Influence of Site Factors on the Response of Sitka Spruce to Fertilizer at Planting in Upland Britain

Data from Forestry Commission fertilizer experiments were analysedto determine the influence of site factors on the growth responseof Sitka spruce (Picea sitchensis (Bong.) Carr.) following applicationsof phosphate and potassium at time of planting. Multiple regressionanalysis revealed that growth response was influenced by soiltype and was related to the foliar nutrient levels of untreatedcontrols. Growth response to application of phosphate was alsoinfluenced by lithology. No relationships were found betweengrowth response and elevation or annual rainfall. Received 29 January 1990.     

Growth Models for Unthinned Stands of Sitka Spruce in Northern Ireland

A model for the net basal area growth of unthinned Sitka spruceis presented in this paper. Additional models express volumeand number of stems as functions of basal area. All models arefound to provide satisfactory fits to the data. It is shownhow such models may be used in the narrow sense of generatingyield tables but in fact possess several advantages over traditionalyield tables.     

The Growth of Sitka Spruce on Poorly Drained Soils in Northern Ireland

A soil survey of Lisnaskea Forest, Co. Fermanagh, showed thatgrowth of Sitka spruce was far from uniform on areas of apparentlyuniform soil. The relation between soil factors, tree growth,and foliar nutrient status on two blocks of trees growing ongleyed soils was therefore studied. Simple regression showed that tree growth was poor when thelevels of foliar nutrients were low and when there was a matof undecomposed needles on the forest floor. It is thereforeconsidered that lack of organic matter breakdown in the soilis causing poor tree nutrition and growth. Multivariate statistical analysis also showed highly significantregressions between tree growth, level of foliar nutrients,and depth of litter layer. The correlations between soil factorsalone and tree growth were barely significant and the multivariatetechnique did not give an acceptable method of predicting treegrowth from soil measurements. Methods of improving soil conditions are discussed.     

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.

     

Comparative Performance of Containerised and Bare-root Sitka Spruce and Lodgepole Pine Seedlings in Upland Britain

Seedlings of Sitka spruce and Lodgepole pine were grown in fivedifferent container types; Ontario tubes, Kopparfors multipots,Finn peat pots, Japanese paperpots and Spencer-Lemaire root-trainers.They were planted in forest experiments in 1972/3 when 8-14weeks old and their subsequent performance compared with 2 years-oldbare-rooted transplants. After 2–3 years' growth, tubed seedlings proved consistentlypoorer than all other treatments for both height and survival.Finn peat pots were marginally the best of the other containerstested. Containerised plants generally showed poorer survivaland substantially less height growth than transplants, withdifferences being greater for Sitka spruce than for Lodgepolepine. For both species well-handled transplants appear the mostappropriate plant type for use in upland Britain. Implications for the future role of containerised seedlingsin upland forestry in Britain are considered. The benefits ofcontainer systems may be greatest in the production of seedlingsof ‘sensitive’ species or of high genetic quality.     

Some Ring-width Patterns in Sitka Spruce Timber from North America

Variations in ring-width pattern of Sitka spruce (Picea sitchensisCarr.) through most of its life in its natural habitat are demonstratedfrom photographs of ten crosssections. It is suggested thatin addition to the annual fluctuations in ring-width due toclimatic variation, the tree in the natural forest is subjectto periodic suppression and release and that it has considerablepowers of recovery; in plantations, therefore, Sitka spruceshould respond to thinnings made even late in the rotation.     

Some Effects of Soil Water Tables on the Growth of Sitka Spruce in Northern Ireland

Soil water tables and the rooting depth of trees were studiedin two areas of gleyed soils in Lisnaskea Forest, Co. Fermanagh,where growth of Sitka spruce is far from uniform. On both areas,poor tree growth is associated with high water tables and shallowrooting. Soils under good trees had a sandy-tertured horizonassociated with rotten rock fragments. This horizon could improvedrainage conditions and must have been present before planting.It is therefore considered that high soil water tables are acause rather than a consequence of poor tree growth.     

