The Interaction of Green Spruce Aphid and Fertilizer Applications on the Growth of Sitka Spruce

In an 11-year-old stand of Sitka spruce (Picea sitchensis [Bong.]Carr.) application of nitrogen fertilizers, at a rate of 10kgN ha^–1 month^–1, increased mean diameter incrementby 12 per cent, while the further addition of phosphorus, at5 kg ha^–1 month^–1, resulted in a 23 per cent increase.An attack by the green spruce aphid (Elatobium albietinum Walker)occurred during the period of fertilizer addition. The mostseverely affected trees showed a reduction in diameter growthof 50 to 56 per cent but the severity of the attack betweentrees was unrelated to the treatments applied. However, fertilizerapplication did hasten the recovery of diameter growth afterdefoliation.     

High Productivity in a Polestage Sitka Spruce Stand and its Relation to Canopy Structure

1. The net annual above ground dry matter production of a 17 yearplantation of Sitka spruce in Scotland was 26.7 t ha^–1y^–1.Total annual production which includes estimates for roots,was 35 t ha^–1y^–1, one of the highest values reportedfor coniferous forest in the temperate zone.
2. When comparedwith other forests with high rates of net productionthis standhad the highest foliage and branch biomass and lowestrate ofproduction per unit of foliage.
3. Gross foliage increment tothe canopy declined following thetime of maximum stand basalarea increment, which coincidedwith the onset of competitionbetween individual trees. Thesechanges in canopy and standstructure are discussed in relationto the decline in net productionwhich has been observed inpolestage conifer plantations.
4. Foliageand branch production were greatest in the top 6 whorlsof thecanopy; over the period studied new foliage became concentratednearer to the top of the trees. Significant branch wood incrementceased below the height where needle death balances needle production.
5. New needles produced at increasing depth in a canopy weighedless per unit needle area. Generally needles lost weight asthey aged. All needles survived for three years, the greatestmortality was of 5-year-old needles but some survived for 8years.
6. Needle area index was 10–11 at age 16, 7–8at age18. Branch area index was 3.6 and the ratio of main stembarksurface area to ground area was 0.4 at age 16.

     

Nutrient Changes in Peaty Gley Soils after Clearfelling of Sitka Spruce Stands

The roots of second-rotation Sitka spruce (Picea sitchensis(Bong.) Carr.) planted on peaty gley sites are restricted tothe old litter (LFH) layer and are dependent on its decompositionfor availability of nutrients. A series of these sites of increasingage from felling were sampled to estimate changes in the nutrientcapital of the LFH horizon over time at Kielder Forest, Northumberland.Previous stand histories were reconstructed from stump data.Geographical, climatic, soil and mensurational data suggestedthat the use of a time series was justified. Nutrient capital in the LFH horizon generally declined overa 5 year period after clearfelling from approximately 997, 51and 83 kg ha^–1 to 676, 30 and 31 kg ha^–1 of N, Pand K, respectively. However, N concentration increased overa 5 year period from 11 mg g^–1 to 14 mg g^–1, P concentrationremained constant at about 0.6 mg g^–1, and K concentrationdecreased from 1.0 mg g^–1 to 0.7 mg g^–1. Nutrientconcentrations and contents of the LFH horizon were higher underthe brash (slash) swathes that resulted from the use of organizedfelling techniques than under clear strips devoid of brash. The patterned input of nutrient capital in brash as a resultof organized felling was also determined. Brash containing 219,20 and 71 kg ha^–1 of N, Pand K, respectively, was systematicallydistributed at a rate of 491 ha^–1 over 66 per cent ofthe site after harvesting. The needles and small branch fractionscontained 71 per cent of the N and 80 per cent of the P andK present in the brash.     

Treatment of Severely Checked Sitka Spruce Trees with Injected Nutrients

Matched pairs of nutrient deficient Sitka spruce (Picea sitchensis(Bong.) Carr.) of mean height 3.0 m on a drained acid infertiledeep peat were injected in early summer by infusion with anaqueous solution of 40, 20, 66 and 0.2 g l^–1 N, P, K,Mg respectively, pH 7.2 and high conductivity. Three growingseasons later there were no responses in injected trees in treeheight increment, foliage nutrient levels of N, P, K, Ca, needlecolour, needle weight or crown density. Foliage Mg levels wereraised significantly. The injection procedure caused severetissue damage around the Infusion point and 84 per cent of thetrees had stain in stem cross sections 50 cm above the treatmentlocation.     

