Arboriculture & Urban Forestry 37(6): November 2011 Arboriculture & Urban Forestry 2011. 37(6): 265–268 265 Evaluation of Ponderosa Pine Seed Sources for Windbreaks in the Central Great Plains of the United States Wayne A. Geyer Abstract. Ponderosa pine (Pinus ponderosa Laws.) has been planted widely in the Great Plains of the United States for windbreaks. Rec- ommendations based on a 1968 study were to use material from south central South Dakota and north central Nebraska. A second test to further delineate seed sources (provenances) in this region was established in 1986. This paper reports results for survival, height, diam- eter, and D2 H measurements in both Kansas and South Dakota, after 15 years. Results identify a wide range of suitable geographic prov- enances within the two-state region. A majority of the tested sources performed well in both states, thus verifying the original recommendations. Key Words. Growth Characteristics; Pinus ponderosa; Ponderosa Pine; Provenance; Seed Source; Tree Selection; Windbreaks. Ponderosa pine (Pinus ponderosa Laws.) is an important com- ponent of the windbreak agroforestry system in the Great Plains (U.S.). Its drought tolerance, dense crown form, and tall growth habit make ponderosa pine excellent for wind- breaks, sight barriers, and ornamental plantings (Flint 1983). It is one of the few tall trees that grow in the region and also provides full year-round protection to fields and farmsteads because of its evergreen nature (Schaefer and Baer 1985). The natural range of ponderosa pine extends from British Co- lumbia, Canada, southward into northern Mexico, and from California eastward into the Great Plains, except for Kansas (Crichfield and Little 1966). The tree has been widely planted in the plains region but has shown inconsistent performance. Western pine tip moth (Rhyacionia bushnelli) has caused widespread damage in the plains (Kopp et al. 1987), but outstand- ing performance of some individual trees in the plains plantations suggests that proper seed selection could improve tree quality. Early studies determined that trees grown from seed collected from the northeastern range of ponderosa pine performed best in most of the provenance test plantations (Deneke and Read 1975; Baer and Collins 1979; Read 1983; Schaefer and Baer 1985; Van Haverbeke 1986; Schaefer and Baer 1992). Also, six-year data from a Kansas plantation showed that early growth appeared to be clinally related to the elevation of seed provenances (Deneke and Read 1975). Therefore, plains nurseries have focused much of their ponderosa pine production on seed collections near Ainsworth and Valentine, Nebraska, and Rosebud, South Dakota. In addition, trees from Jordan, Montana, performed well in more than half of the early plantations (Read 1983). In 1986, a second cooperative ponderosa pine study was ini- tiated by the GP-13 Technical Committee of the Great Plains Agricultural Council in cooperation with the North Central and Rocky Mountain Forest Experiment Stations. The intent of the study was to more intensively sample recommended provenances identified in the 1968 study to locate a wider zone of collection for commercial plant material and/or breeding activities. Col- lection areas are from four states. Nine tests were established in Saskatchewan, Canada; and in the United States, Montana, North Dakota, South Dakota, Nebraska, Kansas, Oklahoma, Texas, and Minnesota. This paper reports data from the South Dakota, Ne- braska, and Kansas tests. No additional tree improvement studies have been initiated in the United States since this effort. Recent- ly, a genetic tree improvement effort was initiated in Argentina (Meier et al. 2004), with intention to establish seed orchards in Patagonia. Tree improvement studies have attributed approxi- mately 2% of the total variation to differences among geographic locations in the southwestern United States (Yow et al. 1992). One generation of tree improvement may lead to gains in yield of 1%–15% or reduce rotations by 1–20 years in ponderosa pine in the Inland Empire Tree Improvement Cooperative in the north- ern Rockies of the United States (Hamilton and Rehfeldt 1994). MATERIALS AND METHODS The tree plantations reported here used seedlings representing 138 open-pollinated families from 13 geographic provenanc- es (Figure 1; Table 1) and were planted in the field following standard provenance testing procedures. An individual tree fac- torial planting design with 6 to 8 replications and sized 1.3 × 2.4 m in South Dakota, or 3.7 × 3.7 m in Kansas plots. Spac- ing within each replication was represented by two (South Da- kota) or five (Kansas) trees in single-tree, noncontiguous plots. Two border rows surrounded each plantation. Weeds were con- trolled by cultivation for the first three years. The Kansas plan- tation was near Milford Lake, and the South Dakota plantation was near Brookings, both located on alluvial sandy loam sites. ©2011 International Society of Arboriculture
November 2011
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