Growth Of Douglas-fir Seedlings Research Articles

Interactive Effects of Stock Type and Forest Vegetation Management Treatments on Douglas-Fir Seedling Growth and Survival—Ten-Year Results

In the Pacific Northwest, the use of forest vegetation management (FVM) and seedling stock type selection are important tools to ensure seedling establishment according to organizational objectives and state laws. Individually, these two reforestation decisions have been shown to increase growth and survival of Douglas-fir seedlings, however, the interaction between seedling stock type and level of vegetation control represents economic and ecologic tradeoffs that are less well understood. This study was designed to test the combined effects of three FVM regimes and three containerized stock types, one of which was experimental at the time, on Douglas-fir growth during the initial ten years of establishment on a site near Belfair, Washington (USA). When compared to the no-action control, FVM treatments reduced competitive plant cover below 20% during the year of application, and differences in vegetation cover persisted through the fifth growing season. Vegetation species diversity recovered quickly after FVM and there were no differences among the treatments by the third growing season. After ten growing seasons, trees in plots treated with FVM were 1.1 m taller with a mean diameter at breast height (DBH) 2.2 cm larger than those in the no-action control. Larger seedlings at the time of planting (styro-60) were 0.6 m taller with a mean DBH 1.1 cm larger than smaller seedlings (styro-8 and styro-15). The only significant stock type by FVM interaction in the experiment occurred with the survival of styro-60 seedlings growing in the no action control which had lower survival than all other treatment combinations (67% vs 91%). The long-term competitive impact of shrub cover was demonstrated by a strong non-linear relationship. Increasing cumulative shrub cover from 10% to 30% during the first two years of establishment reduced stand volume at year 10 by 79%.

Thirteen-Year Height and Diameter Growth of Douglas-Fir Seedlings under Alternative Regeneration Cuts in Pacific Northwest

Abstract Interest in managing Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) forests in the Pacific Northwest under silvicultural systems other than traditional clearcutting has prompted research on the efficacy of alternative systems for successful regeneration and sustained timber productivity of Douglas-fir. The College of Forestry Integrated Research Project, implemented by Oregon State University, was established to compare various ecosystem responses and public perceptions among treatments implemented under clearcutting, shelterwood-with-reserves, and group selection silvicultural systems. The objective of this analysis was to quantify the following three responses of planted Douglas-fir seedlings to initial regeneration cuts: cumulative 13-year height growth (H13yr; 1992–2004), cumulative 13-year diameter growth (D13yr; 1992–2004), and most recent 5-year height growth (ΔH5yr; 2000–2004). Differences in variability of overstory density at the treatment level led to significant differences in the variance of understory growth responses. After accounting for heterogeneous variance, analysis of variance indicated significant treatment effects for all three responses. Treatment effects were explained by the decline in H13yr, D13yr, and ΔH5yr with increasing overstory competition as represented by basal area of residual trees immediately after harvesting (initial basal area). Predicted height:diameter ratio of Douglas-fir seedlings increased as IBA increased. Under regeneration methods that retain a portion of the overstory, a residual overstory with basal area <80 ft2/ac allows establishment, growth, and continued survival of Douglas-fir regeneration during the 13 years following harvest.

Application of chloropicrin to Douglas-fir stumps to control laminated root rot does not affect infection or growth of regeneration 16 growing seasons after treatment

