Grid Ref Research Articles

Soil Factors Affecting the Distribution of Plant Communities on the Cliffs of Craig Breidden, Montgomeryshire

In certain habitats topographical factors have prevented closed plant communities from developing, and often, where the parent rock is basic in nature, a particularly rich flora is present (Pigott & Walters 1954). Cliffs and steep, rocky outcrops of limestone or basic igneous rock provide such habitats; examples include the Avon Gorge (Bristol), the Great Orme (Denbighshire), Arthur's Seat (Edinburgh), Stanner Rock (Radnorshire) and Craig Breidden (Montgomeryshire). The last is an outcrop of basic igneous rock, which possesses a flora that is unique in the British Isles. This comprises not only species that are rare or restricted, e.g. Potentilla rupestrist, Lychnis viscaria (Viscaria vulgaris), Veronica spicata ssp. hybrida, Hieracium peleterianum (Pilosella peleterana), Sedum forsteranum, Geranium sanguineum, but also assemblages of plants that are unusual, for example calcicoles (Origanum vulgare and Scabiosa columbaria) regenerating and growing in close association with calcifuges (Calluna vulgaris and Erica cinerea). Craig Breidden (Nat. Grid Ref. SJ 2914) lies in the extreme north-eastern part of Montgomeryshire in the angle created by the foothills of the Welsh Massif and the Shropshire Hills. The rock mass is a large laccolith of hypersthene dolerite which was intruded into shales during the Ordovician era. Glaciation has removed the surrounding softer rocks and left the hard dolerite as an oversteepened, craggy outcrop rising to a height of 365 m, with extensive cliffs on the southern, western and northern sides of the hill, and it is on the southern and western cliffs (at an altitude of 150-300 m) that the rare species and assemblages of species are found. Because of its geographic position Craig Breidden experiences an unusual climate, being shadowed by the Welsh hills to the west, but receiving more rain than the neighbouring lowland areas of the Shropshire Plain to the east. Furthermore, cliff habitats give rise to heterogeneous microclimatic conditions which probably contribute to the maintenance of the vegetation mosaic. Whilst the importance of climatic conditions was recognized, the following study was undertaken in order to identify soil factors influencing the distribution of plants on Craig Breidden. Details of the mineral nutrition of one of the rare species, Lychnis viscaria, have been discussed elsewhere (Jarvis & Pigott 1973), and in this account particular attention is given to the mixing of calcicoles and calcifuges. There are a number of accounts of such mixtures, but most of these accounts

The sub-Palaeozoic basement in central Ireland

THERE is no direct evidence to indicate the nature of the sub-Palaeozoic basement beneath central Ireland. The recognition of gneissic xenoliths in Visean volcanics in this region is therefore significant. They have been located at Croghan Hill in County Offaly (National grid ref. N4833; Fig. 1), Clare Castle (N2447), and the Dungolman River (N1851) in County Westmeath.

Dispersion Patterns in the Zooplankton Populations of a Eutrophic Reservoir

The spatial distribution or dispersion of individuals in natural populations is seldom random, but is frequently contagious or clumped with the variance significantly greater than the arithmetic mean. Quantitative measures of departure from randomness are of value in assessing the total interaction between an organism and its environment (Taylor 1971). This paper examines the extent to which selected indices and measures of nonrandomness can be used to describe patterns of dispersion in small random samples of freshwater zooplankton. The work formed part of a 2-year study of the temporal and spatial distribution of crustacean zooplankton in Eglwys Nynydd, a water supply reservoir near Port Talbot, South Wales (Grid Ref. SS 795850).

