SPARTINA TOWNSENDIL

New Zealand Journal of Agriculture, Volume XL, Issue 3, 20 March 1930, Page 189

SPARTINA TOWNSENDIL

A VALUABLE GRASS FOR RECLAMATION OF TIDAL

MUD-FLATS

(Concluded from November, 1929, issue.)

H. H. Allan,

Systematic Botanist, Plant Research Station, Palmerston North.

2. Experience in New Zealand.

• The introduction of Spartina into New Zealand was recorded by the writer in the New Zealand Journal of Science and Technology for November, 1924, as follows : “In 1913 a number of plants of Spartina were obtained by Mr. K. W. Dalrymple from Southampton Water and planted out in small clumps on the Foxton mud-flats in the tidal estuary of the Manawatu River. The clumps were considered to consist of specimens of both S. stricta and S. Townsendii, but unfortunately it is not certain that the latter has established itself. All the clumps that have flowered have proved to be S. stricta (this identification being confirmed by Professor Yapp, and at Kew). It may be, indeed, that no S. Townsendii was planted, but a close watch is being kept, and any occurrence of this species will be recorded. The clumps were put in bare mud below high-tide level. One clump has thriven markedly. By 1915 it had formed a dense mat 1-8 m. across. The area was again visited on nth February, 1923, when the patch was found to measure 12-8 m. by 7-2 m. The sheet was dense and short in the central portion, which was becoming mounded by accumulation of mud, and luxuriant on the margin of the deeper tidal channel. There were a few flowering culms that proved the clump to be S. stricta. On the 16th March, 1924, the patch had increased to 14-3 m. by 7-4 m., the longer diameter parallel to the tidal channel. Some slight progress had been made towards crossing the channel, here about Im. below high-tide. level. This patch and several of the others were then flowering rather freely, especially towards the margins.” Additional information has since accrued, and is here recorded.

IDENTITY OF THE SPECIES ESTABLISHED AT FOXTON

Misled by the short growth , of the greater part of the main patch, I had concluded that this was made up of S. stricta. The late Professor Yapp examined specimens and agreed with this determination. He forwarded the specimens to Kew and received confirmation of this identification. Later on specimens taken from the more vigorously growing portion were sent to Professor Oliver, who determined them as S. Townsendii.- Dr. Stapf thoroughly agreed with this view, and also examined the original specimens forwarded, finding them also to be S. Townsendii. In the meantime Dr. J. P. Lotsy had visited the area with me on 9th May, 1925. Fie considered the plants to be definitely not S. stricta, but hesitated to pronounce them as S. Townsendii, as they lacked the characteristic luxuriance* of that species in Great Britain. At the time of his visit the more luxuriant portion was still under water and could not be properly examined. Close examination, of. all the patches, has since shown that the plant

•established is S. Townsendii. Only in one patch is there a bunch of what may be S. stricia, if it. is not the same as the special bunches in the main patch described farther on. This, however, has not so far been observed to flower.

The short growth of the mounded portion is to .be noted. Juncus had not at this date invaded the patch. ■

On the occasion of Dr. Lotsy’s visit I planted out on a piece of soft mud three small clumps taken from the centre of the large patch and representative of . the short dense growth there shown. These clumps were placed in line near a shallow side drainage-channel at 3 ft. apart. Their places in the main patch were filled with luxuriant

marginal clumps. A few clumps were also planted out on a much higher and firmer piece of bare mud-flat, but these did not survive A specimen of 5. stricta that had been kindly sent out by Professor Oliver, and which arrived in very fair condition, was also planted out in the softer mud. This unfortunately was washed out by the scour before it had established itself. • In their new situation the three short-leaved clumps grew luxuriantly, while those that replaced them in the main patch gradually lost vigour. and became indistinguishable from the surrounding growth. ‘ , ■

