The impact of former agriculture on habitat conditions and distribution patterns of ancient woodland plant species in recent black alder (Alnus glutinosa (L.) Gaertn.) woods in south-western Poland

Little is known about the influence of former agricultural use of soils on the forest recovery process in post-agricultural black alder (Alnus glutinosa) woods – the most fertile and the wettest forest habitats among the European temperate forest types. Thus, studies focusing on edaphic, hydrological and light conditions responsible for colonization mechanisms present in such woodlands adjoining ancient ones were undertaken in south-western Poland. In the 16 m² quadrats of the 33 transects laid out perpendicularly across the ancient-recent forest boundary, data were collected on herb layer composition, chemical soil properties, as well as illumination level. Additionally, groundwater level in the spring months was recorded in piezometers. The number and cover of true woodland herbs were higher in ancient woods, regardless of forest type. Soils in ancient woodlands reached higher levels of Al³⁺, K⁺, cation exchange capacity (CEC), available K, P, and organic C, whereas their pH was lower. The illumination level of the forest floor was greater in recent woods. Linear regression showed that recent wood age had a negative effect on pH and base cations, but positive on Fe²⁺, Ca²⁺, available P and Mg, CEC, and on C and N contents. CCA results showed that woodland age, pH, humus type, groundwater level, available Mg and K were always among those variables having the highest contribution in explaining the distribution pattern of woodland species in recent woods. Total N and available P contents were always higher in ancient woodland soils than in recent, and their content grew with time. Thus, they cannot be treated as indicators of former agricultural use of recent alder wood soils. Urtica dioica, Poa trivialis and Galium aparine, the three competitive herbs, avoided sites with a high level of groundwater, combined with poor illumination level. In order to create the best possible conditions allowing for effective forest recovery in habitats of such high fertility, it is essential to maintain a good water regime and shade in the forest floor. This in turn reduces the competitive exclusion of woodland flora by the aggressive herbs and facilitates the immigration of typical woodland herbs.     

Effects of climate and management history on the distribution and growth of sycamore (Acer pseudoplatanus L.) in a southern British woodland in comparison to native competitors

Sycamore (Acer pseudoplatanus L.) is an invasive, non-nativespecies in Great Britain and its management in conservationareas is controversial. Climate change adds further uncertaintyto decision making. We investigated the role of management historyin determining present-day abundance and the effects of climaticvariability on growth, photosynthesis and phenology at WythamWoods, a UK Environmental Change Network (ECN) monitoring site.Relatively few sycamore trees were found in undisturbed ancient,semi-natural woodland and recent plantations, despite beingcommon in other areas of the site. Sycamore grew more slowlythan ash (Fraxinus excelsior L.), its principal competitor,but at a similar rate to pedunculate oak (Quercus robur L.)in the period 1993–2005. There were fewer sycamore thanash seedlings, regardless of which species dominated the canopy.Growth of sycamore was slower in dry periods than wet ones andlower photosynthetic rates were measured in canopy leaves underdry compared with wet soil conditions. This study thereforesuggests that sycamore does not present a serious threat toundisturbed ancient woodland on the site and that it may eventuallydecline in areas of the site where it competes with ash, inthe absence of disturbance. It may also decline under climatechange if summer droughts become more frequent.     

Long-term woodland dynamics in West Glen Affric, northern Scotland

The former woodlands west of Loch Affric are described frompollen analyses. Related records of climate change from theanalysis of lake-level change and peat growth are also presentedto explore the importance of climate in driving woodland change.The woodlands were more diverse than extant pinewoods to theeast, with a very considerable deciduous component. They developedin the early Holocene period, and brief periods of range expansionand contraction are recorded within a pattern of overall woodlandstability over thousands of years, despite the high frequencyand intensity of climatic excursions, until a final collapsein all woodland communities occurred at around 4000 calibratedyears ago (BP). This collapse had a climatic origin, but theprecise character of the climate change is ill-defined.     

Changes in the Ground Flora of a Broadleaved Wood within a Clear Fell, Group Fells and a Coppiced Block

Changes in the ground flora, relative to undisturbed woodland,were measured in permanent (100 m² quadrats in a clear fell,group fells and a coppice area in Sheephouse Wood (Buckinghamshire)from 1984 to 1988. Species numbers rose rapidly in the clearand group fells to about twice that in the undisturbed woodland.Species indicative of higher light, moisture and nutrient conditionsappeared after felling or coppicing and the flora shifted fromone dominated by stress-tolerant species to a flora with morecompetitive and ruderal species. After two years, in both clearand group fells, the ground flora covered 90–100 per centof the quadrats (compared with 30–75 per cent in the undisturbedwoodland), but species richness started to decline. This wasprobably because of increased competition associated with thespread of grasses and rushes (Agrostis stolonifera, Deschampsiacespitosa, Holcus mollis and Juncus spp.). Species richnessdid not increase as much in the coppice area, and bramble (Rubusfruticosus), rather than grasses, became dominant. The subsequentdecline in species richness was more gradual in the coppicearea than in the clear fells. During this period there wereno significant changes in the species richness, total coveror species composition within the undisturbed woodland.     

