Frost Hardiness of Nothofagus procera and Nothofagus obliqua in Britain

The frost hardiness of four seedlots of Nothofagus proccra andsix seedlots of Nothofagus obliqua was measured experimentallyduring three winters. Shoots were taken from saplings growingat the Bush Estate in Scotland. All seedlots set buds in lateSeptember, hardened very slowly in the autumn, were damagedto some extent by temperatures below –14°C in mid-winter,and dehardened during frosty weather in February/March priorto budburst in mid to late April. The range of mid-winter temperaturesgiving 0%, 50% and 100% kill (LT₀, LT₅₀ and LT₁₀₀) were 8–14°C,13%20°C and 14–22°C, respectively. By contrast,British Fagus sylvatica hardened off rapidly in September, wasundamaged by frosts well below –20°C in mid-winter,and did not deharden until late April, prior to budburst atthe end of May. Nothofagus seedlots from Nuble in Chile (the most Equatorialsource) were the most frost susceptible: unfortunately, seedof this origin was supplied to many British nurseries between1976 and 1W9. Seedlots from Neuquen in Argentina, and from maturetrees of Malleco (Chile) origin growing in Britain, were themost host hardy. N. procera tended to be hardier than N. obliqua,and the trees became hardier with age. Past temperature records for Britain suggested that all theNothofagus seedlots had a high risk of suffering severe frostdamage at least once during a timkr rotation in all but mildcoastal regions. Spring and autumn frosts may be more damagingthan winter frosts. However, if it were possible to select individualswithin populations that were 3–6°C more frost hardythan the population means, such trees would be sufficientlyhardy to avoid frost damage in most lowland regions.     

European aspen (Populus tremula L.): a review with particular reference to Scotland I. Distribution, ecology and genetic variation

European aspen (Populus tremula L.) has attracted relativelylittle research attention in Britain. Interest in the specieshas increased in recent years because of efforts to restoreand extend native woodland, of which aspen is an infrequentbut important component species. This paper draws together informationfrom British, European and Russian literature on the ecologyand genetics of aspen. The species is distributed throughoutBritain in many different types of woodland. It is particularlycommon in the Scottish Highlands and Islands where it occurson a diverse range of sites from sea cliffs to near the treeline.It is associated with a distinct insect fauna, several speciesof which are considered endangered. Information is lacking onseveral fundamental aspects of the ecology and genetics of aspenin Scotland including seed production, growth rates, geneticvariation and its conservation value and status in native forestecosystems. Some useful information on these topics is presentedfrom studies of aspen elsewhere in Northern Europe, particularlyNorway.     

Phytophthora pseudosyringae associated with the mortality of Nothofagus obliqua in a pure stand in central‐southern Chile

Mortality of Nothofagus trees in the southern‐central Chile region has been observed for over 30 years. A field survey conducted in 2013 detected partial defoliation and bleeding cankers on Nothofagus obliqua in a pure stand in the Nahuelbuta coastal ranges of the Biobío region. A Phytophthora sp. was isolated from stem cankers and soil samples around symptomatic N. obliqua trees: All isolates were identified as Phytophthora pseudosyringae. These isolates were pathogenic on 1‐year‐old N. obliqua and Nothofagus alpina, and on detached twigs of adult N. obliqua and Nothofagus dombeyi trees. This paper is the first to report association and pathogenicity of P. pseudosyringae with N. obliqua, N. alpina and N. dombeyi native to the Biobío region of Chile. The potential of P. pseudosyringae to cause damage in natural Nothofagus stands in Chile must be determined.     

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.     

Winter Frost Hardiness of two Chilean Provenances of Nothofagus procera in Scotland

The frost hardiness of the shoots of individual trees withintwo Chilean provenances of Nothofagus procera (Poepp & Endl.)Oerst. was measured once in each of the months January, February,November and December 1989 and January and February 1990. Therewere significant (P<0.05) differences of frost hardinessbetween provenances but only one tree could be shown to be significantlymore frost hardy than the others within the same provenance.During the winter of 1989/90 both provenances were hardy toabout –14°C (temperature killing 50 per cent of shoots)in December, but the shoots dehardened to about –9°Cin January before hardening again in February. This patternof alternate hardening and dehardening seemed to mirror changesin air temperature and could render N. procera liable to frostdamage where (as happened in 1988/9 in the UK) mild spells occurin winter followed by severe frosts.     

