Recent pine woodland dynamics in east Glen Affric, northern Scotland, from highly resolved palaeoecological analyses

Glen Affric, a National Nature Reserve of international conservationimportance for plant and animal communities associated withScots pine (Pinus sylvestris) woodland is managed for natureconservation and woodland restoration at a landscape scale.Management plans have drawn on information on current standstructure and variation but have not used in any detailed waythe analyses of past tree population changes from sources, suchas pollen analyses. This paper reports the results of pollenanalyses from three small peat hollows at the head of Loch Beinna' Mheadhoin. The analyses demonstrate, first, that woods inthe east of the reserve several centuries ago were differentin species composition and were more varied than they are todayand, second, that the currently patchy Pinus wood in the westof the reserve, at the head of Loch Beinn a' Mheadhoin, is theresult of recent spread westward onto former heathland. Thistemporal and spatial variability in the recent past has implicationsfor the future management of the woods because future woodsmay not develop with the characteristics of the current stands,and may not be stable over time.     

CONIFEROUS LITTER AMENDMENTS AND THE GROWTH OF SITKA SPRUCE

The growth of semi-checked Sitka spruce (Picea sitcbensis Carr.)on heathland has been stimulated to different degrees by theannual application of litter of Scots pine (Pinus sylvestrisL.), Corsican pine (P. nigra var. calabrica Schneid), Lodgepolepine (P. contorta Dougl.), Japanese larch (Larix leptolepisGord.), and Sitka spruce, at rates corresponding to normal plantationconditions, following an initial heavier rate. Foliar analysissuggests that the response is at least partially attributableto the influence of the litters on the nitrogen nutrition ofthe spruce and differences between litters appear to be largelydetermined by their total nitrogen contents. In this respect,Japanese larch, with an annual needle fall generally greaterthan that of the pines and a higher nitrogen content, offersthe best promise as a nurse species for spruce.     

The Effect of Intercropping Populus 'RAP' with Beans

Dwarf French beans and broad beans were grown at 0.25 m x 0.25m for 2 years with a without cuttings of Populus ‘RAP’at spacings of 2.0 m x 0.5 m and 3.0 m x 0.5 m. The presenceof beans lead to a greater height and diameter growth and greatertotal dry matter production per hectare of the Populus at bothspacings after 2 years. Bean yield was reduced at the end ofthe second year by the presence of Populus; there was no effectat the end of the first year.     

Beech in Wessex - a Perspective on Present Health and Silviculture

The condition of beech (Fagus sylvatica L) growing in thirtywoods in the south of England is described. In older woods,up to 20 per cent of trees were killed or seriously damagedby the summer drought of 1976. Most surviving trees have recoveredfully. Beech snap disease, associated with the fungus Nectria coccineais widespread in younger stands, especially those also affectedby lime-induced chlorosis, beech scale (Cryptococcus fagisuga)or severe competition. Nevertheless, sufficient trees surviveto provide a choice of final crop. In the long term, beech doesnot seem likely to die out through drought or disease. Trees of almost all ages and conditions exhibit a tendency tomultiple forking. The principle remedy is to keep trees in closedcanopy until a 6 to 8 m clean bole has been obtained. Beechresponds well to heavy thinning at this stage. The long term future of beech woodlands depends on timber valuesand on support for their ecological and amenity value. Silviculturally,beech is the best adapted species for the shallowest calcareoussoils, especially on the Jurassic limestone.     

A Reappraisal of the Importance of Cronartium ribicola on Pinus strobus in Great Britain

Because of the possibility of serious infection by Cronartiumribicola (White pine blister rust), Pinus strobus, the Weymouthpine, is now very rarely planted in British forests. An assessment,in 1962, in a number of experimental forest plots of P. strobusestablished in 1953 and 1954 showed that initial infection ofthe trees while growing in the nursery may be an important factorin causing later damage and losses in the forest. The resultsalso indicated that the risk of infection in plantation cropsas a result of spore dispersal from black currants in the localityis much lower than is generally thought. It is suggested thatif P. strobus is raised in nurseries which are relatively isolatedfrom currants and if protective chemical spraying against thedisease in the nursery is carried out, the incidence of infectionin plantations at least half a mile from the nearest currantsis likely to be low. The disease cannot spread within a pinecrop by direct transmission from tree to tree.     

