Atlantic Oakwoods Research Articles

Can epiphytic lichens of remnant Atlantic oakwood trees in a planted ancient woodland site survive early stages of woodland restoration?

Key messageEpiphytic lichens of remnant Atlantic oakwood trees, enclosed within a recently planted conifer matrix, show ability to survive early stages of woodland restoration (conifer removal).ContextAtlantic oakwood, ancient semi-natural woodland (ASNW), supports important epiphytic lichens. Fragmented ASNW, historically in-filled with conifers, are now being restored to reflect ASNW tree and ground flora character. Concerns exist that sudden and total removal of the conifer matrix will be detrimental to the epiphyte diversity of remnant trees retained within the former plantation.AimsHere, we ask whether an unintended consequence of habitat restoration is the loss of epiphyte populations on remnant trees.MethodsDynamics of ground flora development were studied at one 50-ha site on the west coast of Scotland using indicator species occurrence and species traits. Change in cover of lichen species was determined and lichen vitality was assessed in two Lobaria species using chlorophyll fluorescence as a proxy. Assessments pre-, post- and nine years after conifer removal were made in plantation areas (containing remnant oak trees) and ASNW areas.ResultsRe-vegetation of the ground flora was predominantly by ASNW vegetation. Species richness and occurrence of native woodland indicator species increased and the community showed stronger competitor traits. Lichen vitality was initially reduced but recovered. Tests showed change in the abundance of key lichen species and lichen community diversity was non-significant despite the loss of four lichen species on remnant trees.ConclusionGround flora dynamics indicate site recovery was underway within eight years of restoration activities and epiphytic lichens although variable in response were in this study largely unaffected, this restoration approach could be appropriate for other Atlantic oakwoods where lichen conservation is an objective.

The character of the Atlantic oak woods of the Great Hungarian Plain

The aim of this paper is to compare the wood charcoal assemblages from several archaeological sites near Polgár (north-eastern Hungary) with the pollen records of the same area in order to infer the character of forest communities that developed between 7500 and 6500 cal. yr BP. One question of particular interest is the structure of the woodlands in the mid-Holocene, particularly during the Holocene Climatic Optimum, when summer mean temperatures were higher than today. Pollen studies in this period suggest the dominance of wooded steppe with significant, naturally open, steppe-covered habitats. Hazel (Corylus avellana) and oak (Quercus sp.) were the most important pollen components. On the other hand, the anthracological records suggest considerably less hazel, more oak admixed with several other woody taxa, particularly heliophilous Cornus sp. and Rosaceae trees or shrubs that still remain either invisible or are poorly represented in the pollen diagrams. The two types of data thus complement each other, and serve to better characterise this key time interval when Neolithic agriculture spread across the Great Hungarian Plain. Special attention is given to the joint occurrence of cornelian cherry (Cornus sp. cf. C. mas) and European smoke bush (Cotinus coggygria), as these commonly occur in the Sub-Mediterranean-subcontinental wooded steppe and thermophilous oak forest associations in SE Europe these days, under warmer summer conditions than those experienced in Hungary today. Their appearance and, in the case of cornelian cherry, abundance in the Atlantic wood charcoal assemblages suggest that, during the Atlantic phase, the wooded steppes of the north Great Hungarian Plain could have been of a Sub-Mediterranean character.

Oceanic and temperate rainforest climates and their epiphyte indicators in Britain

A biogeographic zone with high oceanicity is a well described feature of the European Atlantic region. This oceanic zone intersects with a zone of European temperate rainforest that has received increasing conservation recognition. Although having a degree of spatial overlap, the terminology applied to these different zones is not synonymous. Temperate rainforest is one example of an oceanic system, alongside others such as blanket bog or liverwort heath. Conversely, oceanic systems provide one type of climatic setting suitable to the development of temperate rainforest, alongside other and contrasting landscapes such as the orographic climate of continental mountains. Zones of high oceanicity and temperate rainforest are both strongly represented in the British Isles, and this study examines the degree of spatial overlap in Britain for standard definitions of each. Lichen epiphyte indicators associated with zones of oceanic woodland or temperate rainforest were quantified, and subsequently tested for conservation priority Atlantic oakwoods (Annex 1 Habitat Code 91A0: old sessile oak woods with Ilex and Blechnum in the British Isles). Discrepancies between oceanic woodland and temperate rainforest led to slightly different sets of indicator species that could be applied in biodiversity and habitat quality assessments. The definition of oceanic systems appeared to include warmer and lowland situations for example in coastal Wales and south-west England. In contrast, temperate rainforest extended to cooler upland areas in north-eastern Scotland. The species indicators for oceanic and temperate rainforest were nevertheless effective in identifying sites with different conservation priorities, such as for protection or restoration.

