The status of Spartina maritima in Suffolk

T H E S T A T U S O F SPARTINA

MARITIMA

IN S U F F O L K

MARGARETA. COOPER Spartina maritima (Curtis) Fernald (native or small cord grass) is a rare saltmarsh grass, which is now locally common only in Essex and Suffolk. 1t is one of the plants for which contemporary distribution data are rare and it has been included in the Scarce Plant Project organised by the B.S.B.I. The resultsof this project will form a basis for deciding future conservation needs.

This paper arises in part f r o m my work in carrying out a survey for S. maritima in Suffolk.

S. maritima is the native species of Spartina\ it hybridized with the northAmerican import Spartina alterniflora Loisel to form the species now known as Spartina x townsendii H . & J . G r o v e s i n a b o u t 1870. Spontaneousdoubling of the chromosomes took place within a few years and the resultant fertile amphidiploid is known as Spartina anglica C. E. H u b b a r d . This is now the most common Spartina and is seen in every estuary in the county.

S. maritima rarely sets seed but spreads by rhizomes. It is usually found in high, mixed marshes growing in the Standing water of salt pans as a monoculture, or as part of a mixed assemblage in wetter areas of the marsh.

It is often found on creek banks where, relatively free from grazing pressure, it tends to grow taller than at other places. In the River Orwell, S. maritima is also found as a pioneer plant on low-lying mud flats in conjunction with S. anglica, although it is often found nearer the river than that plant as it will tolerate longer immersion periods. In the high marshes, S. maritima is nearly always found close to Limonium spp. (Sea Lavender), though not where there is a high frequency of Aster tripolium (Sea Aster).

S. maritima, although generally smaller than either S. anglica or S. x townsendii, is not easily distinguished in the field. This can happen where the plants are grazed and hence reduced in height, or where S. maritima is growing in competition with plants like Halimione portulacoides when it tends to elongate and the distinctive close angle of the leaf to the stem is not obvious. In the winter it appears rather like a 'hedgehog', as nearly all the lower leaves are lost late in the year and the growth habit is very upright.

When it begins to grow in the early summer the new leaves are held fairly close to the stem, in contrast to 5. anglica which has more spreading leaves.

History in Britain T h e first recorded Spartina in this country was found at Brigg in South Humberside, where seeds and rhizomes of a plant subsequently identified as a Spartina were found under a boat that was being excavated. These were dated at c.650 BC and it is assumed that they were remains of S. maritima, or a close relation (McGrail, 1981). No other fossil records have yet been found.

Subsequently the plant was recorded from Kent in 1629 and was first collected by Merret from Creeksea Ferry in Essex in 1666. In 1703 it was found further u p the Crouch at Fambridge ( H u b b a r d , 1965). T h e grass slowly spread, and was reported from Southampton Water in 1805

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(Marchant, 1967). In 1836 the plant was growing below Itchen Ferry and survived at Hythe until 1910 (Marchant, 1967). It was common in South Hampshire and the Isle of Wight by 1883 (Marchant & Goodman, 1969), and was present in the Beaulieu River until 1907. By 1908 the distribution was described as being 'from Lincolnshire to the Thames, and Chichester to the Solent' (Stapf, 1908). Since then the grass has retreated and, apart from one colony at Hayling Island and another near Portsmouth, is confined to Essex and Suffolk (Raybould, 1991b; A. J. Gray, pers. comm.). The distribution of the plant from 650 B.C. to the seventeenth Century may only be surmised. It is possible that the Spartina underwent periodic population fluctuations, perhaps dependent on weather cycles. It is known that S. maritima will grow all the year round and attain higher biomass when the ambient temperature is higher (as in southern Spain today). To be present in South Humberside in 650 B.C., the environment must have been more favourable than it is in that locality today. However, whereas decline of the plant can be very rapid as it can be severely affected by frost damage (Ranwell, 1981), increase will be slow, as it does not set much viable seed near its northern limit.

History in Suffolk S. maritima was collected originally in Suffolk at Landguard Fort in August 1796 by Rev. G . R. Leathes, subsequently by Davy in 1802 at Aldeburgh; and again at Aldeburgh and Havergate Island in 1829. In the 1860 Flora of Suffolk (Henslow and Skepper), S. maritima was described as being at Slaughden Vale and at 'Aldborough and Orford, abundantly'. Hind, in his 1889 Flora of Suffolk, found S. maritima in eight locations including Aldeburgh, Slaughden Vale, Ramsholt and Havergate Island. Simpson (1982) described thirteen locations, also including Aldeburgh and Havergate Island, and described it as 'at one time fairly frequent, now rare or extinct in many of its former habitats'.

Recent surveys of known sites in Suffolk have shown that the grass is now absent from the River Stour. Other losses have included those populations originally found near the tidal limits of rivers such as the Deben and the Aide.

