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Three radiocarbon-dated pollen diagrams are presented from Holocene peat and lake deposits in Snowdonia, close to the Late Iron Age/Romano-British ironworking hill-fort of Bryn y Castell, Gwynedd, in upland north Wales. This paper discusses pollen, charcoal and peat-stratigraphic evidence for major local vegetation changes and for the development of the surrounding cultural landscape during the last 10000 radiocarbon yr. Pollen data from one of the sites (BYC 2) provided a vegetational record for most of the Holocene. The early part of the sequence suggests an oligotrophic lake in a landscape that is being colonized b birch-pine woodland; later, mixed deciduous woodland surrounds an infilling lake basin. Dating of peat deposits at two of the sites (BYC, BYC H) indicated that their pollen records commenced between 5500 and 5000 yr BP. By this time, the lake basin was fringed by alder carr. There followed a gradual and then, c. 2700 yr BP, a more abrupt decline in woodland, such that, by the end of the Bronze Age and with the basin largely terrestrialized, the local landscape became dominated by mire vegetation communities, which have persisted to the present. Human activity seems to have been a major factor in the loss of woodland cover. Although there is some circumstantial evidence for earlier phases of human disturbance at BYC 2, human activity becomes increasingly apparent from c. 5000 yr BP. During the mid Holocene, the impact of Neolithic and early- to mid-Bronze Age cultures appears to be characterized by temporary woodland clearances, for arabIe and pastoral agriculture. By c. 2700 yr BP the majority of woodland cover seems to have been permanently removed from the landscape, but as there is scant archaeological evidence for late Bronze Age cultures in this part of Snowdonia, other factors, especially climate change, could be implicated. During the late Holocene, especially during part of the late Iron Age and Romano-British period, remaining local stands of woodland seem to have been exploited for iron smelting, although the overall impact of ironworking was limited. [ABSTRACT FROM AUTHOR]

Data are presented in summary form in both percentage and influx radiocarbon-dated pollen diagrams from a site (MYG) in a valley mire near Moel y Gerddi, Ardudwy, 4 km north-east of Harlech, north-west Wales. Evidence indicates that this valley mire was dominated by alder (Alnus) carr soon after the inception of peat growth, which dates from 8700 B.P. These data confirm the notion of an early empirical limit of Alnus in north-west Wales (advanced in a previous paper) and, compared with other sites in Wales and the rest of Britain, indicate a very early rational limit here for Alnus (c. 8465 B.P.). Ideas on the migration route and on the spread of Alnus into Britain in the Post-glacial may need substantial revision in the light of this evidence for an earlier presence of Alnus in upland Ardudwy, north-west Wales, than yet known from lowland south-east England. Conceivably, Mesolithic activity might have facilitated the local establishment of Alnus; the evidence for this in upland Ardudwy is evaluated. [ABSTRACT FROM AUTHOR]

The article presents information related to the symposium being organized by the journal The New Phytologist, that will be taking place at the University of Wales, Bangor,Wales, in the month of April, 1997. The topic of the symposium will be putting plant physiology on the map, genetic analysis of developmental and adaptive traits. There is an international panel of invited speakers. The organizers invite both offers of paper and applications to participate from those with active interest in the field. The second symposium will be held in Bangor and will examine another rapidly developing area, the genetic mapping of the physiological character.

This article presents information on the second new phytologist symposium at University of Wales, Bangor, Wales during April 2-3, 1997. Symposium will examine rapidly developing area, the genetic mapping of physiological characters. There is an international panel of invited speakers, including E. Beihassen, K. Bachman, R. Flavell, D. Lydiate, H. Nguyen, S. Quarrie, O. Rognli and S. Tanksley. Additional places are limited but the organizers invite both offers of papers and applications to participate from those with active interests in the field.