Reprint of “Long-term changes and drivers of biodiversity in Atlantic oakwoods”

Atlantic oakwoods are of high conservation value in western Europe. Developing effective conservation management policies requires data on the dynamics of woodland over long time scales. Such data are not available through monitoring or documentary records so palaeoecological data have been investigated. Pollen and charcoal data from four western Irish woods covering up to 7000years have been analysed to provide information on changes in alpha and beta diversity, rates of change and fire history over time. These analyses reveal that the most significant changes in biodiversity relate to the loss of Pinus sylvestris from these woods followed by their exploitation and subsequent management for timber, charcoal and tan bark. The structure and composition of the present day woods still display a strong legacy from their exploitation and this raises important questions relating to the long-term conservation management of these woods.

Long-term changes and drivers of biodiversity in Atlantic oakwoods

Atlantic oakwoods are of high conservation value in western Europe. Developing effective conservation management policies requires data on the dynamics of woodland over long time scales. Such data are not available through monitoring or documentary records so palaeoecological data have been investigated. Pollen and charcoal data from four western Irish woods covering up to 7000years have been analysed to provide information on changes in alpha and beta diversity, rates of change and fire history over time. These analyses reveal that the most significant changes in biodiversity relate to the loss of Pinus sylvestris from these woods followed by their exploitation and subsequent management for timber, charcoal and tan bark. The structure and composition of the present day woods still display a strong legacy from their exploitation and this raises important questions relating to the long-term conservation management of these woods.

A study of the epiphytic communities of Atlantic oak woods along an atmospheric nitrogen deposition gradient

1 Atlantic oak woods are of high conservation value and contain many rare lichens and bryophytes. The effects of nitrogen pollution on these epiphytic communities have not been previously studied. We investigated the composition of Atlantic oak wood epiphytic communities in relation to atmospheric N deposition in order to identify N indicator species and propose a critical load for such communities. 2 The epiphytic communities of seven Atlantic oak woods receiving estimated total nitrogen deposition in the range 10–53 kg N ha−1 year−1 were surveyed. Exposure of epiphytes to atmospheric N over 7 months was measured in terms of stemflow flux and concentration and airborne NH3. 3 Redundancy analysis (RDA) related the species to stemflow chemistry and bark pH. Different groups of species were found at (i) a coastal low N deposition site (Graphina ruiziana, Lecania cyrtella, Lobaria pulmonaria, Opegrapha atra, Orthotrichum affine, Melanelia fuliginosa ssp. glabratula and Pertusaria hymenea), (ii) inland low N deposition sites (I. myosuroides, F. tamarisci, Plagiochila atlantica, Cladonia chlorophaea, C. squamosa, Hypotrachyna laevigata and Thelotrema lepadinum) and (iii) high N deposition sites (Hypnun andoi, Hypnum cupressiforme, Calicium viride, Chrysothrix candelaris, C. coniocraea, Hypogymnia physodes, Parmelia saxatilis, Phyllospora rosei and Usnea subfloridana). 4 RDA analysis showed that bark pH and concentration in the stemflow explained the greatest amount of variation in the species composition among the sites. The sites separated into two groups (low and high concentration) leading to an estimate for the critical load for N deposition for epiphytes in Atlantic oak woods of 11–18 kg N ha−1 year−1. 5 Analysis of the occurrence of species against N levels suggested that I. myosuroides and F. tamarisci are indicators of small N inputs, whereas H. andoi, C. coniocraea, P. saxatilis and H. physodes are tolerant of increased N loads. 6 Different forms of N (, , NH3) were found to significantly affect the occurrence of different species. Some species were sensitive to total flux while others were sensitive to concentration.