Phellinus weirii (Murr.) Gilb. causes laminated root rot (LRR), a major disease affecting growth and survival of Pseudotsuga menziesii (Mirb.) Franco (Douglas-fir) and other commercially important conifer species throughout the Pacific Northwest. This disease is known to spread to a replacement stand by root contact between replacement trees and residual infected stumps and roots from the harvested stand. One strategy to manage LRR is to reduce the residual inoculum on a site through application of a fungicidal chemical to infested stumps. The first two studies in this series established that chloropicrin (trichloronitromethane), applied to infested stumps, largely eliminates P. weirii from most of the belowground biomass and determined the effective dosage to apply. This third study approximated an operational application and based treatment success on reduction of LRR in the replacement stand. The study area was an 8-ha, 65-year-old naturally regenerated second-growth stand that was predominantly Douglas-fir. The stand was surveyed preharvest and postharvest (clearcut). Each P. weirii-infected entity (standing dead or down trees and stumps) was marked, and the location of its center was mapped. Circular plots (0.04 ha) were located so as to include concentrations of infested stumps. Plots were stratified based on their estimated biomass of inoculum into eight replicate blocks of four plots each. Three chloropicrin treatments and an untreated control were assigned randomly to four plots in each of the eight blocks: (a) 100% labeled dosage to all stumps, (b) 20% labeled dosage to all stumps, (c) 100% labeled dosage to only visibly P. weirii-infected (stump-top stain or advanced decay) stumps, and (d) control (nothing done to the stumps). Holes were drilled into stump tops, a dose of chloropicrin poured in, and the holes plugged. The labeled dosage was 3.3 ml of chloropicrin per kilogram of estimated stump and root biomass. Douglas-fir seedlings were planted in the winter following treatment application. When the stand was considered established, each plot was thinned to an inter-tree spacing of 2.4 m and the trees tagged. Diameter at breast height, total height, and mortality of trees were recorded every 2–5 years. A total of 1041 tagged trees were observed for 16 growing seasons following treatment. Application of chloropicrin to stumps in the harvested stand did not influence the rate of LRR-caused mortality or growth of Douglas-fir seedlings in the replacement stand.

Stump removal and fertilization of five Phellinus weirii-infested stands in Washington and Oregon affect mortality and growth of planted Douglas-fir 25 years after treatment

Phellinus weirii (Murr.) Gilb. causes laminated root rot (LRR), a major disease affecting growth and survival of Pseudotsuga menziesii (Mirb.) Franco (Douglas-fir) and other commercially important conifer species throughout the Pacific Northwest. Stump removal or nitrogen (N) fertilization, or both, have been suggested as management strategies for some root diseases but have not been tested previously for LRR in a replicated field study. Independent studies, using the same experimental design, were established in five Douglas-fir stands in Oregon and Washington. The stands were surveyed preharvest and postharvest (clearcut). Each P. weirii-infected entity (standing dead or down trees and stumps) was marked, and the location of its center was mapped. In each clearcut, a 2 × 4 set of factorial treatments of stump removal in combination with N fertilization was applied to 0.04 ha circular plots and replicated five to seven times. Treatments, applied in the fall, included stump removal with a bulldozer (either all stumps removed or the plot left undisturbed) and broadcast fertilization with ammonium nitrate (0, 336, 672, or 1345 kg N ha −1). Douglas-fir seedlings were planted in the winter following treatment application. When the stand was considered established, each plot was thinned to a spacing of about 2.4 m inter-tree spacing and the trees tagged. Diameter at breast height, total height, and mortality of trees were recorded every 2–5 years. A total of 7827 tagged trees on 239 plots were observed for up to 27 growing seasons following treatment. Stumping caused a significant reduction in seedling mortality due to LRR at all five study areas. The mean LRR-caused mortality on stumped and nonstumped plots was 2.4 and 9.1%, respectively. Fertilization did not cause a significant change in LRR-caused mortality of seedlings at any of the study areas. Nitrogen fertilization before planting increased growth of Douglas-fir seedlings but only in some stands. Nitrogen fertilizer can have a positive residual effect on growth of Douglas-fir for at least 23 years. Effects on soil of heavy equipment used in stumping operations did not reduce subsequent Douglas-fir survival or growth. There was a mean reduction in wood volume of 24.8% in areas where LRR was observed compared to areas where it was not found.

