Erica Tetralix Research Articles

An analysis of species response curves and of competition from field data: Some results from heath vegetation

The variation in species composition of plant communities has been described by means of the Gaussian distribution (relations between plant populations and environmental variables) and by linear equations (mutual interference between mixed populations). An important presupposition is the existence of a theoretical population, covering 100% of the soil surface. A numerical approximation of the parameters can be obtained by means of an iterative procedure. This technique has been applied to heath vegetation. A small sample has been used to demonstrate the algorithm. The cover ofCalluna vulgaris, Erica tetralix andMolinia caerulea could be explained to a large extent from phosphate and ground water table. A comparison of the results with those of experiments by other authors showed a reasonable similarity. The linear coefficients of interference as means to describe relations between mixed plant populations in a local area have been evaluated by means of dynamic simulation.

Carbohydrate Concentration of Heath Plants of Different Geographical Origin

(1) The carbohydrate concentration of green shoots of Calluna vulgaris, Erica tetralix and E. cinerea was sampled in early and late winter and in late summer, in plants of different geographical origin grown under similar conditions. (2) When seasonal differences were allowed for, the carbohydrate concentration of Calluna and Erica cinerea was similar, but that of E. tetralix was considerably lower. (3) Erica cinerea and E. tetralix showed a marked increase in carbohydrate concentration over winter, whilst any increase in that in Calluna was slight. (4) The between-site variation of carbohydrate concentration in Calluna, and to some extent in Erica tetralix, was correlated with the latitude and altitude of origin of the material. (5) The pronounced winter increase and the lack of variation in carbohydrate concentration among Erica cinerea and E. tetralix of different provenance may restrict these species to oceanic climates with mild winters, where temperatures would allow continued physiological activity and carbohydrate accumulation. The greater variation observed among Calluna of different provenance may reflect its adaptation to a wider geographical range.

The Density of Viable Seed in Soils of Forest Plantations in Upland Britain

(1) Viable seed in soils of forest plantations was studied by spreading samples of soil in seed trays and recording the number of seedlings that germinated. (2) Numerous seedlings emerged from most samples; it was concluded that many seeds had survived in the soil for at least 30 yr, and in one case probably for about 45 yr. (3) In 30-40-year-old plantations, seed density was typically 1000-5000 seeds m-2 on brown earths, 500-2500 on peaty gleys and 50-250 on deep peat. In younger plantations the seed density was higher, especially on deep peat. (4) Calluna vulgaris was much the most abundant species. Carex spp. (mostly C. binervis and C. pilulifera), Erica tetralix, Galium saxatile, Juncus effusus and J. squarrosus were also frequent in soils of older plantations, together with Agrostis canina and A. tenuis on brown earths. (5) There was apparently no long-term survival of seeds of Betula spp., Deschampsia flexuosa or conifers. Agrostis canina and A. tenuis survived for several decades but perhaps not for the full length of a normal rotation (50 yr). (6) Development of the vegetation following clear-felling depends mainly on seeds and established plants already present. Immigration is largely confined to species with wind-borne propagules.

The annual diet of the Roe deer (Capreolus capreolus) in the New Forest, Hampshire, as determined by rumen content analysis

By analysing rumen content samples from 105 dead specimens, the annual diet of the Roe deer (Capreolus capreolus) in the New Forest, Hampshire, was determined over the period from November 1970 to March 1973. Bramble and rose formed the bulk of the diet throughout the year, comprising the largest food fraction in all months except January and April. In January to March, foliage from felled conifers, Calluna, and ivy were major foods, plus lesser amounts of grasses, herbs and fungi. From May until early winter, herbs and grasses were important. New, tender, spring and summer growth from broadleaved deciduous trees, bilberry and holly was eaten in appreciable quantities. Acorns were a characteristic autumnal food. Abundant potential foods which Roe deer seldom selected included rushes, sedges, mosses, bark and dead hardwood leaves. Widespread species that Roe rarely consumed were Corsican pine, Erica tetralix, E. cinerea, gorses, bog myrtle and the grasses Agrostis setacea, Brachypodium sylvaticum, Deschampsia caespitosa and Molinia caerulea.