This may be because the tidal flows have been altered over the years and S. maritima does not thrive in nearly fresh water. In other areas, reasons for loss can be erosion (as at Erwarton), industrial use (Ipswich, Felixstowe) or reclamation of land for agriculture. Another factor in the demise of S. maritima was thought to be the invasion of its sites by S. anglica, which spread quickly during the initial stages of its colonization by virtue of its greater seed production. This view has been put forward by several authorities (Simpson, 1957; Marchant, 1967; Beeftink, 1975), although recently Raybould (1989) has claimed that none of the former S. maritima sites in Britain are now colonized by S. anglica. In East Anglia, S. maritima is more likely to have been lost by invasion of Halimione portulacoides (as is happening in parts of the marsh at Cranes Hill, River Orwell and on part of Devoys saltings on Havergate Island).

In 1959 it was noticed that S. anglica grew on the River Orwell in Company with S. maritima (Goodman et al, 1959). This is still the case and the

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Nat. Soc. 29 (1993)

T H E STATUS OF SPARTINA

MARITIMA

IN SUFFOLK

49

frequency of this occurring appears to have increased of late. The growth of S. maritima as a pioneer plant on bare mud is rare in this country. It is found only on the River Orwell and Foulness Island, from where it was reported during the course of the Maplin Sands survey (Boorman & Ranwell, 1977).

Unfortunately, access to this area is now difficult. In warmer countries where S. maritima grows prolifically (e.g. Spain) it is known only as a pioneer plant.

In the places where both S. maritima and S. anglica grow together death of neither one of the species has been linked to the survival of the other. T h e most recent theory is that when S. maritima dies, S. anglica may fill the niche, but that one event is not necessarily related to the other (Raybould, 1991b).

T h e distribution of S. maritima in my recent survey in Suffolk is given in Fig. 1. In the River Orwell, colonies occur at Shotley, Cranes Hill, H a r e ' s

itima in Suffolk rivers

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Nat. Soc. 29 (1993)

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Suffolk Natural History, Vol. 29

Creek, Wherstead, scattered along the north shore from Mulberry Middle to Shore Lane, Trimley St. Martin and Trimley Marshes. In the Deben populations are found at King's Marsh, Hemley, Falkenham, Early Creek, Ramsholt and scattered colonies between Ramsholt and Bawdsey. The Alde-Ore-Butley complex has more S. maritima than either of the other rivers. T h e distribution is on suitable locations from the northern end of the Hollesley marshes to a point between Butley Quay and Butley Mill. On the opposite bank of the Butley river, the grass is found just north of Ferry Cottage and intermittently from there to the Chantry Marsh. North of Orford it is found with decreasing frequency up to the northern end of Sudbourne Marshes. S. maritima is also found at Slaughden Quay and this very small colony of about 30 tillers is probably now the northernmost in the country. There are also colonies near the Martello Tower south of Slaughden Quay and on Lantern Marsh. The other site on this river complex where S. maritima is found is Havergate Island and this was the subject of a separate detailed survey.

Distribution on Havergate Island Havergate Island, a RSPB reserve in the River Ore with 27.46ha (67.86 acres) of saltings, has a recorded history of S. maritima since at least 1829.

Because of this and the fact that its salt marshes are relatively undisturbed by people, it was selected for a detailed survey of three types. The first was a generalised survey of all Spartina distribution on the Island. A similar survey had been carried out in 1962 by the Nature Conservancy and I have presented my result in a similar format for comparison. The second survey involves establishment of permanent transects, on which all Single tillers and small clumps of S. maritima are mapped. The third survey is using smaller permanent transects on which all Vegetation is mapped. By following these areas over a period of several years, it is hoped that some knowledge of the population biology of clumps and individual tillers in the high marsh can be gained, as well as the response of the grass to competition.

The saltings on Havergate are divided into four main areas: A) those surrounding Doveys lagoon on the south of the island B) the Dowsings - the shingle and salting area between Doveys and the lagoons to the north of the island C) the marshes on the north-western side D) those to the north-eastern side.

In 1962 all of the areas had S. maritima growing on them (Fig. 2) and growth was sparse to moderate on all marshes. It was noted that dense populations sometimes occurred around some salt pans and creek banks.

By 1992 the southern parts of Doveys saltings ( A - B ) had no S. maritima but the rest of the marsh ( B - C ) was still moderately populated. The Dowsings area was also moderately populated, although the plant became more common from south to north along the marsh. The north-western marshes had also lost most of its populations in the southernmost part ( G - H ) although the rest of the marsh ( H - I ) was highly populated. The same trend prevailed on the north-eastern marsh, where most of the S. maritima was

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Suffolk Natural History, Vol. 29

found in the north of the area ( E - F ) . In summary, the grass is still present on all saltings on the island but seems to have migrated north on each.