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.     

The composition and structure of deciduous woods in County Down,Northern Ireland

The results of an ecological survey of deciduous woods in County Down, Ireland, are presented. Variation in the composition of the ground flora, canopy composition and structure, and patterns of tree regeneration was related to environmental gradients of soil mineral nutrient status, the intensity of grazing and the degree of soil water-logging. The effects of the dominant species of the tree canopy on the ground flora were shown to be secondary. Woodland clearance has occurred mainly at low elevation sites with changes in land use to either coniferous plantation or agricultural land.The woods are very different in character from native Irish Blechno-Quercetum and Corylo-Fraxinetum but are closely related to mixed deciduous woods which have previously been described in England and Scotland. The introduced trees, Fagus sylvatica and Acer pseudoplatanus, have naturalised and their regeneration patterns at different sites are related to edaphic factors. The regeneration status of the current canopy dominants and associated trees, however, suggests that other changes in canopy composition will take place if the woods are not managed further. Replacement of Pinus sylvestris and Fagus sylvatica by Fraxinus excelsior and Acer pseudoplatanus is predicted, particularly at higher elevation sites.     

The Impact of Large Herbivores on the Conservation of Semi-natural Woods in the British Uplands

This review considers the history of woodland grazing and thegrazing ecology of large herbivores in the context of the conservationof semi-natural woods in the British uplands. The impact thatgrazing has on natural regeneration is frequently highlightedbut its effects on other vegetation, particularly the balancebetween bryophytes and higher plants are equally important.Grazing also influences both invertebrate and vertebrate populationsthrough its effect on vegetation structure. A low level of grazingby large herbivores in woodland provides a greater diversityin vegetation structure and species composition than eitherthe current prevalence of overgrazing or the absence of grazingin fenced woods. Low levels of grazing may also create conditionsfor the highest diversity of both plants and animals. The practicalproblems of managing woodland grazing are addressed in relationto conservation objectives for upland woods. Rotational grazing,seasonal grazing and reducing the overall levels of grazingin a wood are identified as possible management options. Furtherwork on these is however needed and topics for future researchare identified.     

Morphological and physiological differences in Scots pine seedlings of six seed origins

One-year-old seedlings of Scots pine (Pinus sylvestris L.) offour native seed origins (Loch Maree Islands, Glengarry/GlenMorriston, Glen Affric and Abernethy), a commercial Britishseedlot, and a seedlot from Hedesunda, in middle Sweden, werecompared at monthly intervals from October 1993 to April 1994.Seedling morphology, root condition, root frost hardiness andbud dry matter were determined at each date. There were clear morphological differences among seed origins.Seedlings raised from the commercial seedlot (A70) were largerbut had a poorer root:shoot ratio than the other seed origins.Of the native pines tested, the Loch Maree Islands origin allocateda larger proportion of its photosynthate to fine roots and needlesand smaller proportion to woody structures. Seedlings raised from the commercial British seedlot tendedto have poorer bud lignification than the other origins andalso, in autumn, higher electrolyte leakage rates from its fineroots. During winter, the Swedish origin had the lowest fineroot electrolyte leakage. Seedlings of all origins showed aprogressive increase in fine root hardiness towards mid-winterwith maximum hardiness (–7°C) in January. Dehardeningoccurred over subsequent months reaching –3°C in April.Differences among origins were evident. The Swedish seedlotdeveloped greater frost resistance than the other origins, hardeningbegan earlier in autumn and dehardening began later in spring.The commercial seedlot hardened later than the other originsbut reached a similar level of frost hardiness by January. Ofthe native pines, seedlings of the Loch Maree Islands originwere slowest to develop root hardiness.     

Woodland Elms in Wessex

A study undertaken by the Wessex Silvicultural Group on thegrowth of elm in woodland disclosed the occurrence of potentiallyvaluable elm stands in many parts of south-west England. Thepaper discusses some aspects of cultivating elm in woodland,and provisional estimates of volume production are made. Muchof the information relates to English elm (Ulmus procera Salisbury),but other species and hybrids are briefly reviewed. Commentson some current elm problems are included.     

Long-term deer exclusion in yew-wood and oakwood habitats in southwest Ireland: Changes in ground flora and species diversity

Changes in ground flora were monitored over a 32-year period in deer exclosures in a yew-wood and a neighbouring oakwood in Killarney National Park, southwest Ireland; both woods are Annex I habitats under the European Habitats Directive. Comparison was made with unfenced plots adjacent to each of the exclosures. During the period of the study, both woods were heavily grazed by introduced sika deer (Cervus nippon). In the yew-wood exclosures, total ground flora cover increased markedly during the period of deer exclusion, the main species to increase in abundance being Rubus fruticosus agg. and Hedera helix. Herbaceous species increased initially in frequency but subsequently declined; herbaceous species had higher total cover in unfenced plots than in fenced plots at the end of the study. In the oakwood, Luzula sylvatica and Vaccinium myrtillus expanded their cover in one exclosure with cover in ferns declining, but in other exclosures where dense holly thickets developed, it was instead R. fruticosus and H. helix that became more abundant within the fences than outside. Overall, long-term fencing has caused a shift from vegetation characterised by woodland specialist to woodland generalist species and there are indications of a long-term decline in diversity. We conclude that chronic heavy grazing in these woodlands has strongly influenced the overall abundance and composition of the ground flora, but that complete exclusion of grazing is also undesirable due to potential declines in diversity of woodland specialists.     

