Long-term ecology of native pinewood communities in East Glen Affric, Scotland

Fossil pollen, stomata and charcoal were examined from a lakesedimentary sequence in the Glen Affric National Nature Reserve,one of the largest areas of remnant native pine woodland inScotland, in order to assess ecosystem dynamics over the last11 000 years. Results reveal that pinewood communities havebeen continuously present in East Glen Affric for the last 8300years. Pinus sylvestris first arrived in the area around 9900cal. BP, but occurred in only low abundance for the subsequent1600 years. Pine populations expanded around 8300 cal. BP andremained in relatively constant abundance throughout the remainderof the Holocene. There is no evidence of a hypothesized regionalmid-Holocene ‘pine decline’ at the site. Charcoalresults reveal that pinewood communities in East Glen Affricdo not appear to have been dependent on fire for either theirestablishment or their maintenance as has previously been suggested.     

Ecology, history and silviculture of Scots pine (Pinus sylvestris L.) in western Norway - a literature review

Results from a literature review on pinewood ecology, silviculture,genetics, aspects of history and forest resources of Scots pine(Pinus sylvestris L.) in western Norway are presented. The pinewoodscover 40 per cent of the forested land, 0.31 million ha. Duringthe last 75 years, the area has increased by 17 per cent andthe growing stock has risen from 10 to 34 million m³. The impactof man in previous times was very marked, and has had a significantinfluence on the present forest conditions. The pronounced climaticgradients mixed with the topographic variation – fromthe coastal plains via the fjord systems to the high mountains– is reflected in rather steep gradients in the pine forestvegetation. Various floristic elements can be distinguished,from oceanic via the suboceanic in the outer islands to thethermophytic, boreonemoral and boreal elements in the innerfjord districts and valleys. The introduction of spruce (Piceaspp.) plantations on 10–15 per cent of former native pineforests has not negatively affected the bird fauna at the landscapescale. Although not particular species rich, the pine forestsharbour species usually not found in other forest types. Sofar, most work in the field of silviculture and forest ecologyin the pinewoods of West Norway has been in the form of casestudies. Implications of the results for forestry in the regionare briefly discussed.     

Hybrid poplars: present status and potential in Britain

Past and potential future use of hybrid poplars for wood productionin Britain is considered, and preliminary results of trialswith new clones imported from Belgium in 1985 are given. A seriesof nine field experiments established in 1991, to a common protocol,was analysed using stepwise multiple regression. The superiorvigour of ‘Beaupré’ compared with ‘Ghoy’,‘Robusta’ and ‘Trichobel’ was clearin almost every case. For ‘Beaupré’ (Populustrichocarpa x P. deltoides) altitude emerged as the variableexplaining most variation in tree height after six growing seasons,height declining with increasing altitude. The four best siteswere characterized by low elevation and low rainfall. At the two older sites planted in 1987, at Ampthill and Bedgebury,the ‘interamerican’ hybrids (P. trichocarpa x P.deltoides) were the most vigorous, and the clones ‘Unal’and ‘Raspalje’, which were thought to be too rustsusceptible to release for commercial use in 1990, achievedsimilar stem sizes to those of ‘Beaupré’and ‘Bolelare’. The General Yield Class (based ona reference spacing of 8 x 8 m) calculated for ‘Beaupré’was 8 at Ampthill and 24 at Bedgebury. Future prospects for poplar planting are considered in relationto possible reform of the Common Agricultural Policy.     

Leaf Scale Traces in Corsican Pine

Discusses briefly a feature observed during an investigationof the structure of leading shoots of 1-year-old Corsican pine(Pinus nigra var. calabrica, Loudon). The feature, which doesnot appear to have been described previously in literature hasbeen tentatively called a ‘Leaf scale trace’.     

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.     