Response of Pole-stage Sitka Spruce to Applications of Fertilizer Nitrogen, Phosphorus and Potassium in Upland Britain

Although there are many reports of growth responses to fertilizerN, P or K in young stands, and to fertilizer N in old stands,there are relatively few reported responses in pole-stage ormiddle-aged stands. Among reasons for this may be lack of experimentalinterest in stands of this age or a relatively scarce occurrenceof a need for additional fertilizer inputs at a time when nutrientcycling, both within the tree and through the litter layer,is very efficient. To explore this, fertilizers were appliedto six stands of spruce, aged 25 or 30 years, in contrastingregions of Scotland and North England. In four experiments nogrowth response was recorded, either to a single dressing ofup to 400 kg N ha^–1, 200 kg P ha^–1 or 300 kg K ha^–1,or various combinations of levels of these elements, or to subsequentheavier applications. In a further experiment on peat therewas a weak response to P. In the remaining experiment a short-termresponse to PK was recorded but it is suggested that this wasdue to transient nutrient stress as the trees recovered fromthinning. The pattern of responses, other than the last mentioned,accorded with predictions based on foliar analysis. Taken togetherthese results seem to confirm the supposition that efficientnutrient cycling in middle-aged stands means that fertilizerresponses are unlikely (but not impossible) at this stage.     

The Development of Stain in Wounded Sitka Spruce Stems

In order to investigate the severity of staining in woundedSitka spruce stems, the vertical extent of two categories ofstain (based on colour and termed ‘light’ and ‘heavy’)was measured in stems at two sites in south Scotland. Data wereobtained from 98 wounds most of which were between 8 and 14years old and most of which had been caused by Red deer. Theupward extent of stain and its rate of upward spread were positivelycorrelated with wound surface area and length. Most stain wasof the light type which, although it was associated with nearlyall wounds, usually constituted an insignificant defect anddid not commonly extend for more than 1 m ahve wounds. Heavystain occurred above less than half of all wounds studied butwas common above wounds exceeding 300 cm² surface area. Forall wounds, the mean value for the upward extent of heavy stainwas 16.1 cm with a mean rate of spread of 1.9 cm y^–1.However, for wounds exceeding 300 cm² surface area, the valueswere 51.7 cm and 5.5 cm y^–1. These results suggest that,although there is an important effect of wound size on the typeand extent of stain, wounds of the type studied are unlikelyto lead to severe stain and decay in Sitka spruce over a periodof 8–14 years. The results are discussed in relation toother studies on wound staining in conifers.     

Morphology of the Structural Root System of Sitka Spruce 2. Computer Simulation of Rooting Patterns

In a previous paper (Henderson et al. 1983), it was suggestedthat the processes of root growth and development proceed witha geometric regularity and that, as a consequence, root distributionis further extended and spatially more even than if growth wereat random. We examine this hypothesis and the relative importanceof the component growth processes through computer simulationof a model for root distribution at a fixed time. Root segments were measured on 16 year trees and statisticaldistributions fitted to the occurrence of lengths, branchingfrequencies and growth directions. These distributions comprisethe model which assumes that a root system consists of a numberof first-order roots originating at the stem, a number of second-orderroots originating on first-order ones and so on. Each root includesa number of bends and lateral branching points and terminatesin either a fork or when diameter reaches 5 mm, smaller rootsnot being included. Parameter manipulation of the fitted distributions and furthersimulation showed that some regular growth mechanisms were necessaryfor the simulation of realistic rooting patterns. In particularit was important that direction changes at bends and of newroots at forks were typically small to ensure that the systemspread outwards, away from the stem. Lateral branches neededto subtend large angles to their parents in order to exploitseparate soil regions. Other necessary rules were that first-orderroots were almost regularly distributed around the stem andfor a tendency for azimuth changes at bends to be alternatelyclockwise then anticlockwise. Simulations were also used to examine the possibility of estimatingtotal root length from a study of only part of a root system.An example of excavating one quarter of the system is consideredand the results indicate that root systems may be so variablethat no reliable estimate can be obtained.     