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.     

Tree Seed Production and Food Conditions for Rodents in an Oak Wood in Southern England

Seed production and seed losses were monitored in an oak (Quercusrobur) wood in southern England between 1975 and 1988. In additionto acorns, seeds from several large beech (Fagus sylvatica)and sweet chestnut (Castanea sativa) trees which occurred withinthe wood, and from the understorey of hazel (Corylus avellana)trees, were also monitored. The seeds from these four tree speciesare all subject to heavy predation by rodents, as well as otherseed-eaters such as birds and insects. Seed fall tended to be irregular and three years, 1976, 1985and 1987 were considered oak mast years. There were too fewyears with large acorn crops to examine whether resource depletionin these years resulted in poor crops in subsequent years. Therewas no correlation in seed production between the four treespecies which does not agree with one of the predictions ofthe predator satiation theory of masting behaviour. The effectsof weather on seed production were investigated but few significantcorrelations were found. In general the results tended to supportprevious findings. Between 1980 and 1982 a serious outbreakof Tortrix moth caterpillars occurred within the wood and mayhave affected acorn production. A negative relationship wasfound between oak defoliation and acorn production in the subsequentyear. The loss of seeds from the forest floor was initially rapidand in 9 years no seeds survived into the following year andfood conditions were poor for granivores. In 3 of the remaining4 years acorns survived well into spring and early summer providinggood food conditions for forest rodents through to the timeswhen alternative food supplies became available. Although oaktrees contributed most seed energy in good years, the othertree species, especially beech, became important when acornproduction was poor. Predispersal losses due to predators werefrequently high and averaged 80 per cent, 40 per cent, 38 percent and 33 per cent in hazel, sweet chestnut, oak and beechrespectively. On average, hazel nuts tended to fall first, some6 weeks before acorns which tended to be the last seeds to fallof the four tree species. Knopper galls and weeviled acornsfell earlier than sound acorns. A key-factor analysis indicatedthat a failure to mature, predispersal predation and insectinfestation from weevils and Knopper galls contributed equallyto changes in numbers of acorns among years.     

Response of oriental beech (Fagus orientalis Lipsky) seedlings to canopy gap size

The response of nursery seedlings and wildings of oriental beech(Fagus orientalis Lipsky) to canopy gap size was studied ina climax beech forest in northern Iran with respect to seedlingsurvival, shoot growth and vitality. These parameters were followedfor 2 years after planting in gaps of 50, 200 and 600 m², aswell as in the open field. Foliage coloration was used as acriterion for vitality. The survival rate of nursery seedlingsand wildings dropped rapidly with increasing gap size from 84per cent in 50-m² canopy openings to     

The north-eastern distribution range of European beech a review

Today, European beech (Fagus sylvatica L.) seems to be a markedlysuccessful tree species in the north-east of its distributionrange. The distribution area may be larger than originally assumed;past forest management is probably the main cause of the contractionin the postglacial European beech range. Numerous attempts consistentlyhave failed to locate a distinct distribution edge for Europeanbeech. Therefore, we define northern and eastern Poland andthe southern regions of the Baltic States as margins of Europeanbeech distribution. Ecophysiological approaches have identifiedthe drought constraints for European beech in terms of (1) thecritical limit for xylem cavitation and loss of hydraulic conductivity,reached at a shoot water potential of –1.9 MPa, and (2)a reduction in gross primary production and total ecosystemrespiration when relative extractable soil water reaches 40and 20 per cent, respectively. However, it is difficult to correlateEuropean beech distribution margins with single macro-climaticfactors. Moreover, the adaptation of European beech populationsand provenances to drought and frost varies. The phenotypicplasticity and evolutionary adaptability of European beech appearto be underestimated. These characteristics may counteract afurther contraction of the European beech range arising fromclimate change in the future.     