Determining productivity gains from herbaceous vegetation management with 'age-shift' calculations

Gains in stand volume that result from competition control andfertilization are sometimes reported as ‘percentage gains’.Because percentage gains arithmetically decline over time asstand volume increases, plantation managers have difficultyin using percentage gains to project growth and revenues. The‘age-shift’ method quantifies the year advancementsin stand growth due to silvicultural treatments and, for herbaceousvegetation management, it has been proposed that this metricis less likely to change after the juvenile growth phase. Totest the sensitivity of the ‘age-shift’ method totime and hardwood competition, we used 20-year volume data from11 loblolly pine (Pinus taeda L.) studies that had early completeherbaceous and woody competition control. Volume growth gainswere expressed in terms of percentages and ‘age-shifts’.On all sites with no woody competition, percentage gains declinedfrom age 8 years to age 20 years. In contrast, age-shift estimateson these plots either remained constant or increased over time.However, in four cases where woody basal areas were greaterthan 4 m² ha^–1 at age 15 years, age-shift gains due toherbaceous control decreased and eventually resulted in volumelosses. When evaluating the response to early herbaceous competitioncontrol, age-shift calculations have promise as a useful predictivetool on sites with low levels of hardwood competition. Fivemethods for calculating age-shift are presented.     

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.     

Diversifying native pinewoods using artificial regeneration

Little is known about broadleaf establishment within the nativepinewoods of Scotland, yet such information is critical to currentrestoration initiatives. A 2-year field trial was set up toassess the growth and performance of seedlings of four broadleavedspecies within different developmental stages of Pinus sylvestris(Scots pine) woodland in the Scottish Highlands. The developmentalstages included stem initiation (establishment stage), stemexclusion (thicket/pole stage) and canopy break up (old-growthcanopy), providing sites of varying shade and resource availability.It was predicted that differences in establishment between siteswould occur due to species-specific differences in ‘tolerance’of shade, low-nutrient availability and poor soil drainage.Analysis of trial results showed high survival but growth rates(relative stem height and basal diameter growth) declined rapidlyin year two. In year two, Ilex aquifolium achieved the highestmean growth rates in the stem exclusion stands (average 15 percent light) where there was a lower percentage of Phytomyzailicis (holly leaf miner) infection and frost damage. Sorbusaucuparia exhibited generalist behaviour with similar growthand performance across all stand treatments. Betula pubescensmaintained similar growth rates across stand types but was moresusceptible to insect damage in deeper shade. Overall, Alnusglutinosa grew more successfully than the other species andachieved highest mean growth rates in canopy break up (average44 per cent light) and stand initiation (average 71 per centlight) stages. Broadleaf establishment within pinewood standsis challenging on account of acidic nutrient-poor soil regimes,and in places, poor drainage, aggressive understorey competitionand canopies that restrict light availability and insect herbivory.Forest restoration techniques, including matching species tosite, accelerating establishment and using framework species(individuals of high field performance that are able to restoresite productivity and nutrient cycles), are discussed.     

CORRIGENDA

Literature References. Wright and Will. Against Scott, R. O.,and Ure, A. M. (1957): Delete ‘Spectrophotometry’and substitute ‘Photometry’. Delete, N.Z.J. Sci.Tech. B. XXXVIII. 699–706 and substitute ‘To appearin The Analyst’.     

The Effect of Drying Quercus robur Acorns to Different Moisture Contents, followed by Storage, either with or without Imbibition

Freshly harvested Quercus robur acorns were spread out, twodeep, in trays, and dried/stored (at +2°C over the courseof 28 weeks) to either 45, 40, 35, 30 or 25 per cent moisturecontent (fresh weight basis). Drying/storage significantly reducedthe germination percentage (P< 0.01). The acorns at eachmoisture content were then either ‘soaked’ or ‘notsoaked’, before immediate germination; or returned tothe same cold store at +2°C, this time in loosely tied polythenebags. Soaking raised the acorns moisture content (M.C.), andalso brought about a significant increase in germination capacity(P<0.01). Regardless of the moisture content immediatelybefore soaking, "soaked" acorns in loosely tied polythene bagsstored better than ‘unsoaked’ acorns. All ‘bagged’acorns (whether ‘soaked’ or ‘unsoaked’)stored better than acorns dried/stored in open trays.     