Effects of ectomycorrhizal inoculants on survival and growth of interior Douglas-fir seedlings on reforestation sites and partially rehabilitated landings

We studied the effects of commercially available (Laccaria laccata (Scop.:Fr.) Berk. & Br. and Rhizopogon parksii Smith (Oregon source)) and native (R. parksii (British Columbia source)) ectomycorrhizal (EM) inoculants on the survival and growth of commercially grown interior Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco) seedlings outplanted on reforestation sites (burned piles and clearcuts) and partially rehabilitated (shallow- and deep-tilled to a depth of 15 and 50 cm, respectively) landings. We also examined the physical and chemical properties of the soil and the EM status and foliar element levels of noninoculated Douglas-fir seedlings to provide information on the growing conditions found on these types of sites. Inoculation treatments did not significantly increase survival and growth of Douglas-fir seedlings 2 years after outplanting. However, because the average percent EM colonization of inoculated seedlings at time of outplanting was low (36%), the beneficial effects of these inoculants may not have been attained. It is possible that nursery conditions partially account for the low EM colonization of inoculated seedlings. We therefore suggest that nurseries try to modify growing conditions to favor good EM formation before outplanting interior Douglas-fir. Benefits of inoculations on landings may have been restricted by the poor soil conditions, potentially toxic levels of Fe and Al, and competition from well-adapted native EM fungi.

Effect of biuret on growth and nutrition of Douglas-fir ( Pseudotsuga menziesii (Mirb) Franco) seedlings

Effects of biuret concentrations on growth and nutrient uptake by two provenances of Douglas-fir ( Pseudotsuga menziesii (Mirb) Franco) seedlings were examined experimentally in sand, solution culture and soil. In sand and solution culture, biuret stimulated the growth of Douglas-fir seedlings at lower concentrations (from 0.001 to 0.097 mM), but inhibited and even killed the seedlings at greater concentrations (from 0.971 to 9.709 mM). Nutrient uptake by seedlings and the net photosynthetic rate in needles increased at lower concentrations of biuret. Biuret stimulation of growth was greater at 7.143 than 2.857 mM of applied nitrogen (N). In soil, biuret applied at 2 and 10 μg g −1 (oven-dry) soil (equivalent to the rates of 5 and 25 kg biuret ha −1) increased seedling height, basal diameter and stem volume while biuret at 100 μg g −1 soil (equivalent to 250 kg biuret ha −1) inhibited height growth and killed the seedlings at 1000 μg g −1 soil (equivalent to 2500 kg biuret ha −1). The stimulation of Douglas-fir seedling growth at lower concentrations of biuret (2 and 10 μg g −1 soil) was associated with improvement of soil N availability while the exact causes of the inhibition of growth at high concentrations (100 and 1000 μg g −1 soil) are unknown but could include direct biuret toxicity or the indirect effect of the elevated H + and/or Al 3+. Provenance 93 was more responsive to lower concentrations of biuret but was more susceptible to biuret toxicity while provenance 98 was more tolerant of high concentrations of biuret but less stimulated by the lower concentrations of biuret. Yellow tip (chlorosis) in needles was a typical symptom of biuret toxicity.

Effect of Aporrectodea trapezoides activity on seedling growth of Pseudotsuga menziesii, nutrient dynamics and microbial activity in different forest soils

The effect of the endogeic earthworm, Aporrectodea trapezoides on the growth of Douglas-fir seedlings grown in three different soils was studied. Soils from pure and mixed stands of Douglas-fir and paper birch were used. Seedlings were grown in earthworm-worked and control soils for 10 months in the laboratory. At 5 and 10 months, differences in plant growth, available N and P, mycorrhizal colonization, microbial functional diversity and microbial activity were assessed. Douglas-fir seedling root biomass was greater in worm-worked compared to control soils. Height of seedlings varied significantly during the 5–8 months period of growth with taller seedlings in worm-worked soils. Foliar calcium levels of seedlings were higher at 10 months in worm-worked soils compared to the control. Effects of A. trapezoides on pH were unclear due to a worm×soil type interaction. Worm-worked mineral soil generally had higher organic matter levels compared to control soils but few differences were apparent in the forest floor layer. Average available NO 3 − and –NH 4 + levels were higher in worm-worked forest floor at 10 months yet there were no differences in the mineral soil at this time. The effect of A. trapezoides on mycorrhizal colonization of Douglas-fir seedling roots differed with the different soil types whereby seedlings grown in pure and mixed birch soils were less colonized compared to the control. Average total bacterial activity, substrate richness and diversity were consistently higher in worm-worked forest floor and mineral soil compared to the control treatment. The trend in microbial respiration in worm-worked forest floor and mineral soil was not clear while effects on microbial biomass in the mineral soil were confounded by a worm×soil type interaction. The metabolic quotient was generally lower in worm-worked soils compared to control soils. Douglas-fir seedlings grown in pure worm-worked fir soils were often affected differently or more dramatically compared to seedlings grown in pure birch or mixed soils. The results of the experiment indicate that A. trapezoides has the potential to enhance Douglas-fir seedling growth.