Nitrogen Transformations and Decomposition in Litter and Humus from beneath Closed-Canopy Sitka Spruce

Samples of litter and humus from beneath 10 m tall, closed-canopySitka spruce planted on a brown forest soil were incubated underboth field and laboratory conditions to measure mineral nitrogenproduction and carbon dioxide evolution. Mineral nitrogen productionin enclosed samples over 12 months was equivalent to 50 and17 kg N ha^–1 in litter and humus, respectively. Applicationsof fertilizer NPK (200 kg N ha^–1 as ammonium nitrate,100 kg P ha^–1 as unground rock phosphate and 150 kg Kha^–1 as potassium chloride), 18 months previously, decreasedthese values slightly, but stimulated the production of nitratein both litter and humus. Compared with samples kept under laboratoryconditions at 10°C, those incubated in the field at a similarmean temperature released less carbon dioxide and, in the caseof fertilized humus produced smaller amounts of mineral nitrogen.     

Development of the Structural Root System of Sitka Spruce

Growth ring analysis was carried out on root systems of Sitkaspruce trees which had been planted 8 and 34 years previously.Retrospective measurements were made on root extension, andon cross-sectional area increment near the root base. The extensionof main lateral roots started slowly, then increased, and theyachieved a mean length of 4.4 m in 8 years. Differentiationinto roots of widely different radial growth rates took placeduring the first 6 years, resulting in 3 to 11 ‘major’woody roots and a large number of small ‘minor’ones, with some of intermediate vigour, radiating from the stump.The major roots established during the first few years constitutedthe main structural root system at 34 years. Many of the minorroots stopped growing in diameter after a few years, but werestill alive and extending at 34 years. The differentiation intomajor and minor roots is discussed with reference to their originon the root system, primary xylem diameter and the local environment.     

Effects of Mounds and Stumps on the Root Architecture of Sitka Spruce on a Peaty Gley Restocking Site

Root systems from Sitka spruce trees planted at stump, awayfrom stumps and on mounds were extracted from a restocking site14 years after planting. Compass direction and diameter of allmain roots were measured and the position of the centre of diameter,a concept analogous to the centre of mass, was calculated. Themagnitude and direction of the centre of diameter from the stemcentre were used in the statistical analysis of root systemsymmetry. The presence of a stump close to the planting positionprevented the development of a uniform root system and causedconsiderable clustering of roots away from the stump. Root systemsof trees planted away from old stumps or on mounds were moreuniform, although there was enhanced root growth in the directionof the mound centre for those trees planted on the side of themound. The implications for tree stability are discussed andalternatives to planting close to stumps are suggested. Received 3 September 1990.     

Soil Solution Chemistry and Throughfall Under Adjacent Stands of Japanese Larch and Sitka Spruce at Three Contrasting Locations in Britain

Soil solution and throughfall chemistry were investigated inadjacent stands of Japanese larch and Sitka spruce at threesites in Britain. Throughfall was collected in open funnel collectorsand soil solution was collected using tensionless tray lysimetersat the base of the H horizon and ceramic cup suction samplersat the base of the B horizon. Sampling took place fortnightlyfor 14 months and samples were analysed for the major ions anddissolved organic carbon. Most ions were present in higher concentrationsunder spruce than larch. Most notably under the spruce at allsites SO₄ in throughfall and NO₃ Ca and Al in the B horizonwere present in greater concentrations. However there were notrends in fortnightly concentrations of any ion, associatedwith the presence and absence of needles on the larch. Whensolutes are expressed as fluxes the only consistent effect ofspecies on the B horizon is higher quantities of NO₃ and NH₄under spruce. The study suggests that in areas exposed to atmosphericpollution, thinned stands of larch could have a beneficial rolerelative to Sitka spruce, in the maintenance of low acidityand aluminium concentrations in drainage water.     

Needle Damage in Sitka Spruce Caused by Early Autumn Frosts

Autumn frosts preceded by warm weather cause distinctive needlebrowning symptoms on young Sitka spruce trees which have completedshoot elongation. Damage is invariably confined to needles ofthe current year and typically consists of pink or reddish-brownpatches in the centres of needles. Needles clustered aroundthe apical buds are usually unaffected but in extreme casesall current year's needles may be entirely reddish-brown. Thesesymptoms were reproduced on young plants by experimentally freezingthem in a programmed chamber. Widespread damage was observed in the field in October 1971,September 1972 and September 1979 and assessments of field trialsshowed that damage was most severe on southerly provenancesand on trees deficient in phosphorus.     