Some Aspects of the Growth and Spread of Fire in the Open

This paper describes some recent experimental and theoreticalwork on the growth and spread of fire in the open and discussessome examples of field data in terms of the theoretical calculationspresented. The lengths of flames from laboratory fires have been relatedto the size and rate of burning of the fuel by formulae derivedfrom a simplified dimensional analysis. The effects of a windblowing across a long fuel bed on the length and orientationof flames are also described. The scaling laws for flame heightsuggest that in the horizontal spread of fire, heat transferfrom the flames above the fuel bed is important primarily withshallow fuel beds. It is suggested that the main effect of a wind on crib firesis aerodynamic. The wind deflects the advancing fire front fromthe vertical, but perpendicular to this deflected front therate of spread of fire, at least for cribs, is roughly the sameas in still air. However, a theory of spread allowing for heattransfer through the fuel bed and radiation from the flamespredicts that there can be a stable ‘fast‘ spreadas well as a ‘slow’ spread. In ‘fast’spread the flames are thick and control the spread. In ‘slow’ spread radiant heat transfer from theburning zone is usually responsible for the spread. The flamesare thin and of low emissivity. The most important factors determiningthe rate of ‘slow’ spread R are ^pb the bulk densityof the fuel bed and ø the deflection from the verticalof the front of burning fuel which varies with wind speed. Rpb cos ø is approximately constant over a wide rangeof conditions with an order of magnitude of 5–10 mg cm^–2s^–1.     

A STUDY OF GROWTH RINGS IN TREES

The frequency of ‘lines’ of denser wood within theannual ring in larch (Larix decidua Mill.) was compared withmonthly records of rainfall and tables of droughts and rain-spellsin the Bristol region. Moderate correlations were found withJune rainfall (inverse), days in summer droughts, and a ratiogiving a measure of the maximum dry-wet contrast between successivemonths from May to August. This ‘contrast ratio’showed a high degree of parallel variation with ‘line’frequency. A study of individual years suggested that the formationof a pronounced ‘line’ is associated with the occurrenceof a spell of dry weather followed by a wet spell during thelater part of the summer. ‘Mid-lines’ were foundto be associated with a June drought breaking in July; late‘lines’ with a dry-wet contrast in July or August,but in some trees these may be suppressed by the stoppage ofgrowth. Vaguer ‘lines’ of lower frequency were associatedin certain years with wet spells not preceded by noticeabledrought. Individual ‘lines’ can thus be identifiedand roughly dated by some weather feature, so that their positionsheds some light on the length of the growing season. It issuggested that ‘lines’ of denser wood may be occasionedby the killing or inactivating of mycorrhizal rootlets eitherby drought or by waterlogging, followed by partial recoverywhen the weather changes. This would accord with the theorythat summer wood formation is normally associated with a developingwater-deficit in the wood.     

A Comparison Between European Continental and British Provenances of Some British Native Trees: Growth, Survival and Stem Form

Data describing the growth, survival and stem form of: a) Europeancontinental, and b) British provenances of trees native to Britainwere collated from Forestry Commission records. The growth ratesof European continental provenances of Scots pine (Pinus sylvestris),silver birch (Betulo pendula), sessile oak (Quercus petraea)and common alder (Alnus glutinosa) were inferior to those ofBritish provenances in 90 per cent of cases. European provenancesof these species also showed inferior survival. The growth ratesof continental provenances of beech (Fagus sylvatica) were superiorto British provenances in about 50 per cent of cases, provenancesfrom northern France, Belgium and Holland being the fastestgrowing. Relationships between the relative height growth offoreign provenances and latitude were demonstrated for Scotspine, silver birch and beech (relative height growth = the heightgrowth of a foreign provenance expressed relative to that ofBritish provenances at the same site). The continental provenancesthat grew best originated at 0–4° south of the latitudesof the planting sites. Relative height growth decreased bothnorth and south of these latitudes. In the case of oak, relativeheight growth did not vary widely between origins. The survivalof continental provenances of Scots pine was particularly pooron exposed upland sites. The stem form of British provenancesof Scots pine was intermediate between Fennoscandian provenancesand provenances from the rest of Europe. In oak and beech therewas generally little difference in stem form between Britishand continental provenances, but the best continental provenances(Belgian beech; French oak) were most reliable. The growth andsurvival of native trees is interpreted in the light of thepost-glacial history of these species. The implications regardingthe continued use of seed of native hardwoods imported fromcontinental Europe are discussed.     