In 1962 it was noted that the growth of S. maritima was generally rather denser in the pan areas and this is still true. Growth is also thicker and taller on pan edges and creek banks and clumps often occur in these areas. This effect is very noticeable on small islands that are never grazed. In the high mixed marsh the plants are sometimes subject to grazing from Brown Hares {Lepus capensis) and from waterfowl. This is not a great problem at the moment and only reduces the average height.

Causes of Death Tillers of S. maritima that have flowered always die and the spikelets are not shed. They remain visible throughout the winter and are a good way of Spotting the grass at this time of the year. Only about 10% of the tillers flower, usually in the second year of growth. Accordingly, tillers are usually found in small groups or larger clumps as the plant ages. Single dead flowering tillers have been found, indicating death of the associated rhizome during the previous year. Observations of this occurrence are not yet numerous enough to know if it is the Start of a large-scale dieback, or just a part of the normal lifecycle. Death of an area of tillers growing as a monoculture in a salt-pan is not uncommon. A recent example occurred in the Ore side of the Boyton Marshes. This feature resembles the phenomenon known as dieback that occurs in S. anglica. Although the subject has been thoroughly researched in that plant (Goodman, 1959, 1960; Goodman etal, 1959; G o o d m a n & Williams, 1961) and its American relative, S. alterniflora (Linthurst & Seneca, 1980; Mendelssohn & McKee, 1988; Wilsey etal, 1992) the reasons for dieback are not yet fully understood.

However, it is thought that S. maritima may be a fairly short-lived perennial which spreads to new locations readily by rhizome fragments (viable seed is rarely set). It is hoped that the permanent transects on Havergate Island and continued observations of S. maritima clones on the River Orwell, which will be reviewed regularly, will help to ascertain the average lifespan of the clumps.

In sheep- and cattle-grazed marshes the plant is spread by the trampling of the hooves that break off shoot/root/rhizome fragments and 'plant' them elsewhere. Very heavy grazing pressure destroys the sward completely. A recent trend towards the total cessation of grazing on some marshes may lead to the eventual loss of the grass on those marshes. However, people can perform the same function that cattle and sheep have done in past years and on several marshes the grass can be seen along the pathways made by walkers (for example, the River Ore side of the Boyton marshes). On Havergate, where there was cattle grazing until the last world war, the wildfowl, hares and visitors may now perform this function.

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T H E STATUS OF SPARTINA

MARITIMA

IN SUFFOLK

53

Conclusion Recent population changes of S. maritima in Suffolk have been significant.

The grass has been lost completely from at least one estuary and is migrating to the seaward end of others. O n Havergate Island S. maritima, although still prolific, has been lost from at least one area. T h e combination of circumstances (erosion, agriculture, industrial use and replacement by other plants) which has led to this retreat is worrying.

Very little is known of the population biology of S. maritima and so more Observation and research is vital to ensure positive conservation of this interesting scarce plant and perhaps even to prevent it becoming extinct in its native environment.

Acknowledgements I thank Mr. John Partridge, the RSPB Warden of Havergate Island, for his co-operation during my stay there, English Nature for permission to use the 1962 results and Dr. A . J. Davy for help and encouragement in the preparation of this manuscript.

This work was undertaken as part of a P h . D . study supported by a S E R C studentship at the University of East Anglia.

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G o o d m a n , P. J. (1959) The possible role of pathogenic fungi in die back of Spartina townsendii agg. Transactions of the British Mycological Society 42(4), 409-415.

G o o d m a n , P. J. (1960) Investigations into 'die-back' in Spartina townsendii agg. 11. T h e morphological structure and composition of the Lymington sward. J. Ecol. 48, 711-724.

G o o d m a n , P. J., Braybrooks, E. M. & Lambert, J. M. (1959) Investigations into 'die-back' in Spartina townsendii agg. 1. T h e present status of Spartina townsendii in Britain. J. Ecol. 47, 651-676.

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Hind, W. M. (1889). The Flora of Suffolk. London: Gurney and Jackson.

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drainage potential on the Spartina alterniflora-substrate complex in a North Carolina salt marsh. Estuarine and Coastal Marine Science 11, 4 1 52.

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Marchant, C. J. & G o o d m a n , P. J. (1969) Spartina maritima (Curtis) Fernald. J. Ecol. 57, 287-291.

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76, 509-521.

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Simpson, F. W. (1982). Simpsons Flora of Suffolk. Ipswich: Suffolk Naturalists' Society.

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Wilsey, B. J., McKee, K. L. & Mendelssohn, I. A . (1992) Effects of increased elevation and macro- and micronutrient additions on Spartina alterniflora transplant success in salt-marsh dieback areas in Louisiana.

Environmental Management 16(4), 505-511.

Mrs. M. Cooper, T h e Gables, Wilby R o a d , Stradbroke, Suffolk.

IP21 5JN

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Plate 5: Cord-grass (Spartina anglica) the River Orwell, 1991. (p. 47).

( b a c k g r o u n d ) a n d Small Cord-grass, (S. maritima)

growing on