Data are presented from pollen analytical investigations of an upland basin peat site (GWC) at c. 395 m.o.d. on Cefn Gwernffrwd, mid-Wales, 15 km north of Llandovery and 15 km south-east of Tregaron Bog. The data are presented in an outline radiocarbon-dated pollen diagram, covering more than 9500 radiocarbon years and zoned in the conventional manner, and in a detailed pollen diagram covering Atlantic and Sub-Boreal times, divided into eight phases. The evidence indicates that pine (Pinus) was not a major post-glacial forest component in this locality, but that hazel (Corylus) may have dominated the upland plateau woods for much of the Boreal. The composition of the Mesolithic forest is discussed and compared with neighbouring areas of the British Isles in the light of this apparent abundance of Corylus and with regard to its migration route into mid-Wales in the Flandrian.. The date for the elm (Ulmus) decline horizon at site GWC is within the expected range and consistent with that obtained from Tregaron Bog. The site is 0.5 km from a recently discovered prehistoric complex of presumed Bronze Age date. Although there is firm evidence for Neolithic clearances, the impact on the forest in this locality was more severe in the Bronze Age. This is apparently at variance with sites elsewhere in mid-Wales, where an open upland landscape has been claimed since the early Neolithic, and more closely parallels findings in Northern Ireland. [ABSTRACT FROM AUTHOR]

Seven megaspore species referable to the genera Hystricosporites and Ancyrospora are described from rocks of lowest Tournasian age in South Wales. Three species, Hystricosporites pyramidalis, Hystrictosporites proximo-tuberculatus, and Ancyrospora cambrica are new, and Hystricosporites bedfordi is a recombination. Further information is added to previously described species, particularly on the exinal layers. The problems of separating the two genera are discussed. [ABSTRACT FROM AUTHOR]

Thalli of four saxicolous lichens on slate rock fragments were transplanted from rock surfaces to horizontal boards and then to south-east-facing and north-west-facing rock surfaces. The radial growth rate of Physcia orbicularis and Parmelia conspersa thalli declined after transplantation to north-west-facing rock surfaces and was unchanged after transplantation to south-east-facing rock surfaces compared with growth rate on the boards. The radial growth rate of P. glabratula ssp. fuliginosa thalli declined after transplantation to south-east-facing rock surfaces and was unchanged after transplantation to north-west-facing rock surfaces compared with growth rate on the boards. The radial growth rate of P. saxatilis thalli was similar on the horizontal boards, south-east-facing and north-west-facing rock surfaces. Those results are discussed in relation to the aspect distributions of the four lichens in South Gwynedd, Wales. [ABSTRACT FROM AUTHOR]

The article presents two reports, one on a meeting on Physiological Mechanisms in Biotrophy and Hemibiotrophy held at the University College of North Wales, Bangor from April 22-23, 1987, and financed by the Transley Fund and the British Society for Plant Pathology, and the other on the second meeting of the Plant Transport Group held at Oaklands College, Saint Albans, from September 14-16, 1987. The Plant Transport Group was formed in 1985 to promote discussion of current research into all aspects of transport in plants.

This article presents information on the second symposium related to plant physiology organized by the journal "New Phytologist," which will be held at University of Wales in Bangor, Wales from April 2-3, 1997. In 1995 the trustees of "New Phytologist," announced the establishment of an annual conference. The proceedings of the first of these meetings, on the topic of molecular approaches to the study of plant-microbe symbioses, have been published in an earlier issue of the journal, as of September 1996. The second symposium will be held in Bangor and will examine another rapidly developing area, the genetic mapping of physiological characters.

Competition between three foliose lichens common on slate rock in south Gwynedd, Wales was studied in the field using a factorial experimental design. The lichens were grown as fragments glued to pieces of slate in two- and three-species mixtures. In the two-species mixtures, Parmelia conspersa (Ehrh. ex Ach.) Ach. outcompeted Parmelia glabratula ssp. fuliginosa (Fr. cx Duby) Laund. strongly and Phzscia orbicularis (Neck.) Poetsch less strongly, while P. orbicularis outcompeted P. glabratula weakly. Significant two-factor interactions indicated that the results from the three-species mixture could not be predicted from the two-species mixtures. Parmelia glabratula and P. orbicularis grew better in the presence of two competitors than one. This result suggests that the three species may co-occur on well-lit rock surfaces at the site. [ABSTRACT FROM AUTHOR]