Floristic Diversity in Some Central Swedish Forests

The species of vascular plants present in 0·5 ha sampleplots were recorded in 19 areas of forest planted on formeragricultural land, 21 areas of old or ‘virgin’ forestand 102 areas of ‘ordinary forest’ in east centralSweden. In the case of the planted forest areas, the main correlationwith floristic diversity was with the amount of daylight reachingthe forest floor. In the ‘old forest’ and ‘ordinaryforest’ sites, however, the main correlations were withthe pH value of the surface soil, the amount which this variedwithin the sample plot, and the proportion of broadleaved treesin the tree canopy; these factors were inter-correlated witheach other to some extent. The ‘old forest’ sites,which had the most acidic surface soil and least diverse flora,did not appear to be serving any particularly useful functionin terms of conservation of the flora, at the present time.It is concluded that, if a diverse forest flora is requiredfor any particular reason, the complete closure of the canopyshould be avoided. A mixture containing some broadleaved treesis likely to be preferable to a pure crop of pine or spruce.There appears to be, however, considerable scope for the developmentof a diverse flora within timber-producing forests consistingmainly of spruce and pine.     

GROWTH STIMULATION OF FOREST TREE SEEDLINGS BY THE ACTIVITY OF FREE-LIVING MYCORRHIZAL MYCELIA

Observations by the late Dr. M. C. Rayner on a field experimentand the results of subsequent pot-culture experiments demonstratethat the soil activity of mycorrhizal fungi can improve thedevelopment of forest tree seedlings (Picea, Pinus, Betula)before actual mycorrhizal infection takes place. Further experimentsshow that ectotrophic mycelia are capable of stimulating endotrophictree species (Fraxinus excelsior, Cbam?cyparis lawsoniana, Robiniapseudacacia), i.e. that these ectotrophic mycorrhiza-formersbring about growth stimulation of the plant although no infectionis formed at a later stage. It is suggested provisionally thatat least some ectotrophic mycelia, Boletus scaber and Rbizopogonluteolus, may influence seedling growth by attacking soil organicmatter and liberating ‘nutrients’ from which thehigher plant benefits.     

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.     

ERRATUM

THE author has called our attention to a mistake in her paper‘Squirrel Populations and their Control’ publishedin the recent Supplement to Forestry ‘Wildlife in theForest’. The mistake occurs in the second paragraph ofpage 19 where the fall in the estimated population of grey squirrelsfollowing a mast failure should be 468 to 66 and not 468 to466.     

An inoculation experiment of Japanese <Emphasis Type="Italic">Bursaphelenchus</Emphasis> nematodes on Japanese black and red pine, <Emphasis Type="Italic">Pinus thunbergii</Emphasis> and <Emphasis Type="Italic">P. densiflora</Emphasis>

The pinewood nematode (PWN) Bursaphelenchus xylophilus is an invasive pathogen that was introduced from North America to Asian countries and Portugal and is devastating native pine forests. Some native European and Asian Bursaphelenchus nematodes also have weak to moderate pathogenicity to native pine species. To evaluate the potential risk of native Bursaphelenchus species, we inoculated ten Japanese Bursaphelenchus species into native pine species (the dominant forest species) in Japan, and evaluated their pathogenicity using mortality and tracheal tissue damage as indices. Inoculation was conducted on August 3, 2007, and the symptoms were observed every 2 weeks until February 1, 2008. None of the inoculated trees, excluding the pathogenic PWN inoculated control, showed external disease symptoms; however, four species [a less pathogenic PWN isolate, B. luxuriosae, Bursaphelenchus sp. NK215 (undescribed), and NK224 (undescribed)] caused tracheal tissue damage in inoculated seedlings and showed weak pathogenicity. Therefore, we conclude that there are some potentially pathogenic native species of nematodes distributed in Japan. Interestingly, two of these weakly pathogenic species, B. luxuriosae and NK215, are not associated with Pinaceae trees, suggesting that nematode pathogenicity may be a pre-adaptive character. More experimental studies under different conditions are necessary to accurately evaluate the potential risk of these pathogens.     

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.