Tall planting stock for enhanced growth and domination of brush in the Douglas-fir region

Two long-term experiments followed development of planted stock of various sizes, origins, and species. In one experiment, multiyear comparisons of container, 2-0 bareroot, and 3-year-old Douglas-fir transplants showed strong positive relationship between initial height and long-term (10–14 years) growth under a range of site conditions with high probability of brush development. In the other experiment, Douglas-fir, western hemlock, and Sitka spruce were planted in salmonberry disturbed by logging 0 and 4 years previously. Half the seedlings were released with glyphosate 6 months after planting. Hemlock and Douglas-fir bare-roots all grew well if planted in a fresh burn, despite rapid regrowth of salmonberry, but virtually all seedlings less than 60 cm tall except Sitka spruce were killed by 4-year-old salmonberry if not released. Release improved growth of seedlings in the fresh burn by 6%, gaining an average of about 0.6 year toward reaching a height of 6 m. Release improved growth of survivors in 4-year-old salmonberry by 51% in height, 72% in diameter, and 325% in volume at age 12. Sitka spruce grew well until damaged by insects. Hemlock growth was equal to or greater than that of Douglas-fir of comparable initial height. In all comparisons, the probability of being overtopped by brush decreased with increasing initial stock height, and the effect of suppression on growth was also inversely related to initial height. Field planting operations may require special logistic measures for the largest stock types.This is Paper 2706 of the Forest Research Laboratory, Oregon State University.     

Some Methods of Cold Storage can Seriously Affect Root Growth Potential and Root Moisture Content and Subsequent Forest Performance of Sitka Spruce and Douglas Fir Transplants

Sitka spruce and Douglas fir transplants were kept under threecold storage regimes: (1) bare-root in a humidified cold store(H); (2) sealed in polythene bags in a humidified cold store(HP); (3) sealed in polythene bags in a direct cold store (D).Regimes H and D are routinely used in current practice. Plants of both species had significantly (P < 0.001) lowerroot moisture content (RMC) in treatment H within 4 weeks ofstorage; this difference was maintained throughout the periodof storage and potentially damaging levels of RMC were reachedwithin 8 weeks. Sitka spruce had significantly (P < 0.001)higher root growth potential (RGP) than Douglas fir throughoutthe storage period. Differences in RGP between storage treatmentswere not significant until 12 weeks after storage when treatmentH was poorer (P < 0.05) than treatments HP and D. The survival of plants from treatment H after 1 year in thefield was significantly poorer (P < 0.001) than the othertreatments in both species. Height increment was also less intreatment H than the other treatments (P < 0.001) after 1year. However, this difference disappeared in the second season.After 1 year there were no differences in root collar diameter(RCD) increment between storage treatments but Douglas fir showedgreater increment (P < 0.001) than Sitka spruce. Rapid assessment of RMC in slightly over 48 h makes this a potentiallyuseful test of planting stock quality during and after coldstorage.     

Interception of precipitation by pole-stage Sitka spruce and lodgepole pine and mature Sitka spruce at Kielder Forest, Northumberland

Interception loss was measured indirectly for 3 years in adjacentunthinned 25-year-old stands of Sitka spruce and lodgepole pineand for 2 years in a 63-year-old selectively thinned stand ofSitka spruce. For each stand measurements were made of grossprecipitation, throughfall and stemflow. Interception loss wasderived by subtracting the sum of throughfall and stemflow (netprecipitation) from gross precipitation. For the years 1977–78, 1978–79 and 1979–80,interception losses in the pole-stage Sitka spruce were 32,28 and 27 per cent of gross precipitation respectively whilethose in the lodgepole pine were 33, 29 and 26 per cent. For1979–80 and 1980–81 interception losses in the matureSitka spruce were 44 and 53 per cent of gross precipitation.The average interception loss was 29 per cent for both pole-stagecrops and 49 per cent for mature Sitka spruce. The proportions of net precipitation reaching the ground asstemflow and throughfall were 0.18 and 0.82 respectively forthe pole-stage Sitka spruce, 0.14 and 0.86 for the pole-stagelodepole pine and 0.02 and 0.98 for the mature Sitka spruce.     

