Editing Plant nursery (section)

===Stock types, sizes and lots===

Nursery stock size typically follows the [[Normal distribution|normal curve]] when lifted for planting stock. The [[runt]]s at the lower end of the scale are usually culled to an arbitrary limit, but, especially among bareroot stock, the range in size is commonly considerable. Dobbs (1976)<ref name="dobb">Dobbs, R.C. 1976. Effect of initial mass of white spruce and lodgepole pine planting stock on field performance in the British Columbia Interior. Can. Dep. Environ., Can. For. Serv., Victoria BC, Inf. Rep. BC-X-149. 14 p.</ref> and McMinn (1985a)<ref name="mcm2">McMinn, R.G. 1985a. Effect of initial mass on the field performance of white spruce planting stock. Can. For. Serv., Victoria BC, File Rep. PC 48-357, Exp. 72-F2. 5 p.</ref> examined how the performance of 2+0 bareroot white spruce related to differences in initial size of planting stock. The stock was regraded into large, medium, and small fractions according to fresh weight. The small fraction (20% of the original stock) had barely one-quarter of the dry matter mass of the large fraction at the time of outplanting. Ten years later, in the blade-scarified site, seedlings of the large fraction had almost 50% greater stem volume than had seedlings of the small fraction. Without site preparation, large stock were more than twice the size of small stock after 10 years.

[[File:Nursery of apricot seedlings.jpg|thumb|Nursery of apricot seedlings]]

Similar results were obtained with regraded 2+1 transplants sampled to determine root growth capacity.<ref name="mcm0">McMinn, R.G. 1980. Root growth capacity and field performance of various types and sizes of white spruce stock following outplanting in the central interior of British Columbia. p. 37–41 ''in'' Schmidt-Vogt, H. (Ed.). Characterization of Plant Material. Proc. IUFRO Working Group S1.05-04 Meet., Waldbau-Institut, Univ. Freiburg, Germany.</ref><ref name="mcm1">McMinn, R.G. 1984. Field performance of various sizes of white spruce stock in recently cut and backlog sites. Can. For. Serv., Victoria BC, File Rep. PC 48-357, Exp. 78-F1. 4 p.</ref> The large stock had higher RGC as well as greater mass than the small stock fraction.

The value of large size at the time of planting is especially apparent when outplants face strong competition from other vegetation, although high initial mass does not guarantee success. That the growth potential of planting stock depends on much more than size seems clear from the indifferent success of the transplanting of small 2+0 seedlings for use as 2+1 "reclaim" transplants.<ref name="mcm2" /> The size of bareroot white spruce [[seedling]]s and transplants also had a major influence on field performance.

The field performance among various stock types in Ontario plantations was examined by Paterson and Hutchison (1989):<ref name="pat">Paterson, J.M.; Hutchison, R.E. 1989. Red pine, white pine, white spruce stock type comparisons. Ont. Min. Nat. Resour., For. Res. Note 47. 4 p.</ref> the white spruce stock types were 2+0, 1.5+0.5, 1.5+1.5, and 3+0. The nursery stock was grown at Midhurst Forest Tree Nursery, and carefully handled through lifting on 3 lift dates, packing, and hot-planting into cultivated weed-free loam. After 7 years, overall survival was 97%, with no significant differences in survival among stock types. The 1.5+1.5 stock with a mean height of 234&nbsp;cm was significantly taller by 18% to 25% than the other stock types. The 1.5+1.5 stock also had significantly greater [[Diameter breast height|dbh]] than the other stock types by 30–43%. The best stock type was 57&nbsp;cm taller and 1&nbsp;cm greater in dbh than the poorest. Lifting date had no significant effect on growth or survival.

High elevation sites in British Columbia's southern mountains are characterized by a short growing season, low air and soil temperatures, severe winters, and deep snow. The survival and growth of [[Picea engelmannii|Engelmann]] spruce and [[Abies lasiocarpa|subalpine fir]] outplanted in 3 silvicultural trials on such sites in gaps of various sizes were compared by Lajzerowicz et al. (2006).<ref name="laj">Lajzerowicz, C.C., Vyse, A., Jull, M., and Newsome, T. 2006. Performance of planted Engelmann spruce and subalpine fir seedlings in British Columbia's southern mountains. For. Chron. 82(1):84–94</ref> Survival after 5 or 6 years decreased with smaller gaps. Height and diameter also decreased with decreasing size of gap; mean heights were 50&nbsp;cm to 78&nbsp;cm after 6 years, in line with height expectations for Engelmann spruce in a high-elevation planting study in southeastern British Columbia.<ref name="thom">Thompson, C. 1995. Preliminary height expectations of Engelmann spruce plantations for three elevations in the Nelson Forest Region. B.C. Min. For. Nelson For. Region, Res. Sum RS-020. (Cited by Lajzerowicz et al. 2006, orig. not seen.)</ref> In the larger gaps (≥1.0 ha), height increment by year 6 was ranging from 10&nbsp;cm to 20&nbsp;cm. Lajzerrowicz et al. Concluded that plantings of [[Pinophyta|conifers]] in clearcuts at high elevations in the southern mountains of British Columbia are likely to be successful, even close to timberline; and group selection silvicultural systems based on gaps 0.1 ha or larger are also likely to succeed. Gaps smaller than 0.1 ha do not provide suitable conditions for obtaining adequate survival or for growth of outplanted conifers.