A Roman Building at Chalk, near Gravesend

Early in 1961 the mechanical grader scooping out the line of the street called Via Romana in the new Readers' Estate at Chalk, Kent (Nat. Grid Ref. TQ, 677730) exposed the corner of a buried building. Trial excavation directed by Mr. A. F. Allen was followed by a full excavation mounted by the Ministry of Works, with the full cooperation of the developers; this was directed by the writer and Mrs. Anne Eastham. The Readers' Estate overlooks the mudflats of the Thames estuary and bears a varied topsoil of clays, flint, pebbles and sand. Between this and the underlying chalk is a layer of weathered chalk, glacially deposited, and known as ‘head’ or ‘bullhead’. The foundations of our buildings were cut into this.

Balls Head: the excavation of a Port Jackson rock shelter

Balls Head is a small headland reserve jutting into the north side of Port Jackson west of the Harbour Bridge (Sydney sheet, map No. SI 56-5 grid ref. 420818). It has preserved its bushland appearance and been comparatively little interfered with. Vegetation consists of a mixture of indigenous and introduced trees and shrubs; grassy areas are maintained for the benefit of picnickers. Bedrock is Hawkesbury sandstone, with frequent outcroppings, particularly where the headland slopes steeply down to the Harbour. These outcroppings are in the form of both smooth, steep-sided or flat slabs and the characteristically weathered small rock shelters typical of the Sydney area. Many of the slabs are decorated with Aboriginal rock engravings and axe-grinding grooves, and some of the shelters bear rock paintings and hand stencils (Campbell 1899: 14, 17; Miles 1964: 343). There is not a great deal of other Aboriginal occupation evidence apart from the site under consideration, and thin open shell middens which may be detected beneath some of the grassed-over areas. The rock shelter forming the subject of this paper is approximately 65 feet above mean water-level, of a north-easterly aspect (plate 17). I t is not large: about 35 feet long, 7 feet from the drip-line to the back wall of the shelter, and 6 feet from ground surface to underside of overhang are its maximum dimensions (figs 1 and 2). Occupational deposit stretches from the back of the shelter, out beyond the drip-line for about IO feet, where it then begins sloping downwards in a steep talus. There are faint hand stencils on the rear wall of the shelter and the roof is blackened, perhaps from the fires of the original occupants. The deposit consists of compacted shell midden, looser disturbed material, and less compacted midden. Its maximum depth is 2 feet 9 inches.

First Diagnostic Carboniferous Fossils from New Zealand

THE first New Zealand fossils indicative of Carboniferous age have been found in rocks from the South Canterbury region of the South Island. They are conodonts, accompanied by rare fish scales, and were obtained from the marble of the Kakahu inlier in a Tertiary area 10 miles south-west of Geraldine1: fossil sample locality No. S102/607, grid ref. 627815 (latitude 44° 09′ S, longitude 171° 04′ 30″ E).

Excavation of a Stone Circle at Croft Moraig, Perthshire, Scotland

The concentration of prehistoric monuments, broadly of the later third and early second millennium B.C., in the upper Tay valley, has been noted by more than one archaeologist in recent years (Stewart, 1958–9; Coles, J. M. and Simpson, 1965). The multiple stone circle to be described lies no more than 2 miles (3·2 km) from the north-eastern end of Loch Tay at Kenmore, and 4 miles (6·2 km) west of Aberfeldy, at Nat. Grid Ref. NN/797472 (fig. 1). It stands some 400 feet (122 m) above sea level, near and to the south of the main Aberfeldy–Kenmore road near the farm of Croft Moraig or Morag, and has long been known as a prehistoric monument: ‘Yon's the Druid Stones!’ shouted the coach drivers to their passengers sixty years ago, and only ‘the begoggled motorist’ of the day was thought likely to miss it (Coles, F.R., 1909–10, 139). Probably the earliest record of the site is that made by Robert Burns on his Highland journey in 1787 (quoted in Gillies, 1938, 14):‘Druid's Temple, three circles of stones. The outermost sunk, the second has thirteen stones remaining; the innermost eight, two large detached ones like a gate to the south-east—say prayers in it’.