The Primulales: Serological contributions to the problem of their systematic position

The distribution of serological determinants in seed proteins from different species of Primulaceae, as well as from Ardisia crenulata (Myrsinaceae), Erica tetralix (Ericaceae), Manilkara zapota (Sapotaceae, Ebenales). Actinidia chinensis (Actinidiaceae) and Armeria maritima (Plumbaginaceae) has been determined by the use of corresponding rabbit immune sera. Serological reactions were carried out using a gel diffusion micro-method in calcium alginate gel, and a special pre-absorption technique was used in order to more closely specify the distribution of serological characteristics in the taxa under examination. While no systematic similarities were found between Primulales and Plumbaginales, a serological correspondence between Primulales and Ericales is very clear. It also occurs between these two taxa and species of the Theales. The Sapotaceae (as representatives of the Ebenales) showed some serological similarities with the Theales.

The annual diet of the Fallow deer (Dama dama) in the New Forest, Hampshire, as determined by rumen content analysis

The diet of Fallow deer (Dama dama L.) in the New Forest, Hampshire, was determined for the period November 1970 to March 1973 by analysing the rumen contents of 325 dead animals. Three main phases to the annual diet were recognized. From about March until September, grasses formed the principal food with herbs and broadleaf browse also of some importance. Acorns and mast were the characteristic food from September until about Christmas. Major winter foods included bramble, bilberry, grasses, Calluna, holly, ivy and browse from felled conifers. Fallow deer fed selectively; plants abundant in the New Forest which were seldom consumed included Erica tetralix, E. cinerea, Myricagale, Rhododendron ponticum, Ulex europea, Agrostis setacea, Deschampsia caespitosa, Motinia caerulea, most Juncaceae, Cyperaceae and Pteridium aquilinum.

The Distribution and Composition of Hybrid Populations of Erica Ciliaris L. and Erica Tetralix L. in Dorset

Erica ciliaris L., the 'Dorset Heath', referred to in earlier Floras as the Fringe-leaved Heath, Ciliated Heath and Four Burrow Heath, has a Lusitanian distribution being found in north-west Morocco, the coastal regions of Portugal, Spain and France, the south of England and the west of Ireland (Hansen 1950). The first British record of E. ciliaris is generally attributed to the Rev. J. S. Tozer who found it near Truro, Cornwall in 1828 (Lindley 1829), although the plant was probably known before that date. A hybrid between E. ciliaris and E. tetralix L., later found growing near Truro, was named E. x watsonii Benth. At present E. ciliaris is less abundant in Cornwall than in south-eastern Dorset where it was first recorded by J. Woods in 1848, while the first Dorset record of E. x watsonii is dated 1891 (see Mansel-Pleydell 1895). Within the British Isles E. ciliaris occurs in the west of Ireland (Webb 1966; McClintock 1968), Cornwall, Devon (at one site on Dartmoor) and on the heathlands and valley mires of south-eastern Dorset. A distribution map of E. ciliaris was given by Good (1948) following his survey of the Dorset flora between the years 1932 and 1937, and he commented: 'The particular interest in this plant is that its local geographical limits follow no obviously recognisable edaphic or climatic boundary and are therefore presumably set by some unusually subtle factor or combination of factors. The rigidity of the limitation is further emphasised by the fact that although the species does from time to time occur as scattered individuals on the neighbouring heathlands, it never spreads there.' A map showing sites for E. ciliaris in Dorset was given by Moore (1962), who used the plant as an indicator species in his evaluation of the conservation interests of Dorset heathland sites (see Fig. 1 for a map of S.E. Dorset). Although the hybrid E. x watsonii is recorded in several County Floras, the distribution and relative composition of hybrid populations of E. ciliaris and E. tetralix have been analysed only by Gay (1957, 1960) using a modification of Anderson's Hybrid Index technique (Anderson 1949). The present paper provides a more detailed account of the current distribution of E. ciliaris in Dorset, characterizing hybrid populations and suggesting ecological implications of the observed patterns of distribution.