THE SHRINKAGE OF RAYS AND FIBRES IN WOOD

1. Shrinkage was measured on sections of the woods of Artocarpusintegra, Canarium zeylanicum, and Acer pseudoplatanus.
2. Shrinkagestresses between rays and fibres were demonstratedby dryingradial strips of tissue containing rays on one sideand fibreson the other.
3. Strains developed by these stresses were removedby dissectionof the rays and fibres, which decreased the radialshrinkageof the rays and increased that of the fibres.
4. Thedifference between the radial and tangential shrinkage ofthefibres was reduced, but not removed by separation from therays,and this inherent anisotropic shrinkage of the fibresmust constitutean important cause of the differential shrinkageof wood.

     

THETFORD CHASE, SWAFFHAM, AND KING'S FORESTS FURTHER NOTES

Continues the history of the development of these East Anglianpine forests from the point reached by James Macdonald in 1938(Forestry, xiii. 1–18). After describing the effect ofthe war on the area, it deals shortly with climate, presentplanting methods, thinning and production, utilization, protection,and organization.     

The Economics of a Private Forestry Enterprise in South-east Scotland

The annual income and expenditure accounts have been summarizedfor the period 1949–61. The woods had not previously beenunder regular management and due to war fellings were only 60per cent, stocked in 1949. The treatment policy has been restockingand rehabilitation with minimum cash investment. The local conditions,management history, and growing stock are briefly described,and a book valuation is presented to show value of land plusgrowing stock at the beginning and at the end of the period.The book profit on 806 acres averaged ?5. 6s. per acre per annum,of which ?3 per acre is increase in book valuation. This isequivalent to a yield of 6.4 per cent, on an average book valueof the land plus growing stock of ?70,000. The yield per cent,is expected to fall as the capital value of the growing stockincreases. Although these figures may give a reasonably accurateaccount of the financial results, it is considered that theyunderestimate the true value of the woodlands to the estateeconomy.     

PINUS CONTORTA IN IRELAND, 1955

A short study of some of the older plantations of Pinus contorta,a species whichhas been planted freely on infertile soils inIreland since 1918. The study was made in connexion with plantingand with provenance experiments being made with this speciesin Great Britain. The author distinguishes only three typesplanted in Ireland, the familiar South Coastal and North Interiortypes and an intermediate type called Rainer Forest, to whichthere is no parallel type in Great Britain. The types are discussedunder growth rate, site influence, spacing, susceptibility tosawfly attack, mixtures, thinning treatment, and wind blow.In Eire, the fast-growing South Coastal type is preferred andis usually planted pure as a pioneer crop, whereas in NorthernIreland both Coastal and Interior types have often been plantedin mixture with Picea sitcbensis. The choice of type and thepractice adopted in Eire seems the more successful.     

Considerations regarding black walnut (Juglans nigra) culture in the north-west of Romania

Black walnut (juglans nigra L.) is one of the most valuableNorth American forest species, and has been cultivated in Europesince 1629. It is now planted in many European countries, ofwhich Hungary, France and Germany are the most representative. In Romania it has been cultivated since the end of the nineteenthcentury, especially in the western and north-western parts ofthe country, and now covers over 2100 ha. This paper focuseson the silviculture applied to the black walnut plantationsin the SÃcueni Forest District (north-west of Romania),a forest unit where mixtures with either North American (e.g.northern red oak, pin oak, bitternut hickory, black cherry,etc.) or European (eg. pedunculate oak, Turkey oak, ash, Norwaymaple, small-leaved lime) forest species, covering hundredsof hectares, are frequently found. The biometrical performances of such plantations show the highpotential of the species when used in favourable ecologicalconditions (e.g. lowlands, with mild climates, rich and deepsoils, permeable and constantly supplied with water, etc.).     

The tolerance of young trees to applications of clopyralid alone and in mixture with foliar-acting herbicides