Atlantic oakwoods in Great Britain: Factors influencing their definition, distribution and occurrence

Summary Atlantic oakwoods are the oceanic oak-dominated woodlands that fringe the western coast of Britain and Ireland and, due to their high humidity and rich and luxuriant lower plant assemblages, have been regarded as ‘temperate rainforest’. However, unlike the similarly iconic Caledonian pinewoods, Atlantic oakwoods have no formal designation or associated woodland classification type, which gives some uncertainty to the extent of the oakwoods habitat on its fringes. This paper examines the various elements central to the concept of an ‘Atlantic oakwood’ and discuses their occurrence in Great Britain.

Population changes of some bird species in Scottish and Welsh Atlantic Oakwoods between the 1980s and 2003/4 using data from the repeat Woodland Bird Survey

Summary Atlantic Oakwoods support a unique breeding avifaunal community, characterised by redstarts, wood warblers, pied flycatchers and tree pipits. We have used a sample of data from the national Repeat Woodland Bird Survey to examine population changes in these four species within Atlantic Oakwoods over the last two decades. We used data from 29 woods in Argyll in western Scotland surveyed in 1985, and from 27 woods in Gwynedd in northwest Wales surveyed in 1983 and compare them with data from repeat surveys carried out in 2003 and 2004. In this paper, we report the population changes for these species between these two periods and examine whether changes differed between Scottish and Welsh sites.

Woodlands at the edge: A European perspective on the Atlantic Oakwood Plant Communities

Summary The Atlantic Oakwoods can be seen as ‘at the edge’ in two ways. First, they lie at the extreme oceanic end of a series of Quercus robur and Q. petraea woodlands which stretches eastwards from the North Atlantic coast to the continental heartland of Europe. Second, they are at the northern limit of a range of oceanic oakwoods which extends southwards to Iberia where Q. pyrenaica is an important canopy companion. This paper outlines the main variations in trees, shrubs, herbs and cryptogams that can be seen along these two climatic gradients, so as to highlight what is truly distinctive about the Atlantic Oakwoods and how we might rightly value them.

A forest habitat network for the Atlantic Oakwoods in Highland region, Scotland

Summary The need to conserve biological diversity and ensure the future viability and integrity of Atlantic oakwoods in a fragmented landscape has led to strategies that facilitate a more holistic view of biodiversity conservation across extensive areas. The Scottish Forestry Strategy contains a major aspiration to develop forest habitat networks through the restoration and improvement of existing woodland and the expansion of new woodland. The Forest Research landscape ecology model BEETLE (Biological and Environmental Evaluation Tools for Landscape Ecology) uses a focal species approach to assess the functional connectivity of habitat within the wider landscape matrix. This model has been used to predict the current habitat network for Atlantic oakwood specialists in the Highland region of Scotland. The analysis outputs are presented with an approach to help practitioners and planners visualise the opportunities to target expansion, conversion or restoration of Atlantic oakwoods and their intrinsic biodiversity.

Route, speed and mode of oak postglacial colonisation across the British Isles: Integrating molecular ecology, palaeoecology and modelling approaches

Summary This paper describes the route, speed and mode of colonisation of oaks by integrating a number of independent analyses using molecular ecology, palaeoecology and simulation modelling approaches. Using a synthetic map of the contemporary distribution of chloroplast DNA (integrating several published and unpublished data sets and describing variation in 1468 trees from 313 autochthonous stands of Q. robur and Q. petraea from Britain and Ireland), and considering the postglacial topographic landscape, the most likely routes of postglacial colonisation across the British Isles are suggested. The overall pattern of these directions agrees with previous interpretations, but several routes, particularly those into Ireland, differ from previous interpretations and benefit here from using a single synthesised data set. Interestingly, the Atlantic oakwoods appear to have been colonised by individuals bearing a single haplotype (type 12). Two palaeoecology data sets, published separately for Britain and Ireland, are synthesised here and used to infer the timing of first arrival of oaks across the British Isles (between 9500 and 6000 years before present). The maximum observed colonisation speed within the British Isles is approximately 500 m year-1 in central and southern England. Outputs from a simulation model, which mimics postglacial colonisation processes, and which has been parameterised for the colonisation rate observed from the pollen core record and contemporary cpDNA structure, predict that the rapid colonisation rate observed, for at least the southern portion of the British Isles, can only be achieved via very rare (an approximate frequency 0.01%), very long distance seed dispersal events (up to 100 km). Potential agents of such dispersal events are birdsor major meteorological disturbances, e.g. hurricanes. Additional simulation modelling and genetic analysis of latitudinally stratified populations indicate that non-synchronous colonisation fronts, topographic barriers and temperature related survival may also have had an effect on the speed of migration and resulting genetic structure. Finally, in an attempt to record predicted long distance seed dispersal events, a novel curve fitting technique is applied to molecular parentage assignment data for field established seedlings from a contemporary population. A notable discrepancy is recorded between contemporary field estimates (just over 1 km) and those predicted by simulation modelling, and is discussed in detail. A concluding section describes future research priorities.