A decade of grey squirrel bark-stripping damage to beech in Lady Park Wood, UK

The scale and distribution of American grey squirrel (Sciuruscarolinensis) bark-stripping damage to beech (Fagus sylvatica)stems was monitored in a mixed broadleaved woodland retainedas a Research Natural Area through the use of permanent transects.During an initial outbreak of debarking damage in 1983 almostone-third of beech individuals 4 cm d.b.h. in stands of 40 years'growth were badly damaged and by 1993 this level of damage hadrisen dramatically to over 50 per cent. One-third of badly damagedindividuals in 1983, including a number of potential canopydominants, died during the decade, but some that survived grewvery vigorously. Throughout squirrels preferentially debarkedintermediate sized (10–25 cm d.b.h.) stems in particularparts of the stands aged 40–50 years, apparently tendingto select stems that were growing rapidly. Other species andstand areas of <100 years' growth remained largely unscathed.Within the 10-year period squirrels had critically affectedthe successional development of the wood.     

Studies on Ulmus: VII. Essex Elms

This biometrical study is based on a collection of nearly 500leaf samples from every ancient parish in the county. Most ofthe elms could be assigned to one of nineteen groups, 9 of U.carpinifolia, 1 of U. glabra, 2 of U. procera, 3 of putativeF₁ U. carpinifolia x U. glabra, 3 of U. carpinifolia with suspectedintrogression from U. glabra, and 1 of U. carpinifolia x U.procera. U. glabra is indigenous. Most of the U. carpinifolia appearto have spread out from six centres of origin, mostly near thecoast. These elms are very similar to forms now occurring innorth-west France, and it is thought probable that they wereintroduced from there, possibly by the settlers responsiblefor the Red Hills salt workings shortly before the Roman occupation.One group of U. carpinifolia came from Cambridgeshire via theEssex branch of the river Cam. Of the two main populations ofU. procera, that characteristic of south-east Essex is believedto have come from northern Kent, probably from the Hoo peninsula,while the group found in south-west Essex is probably a laterintroduction from further west. Hybridization between introduced U. carpinifolia and nativeU. glabra has occurred on a very large scale and putative F₁hybrids extend in a broad band across the county from the Hertfordshireborder to Suffolk. This hybridization most likely occurred duringthe clearing of the heavily forested part of northern Essexin pre-Conquest times. Subsequently, back crossing occurredbetween these hybrids and U. carpinifolia. Occasional hybridizationalso seems to have occurred between U. procera and the othertwo species. An outline of the probable history of the elm in eastern Englandas a whole concludes the paper.     

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.     

Patterns of regeneration and ground vegetation associated with canopy gaps in a managed beechwood in southern England

In autumn 2001, 15 canopy gaps were selected for study in RumerhedgeWood, a semi-natural, mesotrophic beechwood in southern England.The gaps were located in mature, beech-dominated stands, andhad originated from openings created during a thinning in theearly 1980s and wind damage in 1987/1990 and/or the consequentsalvage operations. The extent of each gap and surrounding treeswere mapped. Tree/shrub regeneration, ground vegetation, bareearth, leaf litter and canopy openness (using a canopy-scope)were measured within and around the gaps using a 5 x 5-m gridand placing a 1 x 1-m quadrat at each grid intersection (totalnumber of quadrats = 400). Most of the gaps were <75 m² inarea. The largest was 241 m². They were generally irregularin shape and there was little or no understorey present. Mostsurrounding trees were beech Fagus sylvatica L. Bramble Rubusfruticosus L. formed a moderate to dense ground vegetation belowmost gaps and declined around the edges only once the gap openingwas substantially obscured. Apart from a few larger saplings,most regeneration was small and of beech. Most of the latterappeared to be in their fifth or sixth growing season, were10–35 cm tall, had an erect base and flat top, had increasedby <5 cm in height during 2001 and were not browsed by deer.Their height and growth form was related to (1) their positionwithin gaps, (2) the degree of canopy openness and (3) the coverof ground vegetation. This was translated into the followingzonation—(1) around the centre of larger gaps: canopyopenness increased to >15 per cent; bramble cover was nearcomplete; litter depth was low; many places had no beech seedlings,but some of the few present were among the tallest, most uprightand fastest growing; (2) towards the edges of the large gapsor directly below smaller gaps: canopy openness was about 4–10per cent; bramble cover was slightly less; beech seedlings weremoderately abundant but patchy, generally shorter, more flattopped and slow growing than in the gap centre, albeit somewere still among the tallest, most upright and fastest growing;(3) beyond the edge of the large/medium gaps (with the gap onlypartially visible) or directly below very small gaps: canopyopenness was only about 2–3 per cent; bramble was muchreduced; beech seedlings were at their most abundant but stillpatchy in distribution and even shorter, more flat topped andslower growing than in the above zone; (4) in an outer zonebeyond or almost beyond the sight of the gaps: canopy opennesswas <2 per cent; bramble was weak and sparse; beech seedlingswere mostly at low densities and predominately short, slow growingand flat topped. This ring pattern of beech regeneration appearedto relate mainly to (1) differences in light availability affectingthe survival, growth rate and form of seedlings; (2) competitionfrom bramble and possibly (3) limited dispersal of beech seedinto gaps. Recommendations are given for managers who wish touse natural regeneration to restock beech woodland.     