Pattern and Seasonal Variability in the Environment of a Scots Pine Forest Soil

In studies of plant and animal communities attempts have been made to account for the spatial distribution of the species. On a large scale this can be referred to as the geographical distribution, whilst on the small scale the term 'pattern' has been used. The interest in pattern in plant communities has developed from a relatively qualitative approach (e.g. Watt 1947) to one requiring considerable statistical analysis (e.g. Greig-Smith 1964). In animal communities Lloyd (1967) has introduced the concept of 'mean crowding' for investigating the degree of aggregation, and soil biologists have concentrated on the frequency distribution of counts of soil arthropods (Berthet & Gerard 1965). The patterns themselves have many scales. Thus there are the large scale patterns such as arcs of vegetation (Boaler & Hodge 1964), and smaller scales such as occur in the properties of soils under individual trees (Zinke 1962) or due to the vegetative characteristics of the plants (Kershaw 1958). The scale of these patterns can usually be discerned by the observer. However, when the organisms being studied are not visible to the observer the analysis of pattern may become an artifact of the sample size being used. Thus, Murphy (1962) has shown that the form of frequency distribution of soil animals indicates more aggregation when successively smaller sample sizes are used. Patterns have been detected in the spatial distribution of various organisms, and many studies have correlated the pattern with the environmental variables. Thus, Snaydon (1962) has sampled a grid 10 m square, subdivided into 100 1 m square quadrats, for Trifolium repens L. The occurrence of T. repens in the hollows of the undulating topography typified the pattern, and one environmental variable contributing to the pattern is identified by the correlation between T. repens abundance and the calcium concentration. However, relatively little attention has been paid to the basic pattern of the environment, and especially to the microdistribution of such factors as the chemical constituents of soil. The aim of this study was to investigate the small scale pattern of various physical and chemical properties of a Scots pine forest soil. A total of 1152 samples were collected during a year from the upper 3 cm of the soil of a Scots pine (Pinus sylvestris L. ssp. scotica (Schott) E.F. Warburg) forest on Cnoc Eoghainn in The Black Wood of Rannoch, Perthshire (Nat. Grid Ref. NN551546). The site was at an elevation of 380 m, and was a square of side 20 m on almost flat ground at the summit of the Cnoc. The ground vegetation, mainly composed of Deschampsiaflexuosa (L.) Trin., Galium hercynicum Weigel and Oxalis acetosella L., is sparse because there is considerable grazing by sheep and deer, particularly during the winter months. The climate is cold and moist. The annual precipitation at a meteorological station 5 km east of the site at an elevation of 220 m is 119 cm/year. Quartzose felspathic schistose

The Effects of Stratification on Phyto-Planktonic Diatoms in a Small Body of Water

Abbot's Pool (Nat. Grid ref. ST 536732) is a small artificial body of water near Bristol, England. It is situated in mixed, deciduous woodland, surrounded by agricultural land in a valley of Old Red Sandstone most of which is overlain by Carboniferous Limestone. The pool itself is small (c. 100 x 40 m) and shallow; the majority of the water lies between 2 and 3 m depth and only 18% of the total volume is below 3 m, The inflow is small, becoming virtually non-existent in summer. Despite its size and depth, Abbot's Pool has been shown to stratify both thermally and chemically (Happey 1970a, c); these conditions are summarized in Fig. 1. Other details of the algae and limnology of the pool are given by Fritsch & Rich (1908), Karim (1965), Round (1965), Eaton & Moss (1966), Eaton (1967), Happey & Moss (1967), Moss (1967, 1969a, b, c), Moss & Karim (1969) and Eaton, Karim & Moss (in prep.). Abbot's Pool is a small body of eutrophic water, supporting large standing crops of phytoplankton. Each year these undergo a similar pattern with a large spring diatom crop of Asterionellaformosa Hass. In the summer of 1967 an unusual event was recorded when a large plankton population of diatoms occurred during stable water conditions of thermal stratification. This diatom, Stephanodiscus rotula (Ktitz.) Hendey (formerly S. astraea (Ehr. ex Kiitz.) Grun.), also produced a diatom crop in the autumn, after the autumn overturn. Spring and autumn diatom crops are common in Abbot's Pool, as in larger lakes, but a massive growth of this diatom in conditions of summer stratification has apparently not been reported previously here, or in other lakes (Talling, personal communication).