European aspen (Populus tremula L.): a review with particular reference to Scotland II. Values, silviculture and utilization

Interest in European aspen (Populus tremula L.) has increasedin recent years as a result of efforts to restore and extendnative woodland, and to diversify the range of species usedin forestry plantations. Aspen is a straightforward tree tomanage; it is of considerable ecological value and capable ofproducing utilizable timber. Planting of aspen in native woodlandis currently limited by a shortage of plants of Scottish origin.Propagation from seed, whilst possible, has not been practised,and recent efforts to produce stock have concentrated on vegetativemeans. The use of aspen as a component of plantation forestrycould be increased on appropriate sites; it is an excellentamenity species and its timber is currently acceptable as chipwoodand could complement the production of poplar timber in thelowlands. However, on the basis of limited data, growth ratesand stem form of aspen in Scotland appear to be rather poorerthan on the European continent where aspen is a significanttimber producing species. More would also need to be known aboutits susceptibility to disease before its timber production potentialcould be evaluated properly.     

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.

     

The Dean Nestbox Study, 1942-1964

Regular observations began in 1948 in the Forest of Dean, Gloucestershire,England, on an area of 60 acres carrying eventually c. 275 nestboxes.The area, planted to Quercus robur in 1814, has the appearanceof a Quercetum petraeae. Three-quarters, not grazed since 1947,has a varied shrub layer and a field layer distinguished bybrambles and bracken; the grazed area has a bracken/bluebellfield layer. Invertebrate life has been studied mainly in relationto the food of titmice Parus spp. The breeding bird communityincludes most of the species of British oak woodland. The mainoccupants of the nestboxes are two summer visitors, the PiedFlycatcher Ficedula hypoleuca and Redstart Phoenicurus phoenicurus,and two residents, the Great and Blue Tits, Parus major andP. caeruleus. There is some evidence of interspecific competitionfor nestboxes, but blocking of the entrances to exclude theresidents and favour the summer visitors gave inconclusive results.The populations of both seem to fluctuate independently (Fig.2). All the species were able to tolerate each other as neighbours.The effect of hard weather on the residents is demonstratedgraphically, but is only one factor in a complex situation.No evidence has emerged from the study that small insectivorousbirds can contain a major larval infestation.     

Forest and Woodland in Devon

Based on the 1980 Census, the distribution, composition andownership of woodland in Devon is described. A large proportionof privately-owned woodland is not under formal management andmuch of this is of coppice origin. Although of indifferent timberquality, these woods are considered important features of thelandscape particularly in relation to the Dartmoor NationalPark. Assessment of small woods and park trees suggests a deficiencyof young oak and an increase in colonising broadleaved species. Over much of the county the physical conditions are suited tothe growth of exotic conifers and plantations of these are capableof the economic production of high quality saw timber to satisfylocal and other markets. The scope for expansion is limitedhowever and the future of much of the broadleaved woodland dependson the attitudes adopted by their owners and the local authoritiestogether with the grant aid available.     

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.     

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.     

The potential for developing a normal age-structure in managed ancient woodland at a local scale in three English counties

This paper describes a model for assessing the potential forsustained management of ancient woodland at the local landscapescale, based on the premise that a ‘normal’ foreststructure is the best option for integrating nature conservationwith provision of a regular supply of timber. The concept of‘normality’ is applied to clusters of small ancientwoods which are considered together and treated as a whole. Data on ancient woodland distribution are used from West Sussex,Essex and North Yorkshire. At ten sample points within eachcounty the woodland area within a 25-km² block centred on thepoint was considered to see whether a normal forest structurecould be created and maintained by sustained management usinglikely minimum felling rates and average rotation lengths forthe main species for both high forest and coppice systems. Themodel was also tested for situations where small woods or woodswith conservation status were excluded from the system, as wellas for different minimum felling rates. The areas proposed forfelling within ancient semi-natural woods currently listed withinthe Woodland Grant Scheme (WGS) (II) are higher than can bemaintained in the longer term in West Sussex and Essex. The model provides a preliminary method for setting the contextof individual forestry schemes withn the wooded landscape asa whole.     

A Background to Silviculture in Irish Forestry

The writer traces the history of tree species and woodland inIreland from early times down to the start of state forestryabout 1906. He then considers the influence which the availablityof land, the geology, the distribution of forest types, andthe climate have had on silviculture since. He discusses themain species used, pure and in mixture, and notes that the typeof ground available is the main limiting factor in the choiceof species and that the tendency today is towards a very limitedrange of species in which Picea sitchensis and Pinus contortahave an important part to play.