank.

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