The selective herbicide clopyralid is often used to controlcompeting Cirsium arvense in newly planted woodlands. When appliedas an overall spray at different dates in the spring (at 0.2kg acid equivalent (a.e.) ha^–1) to 10 tree species (Fraxinusexcelsior, Prunus avium, Quercus robur, Acer pseudoplatanus,Populus x canadensis cv. ‘Ghoy’, Pseudotsuga menziesii,Pinus nigra ssp. laricio, Larix kaempferi, Picea abies and Piceasitchensis) it did not reduce survival, and had little effecton growth. However, some species showed distortion of the youngestsprayed leaves or needles for several weeks after treatment,particularly F. excelsior, L. kaempferi and P. x canadensis.Sequential applications of clopyralid (first at 0.1 kg a.e.ha^–1 followed by 0.2 kg a.e. ha^–1 after 3 weeks),which are often required to control C. arvense, did not leadto increased leaf damage or growth reduction. Mixtures of clopyralidwith selective graminicides (cycloxydim at 0.45 kg active ingredient(a.i.) ha^–1; fluazifop-p-butyl at 0.38 kg a.i. ha^–1and propaquizafop at 0.15 kg a.i. ha^–1) did not causesignificant adverse effects on survival or growth of any species.If herbicides are required to control mixed stands of susceptibleproblem weeds such as C. arvense and grasses which are overtoppingyoung trees, these herbicide mixtures, applied as overall sprays,are less likely to cause damage to trees than attempts to usedirected applications of broad-spectrum foliar-acting herbicides.     

Managing birch woodlands for the production of quality timber

Interest in silver birch (Betula pendula Roth) and downy birch(Betula pubescens Ehrh.) has greatly increased in recent yearspartly as a result of pressures to restore and expand nativewoodlands but also due to renewed interest in birch as a treecapable of producing quality timber. Despite the many advantagesof birch as a commercial timber tree—ease of establishment,fast growth on good sites, high value timber and a short rotation,it has a poor reputation in Britain largely as a result of thepoor form of the existing, mainly unmanaged resource. The followingpoints need to be considered if stands of quality birch treesare to be produced in an economical timescale. (1) Sites: silverbirch needs good sites that are relatively well drained withlight mineral soils. Downy birch does well on moist to wet sites.(2) Regeneration: natural regeneration through a shelterwoodis the preferred system of regenerating birch as some overheadprotection is beneficial to germination success. About 20–40seed trees should be left per hectare. Good ground preparationand control of grazing are essential. The vast majority of seedlingsare recruited in the first year of the regeneration cycle thereforeplanting should be considered if the initial regeneration successis poor. Direct seeding is also a successful method of regeneration.Birch readily regenerates naturally into suitably prepared openareas next to existing birch woods but these should not be toobig, e.g. gaps or strips 20–60 m wide have been suggestedin the literature. (3) Maintenance: density of regenerationneeds to be reduced to about 2500–3000 stems ha^–1by the time the trees are about 3–6 m tall. Birch seedlingsmust always be taller than the competing vegetation. (4) Thinning:thinning should begin when the mean height of the stand is about8–10 m. At this point at least half the number of treesshould be removed with the emphasis on retaining dominants andco-dominants of good form. The aim is to maintain about halfthe height of the tree as living crown to sustain a high rateof growth. Additional thinnings will be required at intervalsof 5 to 7 years and final thinning should leave around 300–500stems ha^–1. (5) Rotation: a rotation of 40–50 yearsis possible on good sites and perhaps 50–55 years on lessfavourable sites.     

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.     

Seasonal Trends in Abundance, Diet and Breeding of Common Crossbills (Loxia curvirostra) in an Area of Mixed Species Conifer Plantation Following the 1990 Crossbill 'Irruption'

Crossbills increased in abundance on lower Deeside, north-eastScotland, from July 1990 through the autumn, remaining numerousuntil the following June. Flock size initially increased, butdecreased towards late winter as breeding began. The timingof the population increase, and the sizes of the birds' billssuggested they were mainly immigrant Loxia curvirostra. Theirdiet changed seasonally in a pattern that could be explainedby the seed weight, cone toughness and seedfall phenology ofthe predominant conifers present. No breeding was recorded inautumn and winter when the birds were mainly feeding on Sitkaspruce, but commenced in early spring as they shifted to Scotspine. Breeding was late, and production poor, probably becauseonly some of the birds had large enough bills to feed efficientlyfrom the robust cones of Scots pine. It is argued that plantationforestry, by providing a novel range of conifer seeds, couldaffect selection for bill size in British crossbill populations.     

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.     

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.     

Developments in Yield Control and Inventory in British Forestry

Forecasting timber production many years in advance has becomea problem of considerable importance in this country becauseof the need to co-ordinate the rapid increase in productionwith the establishment of new timber-using industries. Thispaper describes a change in emphasis in state forest WorkingPlan Inventory methods employed in the predominantly young,coniferous forests of Great Britain and is a development ofthe methods described in a previous paper (‘Problems ofYield Control and Inventory in British Forestry’—D.R. Johnston, 1960, Forestry, 33, 19–36). Total enumerationof the growing stock is no longer the main objective of forestinventory and the new approach is directed towards (a) assessmentof the productive potential of each subcompartment and (b) theintensive enumeration of sample or ‘index’ subcompartmentsinitially and at each re-enumeration as a check on growth predictionsand yield control.     

