Great Basin Naturalist Volume 56 Number 4 Article 2 11-21-1996 Stem growth and longevity dynamics for Salix arizonica Dorn Vicki L. Taylor Brigham Young University Kimball T. Harper Brigham Young University Leroy L. Mead Brigham Young University Follow this and additional works at: https://scholarsarchive.byu.edu/gbn Recommended Citation Taylor, Vicki L.; Harper, Kimball T.; and Mead, Leroy L. (1996) "Stem growth and longevity dynamics for Salix arizonica Dorn," Great Basin Naturalist: Vol. 56 : No. 4 , Article 2. Available at: https://scholarsarchive.byu.edu/gbn/vol56/iss4/2 This Article is brought to you for free and open access by the Western North American Naturalist Publications at BYU ScholarsArchive. It has been accepted for inclusion in Great Basin Naturalist by an authorized editor of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. Great Basin Naturalist 56(4), © 1996, pp, 294-299 STEM GROWTH AND LONGEVITY DYNAMICS FOR SALIX ARIZONICA DORN Vicki L. Taylorl , Kimball 1: Harperl , and Leroy L. Meadl AllSTHAGI:-Diameter-age relationships of Salix arizonicu. (Arizona willow) stems were investigated for 5 populations on the Markagunt, Paunsaugunt, and Sevier plateaus in southern and central Utah. Of the 430 stems studied, none exceeded 26 mm in diameter at ground level (estimated age of 19 yr). Equations developed for predicting age from stem diameters consistently accounted for over goo.,f, of the observed variation. Slopes of predictive equations were homoge­ neous across the 3 sites considered in detail. At 2 sites 46% and 38% of the stems exceeded 10 mm (-7 yr old) diameter at ground level. At a 3rd site, no stems survived to exceed that size. Stem-age profiles at specific sites may thus be useful f<)r assessing the relative fuvorability oflocal environments for the species. Key words: Arizona willow, Salix, st.em. diameter, dendrod~ron()logy, southern Utah. The purpose ofthis study was to assess stem 1987). Shrub studies have detailed the effects diameter-age relationships in Salix arizonica of variations in available moisture on plant (Arizona willow), a species so rarc that routine growth in specific habitats or provided infor­ severance of stems for aging cannot be justi­ mation for interpreting archaeological prob­ fied, Our objective was to develop a stem-age lems, Ring counts have also been used to pre­ prediction model based on stem basal diame­ dict stem diameter-age relationships in predic­ ters. Ultimately, we desfred to accurately esti­ tive models for interpreting site quality for var­ mate stem age at a broad range of ecological ious species or for clarification of successional situations without sacrificing stems, We also patterns in vegetation that includes many woody evaluate the possihility of using stem-age pro­ species (Brotherson et aI. 1984, 1987). files at an array of sites to determine their rela­ tive favorability for growth of S. arizonica, THE SPECIES AND ITS DISTRIBUTION DENDROCHRONOLOGY AS A TOOL Salix arizonica is small. Rarely do stcms ex­ ceed 1,0 m in height. The species occurs in such Growth rings of trees and shruhs have been dense carpets of other species (both vascular used for m,my decades for aging stems and and nonvascular) that reproduction via its tiny, dating past climatic events (Douglas 1935, wind-dispersed seeds appears to be uncom­ Glock 1937). Growth rings are also used to mon, Accordingly, the species apparently per­ establish unique sequences of good and poor sists at occupied sites primarily by vegetative years that permit dating nonliving tree frag­ reproduction. In the process, what appear to ments used in prehistoric human structures he large clones (as much as 10 ill across) may (Schulman 1956, FrillS 1971, Stockton and develop. Meko 1975, Harper 1979). Ring-width varia­ Salix arizonica occurs in 2 disjunct locations tions are often used to assess differences in the in the Intermountain West. The species was favorahility of various environments for the first discovered on the White Mountains of growth of selected species (Ferguson and east central Arizona by Carl-Eric Granfelt in Humphrey 1959, Frills 1962, Stockton and 1969 (Galeano-Popp 1988). Robert Dorn (1975) Fritts 1973, Frills 1974). Although these stud­ used ho!otype specimens collected by Granfe!t ies have focused mainly on trees (Glock 1955, to describe the species in 1975. In November Argeter and Glock 1965), some have dealt with 1992, unaware that the species occurred in shrub species (Ferguson 1958, 1959, Ferguson Utah, the U.S. Fish and Wildlife Service pro­ and Humphrey 1959, Brotherson et a!. 1984, posed S, arizonica for listing as endangered with ID"pltrtlm:nt of Botany 11Ild Ran~" S"ienee, Brigham Young UIliversIly, Provo, UT 84602. 