This one-time greenhouse study examined the phenology, morphology, frost hardiness and response to moisture stress of three Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) stocktypes from the same seed lot. The types were mini-plug TM transplants (MPT), 1 + 1 bareroot transplants (1 + 1), and 2 + 0 barefoot seedlings (2 + 0). In late summer and fall before lifting, 2 + 0 seedlings set bud before 1 + 1 seedlings, 1 + 1 seedlings before MPT seedlings, The 2 + 0 seedlings appeared slowest to acquire frost hardiness in fall and seemed to deharden most rapidly in spring. Although the 2 + 0 seedlings were taller than the MPT stocktype, MPT and 2 + 0 seedlings were relatively similar in other morphological respects, but 1 + 1 seedlings were much larger. All stocktypes were potted on January 20, 1989, placed in a greenhouse, and subjected to 39%, 18%, 16%, or 6% soil water content (% dry weight) until the end of the experiment in midJuly 1990. The largest decrease in pre-dawn xylem water potential occurred with 16% and 6% soil water content; pre-dawn xylem water potential averaged over the three stocktypes generally declined 219% from low to high soil moisture stress. The 1 + 1 seedlings used more water than the other two stocktypes, and at maximum soil moisture stress, plant moisture stress increased in the order: MPT < 2 + (I < 1 + 1. During the 6-month greenhouse experiment, the larger 1 + 1 stocktype showed the most absolute growth, but the smaller stocktypes grew more on a relative scale. Growth of the stocktypes appeared to be related to differences in morphology and water-use patterns as the seedlings competed for available water within each pot. The results show that MPT seedlings, a new stocktype, performed as well as the more traditionally used 2 + 0 and 1 3-1 seedlings and that stocktype selection is important in reforestation efforts.Application.Seedlings of three different stocktypes (mini-plug ~ ~ transplants, 2 + 1) bareroot, and 1 3-1 transplants) responded differently to various levels of soil moisture content. Results indicate that mini-plug TM seedlings, a new stocktype, may be an excellent alternative to more traditionally used 2 + 0 and 1 + 1 stocktypes.

Application.The results of this and other studies show that root volume has promise as a seedling grading parameter in addition to height and diameter. Root volume is simple to measure, and several nurseries in the Pacific Northwest already use it as an index of morphological quality to maximize field performance.Abstract. Three seed sources of 2 + 0 Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] seedlings were graded into three root-volume categories ( < 9, 9-1 3, and > 13 cm3) and outplanted to determine (i) differences in survival and growth after one and two growing seasons in the field, (ii) relationship(s) of seedling height after one and two seasons to preplanting nursery root volume, total fresh weight, root-collar diameter, and height, and (iii) differences in field performance due to fertilization at planting. Field survival was > 90 Ol0 among all root-volume categories. Seedlings in the largest category grew significantly better than those in the smaller two categories over two seasons. Apparently, a population of seedlings having a large proportion of high root volumes will outperform a population having a large proportion of low root volumes in the field. Fertilization at the time of planting had no effect on survival or growth because of shallow placement of the fertilizer pellet. The results suggest that targeting root volume, as well as height and diameter, is worthwhile where morphological quality must be maximized to improve field performance. Thus, root volume has potential for use as a criterion for grading seedlings.

Ponderosa pine (Pinusponderosa Laws.) from two seed zones in central Oregon were grown at two nurseries where they were subjected to fall applications of N, N + K, or no fertilizer. For one seed zone, foliar N concentration increased from 1.47 to 1.53% for the N application and to 1.57% for N + K application. For the other seed zone, seedlings did not show any differences in foliar N after nursery fertilization. Seedlings that received the N application appeared to be less susceptible to frost damage, but nursery fertilization had little or no effect on seedling morphology or bud break. One month after outplanting 2 + 0 seedlings back to their respective seed-zone sites, slow-release fertilizer pellets were placed 10–13 cm from half the trees. Soils at the outplanting sites differed in mineral content, percent organic matter, and pH. The nursery-fertilized seedlings with increased N concentration grew more than control seedlings during the first season. Field-fertilized seedlings at the less fertile field site grew more in the second and third growing seasons, indicating that field fertilization after outplanting is more effective on nutrient-poor sites. Soil fertility had a greater impact on seedling performance than did nursery- and field-fertilizer treatments. At the less fertile site, N concentration decreased by 14% during the first growing season and increased by 22% during the second season, whereas at the more fertile site it increased during both the first season (12%) and the second season (6%). Seedlings at the more fertile site almost doubled in height in the 3rd year and were more than 20 cm taller than those at the other site.

In probably one of the first studies of its kind, three different seed sources of 2 + 0 ponderosa pine (Pinus ponderosa) seedlings were graded on the basis of three root-volume categories (< 4.5, 4.5-7, and > 7 cm³) and out-planted to determine differences in survival and growth over 1 and 2 growing seasons, examine the relationship of seedling field height to nursery root volume, total fresh weight, diameter, and height over the same period, and observe differences in nutrient uptake by seedlings among the three categories over 174 days in the field. Seedling survival was good over the two growing seasons. Seedlings graded to the largest root-volume category were significantly taller and grew significantly more than those in the two smaller categories over the 2 years. Nitrogen and potassium contents decreased over the growing season, those seedlings with larger root volumes showing the greatest decrease. The results suggest that root volume has potential as a useful criterion for grading seedlings. West. J. Appl. For. 6(1):11-15.

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