Variation in Fixed Dune Vegetation at Newborough Warren, Anglesey

Although much work has been reported on the vegetation of sand dunes, there is little information on point to point variation within the main vegetation types. The observations reported here are a contribution to an understanding of variation in one type of fixed dune complex. They were made at Newborough Warren National Reserve on the west coast of Anglesey (Grid Ref. SH 4065), an extensive dune system the main features of which have been described by Ranwell (1958, 1959, 1960). The area selected for the present study was a portion 320 x 100 m lying towards the landward site of the Warren, within the part mapped by Ranwell (1958) as 'closed low dune and Salix slack associes'. Physiognomically, the area was predominantly a pasture community dominated by Festuca rubra, but included patches of relict dune with Ammophila arenaria.

The Water Relations of Bracken: A Preliminary Study

In accordance with the pattern of experimentation used during the previous year in some exploratory field studies made in Aberdeen, a site was selected in a young mixed beech woodland with a moderately dense canopy in southern England (Kings Wood, Challock Forest, Kent; Grid Ref. TR025509). The site was located near the bottom of the gently sloping side of a small valley cut into the clay-with-flints plateau. The subsoil was a colluvium of chalk head and admixed clay-with-flints with a mean pH of 4-6, under a humus top stratum. Large clumps of Dryopteris filix-mas (L.) Schott were scattered in the dense stand of Pteridium. Measurements were made of leaf relative water content (relative turgidity; Weatherley 1950) by weighing entire pinnae, allowing them to come to full turgidity by immersing the base in a little water in a closed bottle under dim illumination and then reweighing before drying to a constant weight in an oven at 90? C. All samples were made in triplicate from the second branch from the base of the rachis, only the three or four lowest pinnae being used. Evaporation rate was determined by measuring the weight loss of

II.—The Medieval Pottery Kilns at Laverstock, near Salisbury, Wiltshire

This medieval industry was operating one mile south-east of Salisbury at Nat. Grid Ref. SU/160298 (fig. 1). It lay in the Royal Forest of Clarendon, within which there are other hints of the medieval pottery industry. Medieval sherds from Laverstock were first reported by Mr. Frank Stevens in 1940 and in 1955 further finds made during levelling of land formerly used as allotments and from road work were brought into Salisbury Museum. The site was then examined, revealing a twelfth-century cesspit and two pits with pottery wasters of the thirteenth century (one associated with what is now identified as a potters' workshop) but still no kilns. The first kiln was found on a new road line in 1958 and further investigation was aided by a grant from the Ministry of Public Building and Works. During six months trial trenches were opened over 1½ acres; six kilns, two buildings, and eighteen pits (some of them twelfth century) were excavated. Another kiln was found in 1960, and two more in 1963 when a bank at the edge of Duck Lane was levelled, making nine kilns in all. Some were stratigraphically interrelated, and were also in sequence with some pits.

New Zealand Triassic conodonts

Abstract In 1967 the writer recorded the first discovery of conodonts in New Zealand and the specimens were obtained from a Devonian Reefton limestone sample from the Waitahu River (Jenkins, 1967). The present communication is to record a conodont fauna from a well established Upper Triassic locality of Okuku limestone, Lees Pass, North Canterbury (S67/513*; grid ref. 783160).