History of Peridermium Stem Rust of Scots Pine (Pinus sylvestris L.) in Thetford Forest, East Anglia

‘Peridermium’ stem rust (Peridermium pini (Pers.)Lev.) has been present in Thetford forest for at least 40 years,but has only become a major problem during the last decade.Survey data are presented which show that there has been a dramaticincrease in the disease in crops of Scots pine between 1964,when with less than one per cent of the trees showed symptoms,and 1979, when the figure was 10 per cent. The disease has apparentlyspread outwards from a central focus in the middle of the forest.In four plots the proportion of trees with visible symptomshas increased in five years from an average of 28 per cent to46 per cent. However, only 1–2 per cent of the trees havedied annually, and it appears that many trees with ‘deadtops’ may survive for long periods. The situation in Thetfordseems to contrast with that in north-east Scotland, where limiteddata suggest there has been no appreciable increase in diseaseincidence during recent years. There are only two records ofthe disease on Corsican pine (P. nigra var. maritima (Ait.)Melville) in Thetford.     

Leader Browsing by Red and Roe Deer on Young Sitka Spruce Trees in Western Scotland. II. Effects on Growth and Tree Form

Some 2000 trees at 14 main sites in Glenbranter Forest, Argyll,were monitored during 1978–1990 for damage. Tree state(whether leaderless or with single or multiple leaders or trunks)and tree size were regularly recorded. Browsing of leaders depressed height increment by 5–10cm in the year of ocurrence compared with undamaged trees; therapid development of new leaders minimized the check in growth.Trees initially leaderless had equal height increment over ayear to trees initially with leaders if no damage occurred inthe year. At a subsidiary site where some trees were planted in smallexclosures, the trees protected from deer reached a safe heightafter five seasons of growth, unprotected trees reaching equalheight 1 year later. The girths attained when trees were 10–15 years old wereon average only slightly depressed by earlier browsing damageto leaders, reductions at most equalling one year's increment. Many trees became multi-trunked, there being a significant relationshipbetween the percentage incidence of multi-trunking and the numberof occurrences of leader damage. Unbrowsed trees mostly becamesingle-trunked. We judge that the present high incidence ofmulti-trunking (45 per cent in our 9–15 year-old stands)results largely from deer browsing.     

Forest condition in Tuscany (Central Italy). Field surveys 1987-1991

Between 1987 and 1991 four surveys on the condition of forestsin Tuscany (Central Italy) were carried out. The results, relatingto 2275 trees in 111 sampling plots, show that the overall percentageof damaged trees (defined by the EC regulation 1696/87) increasedbetween 1987–88 (51.4±5.4 per cent; 54.0±5.6per cent) and 1990–91 (67.0±6.2 per cent; 64.0±6.1per cent). The percentage of moderately and severely damagedtrees also displayed an upward trend. The most severely affectedspecies appeared to be Pinus pinea (a Mediterranean conifer,96.7 per cent damaged trees) and Fagus sylvatica (a mountainbroadleaf, 87.1 per cent damaged trees). Crown condition appearedto deteriorate with decreases in mean annual rainfall and wherestand conditions are poor (thin soil, steep slopes). The findingssuggest the possibility of an interaction between several differentstress factors, some of which seem to be linked to local andstand conditions (exposure, silviculture, soil fertility), whileothers seem to be connected with long-term variations, suchas changes in environmental parameters like precipitation. Theactual role of background and/or local pollution can be neitherdemonstrated nor excluded on the basis of the present results.     

The Influence of Early Respacing on the Wood Density of Sitka Spruce

Wood density at breast height in a 32-year-old Sitka sprucerespacing experiment in Northern Ireland ranged from 0.42 gcm^–3 in the narrowest spacing to 0.38 g cm^–3 inthe widest. Estimation of variance components showed that only12 per cent of the variation in wood density could be ascribedto crop spacing and 63 per cent to the differences between treeswithin spacings. Regressions of wood density on the basal areafor each spacing indicated extremely weak relationships, thehighest r² not exceeding 0.25. It is concluded that the possibilitiesof manipulating wood density through spacing and thinning areinsignificant in comparison to the potential from breeding orvegetatively propagating trees with desirable characteristics.     