Pollen diagrams are presented from two upland cwms in Gwynedd, North Wales. The profiles provide a detailed record of vegetational and environmental changes in the uplands of Snowdonia during the early and later Postglacial (Flandrian) periods. Radiocarbon dates indicate that at both sites organic sedimentation commenced at around 100000 B.P., and support geomorphological evidence of cwm glaciation during the Loch Lomond (Younger Dryas) Stadial. Pollen analysis of basal minerogenic sediments, deposited sometime before 100000 B.P., reveal the colonization of the recently deglaciated uplands by grassland communities rich in Rumex and other open habitat taxa. Early herbaceous communities were invaded by Juniperus and Betula, and then replaced by Betula-Corylus woodland, and later by forests of birch, pine, oak, elm and alder. Altitudinal factors ensured the survival of many open habitat taxa in the uplands throughout the Flandrian period. Deteriorating environmental conditions and human interference during mid- to late-Flandrian times resulted in the gradual decline of forests in the uplands and the development of open grassland and heathland communities characteristic of Snowdonia today. [ABSTRACT FROM AUTHOR]

Bulk deposition of nitrate, ammonium and organic nitrogen was greater at a South Pennine blanket peat site than at a similar, relatively unpolluted site in the Berwyn Mountains, North Wales. Sphagnum cuspidatum, transplanted from North Wales to the South Pennines, showed a rapid induction of nitrate reductase activity, which declined after 4 days. A laboratory induction experiment demonstrated a similar phenomenon on solutions containing 1 mM nitrate. In the presence of 1 mM ammonium, much less nitrate reductase: activity was induced.. Ammonium accumulated in both nitrate grown plants in the laboratory and in field transplants, which suggests that it may be responsible for the observed declines in enzyme activity. The results are discussed in relation to the nitrogen nutrition of blanket bog plants. [ABSTRACT FROM AUTHOR]

The basal sediments of three pingo basins from the valleys of the Cledlyn and Cletwr in west Wales have been analysed palynologically. The basal pollen-bearing deposits indicate that sedimentation began in all three basins at a time prior to the invasion of trees and before the initial expansion of Juniperus at the opening of the Flandrian. Radiocarbon dating confirms that the subsequent Juniperus peak is early Flandrian in age rather than belonging to the Allerød interstadial. The vegetational succession documented at the three sites allows a reconstruction of both regional and local developments during the transition from late-Devensian to Flandrian times. These events broadly resemble those described for other parts of mid Wales, but with certain, notable differences. These sites in the Tel fi Valley system have very low proportions of montane and arctic-alpine types represented in their pollen records; this contrasts markedly with the site previously described from the uplands at Elan Valley. Also they do not give indication of the early Corylus rise which occurred just 20 km north at Gwarllyn. The likely explanation for this is that invasion and spread of Corylus was localized in what is now the Cardigan Bay area and pollen derived from this early expansion was carried to the exposed Mynnedd Bach area, but did not penetrate south-eastwards into the Teifi Valley region. Evidence from these sites suggests that Pinus sylvestris and Alnus glutinosa were established locally in the area soon after the demise of Juniperus. In addition to providing data on vegetational history in this area, these studies also supply information concerning the origin and decay of pingos during late-Devensian times. The fact that the basal sediments predate the Juniperus rise demonstrates that the melting of the pingo ice cores and the collapse of their domes occurred before temperatures were high enough to allow Juniperus to attain its maximum flowering potential. [ABSTRACT FROM AUTHOR]

Sediments of Late-glacial origin from the Elan Valley in Cardiganshire have been subjected to close-interval pollen, spore and macrofossil analysis. From the results of this analysis an attempt has been made to reconstruct contemporary plant species assemblages and to follow the changes in these communities during the climatically unstable Late-glacial period. Conventional zonation required some modification for adequate representation of the dynamic state of both environment and vegetation at the time, hence a series of transitional zones has been constructed. Certain species are found to reach their greatest abundance in these transitional periods and are considered to be relatively thermophilous yet intolerant of competition. Certain of the types found, e.g. Artemisia c.f. norvegica, Linnaea borealis, Tofieldia and Scleranthus perennis are of particular interest, both because of the infrequency with which they have been recorded in British quaternary deposits in the past, and because of their present day disjunct and sometimes anomalous distributions. Their presence in mid-Wales during Late-glacial times throws further light upon these distributions. [ABSTRACT FROM AUTHOR]