Peat Deposits of Scar Close, Ingleborough, Yorkshire

The interest of the area known as Scar Close, Yorkshire, is evident from the number and variety of investigations which it has provoked. Jones (1965) has considered its geological aspects, Parry (1960) and Sweeting (1966) its geomorphology, and Moisley (1954) emphasized the need for further study in his account of karstic features of similar sites in the Malham area. This paper is the result of an attempt to add to the substantial body of knowledge from a botanical angle using amongst others the technique of pollen analysis. Scar Close (Grid Ref. SD 750773) is situated at the foot of the north-west side of Park Fell near the steep face of Ingleborough in the Craven district of Yorkshire. It lies on a shelf of Great Scar Limestone at a height of about 1000 ft (305 m). The fell is composed of rocks of the Yoredale Series and the boundary of these with the limestone is marked by a row of swallow holes. The limestone itself has formed pavement with well-developed clints and grykes. The rainfall is high with an annual average of about 70 in. (180 cm), but most of it drains down through the grykes and swallow holes into an underground system. Drainage is impeded to some extent on the inner side of the shelf by a layer of glacial drift, and even on the clints which are practically devoid of soil, some surface water is retained in solution hollows. The drift covered area carries a more or less continuous sheet of wet acid bog, but on the exposed pavement there are only isolated patches of peat lying in direct contact with the limestone and it is these 'islands' which are problematic. They may be relics of a once continuous peat cover or have developed independently from a number of centres and still be advancing. In any case it is unusual to find peat situated immediately upon a well-drained basic substratum. The vegetation of the inner and outer areas of the shelf reflects the difference in edaphic conditions (Fig. 1). The drift-covered limestone bears a typical hummock and pool formation with Eriophorum angustifolium,* E. vaginatum, Vaccinium myrtillus, Calluna vulgaris and various Sphagnum species on the hummocks, and a luxuriant growth of S. cuspidatum in the pools. The peat 'islands' on the pavement are much drier and are dominated by Calluna vulgaris and Vaccinium myrtillus with other species such as Convallaria majalis, Geranium sanguineum and Polypodium vulgare. Most of the peat patches are fringed with mosses including Rhytidiadelphus squarrosus, Pleurozium schreberi and Cratoneuron commutatum. Where small pockets of soil have developed on the clints Sieglingia decumbens and Tortella tortuosa have become established, but they are mostly bare except for crustaceous lichens. A few trees of Acer pseudoplatanus, and Fraxinus excelsior are growing in the grykes with bushes of Corylus avellana, but all are comparatively small and rarely exceed 4 m in height. Other plants found in the grykes are * Nomenclature follows Clapham, Tutin & Warburg (1962) for vascular plants and Richards &

Upper Jurassic “Sandwacke” at Waiwera, Auckland, and regional stratigraphic implications

A drillhole on Mr A. Catlow’s property at Waiwera Beach (Fig. 6, grid ref. N38/219978) was recently deepened from 990 ft to 1,390 ft in an effort to get hotter water. The hole originally yielded ab...

An Ecological Study of Ysgolion Duon, a Mountain Cliff in Snowdonia

The vegetation of Snowdonian mountain cliffs has interested botanists since Thomas Johnson visited Snowdon in 1639. However, except as sections of wider studies, e.g. Ratcliffe (1959), the cliffs have not been studied in detail although Price-Evans (1932, 1945) gave an account of similar cliffs on Cader Idris. The ecological factors affecting cliff vegetation may be conveniently divided into two groups: firstly, those limiting species to cliffs and secondly, those affecting the distributions of species within the cliff vegetation. Preliminary studies of the former were made by comparing the climate of the cliff with the surrounding area and by examining the effects of grazing on cliff species. Variation within the cliff vegetation was studied using ordination procedures to provide an objective assessment of species distributions which were correlated with environmental factors, principally edaphic. The cliff selected for study was Ysgolion Duon in the Carneddau mountain group (Grid Ref. SH 6763) of Snowdonia, between Carnedd Llewelyn and Carnedd Dafydd at an altitude between 600 and 900 m (Fig. 1). The main cliff is a continuous sweep of rock interrupted only by the lines of steep rock gullies. The lower section of the cliff does, however, have larger ledges, often less steeply inclined than those on the upper section. Beneath the cliff is grassland broken in places by block scree and small rocky outcrops. Llech Du and the crag above Llech Du (Fig. 1), which are also included in the study, are also very steep.

