TRANSACTIONS BRECKLAND DERRICK J .
FLORA MARTIN
THE diversity of the flora in the different parts of Breckland itself and the Variation between those of Breckland and of other parts of the country are so obvious, that the question of why this should be demands an answer. The recording of all plants that can be found in the area must, of course, be a first step. This has been done so thoroughly that it is unlikely that any of us will find fresh species. We may, however, find a change in the flora todav compared with the list made in the Suffolk Flora of 1889. There have been so many changes since that time due to the behaviour of man in his changing farming practice, in the planting of the Forestry Commission's forests, in the building of aerodromes and the establishment of battle areas, and in the spread of the towns themselves, that all these must have had their influence on the flora. The decrease in the rabbit population too has made obvious changes and how far these will go is a matter for our Observation at the present time. In spite of changes, our Breckland flora is still distinctive : we are used to seeing fields bright with Viper's Bugloss (Echium vulgare) or white with Campion (Melandrium album) and fields lined with Mignonette (Reseda lutea). The nature of Breckland soil must be the chief influence affecting its flora as elsewhere, and we know that it must have had many changes. T h e soil was laid down during the glacial ages and so, spread Over the area is boulder clay, or glacial drift as ecologists like to call it now, made up of a mixture of chalk and sand. This sand may have been brought down from the Sandringham greensands. This can be very fertile soil, but as the mixture is about 50% sand and 50% calcium carbonate its texture is very porous and in consequence of rain seeping through, the bases are washed out leaving the sand behind. As this leaching takes place, not only are the bases removed, but also the finer particles in the soil and so it becomes even more porous.
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As a result of pollen analysis it has been possible to learn something of the age and series of changes that have led to the formation of the Breck heathlands. It appears that there was a development of woodland as the glaciers receded, first of all alder and birch and later, as the land dried, mixed oak forest. At the time when Neolithic man was working the flint mines at Grimes Graves, the pollen of grasses and herbaceous plants, characteristic of open lands, became much commoner. One of the most characteristic of these was ribwort plantain (Plantago lanceolata). It was also at this time that the knowledge of barley and wheat spread from the Middle East across Europe and this was no doubt one of the great influences that led to the beginning of agriculture and settled communities, who needed open land for grazing and growing grain instead of forests for hunting, which had been adequate for nomadic peoples. It is interesting to speculate upon how these forests were cleared, as it took place before man had bronze implements. One can hardly imagine that a flint axe would be capable of felling a tree. Perhaps the land was cleared by burning, as is still done by native people in the Amazon Forests. Within Breckland today all degrees of leaching can be Seen, with a characteristic flora in each. The assessment of the hydrogen ion concentration of the soil can be done in a simple way by the use of the B.D.H. universal indicator judged against a colour chart supplied by the makers. The specimen of soil, of course, must be taken from the level to which the roots penetrate. More accurate results can be obtained by the insertion of electrodes into the level that one is concerned with and a portable machine of this type is now available, so that measurements can be made on the spot. The Soil Survey Department of the Ministry of Agriculture has prepared maps showing soil reactions. This has, in particular, been done for the Forestry Commission as it has been found that some of the fungus infestations of conifers are less prevalent in acid soils. The ränge of reaction in the Breckland can extend from almost pure chalk to an acid soil. John Ray (c.1704) noted that those plants especially characteristic of this area all needed some bases present in the sand. Around the old chalk pit on Risby Poor's Heath and the Black Ditches the soil has a pH value of about 7. Here you will find flowers similar to those found on Downland, all of them notablv calcicoles, such as Purple Milk Vetch (Astragalus danicus), Squinancywort (Asperula cynanchica), Bastard Toad Flax (Thesium humifusum), Carline Thistle (Carlina vulgaris), Clustered Bell Flower (Campanula glomerata).
