Root system development and physiology of conifer seedlings as affected by nursery treatments and site preparation treatments

Container type and photoperiod extension

Copper-treated Styrofoam containers and containers with side slits have been designed to modify the root systems of seedlings grown in hardwall containers. By chemically or air-pruning major lateral roots, they encourage a more fibrous, branched root system, which is more evenly distributed throughout the root plug. In one of our studies, lodgepole pine (Pinus contorta var. latifolia) seedlings were grown in Copperblocks™, AirBlocks™ or conventional Styroblocks™ and planted into different rooting environments. Before planting, various laboratory tests were performed on the seedlings, which did not predict field response to treatments. Container type influenced root development and potential root viability in the nursery; however, these differences had disappeared in the field after two growing seasons (Jones et al. 2002b). Only in summer-planted seedlings was root egress near the top of the plug greater for copper-treated than for conventional seedlings in the field. Seedlings grown in Copperblocks with exclusively secondary needles were evaluated separately from those with only primary needles. The secondary-needle seedlings had greater height increments in both growing seasons, although no differences in root collar diameter were apparent. However, both types of seedlings were selected from a population grown under cultural conditions to induce secondary needles, and thus some of the differences may have had a genetic basis. Spring-planted seedlings, grown on burnt slopes, grew 5-18% taller than those on screefed plots and 43-67% taller than seedlings on ripped landings. Our major conclusion is that, provided the seedlings are healthy, planting location is more important than stock type.

Container types, mycorrhizal inoculation and site preparation treatments

Interior lodgepole pine (Pinus contorta var. latifolia) seedlings were grown in Styroblocks™, Copperblocks™, or Airblocks™, and inoculated with Rhizopogon rubescens, Hebeloma longicaudum, or left as non-inoculated controls. Seedlings were planted into different rooting environments. In one experiment, seedlings were planted into fully rehabilitated (ash and topsoil incorporated) landings, ripped landings, and unprepared cutblocks in the spring. In a second experiment, seedlings were planted in the summer into a cutblock into manually (i.e. boot) screefed planting sites or undisturbed forest floor planting sites. Growth performance, as measured by seedling height and diameter, was assessed after two field seasons. Differences in rooting environments elicited significant differences in seedling growth over the initial two summers following outplanting. Spring-planted seedlings in ripped landings that received topsoil / burn-pile debris were 21% taller and had 45% larger diameters than seedlings in landings that were simply ripped; however, seedlings planted in the adjacent cutblock were of greater height than those on both landing treatments (Campbell et al. New Forests, in press). Summer-planted seedlings in screefed microsites grew significantly larger (5%) than seedlings planted directly in the forest floor. Spring-planted seedlings grown in Copperblocks, outperformed seedlings from other container types by at least 13%, but summer-planted seedlings produced in Copperblocks and Styroblocks were the same size as each other. After two years in the field, spring-planted seedlings inoculated with ectomycorrhizal fungi were no different in size from non-inoculated seedlings, however inoculated summer-planted seedlings outperformed non-inoculated control seedlings by approximately 5%. Amongst the variables we manipulated, planting environment had the principal effect on seedling performance. Incorporation of burn-pile debris and recovered topsoil into landings, as a mode of landing rehabilitation, is an effective method of increasing early performance of seedlings planted on landings. These trials suggest no benefit to the use of Airblock containers over Styroblock containers for the production of interior lodgepole pine.

This project was part of the M.Sc. thesis work of Bruce Campbell. Other collaborators include Janusz Zwiazek, Steven Kiiskila, Chuck Bulmer, Leanne Philip, Kim Young, Teresa Raabis and Kelly Fay.

Last reviewed 4/8/2015 12:32:35 PM