Wetlands in Lands and Survey Development Blocks, Te Anau - Manapouri Area

BOTANY DIVISION DSIR

REPORT wETLANOS IN LA ~OS hND SURVtY DEVELOP~~t~T BLOCKS, TE ANAU - MANAPCUR I J Rt.A

N.T. MOAR BOT Ai~Y DI V I S I ON, OS IR 1973 WETLANDS IN LAND S AND SURVEY DEVELOPMENT BLOCKS TE ANAU - MANAPOURI AREA

N.T. MOAR BOTANY DIVISION, DSIR

C.J. BURROWS AND A.T. DOBSON BOTANY DEPARTMENT, CANTERBURY UNIVERSITY 1973

SUMMARY

This formally forested area is rich in wetland sites, which_ are rapidly being modified by drainage, fire and grazing. It is important that representative examples of these vegetation types be permanently preserved. Six areas are discussed and recommended for preservation; Ewe Burn Reserve (Dome bog), freestone hill, String bog/Keplers Block, Lake Thomas, Dawson City Swamp and Kakapo Swamp.

Dome bog is recommended for immediate consideration as a flora and fauna Reserve, and Str,ing bog on Kepler block is recommended for immediate reservation.

Apart from the var iety of plants that ex ist in these peat-bog areas and their Quaternary value, these areas are important for regulating run-off, preventing erosion and shingle deposition, and help prevent the effects of eutrophication.

Plant Communities

peat wetland/swamp and bog vegetation flax and Carex swamp silver pine in bog rata and kamahi scrubland WETLANDS IN LANDS AND SURVEY DEVELOPMENT BLOCKS, TE ANAU - MANAPOURI AREA

1973

INTRODUCTION

The rapid development of intensive farming within Lands and Survey development blocks in the Manapouri - Te Anau districts has led to the destruction of wetland sites in these areas. Because of their potential for wild-life refuges and for scientific investigations, including Quaternary botany, the Commissioner, Crown Lands, Invercargill, requested a survey of remaining areas within the boundaries of the various development blocks. The value of particular areas had already been indicated by Dr C. Burrows, University of Canterbury, and it was to these that especial attention was directed.

In attempting such a survey it was necessary to consider the vegetation, the morphology, and the history of each site investigated. To meet these requirements a complete section of peat was examined at most sites in addition to the more usual study of vegetation and morphology. It should be emphasised that wetland sites, especially those containing peat or lake muds contain information which, when properly studied, reveals much about the history of the site and the environment in which the site is located. It is pertinent to note in this context that the area is known the world over for the classic pollen analytical studies carried out by Cranwell and von Post in 1936 who worked on material collected by a famous Swedish geologist, L. Caldenlus, from Mossburn, Freestone Hill, and Richter's Rock bogs during the summer of 1933-1934.

The whole area is rich in wetland sites but they are rapidly being modified by drainage, fire and gr.azing. It is desirable that representative examples of their many vegetation types (other than those in Fiordland National Park) be permanently preserved. The scientific importance of these areas lies in the relationships of their vegetation and its ecology to those of wetland areas throughout New Zealand and elsewhere in the world. A.T.D. and C.J.B. are carrying out a quantitiative survey of the vegetation and investigating its ecology. In due course copies of publications will be available. So far the vegetation of about 140 sites has been measured and a computer programme prepared to deal with the data.

Three factors appear to influence the varied pattern of wetland vegetation in the area. These are:

(1) The effect.of disturbance, especially by fire. (2) The relative fertility of water present in the wetlands. (3) The relative proximity of the water table to the ground surface, and probably the fluctuations of it. 2.