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When leaching has gone a step further a soil of about pH 5 is formed. Such a land is Berner's Heath, typical of Breckland grass land. Here some calcicoles will be missing but some fresh varieties will have appeared. In such land one can find Hairy Rock Cress (Arabis hirsuta), Birdsfoot Trefoil (Lotus corniculatus), Dwarf Thistle (Circium acaulon), Ladies' Bedstraw (Galium verum), Breckland Thyme (Thymus serpyllum), Maiden pink (Dianthus deltoides), Grape Hyacinth (Muscari atlanticum) and Kidney Vetch (Anthyllis vulneraria). When the moisture in the ground is dependent on rain and not on flushing with water rieh in bases from springs and rivers, the process of leaching goes on even faster. Few deeply rooted trees, like oaks and beeches, will grow from seedlings and this lack will in its turn increase the acidity of the surface. For deeply rooted trees, whose roots penetrate down to the chalky layers, bring up bases in their sap and their leaves contain a considerable amount of bases. This is deposited in the autumn, when the leaves fall, as humus rieh in bases ; such shallow rooting trees as pines and birches deposit very little base in their leaves. These factors are all active in producing the next type of soil, now base-deficient with a pH value of about 4 and in this heather will grow. The ordinary heathers Calluna vulgaris and Erica cinerea will grow only in acid soils and so their presence is floristic evidence of this change of reaction. Growing with the heathers will be Sheep's Sorrel (Rumex acetosella) and Heath Bedstraw (Galium saxatile), and the grass is coarser and made up of Sheep's Fescue and bents and is of no agricultural value. Bracken will grow if there is enough moisture for the spores to germinate. Land of this kind can be seen on Wrentham Heath. If there is a further fall in fertility the soil becomes light grey in colour and on it will grow an open colony of lichens, mosses and sand-loving grasses and sedges. This can be seen on Lackford Heath. This greyish soil has had almost all the organic matter washed out of it and a podsol has now been formed. On this sandy soil will be found some of those varieties which have made Breckland famous. Spanish Catchfly (Siletie otites), Night-flowering Catchfly (Melandrium noctiflorum), Spiked Speedwell (Veronica spicata), Star of Bethlehem (Ornithogalum umbellatum), Common Whitlow Grass (Erophila Verna), Hare's Foot Trefoil (Trifolium arvense), Cudweeds (Filago germanica and minima) and Small Fleabane (Pulicaria vulgaris). Wind has an important influence on the life of the plants and it acts in Breckland in two different ways. There is the straighttorward blow making a frontal attack on the sandy soil. T h e sand is blown as a cloud, which may be thick enough to give the appearance of a fog. This occurs most commonly in March and
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April and besides blowing the carrot seeds off the fields it can blanket large areas of Breckland with sand. T h e other way is when cyclonic gusts pass over bare areas of sand and leave " blow-outs " behind. These areas begin in rabbit scrapes or in areas where the precarious cover of lichens has broken down. This happens because the centre of such a patch will die while the edges may still be growing our centrifugally, and so the protection by the plants at the centre is lost. In attempts to limit the damage done by the wind, windbreaks have been planted where the wind has been able to build up considerable velocity through lack of hindrances in its path. These have been of two types. T h e commonest have been Scots Pines (Pinus sylvestris) planted in double or treble rows and allowed to grow to their füll height. T h e other has been of pines pollarded to encourage thicker growth lower down. T h e Forestry Commission's plantings have also acted in this way to an exaggerated degree and have been so successful as windbreaks that they have created frost pockets. T h e area of the blow-outs or of land covered by a blanket of sand is eventually colonised by the spread from the edges by sandloving species growing from rhizomes or from wind-blown seed. Sand Sedge (Carex arenaria) is an example of the former, and Aira praecox and Festuca ovina of the latter. Tiny sand dunes can soon be seen against groups of the plants, showing how effectively they will bind the shifting sand. Before long a surface is established which will again give anchorage to lichens. Patches of this sort with a dominance of grasses and lichens may last for some years and other species will come in of which Ragwort (Seiwao jacobaea) is one. Though an agricultural pest it makes a handsome plant in these bare areas. After a time, however, the process may be repeated by the dying of the grasses and liehen and the surface again disrupts. With the deposition of humus, however, if a blow-out does not occur, a time comes when soil will contain 3 % of humus and grassland may emerge or a heather heath will develop. T h e heathers will last as long as twenty-five years and if they fail to reseed themselves, the dead Vegetation may give a chance for a fresh blow-out to occur. Düring this time the heather may lay down a layer of black mor about two inches thick. In this soil there is an absence of earthworms and nutrifying bacteria and so it is a soil of low fertility. Another factor of importance in the ecology of flowers is the rainfall. In Breckland, it is as low as anywhere in the country and has been as small as eighteen inches per annum, whilst the temperature ränge is greater than on the coast. This is partly due to its being sufficiently far inland not be influenced by the tempering effect of the sea and partly due to the presence of the dry sands,