Some Aspects of the Phytosociology of Heathland and Related Communities in the New Forest, Hampshire, England

Numerical phytosociological methods have been used to establish the characteristics of the main plant associations occurring on Pleistocene terraces in the New Forest; the terraces are one of the main landscape elements in the area. The plant associations identified range from those of wet heathland to those of dry, acid grassland; however the most widespread community is composed of Calluna vulgaris, Erica tetralix and Molinia caerulea, whilst there is also a common dry heath grouping of Agrostis setacea, Ulex minor and Erica cinerea. The dry heath association, and related associations dominated by Ulex europaeus, are proportionally more important on the lower terraces (below 80 m). The same associations occur both on and off the terrace fragments, but their geograp hicalpattern

Primary Production and Distribution of Organic Matter and Metal Elements in Two Heath Ecosystems

This paper deals with the distribution of organic matter and metal elements, above-ground production, biomass increment and litter formation in two heath ecosystems dominated by Calluna vulgaris* and Erica tetralix respectively. The area studied is Skanors Ljung in south-western Sweden (latitude 55?24' N, longitude 12?54' E), one of the largest remaining heathlands in Scandinavia. Quantitative information concerning the chemical structure of heath ecosystems is scanty: almost nothing was known prior to the present study of the productivity and the distribution of organic matter and minerals in E. tetralix wet heaths. Large areas of heathland in northern Europe have changed into woodland during this century and the same fate seems inevitable for many of the remaining heaths; ecological documentation should be a matter of concern. This paper is a contribution to such documentation. A complete distribution analysis of several heavy metals (manganese, iron, nickel, copper, zinc, cadmium, and lead) is recorded in this paper and the amounts present per unit area are related to the calculated annual deposition.

The Responses of Molinia Caerulea and Erica Tetralix to Soil Aeration and Related Factors: III. Effects of Different Gas Concentrations on Growth in Solution Culture; and General Conclusions

Studies of the root distribution of Molinia caerulea and Erica tetralix in relation to the sizes of the soil pores showed that the roots of both the species were confined to pores exceeding 150 ,u diameter. In the soils of the wet-heath sites studied a majority of these large pores contained water for most of the year (Sheikh & Rutter 1969). Therefore, the concentration of the gases dissolved in the soil water (reported by Sheikh 1969b) were of direct importance for the growth of the species in the field. Experiments described below were carried out to study the effects of different concentrations of gases (oxygen, carbon dioxide and hydrogen sulphide), covering the range of concentrations found in the soil water (Sheikh 1969b), on the growth of both Molinia and Erica in water culture.

The Responses of Molinia Caerulea and Erica Tetralix to Soil Aeration and Related Factors: II. Gas Concentrations in Soil Air and Soil Water

Previous studies (Sheikh 1969) described the growth of Molinia caerulea and Erica tetralix on some wet-heath sites at Bramshill Forest, Hampshire, which were described and named Valley-bog, Central associes, wetter Molinietum and drier Molinietum. Both species grew most slowly on the Valley-bog site, and best on the drier Molinietum. In the case of Molinia, differences of growth among sites appeared to be due to different nutrient conditions (see also Loach 1966) since the differences almost disappeared when nutrients were added to experimental plots. In the case of Erica tetralix, however, additional nutrients had no effect in overcoming the poor growth on the Valley-bog site and it was decided to investigate the aeration factor. This paper examines the variation of soil aeration, and related factors, at different depths and times on four sites, as a preliminary to controlled experiments on the significance of the aeration factor. Russell (1952) has emphasized the need of characterizing soil aeration by parameters that are of significance to plant growth. Parameters that describe, or allow the calculation of, conditions at the interface between the plant root and the soil system are an excellent means to this end. In soil, active plant roots are probably covered by a film of water. This is particularly true in the case of the roots growing in wet soils such as those studied in the present work. The concentration of gases at the root surface will depend upon the composition of the soil air, the transfer of gases across the gas-liquid interface, their diffusion across the liquid phase, and the rates of chemical and biological processes involving these gases in the soil. The effects of these various factors will be reflected in concentration gradients from the atmosphere above the soil to the root surfaces, first through the gaseous phase in the soil and then across the liquid phase. It would seem, therefore, that measurement of the concentration of gases in the liquid phase, although not identical with conditions at the root surfaces, does at least indicate these conditions better than the more widely employed analyses of samples of the gaseous phase. Studies on root distribution (Sheikh & Rutter 1969) showed that E. tetralix was a more shallow-rooting species than Molinia caerulea, but even in the latter about 950/ of the roots were found in the first 25 cm of soil on the sites studied. In view of this, analyses of gases in the soil were made mainly in the first 25 cm, although samples from 60 cm, i.e. below the permanent water-table, were also analysed.