Physiology and growth of Douglas-fir seedlings treated with ethanol solutions

Applying 1, 5, 10, and 20% solutions of ethanol to the roots of Douglas-fir ( Pseudotsuga menziesii [Mirb.] Franco) seedlings three times a week was deleterious to their physiology and growth. Ethanol concentrations of 10% or higher were lethal within a week of treatment initiation, while the 5% solution was lethal to seedlings at ∼8 weeks. Seedlings treated with the 1% solution were alive at 8 weeks, but showed signs of physiological decline. If Douglas-fir seedlings have a tolerance threshold for ethanol solutions applied to their roots, it appears to be at a concentration below 1%. Ethanol moved up the stems and into needles, yielding concentrations in the stems 9 times higher than in needles. Ethanol vapors in the atmosphere surrounding seedlings readily diffused into needles, but not into stems. After 1 week of treatments, net photosynthesis, stomatal conductance, and transpiration declined as ethanol concentrations increased. However, seedlings treated with the control (0%) and 1% ethanol solutions had the same xylem water potentials, which were higher than for seedlings treated with the 5% solutions. High ethanol concentrations (≥1%) may have damaged membranes involved in photosynthesis and stomatal function thereby causing the observed decline in net photosynthesis and stomatal conductance. At concentrations ≥5%, water uptake was impaired, suggesting that root membranes may have been damaged.

Effect of Western Spruce Budworm Defoliation on the Physiology and Growth of Potted Douglas-Fir Seedlings

Abstract Interactions between effects of insect defoliators on tree physiology and growth and soil nutrient and water availability are poorly understood. We addressed whether the western spruce budworm influences nutrient and water relations, ectomycorrhizae, leaf gas exchange, and growth of Douglas-fir seedlings under different environmental conditions. Four-year-old, potted seedlings were grown in two soil types (basalt-derived, limestone-derived) with two levels of soil moisture (high, low) and were subjected to three levels of budworm defoliation (none, moderate, heavy) and two levels of frass and litter produced by budworm feeding (with, without) over 2 yr in a greenhouse environment. Defoliation, soil moisture, and soil type influenced allocation of seedling biomass to leaves, stems, and roots. The addition of frass and litter had no effect on any measured soil or tree characteristic. Interactions between defoliation and other experimental factors were not important except for the defoliation x soil moisture interaction where heavy defoliation reduced the negative effects of low soil moisture on seedling predawn water potential, net photosynthetic rate, and stomatal conductance. Heavily defoliated seedlings had less biomass, higher foliar concentrations of N, Ca, and Mg, less ectomycorrhizae, and higher net photosynthetic rate and stomatal conductance compared with nondefoliated seedlings. For. Sci. 45(2):280-291.

Three-Year Survival and Growth of Douglas-Fir Seedlings Under Various Vegetation-Free Regimes