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which are poor conductors of heat and so heat up quickly by day and cool quickly at night. This, coupled with the clear skies so common in Breckland, will lead to ground frost. Late frosts are common and there is not any month of the year in which ground frosts have not been recorded. When there is cold air over East Anglia the night temperature in Breckland can be fifteen degrees lower than on the coast. This gives rise to a Continental type of weather in contrast to the Atlantic type in the West. Even the colour of the sand makes a difference to the ground temperature ; thus on the surface of yellow sand the temperature will be slightly lower than of grey sand : but lower down, even two inches, the temperature of yellow will be higher than that of dark sand. This is due to the dark sand, like a dark bulb thermometer, absorbing heat more quickly than the light sand and conducting the heat away more quickly because of the humus present leading to a closer contact of the particles. In order to maintain life in the dry sandy areas, plants have to be able to behave differently from those living in other environments. T h e osmotic pressure in cells of xerophytes is much higher than in mesophytes. In these the pressure is about ten atmospheres but in xerophytes it may be as much as forty atmospheres and some desert plants have been shown to exert pressures u p to one hundred atmospheres. This enormously increased suction must be of assistance to plants growing in arid soils in enabling them to obtain what little water is available there. Surplus water is disposed of through the leaves by transpiration. On the surface of any leaf a number of minute openings are to be found which are called stomata. Each S t o m a usually takes the form of a slit between two elongated cells called guard cells, lying side by side. T h e opening or closing of this pore is controlled by the swelling or contracting of these guard cells. In some plants transpiration can go on through the whole surface of the plant, but in those with a thick cuticle the process is confined to the stomata which are found on the under surface of the leaves so as to be better protected from the drying influence of the sun. T h e effect of transpiration is twofold. First it maintains a constant flow of water from root to leaf through the wood of the plant, bringing with it small quantities of dissolved salts essential to the plant's life. Secondly, it tends to reduce the temperature of a leaf when exposed to the sun through the latent heat of evaporation. The chief danger for the xerophytes is that the loss of water by transpiration may be so rapid that it cannot replace it from the scanty supply of water available at its roots. T o check this excessive transpiration various devices are used by plants. T h e development of a thickened cuticle is the simplest and most frequently found. T h e leathery feel of the leaves is
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characteristic and can hardly be overlooked. T h e amount of protection by this method may vary with the conditions under which a plant is grown, thus the leaves of the Scarlet Pimpernel (.Anagallis arvensis) become thick and leathery when it is grown in a sandy spot, but under normal conditions the leaves are soft and slender. T h e stomata may be protected by being placed in grooves and hollows sunk well below the surface of the leaf. This can be Seen in Festuca rubra but much more easily in the grass of sand-dunes Marram Grass (Ammophila arenaria) when the stomata are confined to the bottom and sides of deep grooves in the leaves. This means of protection is much improved by the capacity of the leaves to roll up into narrow tubes in dry weather, which has the effect of maintaining a layer of air largely saturated with water vapour between the stomata and the outside air. Another common way in which stomata are protected is by the growth of hairs on the surface of the leaf. These can also help in maintaining a damp atmosphere round the openings since moisture tends to condense on these hairs as in Heath Groundsel (Senecio sylvaticus). The silvery appearance of some leaves is due to these hairs. When the leaf is mature the hairs may be dead and contain only air : they are useful then in reflecting some of the sun's heat as well as in the retention of moisture. Damp air may be maintained over the surface of leaves by the plant adopting a dense mat habit so that transpired air is imprisoned between the surfaces of the leaves that are in close contact with each other as in Common Whitlow Grass (Erophila verna). The formation of a rosette from which a flowering stem grows up can also help by exposing only the top surface of the leaf while the under surface is kept closely pressed against the surface of the sand which can then remain cool and moist as in Thale Cress (.Arabidopsis thaliana). T h e shape of leaves can help in Controlling transpiration by reducing the actual leaf surface as can be seen in the conifers and in gorse. Apart from the shapes characteristic of the species, many common plants vary greatly with the conditions under which they grow. T h u s a dandelion growing in a moist place will have leaves with much wider serrations than those of a plant growing in conditions of water shortage. Some xerophytes employ a quite different method against water shortage by developing fleshy succulent leaves. In these are large colourless cells capable of storing water. Such a one is Stonecrop (Sedum acris).