Sitka Spruce and Douglas fir Seedlings in the Nursery and in Cold Storage: Root Growth Potential, Carbohydrate Content, Dormancy, Frost Hardiness and Mitotic Index

Seedlings (transplants) of 2+1 Sitka spruce (Picea sitchensis(Bong.) Carr.) and 1 + 1 Douglas fir (Pseudotsuga menziesii(Mirb.) Franco) were grown in a nursery at the Bush Estate,Scotland. Batches were lifted and cold stored at 0.5°C inNovember, December and January. Changes in growth, shoot apicalmitotic index, root growth potential (RGP), carbohydrate content,bud dormancy and shoot frost hardiness were monitored throughoutthe winter by taking samples at intervals from the nursery andfrom cold storage. Frost hardening occurred during the later stages of bud development(as mitotic indices decreased); autumn hardening was arrestedwhen seedlings were put in cold store, and some dehardeningoccurred in cold storage, especially in spring. Bud dormancystarted, and was greatest, just after bud growth (mitotic activity)virtually ceased; chilling in cold store was almost as effectivein releasing dormancy as natural chilling. The concentrationof total nonstructural carbohydrates stayed more or less constantat 100–150mg g^–1 from September to April in thenursery; in cold storage carbohydrates were depleted at 0.4–0.6mgg^–1 d^–1 (corresponding to respiration at 0.03–0.05mgCO₂ g^–1 h^–1) until there was only 40–50mgg^–1. Root growth potentials in the nursery increased in December,once the buds ceased growth, became dormant and had receivedsome chilling. Sitka spruce was ‘storable’ in November,before RGPs increased, but they then failed to achieve maximalfrost hardiness or ROP. Winter RGPs were high in Sitka spruceand were increased or maintained in cold storage, whereas RGPswere low in Douglas fir and decreased immediately after storage(except when stored in January). By the end of April, the RGPof cold stored Sitka spruce was much higher than that of directlifted plants. ROP changes in the nursery and in cold storagewere not consistently related to changes in seedling carbohydratecontents, shoot frost hardiness or bud dormancy. In practical terms, it was concluded that (1) the optimum dateto start lifting bare- rooted conifer transplants in the autumnis when their shoot apical mitotic indices have decreased tonear zero, and their RGPs have risen sharply; (2) high RGPsmay depend as much on the morphology of the roots (e.g. numberof undamaged root apices) as on the physiology of the shoots(e.g. carbohydrate status, dormancy and frost hardiness); and(3) in spring, transplants kept in cold storage since November,December or January are more frost hardy, slightly more dormant,and (in May) have higher RGPs than transplants lifted from thenursery.     

THE PLACE OF A SPECIES IN THE FOREST, WITH SPECIAL REFERENCE TO WESTERN NORTH AMERICAN SPECIES OF CONIFER USED IN BRITAIN

The nature of the differences between the climates of the QueenCharlotte Islands and of England and Wales are discussed briefly.The author then examines the site tolerance of the principalspecies within their own natural range, comparing particularlythe place of Sitka spruce (Picea sitcbensis Carr.) in the foreston Graham Island with its place around Terrace and describingthe Douglas fir forests of the drier eastern side of VancouverIsland and the place that Sitka spruce has in them. Factorsaffecting the growth of Douglas fir (Pseudotsuga taxifolia Brit.)are discussed. It is suggested that care is needed before itis assumed that a markedly dry summer period such as occursin much of the Douglas fir region entails a ‘dry’period as regards supply to the tree. Illustrations are givenfrom eastern North America of changes in type of site occupiedby a species with change in climatic or edaphic environment.Observation of the relative position of a species in the forestas climate changes makes it possible to suggest the place ofSitka spruce and Douglas fir in Great Britain.     

Effect of Late-season Top-dressings of N (and K) applied to Conifer Transplants in the Nursery on their Survival and Growth on British Forest Sites

At two English forest nurseries, transplants of five coniferspecies—Picea sitchensis, Picea abies, Tsuga heterophylla,Abies grandis, and Pinus contorta—were grown with fertilizersupplying N, P, K, and Mg in amounts intended to be adequatefor producing healthy green trees with nutrient concentrationsin the ‘sufficiency range’ as determined by earlierexperiments. ‘Luxury uptake’ of nitrogen was obtainedwith top-dressings of ‘Nitro-Chalk’ applied in thenursery during early September, when top growth had nearly ceased.Tests of the effect of this extra N on forest establishmentwere repeated in four successive years under a wide range ofsoil and climatic conditions, keeping the trees in a cold storeduring each winter and planting them on forest sites in England,Scotland, or Wales during the following spring. Except for Grandfir, nitrogen advanced bud-break of all species during the firstsummer after planting and had no deleterious influence on survival.It tended to increase growth of Sitka spruce during the seasonafter planting, but in later years the differences became smallin relation to tree size. The effects on other species weresmall, except for one considerable decrease in the growth responseof Grand fir at a single site. Frost damage of Sitka spruce of Washington origin was severeon a Welsh and a Scottish site where this frost-sensitive provenancewould not normally be grown. At the Welsh, but not the Scottishsite, the nitrogen treatment increased the damage. In the few experiments (confined to Picea sitchensis) whichtested late-season potassium in the nursery, K concentrationswere increased from deficiency to barely sufficiency level;growth in the forest was increased in two of the four experiments.The extra K had no effect on frost damage.     