The Amount and Nutrient Content of Litter Fall under Sitka Spruce on Poorly Drained Soils

Litter fall was collected every three months for four yearsfrom twenty-one vigorous (Yield Class 18–20 m³ ha^–1y^–1) and sixteen less vigorous (Yield Class 10–12)plots of Sitka spruce on gleyed soils in Northern Ireland. Forty-fourper cent of all litter fell in the June-August quarter, andlitter fall was heaviest in years when there was green spruceaphis attack. Beneath YC 10–12 crops, both rate and quantityof litter fall was less and nutrient concentrations were lower,than under YC 18–20 crops. As the pool of organic matterand nutrients on the forest floor was greater under trees ofYC 10–12, poor growth was associated with a slow organicmatter and nutrient turnover.     

Report of a Twelve-year study of Litter Fall and Productivity in a Stand of Mature Scots pine

Litter collections were made in a Scots pine (Pinus sylvestrisL. ) plantation between its first major thinning at 40 years(effectively 35 years because of early stagnation) and its secondthinning at 52 years. The response to thinning was immediatewith no lag phase. Needle production peaked in the third growingseason and remained more or less constant thereafter. Needlebiomass peaked in the eighth year (10. 3 tonnes per hectare)after a year in which the retention of third year needles hadbeen greater than usual. Cone production reached its first maximumin the fourth year, its second in the sixth year, but, thereafter,changed to a three-year cycle: it is suggested that the dipin overall productivity in the sixth and ninth years led tofewer flower bud initials being laid down in those years. Priorityin resource allocation seems to have gone to cone production,once set in train, and then to needle production which stayedup in 1977 (the sixth year) but fell in 1980. Production of litter items was 20 per cent greater than litterfall over the first four years (range –minus; 0. 3% to+plus; 28. 3%) and 0. 4 per cent greater over the last eightyears (range – 14. 5% to +plus; 12. 2%). The differenceswere due in the main to the two-year delay between productionand fall of needles and the one-year delay for cones. However,the differences were not predictable because of greater third-yearneedle retention in certain years and the variable proportionof cones dismantled by squirrels and falling as fragments inthe year of their production.     

Changes in Amount and Distribution of Stem Growth in Pole-Stage Corsican Pine Following Application of Nitrogen Fertilizer

Ring-width measurements on trees felled in a nitrogen-deficientpole-stage crop of Corsican pine on the sand dunes of Culbinforest (Morayshire) showed that, in addition to a growth checkascribed to the low nitrogen content of the soil, there wasevidence for decreasing site quality, tree growth decliningprogressively with time. This feature is ascribed to the continuingimmobilization of the limited nitrogen capital in the newlydeveloping mor humus layer. Ammonium sulphate, at rates equivalentto 84, 168, 336, and 504 kg elemental nitrogen ha^–1, wasapplied to this crop when it was 36 years old, and the treatmentsrepeated for a further 2 years. Nitrogen levels in the foliagerose from 0.9 per cent to as high as 20 per cent in the firstyear, increasing to 2.6 per cent after the third year of application.Response in terms of basal area appeared in the year after firstapplication but was not accompanied by any changes in the patternof growth throughout the season, nor was there a significanteffect of tree size on the proportional change in relative basalarea growth induced by the fertilizer, except for a slightlyreduced response by the smallest trees to the lower rates ofapplication. A similar low response by the smallest trees wasfound for height, but, in addition, height growth after treatmentwas greatest for the middle-sized trees, despite the fact thatthese had been growing significantly more slowly than the largesttrees prior to application of the fertilizer. Form factor remainedunaltered by the treatments but taper changed slightly. Heightand basal area showed very different response patterns to thetreatments. Thus, whereas maximum height growth occurred atthe 168 kg N ha^–1 treatment rate (2.41 m over 7 years,1.4 times the control growth) maximum basal area growth occurredat the 504 kg N ha^–1 rate, the highest rate used (13.0m² ha^–1 over seven years, 2.4 times the control growth);volume growth was maximum at the 336 kg N ha^–1 rate (126m³ ha^–1 over 7 years, 2.6 times the control growth). Whenrelated to levels of foliar nitrogen in the previous year, annualheight growth was maximum at 1.6 per cent with maximum basalarea growth occurring nearer 2.2 per cent. It is estimated thatvolume growth would be maximised at just over 20 per cent nitrogen.     