Growth and provenance of Norway maple (Acer platanoides) in lowland Britain

The results of an experiment to investigate the early growthand form of ten different provenances of Norway maple (Acerplatanoides L.) are described. Two sites were planted and after8 years survival was 88 per cent and 95 per cent and heightincrement was 402 cm and 201 cm; confirmmg the potential ofNorway maple to be a productive forest tree. Provenances thatperformed well were from Germany, the Netherlands, Denmark andYugoslavia; exact locations were not known for all seed collections.A provenance from Russia was included, material from this fareast has rarely been tested in Britain. However, as expected,its performance was relatively poor. The main constraint tofurther planting of Norway maple is the palatability of thebark to grey squirrels (Sciurus carolinensis Gmelin.). However,it is a useful tree for high pH and heavy soils and as an alternativespecies to sycamore (Acer pseudoplatanus L.).     

CONTROL OF CUTWORM IN FOREST NURSERIES

Larvae of Agrotis segetum Schiff (cutworms) damaged seedlingson a light loam soil at Ken nington Nursery, Oxford. Experimentscarried out in 1955–7 investigated the effect of BHC,DDT, aldrin, and dieldrin on cutworms and their phytotoxicityto Sitka spruce (Picea sitcbensis) seedlings. A spray containing 3 lb. aldrin per acre (as a 30 per cent,miscible oil) or 1? lb. dieldrin per acre (as a 15 per cent,miscible oil) gave excellent control of Agrotis segetum larvaeand did no damage to the seedling crop. Both insecticides wereapplied in 100 gallons water per acre. Immediate control ofcutworm was obtained with applications at time of expected larvalemergence (mid-June) or at time of first visible crop damage(mid-July); applications one month later gave good control after3 days. Stock beds containing seedlings of all the conifers commonlyused in Britain have been sprayed in mid-July with aldrin anddieldrin at half the rate used in the experiments. No specieswas damaged and control of cutworm was good.     

Assessing toxicity of post-emergence herbicides to the Spilarctia obliqua Walker (Lepidoptera: Arctiidae)

The lethal and sublethal effects of three post-emergence herbicides, 2,4-D ethyl ester (Weedkill 80WP), imazethapyr (Pursuit 10EC) and quizalofop ethyl (Tergasuper 5EC) fortified with artificial diets were studied on larvae of Spilarctia obliqua Walker (Lepidoptera: Arctiidae). Quizalofop ethyl and imazethapyr caused significant reduction of pest survival at almost all levels; however, 2,4-D ethyl ester was nontoxic. Interestingly, LC₅₀ data (0.230 and 0.855% for quizalofop ethyl and imazethapyr, respectively) obtained from probit analysis were almost equal to labeled doses (x) of quizalofop ethyl (x = 0.16%) and imazethapyr (x = 0.625%), which shows the high toxicity of these compounds against S. obliqua larvae. Among the three herbicides, imazethapyr caused sublethal effects on this pest, increasing the larval period at almost all concentrations tested in the artificial diet. Considering the markedly significant effect of quizalofop ethyl on pest survivorship with no sublethal effect, we suggest incorporating it into the integrated pest management module for S. obliqua in legumes or oilseed crops with other biorational insecticides. Based on toxicity, imazethapyr can be a potential candidate for integrated management of S. obliqua. However, because of its sublethal effects, we advocate caution while using it in the presence of pest infestations.     

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.     