Annual and spatial variation in coning shown by the Forest Condition Monitoring programme data for Norway spruce, Sitka spruce and Scots pine in Britain

Conifer seed is a valuable forest resource; as well as beingreproductive material, it is an important foodstuff for manywoodland species. Information on cone and therefore seed productionof the main forest species are useful in the fields of bothforest management and forest ecology. Coning has been recordedsince 1989 in plots of Norway spruce, Sitka spruce and Scotspine across Britain as part of the Forestry Commission's ForestCondition Monitoring programme. An 11-year period of these recordswas analysed and a summary of annual cone production by speciesand coning synchrony is presented. Both Norway spruce and Sitkaspruce coned sporadically, with a 4-year period between mastcrops during which cone density was very low or cone productionabsent, whereas Scots pine produced a good cone crop in mostyears throughout Britain. Coning was synchronous within andbetween Norway and Sitka spruce across the whole of Britain(at distances >600 km) but coning within Scots pine was insynchrony only over distances of up to 200 km. Synchrony ofcone production was not evident between the spruce species andScots pine. These findings have implications when planning andinterpreting monitoring used to predict cone crops and in thedesign of forests for wildlife conservation.     

Variation of Density and Growth Ring Width in Stems of Sitka and Norway Spruce

The variation with height and radial distance from the pithof basic density and ring width has been determined in stemsof 48-year-old Sitka and Norway spruce planted at two spacingsat Durris, Kincardineshire. The pattern of radial variationof density was broadly similar at all heights: high near thepith, falling to a minimum and then a gradual increase. Themean whole-stem densities were significantly different at thetwo spacings in Sitka but not in Norway spruce. Density at breastheight was inversely correlated with ring width, strongly inSitka but weakly in Norway spruce. The density/ ring width regressionequation for outer wood in Sitka spruce at age 48 differed fromthat at age 31. In Norway spruce a high correlation was foundbetween whole-stem density and the density of rings 16–25at breast height.     

Susceptibility of Sitka spruce and grand fir trees to decay by Heterobasidion annosum

The susceptibility of Sitka spruce (Picea sitchensis) and grand fir (Abies grandis) to decay by Heterobasidion annosum was compared on a site with a previous history of serious disease. The incidence of decay 15–16 years after planting was 1.5% in grand fir, compared with 34.8% in Sitka spruce. These results are broadly similar to those reported from other trials. More information is required for older trees in Britain but the evidence so far available suggests that grand fir is more resistant to H. annosum than Sitka spruce. Planting grand fir on severely infested sites may therefore significantly reduce the serious losses that could be expected with Sitka spruce. In 14 out of 271 decayed Sitka spruce H. annosum was absent from the middle or base of the decay column but present at the top. Approximately 3% of infected spruce showed features suggesting some degree of resistance. Resin bleeding was observed at the base of 23.2% of the infected spruce, and the mean height of the decay column in these trees was significantly greater (0.96 m) than in those without this feature (0.66 m). The inoculum for infection was provided by stumps of the previous crop, and the genets of H. annosum that were present in some infected trees were also identified in stumps. The majority of infected trees contained only a single genet but three trees contained two genets. In this young crop individual genets were smaller than those found elsewhere; the largest extended to include six trees.     

Norway or Sitka Spruce?