The Responses of Molinia Caerulea and Erica Tetralix to Soil Aeration and Related Factors: I. Root Distribution in Relation to Soil Porosity

The Responses of Molinia Caerulea and Erica Tetralix to Soil Aeration and Related Factors: I. Root Distribution in Relation to Soil Porosity

The Effects of Competition and Nutrition on the Inter-Relations of Some Wet-Heath Plants

The wet-heath vegetation which forms the subject matter of this paper is found in an Ecological Reserve set aside by the Forestry Commission in Bramshill Forest, northeast Hampshire. It is a variable association of three species-Molinia caerulea (L.) Moench, Calluna vulgaris (L.) Hull and Erica tetralix L.-the distribution and relative proportions of which vary according to local conditions of soil and drainage (Rutter 1955). Webster (1962) showed that the proportion of Molinia in the vegetation was negatively correlated with the concentrations of carbon dioxide and hydrogen sulphide in the ground-water. Loach (1964, 1966) analysed soil profiles and measured the growth of all three species, in the absence of interspecific competition, on sites representative of the various facies of wet-heath vegetation. He found that all three species made most growth in the soil of a Molinietum and least in the soil of a small area of Valley-bog. Analyses of soils and plants, and an experiment in which the responses of Molinia to nutrients were tested, all suggested that the Valley-bog soil was the most deficient in nutrients, especially phosphorus and to a less extent nitrogen and potassium. He tentatively concluded that either inadequate nutrition or poor aeration, or both, on the Valley-bog site so limited the growth of Molinia as to allow Erica tetralix to become more abundant in the vegetation. However, he did not directly investigate the significance of the aeration factor and his experiment on the responses of Molinia to nutrients was made with blocks of soil removed from the natural sites and subjected to uniform drainage conditions. In the present paper, field studies relevant to competition between the species and their responses to nutrition will be described, and in later papers aeration conditions and their ecological effects will be analysed in detail. Studies have been made on four sites within the reserve, characterized by different proportions of the three species under investigation. Three of the sites, designated Valley-bog, Central associes and drier Molinietum are the same as those investigated by Loach (1966) and point quadrat analysis of cover repetition are reproduced from his paper in Table 1. In the Valley-bog Erica was more abundant than elsewhere; in the Central associes Calluna was more abundant than on the other sites. There was very

The Effects of Waterlogging on the Growth of Molinia Caerulea and Eriophorum Vaginatum

It is well known (Jefferies 1915; Fraser 1933; Pearsall 1950) that Molinia caerulea is usually associated with situations which have moving soil water whereas Eriophorum vaginatum is found in more stagnant places, but the reasons for this difference are little understood. Pearsall (1938) concluded that under acid peat conditions (pH 4 Molinia occurred in reducing conditions (Eh5 110-270). Rutter (1955) showed that the best development of Molinia on a heathland site occurred in places with the greatest amplitude of water table fluctuation, and suggested that fluctuation in the water table may result in the sweeping away of toxic products or renewal of soluble nutrients. Webster (1962) showed that Molinia was adversely affected by hydrogen sulphide and carbon dioxide concentrations in the soil which were apparently not harmful to Erica tetralix. Conway (1940) drew attention to the possible importance of root distribution with depth. Molinia caerulea appears to be more sensitive to some anaerobic peat conditions than Eriophorum vaginatum but it is not clear what these conditions are or how they operate differentially on these two species. The work described here has examined a differential growth response of possible relevance to this problem using redox potentials as the method of characterizing soil aeration. Gillespie (1920) and van Raalte (1944) have shown this method to be useful in waterlogged soils containing organic matter.