In the main patch are two or three small bunches closely resembling the bunch that I have suggested may be S. stricta. These were noticed in 1923, and have increased very little in area since that date. They are at once distinguished from the rest of the patch by the almost erect; rolled-up leaves. They have flowered this season, and, as the following table shows, possess characters closely approximating to those of S. stricta. A difficulty that has been felt as to the hypothesis that S. Townsendii is really a first cross between S. stricta and S.. Townsendii is that the seedlings, of the latter show no evidence of segregation, .This is surprising'if,, as Oliver (“Spartina Problems," Annals of Applied 'Biology, vol. 7, 1920, p. 29) says, "as seem almost certain, it is largely propagated and spread by seed.” While nonsegregation does not absolutely preclude the possibility of S. Townsendii being a first-cross hybrid, such cases are quite uncommon. .The clumps here discussed certainly suggest strongly that segregation may occur to a greater extent than has been suspected. The offspring more closely approximating to S. stricta would tend to be crowded out and suppressed by those more closely approximating to S. Townsendii, unless, as in the Foxton patch, the growth of S. Townsendii is checked for any reason. It is impossible to say whether these strictaAike bunches are seedlings from the Townsendii or are the original clumps planted as S. stricta. Certainly in the vegetative state, there is little to differentiate them from S. stricta.

RATE OF GROWTH AND ESTABLISHMENT

The main patch was remeasured on 22nd November, 1926, showing then a length of 52 ft., with a breadth of 28 ft. On the seaward side it had almost reached the Juncus maritimus association, while on the landward it was still held up by . the side drainage-channel. Measurements taken on 22nd February, 1930, gave 57 ft. ■ for the. length and 33 ft. for the width. The patch had then extended round the shallower end of the side drainage-channel for about 3 ft. Growth along the edge of the main . drainage-channel was very luxuriant, but the grass had not succeeded in crossing- it. The banking-up of the channel by the grass has caused increased scour and deepening, and in places it was evident that the bank had been undermined and clumps of the grass . carried away. One clump had established itself farther down the channel near the point where it-reaches the estuary, waters. On the seaward margin the patch had joined the Juncus association. The marginal growth on the side more remote from the channel was much less vigorous. Here the grass is submerged . for only a short period per tide, and the- mud is of a much firmer consistency, the feet hardly sinking in at all as one walks over it.

As will be seen from the accompanying graphs, the growth is fairly comparable with that recorded for Great Britain- 2 ft. to 3 ft. per annum. But there has been no sign of increase by seedlings} and only small increase by detached clumps. In the seventeen years since planting the main patch has grown to roughly acre. All the original clumps show considerable increase, this being more marked in those at lower levels in the softer mud, where too the plants are much more luxuriant. The three clumps taken from the short growth of the main patch in 1925 have made good growth, and. there is now a continuous patch of luxuriant grass 18 ft. long by 7 ft. wide. The slackening- of the rate of growth in the period 1925-30 as compared with that. of 1920-25 may be attributed to the barrier opposed by the tidal channel, the higher firmer mud on the further margin, and the competition with the surrounding Juncus association.

COMPETITION WITH INDIGENOUS VEGETATION.

In the paper cited. I..said..of the .indigenous, .vegetation of the Foxton mud-flats: “ Juncus maritimus var. aliensis and Leptocarpus simplex are dominants, both forming very extensive dense sheets, the latter usually seaward of the former and less in extent. There is. not wanting evidence that in this locality ■ the Juncus invades the Leptocarpus sheets and tends to subdue them. The areas of bare mud are not extensive, and ; in the Spartina neighbourhood border the tidal channels. ■ Between the -margins -of - the - dominants and the bare mud there may be patches of Scirpus americanus, Salicornia australis, or Triglochin striata var. filifolia, the latter pair with or without other small species. . Certain of the Spartina patches have. now approached closely to the margins of the various species mentioned, and careful measurements and notes have been taken with a view to studying future changes. Present observations suggest ' that the Juncus will take advantage of the raising of the level of the mud by the Spartina and invade its territory.”