The deep and wide continental range and climate occupied bythe European species Picea abies is contrasted with the long,narrow, and humid coastal strip which the American species Piceasitchensis inhabits. Norway is the more plastic spruce and cansuffer thinner soils and much more drought, but neither spruceis a shallow rooter where soils are good and deep. Of the two,the litter of Sitka is less harmful to the soil. To date thereis no evidence that height for height Norway is more stableunder high wind pressures, but the belief that it is less sensitiveto frost than Sitka is well established. Sitka is far superiorto Norway for planting at high altitudes and in exposed placesand on Molinia peatlands in Britain, which accounts for thevast preponderance of the American species used in the westand north of the British Isles. The present popularity of Norwayspruce with foresters and timber merchants is admitted, butthe point is made that in planting it where Sitka could growwell, only some 75 per cent, of the volume will be secured.Finally, the types of site which each spruce requires and alsowhich each cannot take are considered in detail. A plea is madefor mixtures in certain circumstances, and the belief expoundedthat only deeper and better cultivation of the hardpacked materialunder-lying thin soils will make it possible to extend considerablyour acreage of really stable crops of these high-volume producers.     

Early Growth of Picea sitchensis (Bong.) Carr. on Deep Oligotrophic Peat in Northern Ireland

Relationships are examined between growth of young Sitka spruce,planted on deep oligotrophic blanket peat, and uptake of N,P, and K by the trees under various fertilizer and herbicideregimes. Despite the provision of adequate P, tree growth eventuallybecomes limited by a shortage of available N. This can be overcomeat present only by repeated applications of fertilizer N. Theuse of herbicides to kill heather in checked crops increasesthe availability of N temporarily, and fertilizer K in all situationsimproves growth, though often only slightly. It is suggested that following the initial application of phosphatea finite fraction of the total N content of the peat becomesavailable to the trees. Once this has been used the releaseof mineral nitrogen is so slow that crops become N-deficientand growth is limited. There is no evidence to suggest thatonce canopy closes the situation will change, so that on oligotrophicpeat sites managers are faced with the possibility of havingto apply nitrogenous fertilizers every 3 or 4 years to maintaingrowth at a satisfactory level. Although there is as yet nodirect evidence on oligotrophic peat that there will not bean increase in the rate of N mineralization once crops reach5–7 m in height, work on other poorly drained soils inNorthern Ireland indicates that it is unlikely to happen.     

Some Effects of CO2, Daylength and Nutrition on the Growth of Young Forest Tree Plants I. In the Seedling Stage: I. In the Seedling Stage

An experiment was carried out to investigate the possibilitiesof accelerating seedling growth in three of the most importantforest tree species by increasing CO₂ concentration, daylengthand nutrition. Doubling the frequency of application of a standard liquid feedincreased plant height by 8–10 per cent but extendingthe daylength to 18 h had only a small initial effect whichwas not sustained. Increasing the CO₂ concentration significantly increased growthin both Sitka spruce and lodgepole pine but similar increaseswith Corsican pine were not statistically significant. The results indicated that under the conditions of the experimentthe tree height normally achieved after 16 weeks could be attainedin 14 to 15 weeks by increasing the CO₂ concentration fourfold.     

Grass and legume seeding on a scarified coastal alluvial site in northwestern British Columbia: response of native non-crop vegetation and planted Sitka spruce (Picea sitchensis (Bong.) Carr.) seedlings

The success of various grass-legume mixtures in controlling competing vegetation, and their effect on subsequent survival and growth of Sitka spruce seedlings was studied on a coastal alluvial site in northwestern British Columbia. Mechanically scarified (bladed) strips were hand seeded to pure and combined mixtures of legumes, bunchgrasses, and sodforming grasses. An unseeded control (bladed but not seeded) was also established.Alsike clover (Trifolium hybridum L.) was the most successful legume species. Orchardgrass (Dactylis glomerata L.), big bluegrass (Poa ampla Merr.), and creeping red fescue (Festuca rubra L.) were the most successful grass species. Red alder (Alnus rubra Bong.) density and height were lower in legume-seeded treatments. Red elderberry (Sambucus racemosa L.) and salmonberry (Rubus spectabilis Pursh.) were effectively reduced by blading and have reestablished slowly. A combination of blading and early establishment of either sodforming grasses or bunchgrasses effectively decreased reinvasion by thimbleberry (Rubus parviflorus Nutt.).Growth of Sitka spruce was best in the unseeded control treatment or in the treatments with legumes but no sodforming grasses. Presence of sodforming grasses decreased both diameter and height growth. Sitka spruce diameter decreased with increasing red alder density. After 5 growing seasons, spruce has outgrown all competitors except red alder.     

