Arboriculture & Urban Forestry 33(5): September 2007 Arboriculture & Urban Forestry 2007. 33(5):325–329. 325 Rocky Mountain Juniper Seed Source Test in Western Kansas, U.S. Wayne A. Geyer, Keith D. Lynch, and Charles J. Barden Abstract. Twenty-six sources of Rocky Mountain juniper (Juniperus scopulorum Sarg.) were established as a provenance test near Colby, Kansas, U.S. in 1980. Height, diameter, survival, number of stems, crown density, branch angle, and vigor were evaluated with analysis of variance, cluster analysis, simple correlation, and regression analysis techniques. Source differences were found. Total height at 23 years ranged from 3.6 to 5.4 m (11.9 to 17.8 ft), diameter breast height (dbh) ranged from 5.6 to 10.4 cm (2.2 to 4.2 in), and survival from 10% to 100%. Height growth was weakly related to geographic variables, but dbh was related to latitude, longitude, and elevation. Selection of fast-growing sources may begin at 5 years after field planting. Key Words. Growth characteristics; juniper; Juniperus scopulorum; Rocky Mountain juniper; seed sources. Rocky Mountain juniper (Juniperus scopulorum Sarg.) grows on the western edge of the Great Plains, U.S. as essentially a lower-elevation pine tree, on the upper Puget Sound basin, and on Vancouver Island, British Columbia, at or near sea level. It ranges in size from a small tree to a sprawling shrub on dry mountain sites (Harlow and Harrar 1969). Taxonomic studies have been numerous (Fassett 1944; Comer et al. 1982; Adams 1983; Schaefer 1995). Genetic variation of various major traits were determined for 10-year-old plantings, and seed-source selection zones in the Great Plains were identi- fied by Cunningham and King (2000). This test is part of a larger regional study initiated by the Technical Committee of the Great Plains Agricultural Coun- cil in 1973. The objectives were to determine the genetic variation of major traits and to identify the best sources of seed for windbreak applications. This article presents the por- tion of the study established in Colby, Kansas after 23 years of growth in the field. MATERIALS AND METHODS A complete description of the methodology used is found in Van Haverbeke and King (1990). Seed cones were collected from 26 trees in natural stands and windbreaks across the Great Plains (Figure 1; Table 1). Seed trees that had favorable windbreak characteristics (abundant branches, dense foliage) were selected. Seed lots were sown in the USDA Forest Ser- vice Bessey Nursery near Halsey, Nebraska, in 1977 and were outplanted at 12 test sites in 1980. This study site is Colby, Kansas (39.38°N and 101.07°W) located in the central geographic region of zones established by Van Haverbeke (1968). Soil is from the series of Keith loam (fine-silty, mixed, mesic Aridic Haplustolls) and Richfield silty clay loam (fine, montmorillonitic, mesic Aridic Haplustolls). A randomized complete-block with five replications of four- tree, linear plots was established having 20 trees maximum for each source. A total of 520 trees were planted along with 2320 eastern redcedar (Juniperus virginia L.). Spacings in the plantation were 2.4 m (7.9 ft) within rows and 3.6 m (11.9 ft) between rows. A single row was planted on all sides as a border. Complete cultivation was maintained for 5 years. Growth evaluations were made at 5, 10, and 23 growing seasons at this site. Statistical analyses were performed with SAS software (Statistical Analysis System; SAS Institute Inc., Cary, NC). Data were analyzed by using the analysis of variance proce- dure and the Duncan’s means test was used for mean sepa- ration. Cluster analyses (Ward’s minimum variance) were used to identify seed sources with similar performance char- acteristics. Variables used in those analyses were survival, total height, diameter breast height (dbh), number of stems, crown density, branch angle, vigor, latitude, longitude, and elevation. If trees had multiple stems, then only the largest was evaluated for height and diameter. Simple Pearson cor- relations were computed among seed sources of individual trees for each trait. The correlation of each trait with latitude and longitude was also examined. Least squares regression models of differences in latitude, longitude, and elevation between source locations and the Colby plantation were run to find the extent of geographic area from which seed may be collected to give good tree growth performance in western ©2007 International Society of Arboriculture
September 2007
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