Impregnation of Norway spruce (Picea abies L. Karst.) wood by hydrophobic oil and dispersion patterns in different tissues

Wood from Norway spruce (Picea abies L. Karst.) is biologicallydegraded in exposed conditions. It also has anatomical featuresthat make it difficult to impregnate with preservatives by currentlyavailable industrial processes. In the study reported here,we used the new Linotech process to impregnate Norway sprucewood with hydrophobic linseed oil and then quantified its uptakeand dispersal in anatomically distinct wood tissues. We alsoinvestigated the effects of the wood moisture content on theresults of the impregnation. Samples (500 x 25 x 25 mm) weretaken from 15 trees in a coniferous forest in northern Sweden(64° 10' N, 160–320 m a.s.l.). The parameters forthe Linotech process were 2–3 h treatment time at 0.8–1.4MPa and 60–140°C. To determine the level of uptake,the linseed oil was extracted from the impregnated wood usingmethyl-tertiary-butyl-ether. The uptake was quantitatively analysedby comparing X-ray microdensitometry values obtained followingimpregnation both before and after oil removal. In earlywood,initial moisture content had an obvious effect on the impregnationresult. Six times more oil was taken up when the moisture contentwas greater than ~150 per cent than when it was less than 30per cent. Theoretical calculations, based on density levels,suggest that the water-filled porosity of the wood (water volumedivided by porosity volume) was positively correlated with thelinseed oil uptake, and more strongly correlated in earlywoodthan in latewood. There were also significant differences inuptake between different wood tissues; heartwood/mature woodand heartwood/juvenile wood showed 10–20 per cent weightincreases due to linseed oil uptake, compared with 30–50per cent in sapwood/mature wood. Examination by scanning electronmicroscopy confirmed these uptake patterns. The moisture contentafter impregnation was about 5 per cent, irrespective of theLinotech process parameters, tissue type and initial moisturecontent. In conclusion, the impregnation process used here resultsin high levels of well-dispersed linseed oil uptake and shouldfacilitate drying.     

Physiological Effects of Natural and Artificial Defoliation on the Growth of Young Crops of Lodgepole Pine

Field experiments involving naturally occurring population levelsof larval European pine sawfly Neodiprion sertifer (Geoff. )and artificial defoliation in both field and glasshouse experimentswere used to investigate physiological effects of defoliationon lodgepole pine. Reductions in total projected leaf area,annual height and volume increments of 19, 33 and 32 per cent,respectively, were recorded on trees where larvae had consumedall mature foliage. Leader growth was up to 48 per cent lesson defoliated trees after two years reflecting a delayed growthimpact. Similar effects were found on trees which had been defoliatedby hand in a manner resembling sawfly feeding. Artificial defoliationof transplants also showed that this type of damage can haveserious consequences on below-ground growth, particularly offine roots. Root:shoot ratios were found to be 0.64 in undamagedplants and 1. 05 in defoliated plants. A high concentration(1300 ppm) of the insecticide fenitrothion, used to maintaincontrol treatments in the field, was found to have no significanteffects on the major growth parameters being assessed.     

Bark Stripping Damage by Red Deer in a Sitka Spruce Forest in Western Scotland: II. Wound Size and Position

Wounds to bark were measured within a few months of being inflictedby red deer in Glenbranter Forest, Argyll. About 8000 treeson 240 permanent plots were monitored; all the wounds occurringover a period of seven years were examined. Wound length varied little between forest stages, averaging12 cm. Wound breadth was greater on older trees, averaging 5cm in Sitka spruce and 6 cm in Norway spruce for the pole andhigh-canopy^* forest stages. A few wounds were large, maximumlengths being 95 and 80 cm in Sitka spruce and Norway sprucerespectively, but less than 20 per cent of the Sitka sprucewounds exceeded 100 cm² in surface area. Seasonal variationin size was modest; wounds were longest in spring (April–June). Often a single tree received two or more wounds during the 3-or6-month-long observation periods. For Sitka spruce there were89 instances of multiple wounding and 142 of single wounding,but these single wounds contributed only 37 per cent of thetotal of 383 wounds observed. The area of trunk wounded wasmore dependent on the size of the largest wound than on woundnumber, multiple wounds often being small. Trunks received most damage between 50 and 100 cm above ground,the lower and upper limits of wounding being 2 and 150 cm. Thepeaking in the incidence of damage with regard to height wasmost marked in pole-stage forest, whereas wounds were spreadmore evenly up the trunks on younger trees. Wound height waslittle affected by season, mean basal heights being 68, 70,74 and 67 cm in winter, spring, summer and autumn. Woundingon the trunk was not correlated with aspect.     