Species-specific drought effects on flower and fruit production in a Mediterranean holm oak forest

A holm oak forest was exposed to an experimental drought (reductionof 15 per cent soil moisture as predicted for this area forthe next decades by General Circulation Models and ecophysiologicalmodels) during 7 years to elucidate the reproductive responsesof the dominant species Quercus ilex L., Arbutus unedo L. andPhillyrea latifolia L. Soil moisture was partially reduced byplastic strips intercepting rainfall and by ditch exclusionof water runoff. During the period studied, meteorological conditionsand soil moisture were continuously monitored, together withflower and fruit production in the three dominant species. InQ. ilex and A. unedo, flower and specially fruit productionwere strongly correlated with annual rainfall, but not in P.latifolia. The experimental drought reduced flower and fruitproduction in Q. ilex by 30 per cent and 45 per cent, respectively.Reductions in flower and fruit production were not significantin A. unedo and were not observed in P. latifolia. A decreasein production of reproductive structures and the different responseof the species studied to a decrease in water availability couldinduce important changes in the competitive ability of the differentspecies and in the long term in the community species compositionand future distribution of these Mediterranean species.     

The Pine Shoot Beetle Tomicus piniperda as a Vector of Blue Stain Fungi to Windblown Pine

After the great gale of 1987, the role of the pine shoot beetle,Tomicus piniperda, as a vector of blue stain fungi to windblownpine in southern England was examined by macerating adult beetlesand culturing the macerate on various agar media. Isolationswere also made from pine tissue associated with beetle galleriesand tunnels. Using data from between three and nine sites, it was found that17 per cent of the overwintered adult beetles were carryingfast-growing Leptographium spp. as they began to construct breedinggalleries in spring 1988. More than half the new generationof adult beetles were contaminated with these fungi when theyemerged in June-July 1988, but this proportion dropped as thelife cycle of shoot-feeding and overwintering progressed. Itaveraged 26 per cent at the time of brood gallery constructionin spring 1989. Isolations made from pine tissue around the galleries also showedchanges in the frequency of blue stain fungi. Of early broodgalleries 25 per cent yielded Leptographium, while the figurefor late galleries was 51 per cent. These results were consistentwith the direct introduction of Leptographium by the parentbeetles into some galleries, and the subsequent rapid hyphalgrowth of the fungus within the tree to colonize tissue adjacentto other galleries. The principal species identified was L. wingfieldii. However,L. lundbergii, L. huntii, L. procerum and an unidentified Leptographiumspecies were occasionally recorded, both on the beetles andin the trees. Graphium species were quite common also. In addition,the black yeasts, Hormonema dematioides and Aureobasidium pullulans,were frequently present, particularly in the pine shoot samples.     

Frost hardening and dehardening in Abies procera and other conifers under differing temperature regimes and warm-spell treatments

Frequent bud frost damage in cultivation of Abies procera Rehderand pending climate changes are the background for this studyof cold hardiness under varying acclimation regime (in closed-topchambers) and experimental warm spells during the cold season.LT₅₀ values were established by freezing tests at differenttimes of year. Damage and deaths were assessed on leader buds,subapical lateral buds, needles and cambium. Minor parallelexperiments involved Abies nordmanniana, Picea abies and Piceasitchensis. Lower acclimation temperatures resulted in deeperfrost hardiness during late autumn but less during spring, comparedwith ambient temperature controls. Elevated temperatures resultedin less deep frost resistance. Apical buds generally developeddeeper frost hardiness than lateral buds but less deep thanthe cambium, varying with species, however. Frost damage inbuds ranged from death over partially destroyed bud contentsresulting in distorted shoots to buds seemingly remaining dormant.Responses to warm spells differed with duration, timing andspecies, ranging from dramatic decrease in frost hardiness withor without subsequent recovery to no reaction. Furthermore,the reactions did not show any clear relation to dormancy level.For A. procera, exposure to fluctuating temperatures appearedto be particularly problematic. This explains why this speciesdevelops best in coastal climates, and in sites sheltered fromtemperature extremes either by hedging, a winter snow cover,or topography. The Christmas tree production will suffer severelyon sites with harsh temperatures due to losses of lateral andterminal buds, which destroy the crown symmetry. Clipping ofgreenery is less influenced by frost damages, although the developmentof normal branch whorls is often disturbed.