Abstract Responses of Douglas-fir seedlings were studied for 3 yr following eight vegetation-control treatments in three western Oregon clearcuts. The objectives were to determine seedling growth response to different areas of spot vegetation control and to determine the relative influence of early woody and herbaceous competition on seedling growth. Herbicide treatment areas varied in size from those receiving no control to full control (9.3 m2). Controlled areas were maintained free of herbaceous vegetation for 2 yr and all woody vegetation was controlled for 3 yr. Two additional treatments, complete control of woody vegetation only and complete control of herbaceous vegetation only, were also examined. On two sites (Summit and Marcola), seedling growth parameters were maximized at or near full vegetation control with a tree spacing of 3 m x 3 m. On the third site (Pedee), maximum growth response occurred between 5 and 6 m2; of control. Herbaceous vegetation control resulted in increased seedling growth at all sites while woody vegetation control yielded increased seedling growth only at the Pedee site. Cumulative 3 yr herbaceous cover accounted for 68% and 41% of the variability in stem volume at Summit and Marcola, respectively. Adding cumulative 3 yr woody cover to the model accounted for an additional 18% and 49% of the variability in stem volume at Summit and Marcola, respectively. At Pedee, neither herbaceous nor woody cover significantly influenced 3 yr stem volume, suggesting that factors other than vegetation cover were responsible for differences measured. For. Sci. 45(1):117-126.

Growth and ectomycorrhizal formation of container-grown Douglas-fir seedlings inoculated with Laccariabicolor under four levels of nitrogen fertilization

Container-grown Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) seedlings were inoculated at the time of sowing with a Laccariabicolor (Maire) Orton mycelial suspension produced in a fermentor. They were grown in a peat moss–vermiculite substrate under four levels of N fertilization (7.2, 14.4, 21.6, and 28.7 mg/seedling per season (N1, N2, N3, and N4, respectively)) to determine the N level suitable for both ectomycorrhizal development and seedling growth. After 18 weeks in the greenhouse, seedlings inoculated with L. bicolor had 44%, 32%, 44%, and 5% of their short roots mycorrhizal when fertilized with N1, N2, N3, and N4, respectively. Only when they were fertilized with N4 did the L. bicolor seedlings have significantly greater shoot height than the controls. For the other growth parameters, they were not significantly different from control seedlings for any of the N levels. After 18 weeks, regardless of the level of N, seedlings inoculated with L. bicolor had significantly lower N concentrations (%) and contents (mg/seedling) than the uninoculated ones. Consequently, for the same production of biomass, the mycorrhizal seedlings had taken up less N than the nonmycorrhizal ones. The efficiency of applied N, expressed in terms of produced biomass, decreased when the N fertilization increased; mycorrhizal and nonmycorrhizal seedlings did not tend to be different. The efficiency of the absorbed N also decreased with the level of applied N, but less rapidly, and tended to be greater for the mycorrhizal seedlings than for the nonmycorrhizal ones. Therefore, the mycorrhizal infection improved the utilization of the absorbed N. N3 was the best of the four N levels used, since it was the only one that maximized both the ectomycorrhizal formation and the growth of the seedlings. In other words, a total seedling N concentration of 1.6% and a substrate fertility of 52 ppm N are appropriate to optimize both the ectomycorrhizal development and the growth of Douglas-fir seedlings.

Spring growth of Douglas-fir seedlings from two bud development regimes

The effect of two bud development treatments on post-dormancy shoot growth was investigated with 1-year-old container-grown Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings. A difference in the date of budset and number of overwintering primordia was obtained by applying 8-hour or 17-hour photoperiods in growth rooms during summer months. Seedlings were then chilled for 14 weeks at 4 °C and finally held 2 months at 22 °C under either an 8-hour or 16-hour photoperiod. The new shoot growth of seedlings with early budset had greater length, stem unit numbers, average stem unit length, and dry weight. Stem unit number of the post-dormancy seedlings was unaffected by photoperiod during flushing. Significant free growth occurred only in late budset seedlings and accounted for 40% and 46% of the fixed growth under 16-hour and 8-hour flushing photoperiods, respectively.