Growth and Wood Properties of Sitka Spruce (Picea sitchensis (Bong.) Carr.) in Nursing Mixtures Established on Nitrogen-deficient Mineral Soils

Rate of growth and wood properties of Sitka spruce (Picea sitchensis (Bong.) Carr.) were investigated in triplet mixtures with lodgepole pine (Pinus contorta Loud.) (Alaskan provenance) and Japanese larch (Larix kaempferi (Lamb.) Carr.), established on nitrogen-deficient, iron pan soils. These ?nursing? mixtures were compared with pure stands of Sitka spruce that had been either regularly or periodically fertilized with nitrogen. Japanese larch promoted a growth rate in Sitka spruce greater than that achieved in the lodgepole pine-nursed spruce and equivalent to the two pure spruce treatments over the duration of the experiment (current age 28 yrs). Growth of regularly fertilized pure Sitka spruce was not significantly greater than that of periodically fertilized pure spruce. Alaskan lodgepole pine controlled branch size on the lower part of the spruce stems more effectively than the other treatments, although this may have been a function of tree size. Branch characteristics of Japanese larch-nursed spruce, however, were similar to those of the pure spruce treatments. Japanese larch caused an imbalance in crown development in the spruce, although it is unclear from the present study whether this will have an influence on stem and wood quality by the end of the rotation. Overall, the evidence from this study suggests that Japanese larch is an effective nurse of Sitka spruce on nitrogen-deficient iron pans, maintaining a rate of growth similar to that of pure Sitka spruce periodically fertilized with nitrogen and higher than that observed in spruce nursed by Alaskan lodgepole pine.     

Tolerance of 2-year-old Forestry Trees to Five Herbicides

There is a need for selective foliar-acting herbicides for transplantlines in forestry nurseries and new forestry plantings. Toleranceof 2-year-old pot-grown trees of beech, birch, sycamore, ash,cherry, oak, red alder, Japanese larch and Sitka spruce to contactherbicides applied at different dates in the growing seasonwas investigated.Clopyralid was safe to use on all species apartfrom some fresh weight reduction in Japanese larch. Bentazoneand phenmedipham caused initial necrosis on most species tested;however, most trees outgrew the effect of phenmedipham in thefollowing season. Bentazone, generally, had a long-term inhibitoryeffect on growth of alder and at the highest dose tested (5.2kg ha^–1 ) also affected ash and beech.Metsulfuron-methyland tribenuron-methyl were safe on most species tested.However,fresh weight reductions were caused by metsulfuron-methyl inash and cherry and by tribenuron-methyl in alder. Mecoprop damagedall species, apart from Sitka spruce.     

Carbon pools and sequestration in forest ecosystems in Britain

British vegetation is estimated to contain 113.8 million tC,80 per cent of which is in forests and woodlands (91.9 milliontC). Sitka spruce plantations, although covering 21.4 per centof the forest/woodland area, contain only 8.2 per cent of theforest/woodland carbon, because the plantations are young andhave an average of only 14.1 tC ha^–1. Broadleaved woodlandsin Britain have an average of 61.9 tC ha^–1 and contain46.8 per cent of the total carbon in all vegetation. A breakdownis given of the carbon density (tC ha^–1) and content ofdifferent tree species. A carbon density map of Britain highlightsthe concentration of carbon in the broadleaved woodlands insouthern England and in the large conifer plantations in southernScotland and northern England. Carbon storage in the trees, products, litter and soil can beevaluated in terms of long-term equilibrium storage or short-termrate of storage. These two components vary among forest typesin Britain and globally. Plantations harvested at the time ofmaximum mean annual increment (MAI) will not store as much carbonas mature, old-growth forests on the same site unless they havelong-lasting products and/or are very fast growing. Maximumequilibrium carbon storage is generally achieved by harvestingat the time of maximum MAI when the lifetime of products exceedsthe time to maximum MAI. Undisturbed peatlands sequester CO₂and emit CH₄, and may be greenhouse neutral. When peatlandsare drained and planted with trees, they stop emitting CH₄ andstore carbon in the trees, forest litter, forest soil and woodproducts. However, these greenhouse gas ‘gains’are offset by the oxidation to CO₂ of the peat, and the gainsare exceeded by CO₂ losses when 20–40 cm depth of peathas been oxidized. Forests in Britain are currently sequestering1.5–1.7 million tC a^–1 in trees, 0.3–0.5 tCa^–1 in litter and 0.5 million tC a^–1 in wood products,totalling about 2.5 million tC, equivalent to about 1.5 percent of the carbon currently emitted by burning fossil fuelsin the UK. In order to maintain the current forest carbon sink,the forest area needs to continue to expand at about 25 000ha a^–1 of upland conifers or 10 000 ha a^–1 of poplarson good land.     