Shading Reduces both Visible and Invisible Frost Damage to Norway Spruce Seedlings in the Field

Two-year-old cuttings of Norway spruce were subjected to nightfrosts in spring on an exposed site in southern Sweden. Shadingwas used to assess the influence of sunlight on the extent ofdamage resulting from night frost. Chlorophyll fluorescencewas measured in needles in flushing shoots, and in shoots atthe stage of bud burst. The F_v:F_m ratio was significantly lowerfor plants exposed to light, compared with shaded plants onthe days following the night frost (minimum temperature –6°C).The effect was similar both in 1-year-old and current year needles.The low F_v:F_m ratios indicate damage to photosystem H, causedby an interaction between sub freezing temperatures and highlight intensity. Shading also increased the survival of flushingshoots. It is suggested that regeneration of Norway spruce onsites exposed to frost should be carried out in partial shade,for example under a shelterwood.     

Carbon storage and sequestration in the forests of Northern Ireland

The rate of accumulation of carbon in forests and woodlandsin Northern Ireland was estimated using the record of forestplanting since 1900 and a model that calculated the flow ofcarbon from the atmosphere to trees, litter, soil, wood productsand back to the atmosphere. It was assumed that all coniferforests had the carbon accumulation characteristics of Piceasitchensis, and upper and lower estimates of carbon storagewere calculated assuming Yield Class 16 m³ha^–1 a^–1unthinned and Yield Class 14 m³ ha^–1 a^–1 thinned.Broadleaved woodlands were assume to have the carbon accumulationcharacteristics of Fagus sylvatica, Yield Class 6 m³ha^–1a^–1. Northern Ireland currently has about 78 300 ha offorest, 83 per cent of which is coniferous, 77 per cent state-owned,mostly planted since 1945, with peak planting in 1960–1975.In 1990, conifer forests contained 3–4 MtC (trees + litter)and broadleaved wdlands contained about 0.8 MtC (trees + litter+ new forest soil). In 1990, conifer forests were sequestering0.15–0.20 MtC a^–1 and broadleaved woodlands about0.025 MtC a^–1. To maintain these sink sizes, new coniferforests need to be planted at 1500–2000 ha a^–1,and new broadleaved woodland at100–150 ha a^–1 inaddition to full restocking. Current carbon sequestration byNorthern Ireland forests represents around 6.5–8.2 percent of the total for UK forests and is greater per hectar thanin Britain because the average forest age is younger in NorthernIreland     

Effects of Refertilization on Growth and Nutrition of Lodgepole Pine (Pinus contorta Dougl.) Planted on a Minerotrophic Peatland in Central Newfoundland, Canada

A plantation of lodgepole pine (Pinus contorta Dougl.), whichwas established in 1973 on a ditched minerotrophic fen at plantingspacings of 1.2 m, 1.8 m, and 2.4 m, was refertilized in 1985with control, P, PK and NPK treatments consisting of 60 kg ha^–1phosphorus, 100 kg ha^–1 potassium and 200 kg ha^–1nitrogen. Although each seedling had been spot-fertilized in1973 with a mixture of 71 g urea, 99 g ground rock phosphateand 41 g potassium sulphate, height and needle nutrient assessmentsof the plantation in 1984 indicated poor growth, low concentrationsof needle nitrogen (1.26 per cent) and possible deficiency levelsof needle phosphorus (0.10 per cent) and potassium (0.36 percent). Between 1985 and 1991, height and diameter growth increasedsignificantly in all refertilization treatments. Growth responsewas greatest in the PK treatment and least in the P treatment.Needle weights, determined from 1987 to 1991, did not responduniformly to any of the refertilization treatments. Needle concentrationsof phosphorus increased to levels between 0.20 per cent and0.23 per cent following refertilization with P, PK, and NPK,but by 1988 had decreased to about 0.14 per cent. Needle concentrationsof potassium also increased sharply to 0.60 per cent in 1985following refertilization with PK and NPK, but by 1988 had decreasedto levels between 0.35 per cent and 0.45 per cent. Similarly,needle nitrogen concentrations increased to 1.84 per cent in1985 following refertilization with NPK, then decreased to levelsbetween 1.20 per cent and 1.33 per cent in 1986 and remainedat those levels each year thereafter. Although needle nutrientlevels fell sharply following an initial peak after refertilization,height and diameter growth did not decrease significantly, especiallyin the PK treatment, suggesting that nutrient levels remainedadequate for optimum growth.     