Ectomycorrhizae and growth of Douglas-fir seedlings preinoculated with Rhizopogonvinicolor and outplanted on eastern Vancouver Island

Ectomycorrhizal colonization of container-grown Pseudotsugamenziesii (Mirb.) Franco (Douglas-fir) inoculated with Rhizopogonvinicolor A.H. Smith was determined after cold storage and after one growing season on a clearcut on eastern Vancouver Island. Inoculated Douglas-fir seedlings were taller than noninoculated controls when outplanted but, perhaps because of browse damage, no growth differences were found after one field season. Rhizopogonvinicolor colonized all of the inoculated but none of the control seedlings examined after cold storage. Volunteer Thelephoraterrestris Fr. colonized almost half of the control and 10% of the inoculated seedlings before outplanting. After one field season, inoculated and control seedlings were colonized by 15 ectomycorrhizal fungi each, only eight of which were found on both. Rhizopogonvinicolor persisted on the roots of inoculated plants, but was also present in the field soil since the control seedlings also bore these mycorrhizae after one growing season. The relative abundance of T. terrestris decreased from the nursery to the field. The other common ectomycorrhizae in the field included Myceliumradicisatrovirens Melin, Cenococcumgeophilum Fr., and types resembling Tuber and Endogone.

Absolute and relative growth of Douglas-fir seedlings of different sizes.

Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings of a single seed source were grown in a bare-root nursery for two years to produce five different stock types by varying spacing and transplanting treatments. They were then planted in the forest together with one-year-old container seedlings of the same seed source, which constituted a sixth treatment. Stem volume mean relative growth rate (R(v)) was low immediately after planting for all stock types except the container seedlings, and increased over the following 7.6 years. An 8-week greenhouse test of the six stock types showed that dry weight mean relative growth rate (R(w)) generally decreased with seedling dry weight, but this effect was less obvious after planting, because only the three smaller stock types showed a decrease in R(w) with size. In another experiment, bare-root Douglas-fir seedlings were grown at five different spacings in a nursery for two years, and seedlings from each spacing treatment were sorted into large or small by height. The resulting 10 treatments were planted in the forest and stem volumes determined over 6.7 years. The linear effect of nursery spacing on stem volume was no longer evident 3.6 years after planting, but large seedlings had greater stem volume than the small seedlings throughout the 6.7 years of the study. There was no indication that R(v) declined with time, but small seedlings had higher R(v) than large seedlings. Relative growth rates of two-year-old Douglas-fir were depressed for a year or two after planting, but then remained relatively constant, or increased during the ensuing 5 years. Relative growth rates of smaller seedlings were greater than those of larger seedlings so that relative biomass differences decreased with time, and the time advantage (the time necessary for small seedlings to reach the present biomass of large stock) of larger stock decreased. Absolute size differences increased with time.

Survival and Growth of Douglas-Fir Seedlings after Prescribed Burning of a Brushfield in Southwest Oregon1

Abstract The effects of prescribed fire on reforestation were assessed on a north-facing brushfield in southwest Oregon. For site preparation, the brush was slashed and either burned or left unburned. Five years after planting, survival of 2-0 bareroot seedlings of Douglas-fir (Pseudotsuga menziesii var. menziesii) was high, irrespective of treatment, but seedlings were larger and grew significantly faster in burned than in unburned areas. The initially greater annual relative growth rate of seedlings in burned areas declined as brush recovered. Brush recovered at similar rates on burned and unburned areas, but significantly greater brush cover was present on the unburned area because of an extra season's growth before planting. Planting should occur as soon as possible after disturbance by slashing or burning to minimize competition from brush. West. J. Appl. For. 6(3):55-59.

New root growth of Douglas-fir seedlings at low carbon dioxide concentration

New root growth of conifer nursery seedlings is dependent on light, but whether this is necessary only for photosynthesis, or also has some other root growth promoting effect is unknown. This question was investigated using one-year-old Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings grown at two nurseries from the same seed lot and taken from cold storage in March and April. New root production was examined in two 10-day root growth capacity (RGC) experiments. Seedlings were subjected to one of four treatments: (1) control, (2) exclusion of light, (3) low CO(2) concentration, and (4) girdling to separate the phloem connection between shoot and root. Shoots were enclosed in Plexiglas cuvettes and supplied with scrubbed air to reduce the CO(2) concentration to 11 to 22 microl l(-1) in the light. The closed system used in Experiment 1 was opened to the atmosphere briefly each day to restore O(2) to ambient, but this was unnecessary for the open system used in Experiment 2. In Experiment 1, new root production was affected by treatments in the order: control > low CO(2) concentration > dark > girdling. Greater new root production in the low CO(2) treatment compared with the dark treatment was attributed to brief increases in CO(2) to ambient concentrations when O(2) was restored each day. In Experiment 2, new root production at the low CO(2) concentration in the light was essentially the same as in darkness, but only 17% of the control value. Thus light appeared to play no part in new root production other than permitting photosynthesis. Limited production of new roots occurred in the absence of photosynthesis, which was further reduced by girdling, presumably because, after girdling, only root system reserves could be used.