Ecological and Morphological Observations on a Population of Cyclotella Pseudostelligera Hustedt

During the spring and summer of 1963, regular samples collected from Priest Pot, near Esthwaite North Fen, Lancashire (Grid Ref. 35/357978), revealed appreciable populations of a small centric diatom at first thought to be Cyclotella woltereckii Hustedt (1942) and later found to be identical with C. pseudostelligera Hustedt (1939), previously recorded from here by Lund (1960). Because the cells were seen to show considerable variation in valve pattern a more detailed study was undertaken. Priest Pot has an area of approximately 1-3 ha and a maximum depth of 5 m. Except for two small areas at the northern and southern ends the banks drop vertically to a depth of about 1 m, whence the bottom slopes smoothly down to the centre. A zone of intermittent alder and willow carr, approximately 4 m in height, surrounds the pool, beyond which to the south is Esthwaite North Fen, while in the other directions are open meadows. The water is readily circulated and mixed by the wind and can often be seen in motion. The only apparent inflows are two or three slow-flowing ditches, a few field drains and ground water. Into one of the ditches a neighbouring farm discharges effluent with a high nitrogen and phosphorus content.

ISOLATION OF FOSSIL OSTEOCYTES.

During routine maceration of shales for the extraction of fossil spores, a number of unusual structures appeared which were eventually identified as osteocytes from scales belonging to a palaeoniscid, a primitive bony fish. No vertebrate tissues had been expected, since the technique employed destroys virtually all substances with the exception of carbon, chitin and cellulose. It thus appears that certain vertebrate tissues are far more resistant than was generally believed.The specimen comes from rocks of Upper Carboniferous age (Namurian, Arnsbergian Stage, zone E2b), which outcrops at Hollywood Dingle, near Endon, Staffordshire (Grid ref. SJ.945509), and the palaeoniscid was kindly identified by Mr. H. A. Toombs of the British Museum (Natural History) as Elonichthys semi‐striatus Traquair.

A Late Bronze Age Find from Pyotdykes, Angus, Scotland, with associated Gold, Cloth, Leather and Wood Remains

On the 29th October, 1963, a group of bronze objects was ploughed up in the ‘Old Road Field’, Pyotdykes farm, near Dundee, Angus (Nat. Grid Ref. NO 345348). The objects recovered were a bronze spearhead and two bronze swords (fig. 1). After news of the find had been communicated to the Museum and Art Gallery, Dundee, the area around the original find-spot was excavated by museum staff, and this yielded three additional pieces of bronze wire rivets from sword (2), but no other objects. Before the bronzes were revealed by ploughing, they must have been lying about 30 centimetres below the surface, just above a hard-pan layer which forms the subsoil in that part of the field.Cleaning and treatment of the bronzes was carried out at the museum, when a plug of material was extracted from inside the spearhead socket (see App. I). This was sent to Dr M. L. Ryder for examination along with two pieces of wood and leather which the farmer had found adhering to sword (2) (see Part III). Subsequently the wooden fragments were examined in the Sub-department of Quaternary Research, University of Cambridge (see App. II).

A record ofGlobigerinatella InsuetaCushman and Stainforth from New Zealand

Abstract Although planktonic Foraminifera are abundant in the Miocene in New Zealand, there are no published records of Globigerinatella insueta, an important lower Miocene zonal species in the Caribbean. A definite occurrence of insueta in Hawke's Bay is recorded here from a sample collected by Dr J. T. Kingma from a greenish grey mudstone cropping out in the bed of the J'ukituki River (N.Z.M.S. 1, Sheet N134, 1943 ed., grid ref. 336114). Dr Kingma has informed the writer that the stratigraphic position of the mudstone is obscured by terrace gravels and that it has been faulted into its present position.