THINNING GRADES BASED ON THE THICKNESS OF ANNUAL RINGS

This paper propounds a new method of calculating numerical thinningschedules for conifers which are designed to give, on the average,any reasonable pattern of ring width at breast height in the100 largest trees in a plantation. It starts from the ForestryCommission's Revised yield Tables for Conifers in Great Britainand is based on the principle that, if the current annual incrementin a plantation is unaffected by the grade of thinning, thering widths must be inversely proportional to the bole areaper acre, i.e. the total area of cambium on the main stems ofthe trees. Sources of error in the method of calculation arediscussed, and it is considered that such errors are not soserious as to endanger the use of the method as a means of calculatingapproximate thinning schedules. As an approximate yield tablecan be constructed for each thinning grade, the method can beused to estimate the relative costs of growing trees of variousdiameters with various ring width patterns.     

Colonization of Two Nothofagus species by Lepidoptera in Southern Britain

Between 1975 and 1982 a study was made of the invertebrate faunacolonizing two deciduous species of southern beech, Nothofagusobliqua and N. procera, introduced into Britain from South America.Special attention was paid to the folivorous larvae of Lepidopterawhich were sampled at 15 localities in southern England, mostlyin Forestry Commission trial plots and arboreta in Gloucestershire. The literature describing the native insect fauna of Nothofagusin Chile and Argentina is briefly reviewed. Mention is alsomade of the few previous records of lepidopterous larvae observedfeeding on Nothofagus in Britain. The larvae of 81 species Lepidoptera are recorded from Nothofagus.Seventy-eight of these were feeding on the foliage, of which73 were found on N. procera and 62 on N. obliqua, although approximately62 per cent of all the larvae collected were from N. obliqua.Faunal differences between the sites studied are briefly described.Two additional species of cutworm larvae are also reported attackingthe roots of Nothofagus seedlings. The changing lepidopterous fauna on Nothofagus from May untilSeptember is described and discussed. Spring-feeding larvaeof Operophtera brumata (L.), Agriopis aurantiaria (Hübn.)and Erannis defoliaria (Clerck) comprised 55 per cent of alllarvae collected on the two hosts, and represented between 68per cent and 87 per cent of those larvae in beating samplescollected in late May and early June. Most of the larvae collected were reared to adult in the laboratoryon a diet of Nothofagus leaves. The majority of these are regardedas polyphagus species although 64 are known to have one of thetwo native Quercus as a host-plant, while 24 have been recordedas feeding on Fagus sylvatica. The relevance of these two generaas sources for the Lepidoptera fauna colonizing Nothofagus isdiscussed. Nothofagus obliqua and N. procera are shown to have acquireda substantial lepidopterous fauna since their introduction intoBritain near the beginning of this century, although most ofthe trees sampled were less than 25 years old. These two speciesof Nothofagus may be vulnerable to defoliation by several speciesof caterpillar, especially if planted as monocultures in areaswhere oak and beech are plentiful. However, their surprisinglylarge insect fauna may be seen to have some value for natureconservation purposes.     

Variography and kriging allow screening Pinus pinaster resistant to Armillaria ostoyae in field conditions

Armillaria ostoyae is an important disease of Pinus pinasterin north-west Spain, which kills trees following a heterogeneousspatial structure. In a progeny trial of P. pinaster seedlings,spatial heterogeneity and autocorrelation of neighbour mortalitycaused by A. ostoyae impeded proper analysis of the diseaseincidence. We used variography and kriging methods to describethe spatial distribution of the infection probability and thegenetic variation of the resistance to A. ostoyae among families.The spatial structure of disease incidence was modelled, andthe probability of survival was corrected by kriging at eachtree location. Cumulative mortality 3 years after planting was65.1 per cent. Significant differences among P. pinaster familiesin terms of mortality to A. ostoyae were found, with low individual(h = 0.08) and moderate family (h = 0.35) heritability estimates. According to a theoretical semivariogram, the patch size ofthe disease incidence was 63 m wide. This is the first timevariography and kriging are used to select P. pinaster resistantto Armillaria root rot. It is concluded that geostatistics providesforest pathologists with a powerful tool for screening resistanttrees in field conditions.