Argyll oakwoods: Use and ecological change, 1000 to 2000 AD — a palynological-historical investigation

Summary This paper explores the relationship between ecological change and human use in Atlantic oakwoods during the last millennium. Information on vegetation change derived from high resolution pollen analytical studies can sometimes be satisfactorily linked with localised documentary evidence of historical woodland management. Key findings based on this approach using case studies of individual woods in Lorn are presented. Relatively diverse woods, probably containing old-growth, were transformed in the medieval period into disturbed open stands used for pasturage and local domestic wood supply. Around or prior to 1700 AD commercial management began and modes of exploitation changed so that, for a period until the late 19th or early 20th century, stands were cropped intensively. In the most recent 100 years or so, use of the woods has been relatively minor except as a grazing resource. The consequences of this history for the development of the current condition and character of Atlantic oakwood resour...

Oceanic bryophytes in Atlantic oakwoods

Summary The oceanic bryophyte element of the vegetation of British and Irish Atlantic oakwoods is not only the richest bryophyte flora in Europe, it is also one of the richest bryophyte floras in the world. The oceanic climate and the buffering provided by the tree canopy are critical in maintaining the constant humidity and equable temperatures which provide the basis for this diversity. Though the initial impression of these woodlands is of a homogeneous green carpet over both rocks and trees, most good woodlands will have over 200 different species of moss and liverwort, many of which are very specific as regards micro-habitat. Within the woodlands, a recently glaciated landscape gives much exposed rock of different aspect, texture and chemistry, and also turbulent burns in deep ravines which enhance the humidity. These niches are exploited by different bryophyte communities which may contain a number of species that are very rare in European terms and for which we have a special responsibility. Any management plans for these woodlands should take account of this variety of micro-habitat, and monitoring of the effects on bryophyte populations of any resulting change in the structure of ground vegetation is vital.

Regeneration in Atlantic oakwoods: has deer management had a beneficial effect?

Summary The fragmented Atlantic oakwoods of western Europe are a habitat of conservation importance, and in the UK are threatened by browsing of young trees, invasion by exotic species and under-planting with conifers. Previous research showed that small tree saplings were abundant in Scottish oakwoods, but growth was limited by shading and frequent browsing. Within this study, we aimed to assess whether subsequent changes in deer management had resulted in increased sapling growth, and to determine whether planting of oak within lines of brash left after conifer clearance had offered long-term protection from browsing. Pellet group counts at two sites in Glen Nant, Argyll, indicated that use by red deer, roe deer and sheep was lower than five years previously. Within one site, sapling survival was high despite continued browsing, and some saplings, particularly hazel, had gained substantial height increments. In contrast, at the second site, survival was low and the surviving saplings had managed no net growth. At a third site in Glen Etive, Argyll, partially protected by fencing, survival of oak saplings was high, and two thirds had increased in height. Planting oak saplings amongst lines of conifer brash did not offer long-term protection, but within a fenced exclosure saplings had grown substantially, despite vigorous competition from the field layer. Deer management policies within these woods are beginning to show some success in promoting regeneration, but they will need to be continued for a long period to overcome the low growth rates of hardwood species.

Biodiversity and ecology of the invertebrates of Atlantic Oakwoods

Summary Woodland in general supports the richest invertebrate fauna of any habitat in Britain. The number of species depends on the structure of the wood and the age of the trees within it. The greatest biodiversity is associated with oaks although the difference between the communities found on the two oak species is not clearly understood, the Sessile Oak woods have been less well studied than their lowland equivalents, particularly so in Scotland. A number of minor habitats within the wood are important for many invertebrates and the presence of many of these may be due to past management. Every part of the oak tree, the leaves, flowers, acorns, bark and wood, supports invertebrates, herbivores, predators and parasites, and the fallen leaves and deadwood provides habitat for a complex of detritus feeders. Within the woodland the other trees, the fungi and the ground flora all have characteristic woodland invertebrates. Only a few studies, on beetles and spiders, have looked at which invertebrates are p...