LATE‐QUATERNARY DEPOSITS AT LE MOURA, BIARRITZ, SOUTH‐WEST FRANCE

SummaryThe present paper describes pollen‐analytical and stratigraphic evidence and macroscopic plant remains from Full‐, Late‐ and Post‐glacial deposits at Le Moura, a valley bog near Biarritz, South West France. The last part of the Full‐glacial period probably saw the existence of treeless conditions in the area whilst during the Late‐glacial period, pine (including Pinus uncinata) and tree birches spread into the area and forested episodes alternated with periods of park woodland and steppe‐tundra. In the Late‐glacial deposits at Le Moura, indications of hydroseral and terrestial plant successions intermingle in contrapuntal fashion, and only when a detailed palaeo‐ecological analysis of the evidence was carried out did any satisfactory indication of climatic change during the period emerge. The main Late‐glacial episodes closely parallel those from north‐west Europe, a mild forested phase presumably contemporary with the Allerod (zone II) occurs, preceded and succeeded by less wooded, cooler episodes. A pre‐Allerød climatic oscillation of apparently short duration and narrow amplitude is tentatively detected. Among the Full‐ and Late‐glacial plant records, Armeria sp., Cryptogramma crispa, Centaurea cyanus, Empetrum nigrum, Ephedra cf. distachya, Erica tetralix, Euphorbia amygdaloides, Pinus sylvestris and P. uncinata, Polygonum cf. viviparum and Valeriana dioica may be noted. The Post‐glacial record is incomplete, there being a discontinuity in deposition giving rise to the absence of any records from the whole of the period considered equivalent to British pollen zone VIIb, early zone VIII and late zone VIIa. The dominant woodland species throughout the earlier part of the Post‐glacial period are the oaks and pine, with hazel, whilst alder and beech appear towards the top of the diagram. Other mixed oak forest elements are very scarce. Both the strati‐graphic and pollen‐analytical records show that the end of phase P2 (approximately equivalent to British zone VI) at the site was a relatively dry continental period. Whilst the highest levels of the series include records for recently introduced plants such as maize and a species of cedar, earlier pre‐cultural levels include pollen records of Vitis, Olea, Daboecia cantabrica, Erica vagans and Quercus ilex. The biogeographical significance of the plant records and the palaeo‐climato‐logical reconstructions is briefly discussed.

The Ability of Sphagnum to Absorb Cations Preferentially from Dilute Solutions Resembling Natural Waters

During a visit to the Beinn Eighe Nature Reserve in 1955, two water samples were taken from a bog in the pine forest a little west of Rhua Noa, near the foot of the low cliffs of Cambrian limestone, from which the drainage entering the bog appeared mainly to come. The bog was roughly circular, about 60 ft (18 m) in diameter, and flat. One sample was from a small stream entering the bog on the west side, and the other from a shallow pool near the centre. The vegetation of the bog, consisting principally of a carpet of Sphagnum magellanicum, S. papillosum, S. plumulosum, S. quinquefarium, S. rubellum, S. subsecundum and S. tenellum, with scattered angiosperms, predominantly Erica tetralix, Eriophorum angustifolium, Narthecium ossifragum, Rhynchospora alba, Drosera rotundifolia and Molinia caerulea, was either at or a little above water level. Sphagnum cuspidatum was frequent in the pools. The visit was made in July, after a period of exceptionally dry weather, and it is likely that the surface of the bog was normally swampy.