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1 here IS another group of flowers which have a characteristic behaviour when living in sandy soil. These are the ephemerals of the type known as the winter annuals. They have a mass of short roots that can make use of surface water. They are common plants with light seeds scattered by wind and germinate where there is not much competition. They persist as seedlings during the winter : in the spring they grow quickly, flower, and set seed before the heat of summer makes their habitat untenable. As examples of these in Breckland are Mouse-ear Chickweed (Cerastium arvense) and Thvmeleaved Sandwort (Arenaria serpyllifolia). The influence of water too is of importance in producing a typical flora. T h e slow flowing rivers with their alluvial meadows at their sxdes produce a flora similar to streams in other parts of the country, but one does not have to get far away from the river to see the influence that the lack of water has on Breckland as a whole. Human Settlements were dependent on water and so in the early days, these were found associated with the Thet, the Wisse) , the Little Ouse and the Lark. Four parishes appear to have häd no direct access to stream, fen or mere. These are Swaffham Elveden, Ingham and Wordwell. Nine parishes meet within ä short distance from the mere at Rymer's Point [ T L 52/8667581. This and the other meres of the Breck are very variable in the amount of water they contain. Though some may be supplied by Springs, there is no doubt that mostly they depend upon the water level in the underlving chalk, and rise and fall with that. T h e rushes from these rivers and meres have met the needs of the neighbourhood as thatch, litter and perhaps most interesting of all as hassocks in church. At Icklingham there is a set of six hassocks made from the matted bases of the Sedge (Carex panniculata). The gloom and eeriness of Breckland have been frequently commented upon by travellers in the past who have made their way through the long straight roads. This may have been an understandable response of those who have only passed through but those of us who have been alone in the Breck in all its seasons know that there is indeed nothing forbidding in the district. The beauty is one of changing colours, changing through the hours of the day and through the seasons of the year. Along Breckland roadsides may be seen in the spring the Saxifrage ( S a x i f r a g a tridactylites) and later in the year Common Hound's Tongue (iCynoglossum officinale) and Yellow Melilot (.Melilotus officinalis) and also its white variety. Wonderful thistles too can be seen, of which one , t h e m o s t handsome is the Musk Thistle (Carduus nutans). On the chalky banks there is Dropwort (.Filipendula vulgaris) and in some places Sickle Medick (Medicago falcata). This is a true
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Breckland flower which can be easily overlooked. It hybridises with the well known fodder plant, lucerne, and the hybrid form (Medicago varia) has a mixture of dirty yellow and purplish flowers on the same plant. Even in winter when the grass is dun coloured, bleached by the frost, on a sunny day the purple of the silver birches makes wonderful patches of colour. These may have been seif sown in the heathland or may have been planted as nursing plantations set by the Forestry Commission to give protection to more valuable timber growing among them. Gorse may be flowering throughout the year, but comes to its best in April. Crab Apple trees (Malus sylvestris) flower magnificently in Breckland : Broom (Sarothamnus scoparius) will be seen in brilliant patches where there is little lime in the soil and the Hawthorn blossoms (Crataegus monogyna) make the trees look snow-covered. In June when the grasses are in bloom their swaying heads are fĂźll of purple, grey and pink. These continue until the purple of heather Covers wide areas. Rosebay (Chaemaenerion angustifolium) and lilac hedges add colour to the scene. When Autumn comes the beeches turn brown and the larches golden and the leaves fall so slowly that the colour remains well into Winter.
WORKS
CONSULTED
W a t t , A. S. Studies in the Ecologv of the Breckland. 28 (1940).
Journal of Ecoloey
W a t t , A. S. 25 ; 91.
Journal of Ecoloev
Origin a n d D e v e l o p m e n t of Blowouts.
G o d w i n , H. Age and Origin of the Breckland H e a t h s of East Anglia. Nattire 154 ; 1944.