Overall biodiversity and the spatial patterns of atlantic oakwoods

Summary Maintenance of biodiversity in these complex woodlands, that have been historically much altered, is based on actions promoting conservation of existing values but which may also prepare them for future changes, such as a decline in the dominance of oak in the canopy. Site condition monitoring of the 9000 ha of Atlantic oakwoods already designated indicates damage from excessive browsing, invading species and lack of deadwood. These conditions and potential hazards from climate change are being addressed by attempting to expand and interconnect existing woodlands to reduce fragmentation and increase possibilities for species to migrate.

Postglacial history of Atlantic oakwoods: Context, dynamics and controlling factors

Summary We present here a review of the recolonisation of the Atlantic oakwoods following the end of the last glacial period. The study is based on two independent data sources: palaeoecological and phylogeographical data. The spread of oak is examined at two scales: (1) continental, allowing a consideration of the location of glacial refugia and the broad outlines of the migration, (2) the Atlantic coastal region, in order to establish the specific history of the Atlantic oakwoods. Climatic and human controls on the timing, speed and pattern of spread are considered, in particular, the conditions of the early Holocene period during which the majority of the recolonisation took place.

Oak as a commercial crop in the eighteenth and nineteenth centuries

Summary The main period of the exploitation of the Atlantic oakwoods lasted from around 1700 –1900, and was intense only from 1750–1850, though it had been preceded by a long period of anthropogenic interference of which medieval boatbuilding at least had the potential to alter the character of the woods. The Irish were pioneers when they began to search the coast from the Solway to the Great Glen for fresh supplies of oak bark for their tanning industry, and early in the 18th century this involved an attempt to buy large swathes of Argyll oakwoods, and also to create iron works at Glen Kinglas to utilise local charcoal. This failed, but by mid-century English ironmasters had followed them at Bunawe and Craleckan, works ambitious enough to draw fuel from most of the area within reach of the sea, and this led to greater care being taken of the woods involving the exclusion of stock, systematic rotational coppicing and apparently species selection in favour of oak. Management for tanbark by Scots to supply ...

The fungi of Scottish Western oakwoods

Summary Unfortunately the Atlantic oakwoods of Scotland have never been targeted by mycologists and information is very patchy. The best data lie in the lists of fungi from the Inner Hebridean oakwoods and it is on these records which go back to the end of the 19th century, and limited information from the mainland that a potential picture is offered. There appear to be no fungi specific to Western oakwoods and there are few differences between eastern and western oak communities in Scotland. Emphasis is placed on the need for more funding for those who can identify and recognise potential indicator species so that progress can be made.

Growth and tissue nitrogen of epiphytic Atlantic bryophytes: effects of increased and decreased atmospheric N deposition

Summary Atlantic bryophytes are of European conservation importance, yet the effect on them of excess atmospheric nitrogen is relatively unknown. This study assesses the effects of increased atmospheric N deposition on the growth and tissue N of epiphytic Atlantic bryophytes, and their potential to recover following a decline in N deposition. The N received in stemflow by bryophytes at two sites was measured and compared to model predictions. Four species of epiphytic bryophytes (Isothecium myosuroides, Dicranum scoparium, Frullania tamarisci and Ulota crispa), typical of Atlantic Oak woods, were studied in a 12‐month reciprocal transplant experiment between a pristine Oak woodland receiving a modelled atmospheric deposition of 12 kg N ha−1 year−1 and a polluted one receiving 54 kg N ha−1 year−1. Tissue N concentration increased and growth declined following an increase in atmospheric N deposition in all species except Ulota crispa. Conversely, tissue N concentration decreased and growth increased in Frullania tamarisci following a decrease in atmospheric N deposition, with similar non‐significant patterns in the other species. The reciprocal transplants indicate a detrimental effect of increased N deposition on the bryophyte species studied. The study indicated recovery following a decrease in atmospheric N deposition, but the responses caused by decreased N deposition were smaller than those due to increased N deposition. This suggests that the time‐scale for recovery of bryophytes from excess N deposition is longer than the timescale of nitrogen impacts.