Effect of Desiccation on Water Status and Forest Performance of Bare-rooted Sitka Spruce and Douglas Fir Transplants

Sitka spruce transplants which had been exposed to drying conditionswere assessed for shoot water potential (), shoot moisture content(MC), water saturation deficit (WSD) and root moisture content(RMC) before forest planting. Exposure for 1 hour 44 minuteshad no effect on subsequent survival or growth, but exposurefor 3 hours 18 minutes reduced survival to 68 per cent aftertwo years and significantly reduced height growth. The damagedplants were clearly distinguished at the time of planting by and RMC but not by MC or WSD. After a range of desiccation treatments, survival was high inSitka spruce unless RMC had fallen below 180 per cent but survivalwas reduced in Douglas fir with smaller reductions in RMC or. During the desiccation treatment, Douglas fir started withand maintained a higher RMC than Sitka spruce and reached lowlevels of less rapidly. The poor performance of desiccatedDouglas fir was therefore not the result of an inability toconserve water. After rewetting for one hour in the dark RMC was restored butnot , and there was no significant effect on survival or growthin either species. It may be possible to devise a method to establish when plantsare in poor condition by direct or indirect measurement of RMC,but high levels of RMC can be misleading if rewetting has occurred. Handling systems which involve brief periods of exposure aretolerable for Sitka spruce but not for Douglas fir, and specialmeasures are justified to ensure that the latter species isnever subjected to root desiccation during handling.     

Effect of Air-filled Porosity and Organic Matter Concentration of Soil on Growth of Picea abies Seedlings after Transplanting

The effects of air-filled porosity (AFP) and organic matter concentration (OMC) of soil on the growth of Norway spruce [Picea abies (L.) Karst.] seedlings were studied in a greenhouse experiment. One-year-old seedlings were planted into 250 pots filled with five different growth media based on low-humified sphagnum peat and fine sand. The media were mixed to achieve five levels of OMC (1, 25, 50, 75 and 97% by mass). Five AFP levels (5, 10, 20, 30 and 40%) were applied to the mixtures of growth media during irrigation. The growth attributes of the seedlings were measured after seedlings had grown in the greenhouse for 15 weeks. The shoot height and mass growth as well as root mass were significantly higher in 20, 30 and 40% AFP than in 5 and 10% AFP (p<0.05). The longest shoots were produced in growth media with 25, 50 and 75% OMC (p<0.05). The effect of OMC on root mass, while significant (p=0.03), was less pronounced than the effect on height growth and mass of the shoots (p<0.001). The results indicate that, for good seedling growth in pots in greenhouse conditions, AFP should be 20-40% and OMC 25-75% in the growth medium.     

Effects of silicon-rich soil amendments on growth,mortality and bark feeding damage of Sitka spruce (Picea sitchensis) seedlings under field conditions

Alternative methods of protection are required against feeding by the large pine weevil (Hylobius abietis) on the bark of conifer seedlings. Silicon (Si) has been shown to enhance the resistance of plants to insect herbivores. This study investigated the effects of low doses of Si-rich soil amendments on growth, mortality and bark feeding damage of Sitka spruce (Picea sitchensis) seedlings. Two-year old seedlings were grown, individually, in soil taken from a tree nursery treated with coal ash, peat ash, rice husk ash, slag, sodium metasilicate or a commercially available Si fertiliser (Pro-Tekt) and planted out on two reforestation sites in Ireland. Seedlings grew well (about 20% growth in terms of height, 66% in root collar diameter, after two growing seasons), and Si-rich amendments did not have a significant effect on growth or mortality. Bark feeding damage on Si-treated seedlings did not vary significantly from control seedlings. Bark Si concentrations were not significantly larger in treated seedlings than in control seedlings, but control seedlings already had comparatively high bark Si concentrations (560?mg?kg^?1 dry tissue). In conclusion, Sitka spruce seedlings grown in the presence of Si-rich soil amendments prior to planting did not show greater resistance to weevil feeding under the present conditions.     

Erratum

The interaction of green spruce aphid and fertilizer applicationson the growth of Sitka spruce by R. C. Thomas and H. G. Miller,Forestry 67, 329–342, 1994.