Purshia: The Wild And Bitter Roses

5 Purshia Seed Physiology

66 Purshia after fires. Blaisdell and Mueggler reported that antelope bitterbrush on the upper Snake River Plains commonly sprouted after a wildfire or top removal.21 An important consideration in evaluating antelope bitterbrush sprouts from burned or cut surfaces is the persistence of sprouts in subsequent seasons.22 Hormay, who age-dated a considerable number of antelope bitterbrush plants, was the first to suggest that growth rings offer a fairly precise estimate of age. Using that technique he estimated the common longevity of antelope bitterbrush plants in California at 60 –70 years. The oldest plant he encountered had 82 growth rings on the stem at the soil surface. Nord reported a plant from Panum Crater in the volcanic highlands south of Mono Lake with 128 growth rings. Most likely this was a desert bitterbrush plant, although Nord did not refer to the Mono Lake–volcanic highland Purshia plants as antelope or desert bitterbrush, but instead classified them as transition plants. Nord claimed that the largest antelope bitterbrush plant on record was growing 6 miles south of Janesville, California.23 The stem circumference was 36 inches and the plant was 12 feet tall with a maximum crown circumference of nearly 20 feet. Richard Driscoll immediately countered with a plant in Cove Palisade State Park in Jefferson County, Oregon, that was 38 inches in circumference at the stem base, 14.2 feet tall, and had a crown circumference of 21.7 feet.24 This giant arborescent form of antelope bitterbrush also occurs at Mount Pleasant in Sanpete County, Utah.25 Obviously, the tall, treelike growth form is not restricted to the Lassen County area. During the 1970s and 1980s many common garden studies were initiated to study the performance of antelope bitterbrush accessions. We have already discussed Shaw and Monsen’s phenological observations made on one such garden planted near Boise. A more common practice was to plant gardens and record stand establishment, growth, and persistence. J. N. Davis reported on the results of numerous plantings throughout Utah, including 141 accessions of antelope bitterbrush, 49 accessions of cliffrose, 46 accessions of antelope bitterbrush– cliffrose hybrids, and 1 desert antelope bitterbrush hybrid. Differences in stand establishment, vigor, and various growth measurements led him to conclude that only 24 of these accessions were suitable for planting in the pinyon-juniper woodland zone of Utah.26 P. J. Edgerton et al. established a similar garden about 30 miles east of Baker, Oregon. The Keating site was a degraded big sagebrush community that had once been an important antelope bitterbrush stand for mule deer.27 The accessions planted in this garden are described in Table 4.9. The first season was favorable for shrub establishment, but drought set in the second growing season. The influence of the drought was compounded by a severe grasshopper infestation (seven grasshoppers per square yard). The defoliation of the antelope bit- Ecophysiology of Purshia 67 table 4.9. Shrub Accessions Evaluated in the Baker, Oregon, Common Garden PrecipiElevation tation Growth Species-Accession (feet) (inches) Soils Habit Antelope bitterbrush Janesville, CA 4,036 10 granitic erect Boise Basin, ID 3,753 30 granitic decumbent Fort Hall, ID 3,753 17 alluvial semierect Garden Valley, ID 3,568 20 lacustrine erect Hat Rock, OR 3,348 17 granitic erect Keating, OR 2,577 16 granitic erect Pringle Falls, OR 4,264 20 pumiceous decumbent Warner Mountains, OR 5,946 20 basaltic decumbent Cliffrose American Fork, UT 4,163 15 sedimentary erect Apache plume Richfield, UT 5,252 13 sedimentary erect Adapted from P. J. Edgerton, J. M. Geist, and W. G. Williams, “Survival and Growth of Apache Plume, Stansbury Cliffrose, and Selected Sources of Antelope Bitterbrush in Northeastern Oregon ,” in Tiedemann and Johnson 1983, 44 –54. terbrush plants varied among accessions. Pringle Falls, Oregon, was particularly hard-hit by the grasshoppers. (We discuss plant-insect relations in more detail in Chapter 9.) Cliffrose and Apache plume were well north of their natural range in this common garden, but both species persisted and grew very well. Edgerton et al. collected data on crown diameter and yearly aboveground biomass of the shrub seedlings. The average aboveground biomass for all antelope bitterbrush seedlings was 8, 70, 604, and 687 grams, for one, two, three, and four years, respectively, after the garden was established (Table 4.10). Shaw and Monsen, who also collected height and crown diameter data in their Boise common garden, considered the plants within accessions to exhibit great variation in...