294 1996] ARIZONA WILLOW STEM GROWTH 295 designation of critical habitat (Atwood 1995). tally intermediate (Lowder Creek) as well as In June 1993 a previously misidentified herb­ extreme environmental conditions for S. ari­ arium specimen ofS. arizonica was discovered; zonica in Utah. The Rainbow Meadows sHe it bad been c-ollected on the "Sevier Forest" occurs on acid soils at near maximal elevations (now Dixie National Forest) in 1913. During for the species, while the East Fork of the June 1994, 5. arizonica was discovered on the Sevier River population occurs on aUuvium Markagunt Plateau near Brianhead resort area. derived from C'ellcareous substr.1tes at the low­ Subscquent searching revealed a small popula­ est elevation known for the species. tion on the Paunsaugunt Plateau and 2 more Depth of peat layer was determined at each farther nurth on the Se,~er Plateau (Mead site hy digging pit, to expose soil profile. (Mead 1996). Following this "rediseovery" of S. ari­ 1996). At Lowder Creek, Sheepherder Camp, zonica in Utah, USDA Forest Service, USDr and Sevenmile Creek, depth to water table w,," Fish and Wildlife Service, and USDI National dete'mined by opening a hole approximately 1 Park Service officials cooperated in developing m deep with a 1.27-em-diameter pointed rod, a conservation agreement and strategy that then inserting a O.64-cm-diameter wooden outlines the "actions, costs and skiUs needed to dowel into the hole to me""ure depth to water. implement protective measures and research This measurement was taken at each plant sam­ studies needed lor the species" (Atwood 1995). pled and an average value was computed f()r As a result of the conservation agreement and each site. Dcpth to water table at Rainhow stmtegy, which documents loog-term plans for Meadows was determined by measuring dis­ conservation of S. arizonica, the Fish and \i\'ild­ tance from soil surface to Welter table surface in life Service withdrew their proposed rule to a soil pit (Mead 1996). Depth to water table list the species a., endangered (Arizona Willow was determined at the East Fork site by mea­ Interageney Technical Team 1995). suring distance {'Tom the soil surhlce to the sur­ Although the species is locally ahundant ncar face of water running in the creek. This mea­ Brianhead, its total range is small in both Ari­ surement was taken at each S, arizonica clone; zona and Utah, and populations rarely include the mean distance is reported in Table 1. Depth more than a few score plants. This rarity seems ofpeat layer and depth to water table are vari­ related to the plant's preference for an uncom­ able among the study sites, with the Rainbow mon habitat: it grows preferentially on igneous Meadows site having the highest water table soils in cold, wet sites. In addition, in the White and greatest peat depth (Table 1). Y!ountains, management has favored conifers Two other populations of S. arizonica are con­ that reduce flow in riparian systems, leading sidered in this report. Populations at Sheep­ to poor drainage as watenvays become peat­ herder Camp, Sevenmile Creek, and Lowder choked. Such tmvironments become poorly aer­ Creek have been sampled to establish stem­ ated and less suitable habitat for S. arizonica. diameter prome. based on samples nf many Heavy use by elk has also adversely affected randomly chosen stems (154, 104, and 130 the species in Arizona (Arizona Willow Iotenl­ stems, respectively, sampled at the 3 forcgoing geney Technical Team 1995). This study has sites). No stems were severed for aging at the been confined to the Utab populations of Salix Sheepherder or Sevenmile sites. arizonica (Fig. 1), hut we have attempted to The Rainbow :Meadows site is approximately sample the full range of conditions associated 1.6 k-m south and slightly cast ofBrianhead Peak with the species in our study area, at approximately 3155 m elevation (37'40' , 112·56'W). Suils are derived from tertiary vol­ METHODS AND STUDY AREAS canics with a histosol surface horizon (Mead 1996). The Lowder Creek population is approx­ Ibe diameter-age data for S. arizonica were imately 4 km east and slightly soutb of llJ"ian­ collected from 3 populations: 2 on the Cedar head Peak (37'41'N, 112·48'W). Soil at this City Ranger District and anotller on the Powell site is developed from tertiary volcanic mater­ Ranger District, Dixie National Forest (Fig. 1). ial below an alluvium surface layer (Mead The Rainhow Meadmvs, Lowder Creek, and 1996). The East Fl'rk population, approximately East Fork oftbe Sevier River populations were 48 km from the Lowder populatioo (37'26'N, chosen because they represent cnvironmen~ 112'21'W), is at the lowest elevation knowo for 296 GREAT BASIN NATURALIST [Volume 56 &0" Eld•• Cache '-,r'- lich UTAH Too,l, ""'mil Solt to!<. Juob ... Corbon Millo,d Em.ry Grond Pillt. Woyn. I,on .E Kone Fig. L A, Rainbow Meadows; B, Lowder Creek; C, Sheepherder Camp; D, Sevenmile Creek; E, East Fork of the Sevier River.