Subsequent observations show that where the Spartina meets the advancing J uncus or Leptocarpus it penetrates for a short distance,, but is dominated and suppressed by both indigenous species. The dense growth of the rush cuts off the light, and at the same time the presence of J uncus or Leptocarpus shows that the level is higher than the optimum for Spartina, while the mud is much firmer than suits Spartina best. It would also appear that Scirpus .americanus is a potential dangerous competitor, favouring as it does muds rather softer than those on which the Juncus and Leptocarpus flourish.. The mounded top of the main patch of Spartina has now been invaded by

Juncus, apparently from seedling attack. There are now well established on it five clumps that have reached the flowering stage. Thus the higher parts of the patch appear likely to be dominated by the Juncus.

OTHER EXPERIMENTAL AREAS.

Numerous small clumps have been taken by Mr. Dalrymple and distributed for experiment elsewhere. Some of the localities are Kaitaia, Kaeo, Maharau, Kaipara Harbour, Kaukapakapa, Waiuku, Whangarei, Tauranga, Tutaekuri estuary, mouth of Hutt River, and Blind Bay. No definite reports are as yet available concerning the fate of these experiments, but it is hoped to secure and publish such later.

Conclusions.

(i) Spartina Townsendii has definitely been established in New Zealand at Foxton.-

(2) The growth during the past seventeen years has been very satisfactory, and the grass promises to play an extremely useful part on mud-flat areas;

(3) The optimum requirements for Spartina in New Zealand have not yet been thoroughly established. It is clear, however, that Spartina does not thrive in. the more consolidated muds, nor above a certain level in relation to high tide.

(4) For rapid covering of an area extensive planting at regular intervals is required, as increase by seedlings appears to be rare, and increase by natural dissemination of clumps infrequent and irregular. (5) Spartina will not hold its own in competition with Juncus maritimus or Leptocarpus simplex. Rather it prepares the ground for their more rapid extension. The best field for' Spartina, therefore, is where there are extensive areas of bare soft mud-flat sufficiently below high-tide level to discourage the entry of Juncus or Leptocarpus. REFERENCE. Allan, H. H., 1924. Spartina-grass and its Introduction into New Zealand. N.Z. Jour. Sci. and Tech., vol. 7,. No. 4, pp. 253-256. • •

Gorse Parasite. — The , utilization of a new design of breeding - cage by the Cawthron Institute has proved more successful with Apion ulicis, and the indications now are that the acclimatization of this gorse parasite, which up to the present has proved very baffling, will be eventually achieved.

■ ’ — ■ S. strict a (Herbarium Specimens). Suspected Segregate from S. Townsendii . at Foxton. ■ S. Townsendii at Foxton. Culms ... .. . ± 45 cm. long ± 55 cm. long, close together ' . ± 70 cm. long, more distant. Leaf-blades ± 20 cm. long, ± 5 mm. wide at base ; cori- . aceous, strict, erect, convolute, pungentpointed, polished ± 20 cm. long, ± 7 mm. wide at base ; coriaceous, strict, ascend- , ing at a narrow angle, convolute, terete in outline, pungent-pointed, . polished + 25 cm. long, ± 9 mm. wide at base ; less coriaceous, ascending at wider angle, drooping at tips, flat or very slightly inrolled, subpungent, : hardly shining. Panicle . . • ±15 cm. of 2 to 3 spikes, + 6 cm. long • . ±15 cm. of 2 spikes, ± 12 cm. long- - ± 30 cm. of 4 to 9 spikes, ±17 cm. long. Lower glume .. ±15 mm. long, linear, acuminate, very silky • —hairy ±15 mm. long, linear, acuminate, silkyhairy ± 12 mm. long, linear, obtuse to subacute, less " silky—hairy. Upper glume ± 20 mm. long, linear■ ■. lanceolate, bifid, awntipped, keel scabrid . ± 20 mm. long, linear■ lanceolate, bifid, awn- ■ tipped or nearly awnless, keel somewhat scabrid , ±18 mm; long, narrow — lanceolate, not bifid, acute to almost acuminate, awnless, hardly at all scabrid. Rachis ... ... Just protruding beyond last spikelet Protruding for ± 1 cm. beyond last spikelet, practically straight . Protruding for . ± 2 cm. beyond last spikelet, flexuose.