Effects of Site Preparation on Douglas-Fir Seedling Growth and Survival

Abstract The effects of five yarding-slash treatment combinations on Douglas-fir (Pseudotsuga menziesii) growth and survival were compared by obtaining seedling heights, potential seedling heights, survival percentages, soil-penetration resistances, and the occurrence of visible soil-humus for 149 progeny-test plantations in western Oregon. Survival was not improved by mechanical site preparation, and seedlings grown on the compacted, low-humus soils associated with piling slash off site did not grow as tall during their first 5 years as seedlings growing on similar sites where slash had been broadcast-burned. Tilling (disking or ripping) did not benefit seedling height growth. West. J. Appl. For. 5(2):49-51, April 1990.

Effect of inoculum type and inoculation dose on ectomycorrhizal development, root necrosis and growth of Douglas fir seedlings inoculated with Laccaria laccata in a nursery

L'inoculation a ete realisee a l'aide de mycelium ayant pousse dans un melange de vermiculite et de tourbe ou de mycelium produit en milieu liquide et inclus dans un gel d'alginate de calcium, avec trois doses differentes. Les observations ont porte sur la croissance des semis dans un sol sablo-limoneux, l'infection ectomycorhizienne et le developpement des necroses racinaires dues a Fusarium oxysporum

Survival and Growth of Douglas-Fir Seedlings with Spot-Spraying, Mulching and Root-Dipping

Abstract Two vegetation management methods, paper mulching and spot-spraying with glyphosate, were combined with a root-dipping treatment, Terra Sorb®, to test effects on seedling survival and height growth on a harsh site in Oregon. Survival of Douglas-fir (Pseudotsuga menziesii) seedlings was significantly higher after the third growing season when competing vegetation had been controlled with mulch or glyphosate during the first two growing seasons. Seedlings retreated with paper mulch and glyphosate before the second growing season had 36 and 25% higher survival than those that were not retreated. None of the seedlings was retreated before the third season; after this season, survival of seedlings treated twice with glyphosate was 26, 23, and 21% higher than seedlings receiving one glyphosate treatment and one or two mulch applications, respectively. There were no differences in seedling height growth among treatments. Rootdipping with Terra Sorb® did not influence survival or growth. West. J. Appl. For. 1:108-111 Oct. 86.

Effects of soil fumigation and inoculation with pure culture of Hebeloma cylindrosporum on survival, growth and ectomycorrhizal development of Norway spruce and douglas fir seedlings

AbstractIn a bare‐root nursery we have determined the incidence of soil fumigation and mycorrhizal inoculation on survival growth and ectomycorrhizal development of Norway spruce and Douglas fir seedlings. Three experimental designes were installed in 1978, 1981 and 1982.Soil fumigation eliminated or reduced Rbizoctonia solani, Pytbium sp. and probably Fusarium oxysporum propagules. Fumigation improved Norway spruce seedlings performance, particularly in the second year. Douglas fir seedlings seemed less sensitive to soil‐borne pathogens tha Norway spruce seedlings.Two years after inoculation, Hebeloma cylindrosporum increased Norway spruce growth by 40% and Douglas fir growth by 30 % in comparison with seedlings grown in fumigated soil and mycorrhizal with the naturally occurring fungus Thelephora terrestris.Both, fumigation and artificial inoculation increased Norway spruce seedling growth by 110 % and Douglas fir seedling growth by 50 %.