The Composition of Wet-Heath Vegetation in Relation to the Water-Table

Introduction. The vegetation which is the subject of this paper is found on extensive areas of wet heath-land in south-eastern England. What will be called the central associes is a community dominated by Molinia caerulea and Calluna vulgaris, and in which Erica tetralix is usually abundant. The bases of dead Molinia shoots decay rather slowly in the wet habitat and thus there are built up tussocks of varying height, which are an important rooting medium both for the Molinia itself and for the Ericaceae. Under varying conditions any one of these plants may increase in importance at the expense of the other two. As would be expected, increase in Calluna is the usual accompaniment of transition to drier sites, and the change from wet-heath to Callunetum is commonly marked by the entry of Erica cinerea, Ulex minor and Deschampsia flexuosa. Relatively greater abundance of Erica tetralix is found in transitional stages between the central associes and valley-bog communities dominated by Sphagnum spp. In other wet situations Molinia assumes complete dominance. It has then a markedly tussocky habit, the tussocks reaching 30 cm. and sometimes much more in height; and Myrica gale is often associated with it. The wet Molinietum is frequently seen in the bottoms of sloping valleys cut into the sides of plateaux, and in other situations where the ground-water may be supposed to have appreciable flow. The association of Molinia with moving ground-water is well known; it was described on the Yorkshire moors by Jefferies (1915) and on Scottish moors by Fraser (1933). Transitions of the central associes to a rather drier type of Molinietum are also found. In this, tussock building is less pronounced, but there is no ciearly marked distinction between the drier and wetter types of Molinietum; they grade imperceptibly into one another. But whereas at the wet extreme the growth of pine and birch invaders is extremely stunted, and the development of woodland seems impossible, the drier Molinietum is readily colonized by vigorously growing Betula spp., especially B. pubescens. Molinia may also dominate considerable areas of dry heath. But this quite distinct community, in which there is no accumulation of dead shoot bases, and which includes

Fertilization of Erica Carnea

ALL our Vaccinieæ and Ericaceæ, with tubular corolla, as far as hitherto known, are adapted to cross fertilization by Apidæ; for instance, Vaccinium myrtillus and Vitis idæa, Arctostaphylos uva ursi and Erica tetralix. I was, therefore, much struck yesterday by the observation that Erica carnea is abundantly visited and cross fertilized by a butterfly, Vanessa cardui, but not by a single bee. And, indeed, the colour and structure of this flower corresponds far more to the taste and habits of butterflies than of Apidæ. Like all other alpine flowers adapted to butterflies (Saponaria ocymoides, Silene acaulis, species of Dianthus, etc.), Erica carnea is also of a gay red (pink) colour, and its inclined tubular corolla is so narrowed downwards that its small opening is almost completely occupied by the anthers projecting from it. Hence butterflies which are most distinctly attracted by the colour of this flower, as also by its structure, are alone able easily to insert their thin proboscis into its corolla and to reach its honey.

Common Wild Flowers Considered in Relation to Insects* II

THE Common Heaths (Erica tetralix and E. cinerea) offer us another very ingenious arrangement. In E. tetralix (the Cross-leaved Heath), for instance, the flower is in the form of a bell (Fig. 15), which hangs with its mouth downwards, and is almost closed by the pistil (st), which represents the clapper. The stamens are eight in number, and each terminates in two cells, which diverge slightly, and have at their lower end an oval opening. But though this opening is at the lower end of the anther cells the pollen cannot fall out, because each cell, just where the opening is situated, touches the next anther cell, and the series of anthers thus form a circle surrounding the pistil and not far from the centre of the bell. Each anther cell also sends out a long process, which thus forms a series of spokes, standing out from the circle of anthers. Under these circumstances, a bee endeavouring to suck the honey from the nectary cannot fail firstly to bring its head in contact with the viscid stigma, and thus to deposit upon it any pollen derived from a previous visit; and secondly, in thrusting its proboscis up the bell, it inevitably comes in contact with one of the anther processes, which acts like a lever and dislocates the whole chain of anther cells when a shower of pollen falls from the open anther cells on to the head of the bee.†