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.     

The Effects of Nitrogen Fertiliser at Different Rates and Times of Application on the Growth of Sitka Spruce in Upland Britain

At seven experiment sites in Scotland and northern England theeffects of different rates (0 to 150 kg N ha^–1) and seasonof nitrogen (N) fertiliser application on the height growthof Sitka spruce were examined. A comparison of urea and ammoniumnitrate was included to determine the most effective sourceof N. At each site, height and foliar nutrient concentrationswere measured. The sites chosen displayed different degrees of N-deficiencywhich was reflected in foliar N levels and height growth responses.The largest responses to application of N occurred at the mostdeficient sites and foliar N concentration of the untreatedcrop could be used to predict the likely magnitude of response.However, neither the season of application nor the differentfertilisers used had any effect on height growth.     

Timber Improvement: II. The Effect of Vigour on Young-Growth Sitka Spruce

A study of the effect of vigour on the within-ring componentsof young, plantation-grown Sitka spruce (Picea sitchensis (Bong.)Carr.) has been made as a contribution to a more effective selectionof timber having superior timber yields and to appraise thelikely effect of forest management practices which, by influencingvigour of growth, affect wood quality. It was found that as ring width in Sitka spruce increases:

1. Thereis an increase in early wood width without a correspondingincreasein late wood and so a greater proportion of early wood.
2. Thereis a reduction in the average density of the early woodcomponentof the rings.
3. Because of the combined effects of 1 and 2,there is a reductionin wood density as vigour of growth increases.
4. There is a lower minimum early wood density.

The significance of these observations on the growth and technicalperformance of Sitka spruce timber is considered. The possibility of appraising adult wood characteristics onthe basis of juvenile wood performance is examined and the scopefor assessing fibre length and density of adult wood from anexamination of wood laid down at about six years from the pithis demonstrated.     

Components of Tree Stability in Sitka Spruce on Peaty Gley Soil

The stability of 20 m tall trees was investigated by pullingthem over with a winch. The turning moment at the stem basewas resolved into two components, one due to the applied force,and the other to the horizontally displaced weight of the stemand crown. Vertical displacement of the root-soil system wasmeasured and observations made of the progressive failure ofthe soil around and underneath the root-soil plate. When trees were pulled from the crown region, the soil failedwhen the crown had deflected c. 4 rn horizontally and when theapplied force wasonly about 70% of that required for uprooting.By the time that the maximum turning moment at the stem basedue to the applied force had been reached, many roots had broken,crown deflection was c. 8 m and the deflected weight of thestem and crown made a substantial contribution to the uprootingforces. By repeatedly pulling trees during a sequence of cutting orbreaking the roots and soil, the total resistive turning momentafforded by the anchorage was resolved into the following components:i. soil resistance (the resistance to uprooting afforded bythe soil underneath and at the sides of the root system); ii.the resistance of roots placed under tension on the windwardperimeter; iii. the weight of the root-soil plate; and iv. resistanceto bending at the hinge on the leeside. The importance of these components varied between trees andchanged during the course of uprooting. Soil resistance wasthe largest component in the early stages, but when the turningmoment due to the applied force was maximal, the componentsof anchorage were in the order windward roots < weight <hinge < soil resistance. The major effect of the windwardroots on anchorage in these shallow root systems highlightsthe importance of features which interfere with their lateraldevelopment, such as the furrows produced by spaced ploughing.     

The Effects of Drainage and Ploughing of Surface Water Gleys on Rooting and Windthrow of Sitka Spruce in Northern Ireland

Rooting depth of Sitka spruce on surface water gleys is unlikelyto be increased by intensive deep drainage, so trees must beencouraged to develop wide-spreading surface root-plates tomaintain stability. Plough furrows, and even shallow turf ditchesseverely restrict root-plate development. Thus crops plantedon ploughed sites are likely to suffer from windthrow much soonerand more seriously than those on turfplanted sites, where thereare considerably fewer ditches. It is recommended that singlemouldboard ploughing should be replaced either by double mouldboardploughing or turf planting on gleys.