Characteristics of lowland broadleaved woodland being restocked by natural regeneration

A survey of 78 sites in southern England with approved managementplans for restocking by natural regeneration was made duringthe summers of 1993 and 1994. The following features were recorded:species, stocking, canopy cover and seed-bearing potential oftrees present in the overstorey; species and canopy cover ofthe understorey; ground cover; species, browsing damage, numberand heights of tree seedlings. In general, sites were poorlystocked with overstorey trees having an average of 135 stemsha^–1 and a mean canopy cover of 36 per cent. Similarly,the understoreys were poorly developed with an average coverof only 23 per cent. Twenty-nine species of tree were foundin the overstorey, Quercus spp. and Fraxinus excelsior werethe most common. Many of the stems present had poor seed-bearingpotential. Cover of the ground flora often exceeded 75 per cent.Seedlings were present on most sites, with F. excelsior andBetula pendula being most abundant with mean seedling densitiesexceeding 10000 ha^–1. Most seedlings were >20 cm tall,few exceeded 120 cm. About 30 per cent of seedlings were browsed.The results are related to current guidance and the future prospectsfor use of natural regeneration.     

An Analysis of Peridermium Stem Rust of Scots Pine in Thetford Forest in 1984 and 1985

The status of stem rust (Peridermium pini or (Pers.) Lev.) inScots pine (Pinus sylvestris L.) in the central block of Thetfordforest, East Anglia was determined by means of detailed analysisof freshly felled trees. A total of 935 trees was examined,these comprising c. 100 from each of nine compartments plantedbetween 1922 and 1933. Lesions in all stages of development were found; from thosein their first year of sporulation on young twigs to those whichhad been established for many years on the trunk and main branches.Death of cambium occurred typically on lesions on shoots thatwere more than five years of age. Downward growth of the funguswas estimated to average between 4.7 and 5.6 cm per year, whenbased on the length of sporulating tissue on young twigs, and6.3 cm per year when based on cambial killing in trunk lesions.The average rate of circumferential killing of trunk lesionsaveraged 4.3 crn per year (i.e. 2.2 cm in each direction). Therewas no evidence that wounds provided a significant infectioncourt. A strong association was found between the presence of the ‘purplemould’ (Tuberculina maxima) and an absence of sporulationby the rust fungus. However, there was no evidence for lesioninactivation by T. maxima. Data are presented on the distribution of disease between sitesand between trees. Five per cent of the total sample of treeswere dead and an additional 12 per cent had crown symptoms associatedwith girdling trunk lesions. Among the 775 trees with predominantlyhealthy crowns, it is estimated that 9 per cent would have diedwithin 5 years, 15 per cent within 10 years and 22 per centwithin 20 years. By contrast 66 per cent had no disease at all,probably for genetic reasons. It is concluded that, althoughthe disease situation is serious, there is no requirement fora major change to be made in the felling programme for the pre-warScots pine in Thetford.     

Overstorey density influence on the height of Picea abies regeneration in northern Sweden

The study aimed specifically at investigating if canopy opennesswas a better predictor of the height growth of Norway spruce(Picea abies (L.) Karst.) advance regeneration than overstoreybasal area or overstorey standing volume. In 1990, a field experimentwith 3 x 2 factorial design and two replications (blocks) wasestablished in an uneven-aged Norway spruce forest. Plots hada net plot area of 30 x 30 m, each with a 10-m-wide treatedbuffer zone. Three overstorey density levels retained approximately15, 40 and 70 per cent of the pre-harvest overstorey standingvolume and were allotted to the plots. Two types of thinningthat harvested smaller trees or harvested larger trees wererandomly allocated to each pair of overstorey density plots.In mid-June 2000, canopy openness was estimated from hemisphericalphotographs taken at five marked points in the centre of eachof the plots at 0.9 m from ground to the top of the ‘fish-eye’camera lens. Regression results showed that canopy opennesswas a better predictor of height increments of spruce seedlings(0.1< height < 0.5 m), saplings (0.5 height < 2.0m), and small trees (height 2.0 m, diameter at 1.3 m height< 5 cm) than with overstorey basal area (m² ha^–1) oroverstorey standing volume (m³ ha^–1). The height incrementof the spruce advance regeneration was not significantly correlatedto stand basal area or to standing volume. Overstorey basalarea in the net plots was significantly negative (P 0.05) withmean canopy openness estimates, and the r² value was 0.40. Resultsindicated that basal area was not linearly related to canopyopenness as it increased, which might explain the lack of predictivepower of retained basal area on spruce regeneration height indense stands in boreal Sweden.