Fires occurred in pre-European times and have continued present up to the day. North~east and east of Lakes Te Anau and Manapouri wetland the surfaces have probably been burned many times and existing some of the vegetation patterns result from this. Thus, the turpentine plant (Dracophyllum), the bog pines (Dacrydium bidwillii and D. biforme), and manuka (Leptospermum sc6parium) are depleted by fire, and wire-rush (Calorophus minor)_ may become dominant. The fires have, of course, affected the entire area which shows unmistakable signs of former forests. Different plant species tolerate, or require, different conditions in respect of height of water-table and dissolved nutrients in the water. Thus, true 8Wamps in which relatively fertile water maintains a constant level, up to about 4 ft deep, are characterised by luxuriant tenax) flax (Phormium and niggerhead (Carex secta). Flax becomes less luxuriant fertility as drops and in deeper water tall sedges (Baumea rubiginosa Eleocharissphacelata). and may dominate. Large plants are usually absent from deep, infertile, acid water. In other wetland areas water flows sluggishly throught the peat or in ill~defined channels and the more fertile of these, which may be calle.dfens, may carry stunted niggerhead, flax, and large stands of Carex diandra. · Baumea rubiginosa, usually with another sedge, Lepidosperma australe, occurs in less fertile areas in which manuka may also be found. True bogs, often with raised surfaces, depend upon rainfall for their water supply. Many of these bogs, which are strongly acidic and very infertile, have complex pool systems containing stunted rubiginosa and Sphagnum !· falcatulum. Such bog complexes are particularly well developed in the area studied. Turpentine plants (Dracophyllum and.wire-rush 6liveri) (Calorophus minor) are more prominent in the drier parts of very infertile bogs in which hummocks are formed by Sphagnum cristatum. To gain a broad perspective, sites already gazetted, e.g. Pamparts Road reserve and Luxmore Lake, the sites within the Fiordland National Park were visited. It was clear that gazetted reserves did not cover the range available, and that in terms of bog morphology they were of great value. no Accordingly attention was directed to those areas reported already on by Dr Burrows, and in particular a variety of sites vicinity in the of the existing Ewe Burn Reserve were examined in considerable detail. Nevertheless, notes on every site examined in the Lands and Survey development blocks are presented. In general Dr Burrows paid special attention to the vegetation and Dr Moar confined attention. to historical aspects of the sites visited. It must be emphasised however, that the survey was c.onducted as a joint enterprise and that we owe much to field discussion with Lands and Survey staff in Te Anau and to Mr I.C. McKellar, Geological Survey, DSIR, Dunedin.

AREA OF EWE BURN RESERVE This area includes those sites marked on the accompanying map reproduced from a working map of the Point Burn sheet. (a) · Dome Bog: This site lies beside the Te Anau Bush section (sometimes called Six Mile Bush) of the Fiordland National Patk and C.J.B. has already discussed it in his report of June 10, 1970. It is the best example of a raised bog (domed S4rface) which we have seen in New Zealand.

Although there is nothing remarkable about the plant life on the domed part of it, the bog margins are of great interest. The most important botanical discovery was a strip of silver pine (Dacrydium colensoi) on the north-western and north-eastern margins of the bog. This is the first record of the species east of the Main Divide, and may be all that remains of a tree formerly more widespread in the area. In this context it is worth noting that sub-fossil wood of silver pine was found in a drained bog on the eastern side of Lagoon Creek Road not far from the junction with Wilderness Road. A small orchid (Acianthus fornicatus) was found in the fen just south of the main bog, considerably extending its known distribution.

The morphology of the bog, with its domed centre, is of great interest, ·as is a·series of pools, arranged concentrically around the dome. These are not shown as such on the map, N.Z.M.S. 2, Sl40/6. Water drains from the bog westwards to Lake Te Anau and southwards to the Ewe Burn which eventually drains into the lake.

The bog is a haven for wildlife. Nesting black-becked gulls, black-fronted terns, grey ducks, and fern birds were observed.

A boring was made in the peat at the margin of one of the smaller pools with the following result.

O - 150 cm fibrous peat with rootlets of·cal6:t6phus and Dracophyllum.

150 - 200 cm muddy peat with fine fibrous material and small wood fragments; wood struck at 200 cm.

200 - .475 cm coarse fibrous peat with wood fragments throughout; wood struck at 350 cm.

475 - 537 cm finely fibrous peat.

537 - 540 cm silt.

540 cm shingle (not penetrated).

It is clear that at this particular sampling point peat accumulated as a consequence of swamping of a former channel and there is no evidence of a former lake.

(b) Ewe.Burn Reserve: The value of this reserve has already been established and further comment is unnecessary here. The botanical interest lies in the regeneration of scrub on acid soils following forest destruction by fire. Borings were made in the peat at two places.

At the first, near the north-western end of the bog, a depth of 500 cm was recorded, there being much wood in the peat at this point, especially in the upper 200 cm. A second boring to 800 cm was made towards the south western end close to the edge of the tarn. 0 - 700 cm Sphagnum peat 700 - 750 cm fibrous mud, grading to mud with slight silt content. 750 - 800 cm mud with silt content increasing to 800 cm; stones at 775 cm; sediment very compacted at bottom.

A small kettle between Dome Bog and the Ewe Burn Reserve is similar, and requires no further comment here.

(c) Dismal'Swamp: The vegetation in this large area is clearly different from that of the sites already briefly discussed and depends upon a high water table with slowly moving water draining the whole complex. The vegetation is therefore diverse and ranges from rich fen with flax (Photmium tenax) and sedges (Carex spp.) to bog. Of especial interest was the discovery of a large area of a moss (Acrocladium cuspidatum) which is scarce in New Zealand. On a small scale Dismal Swamp contains many of the main kinds of wetland in the Te Anau region and is worthy of reservation. No attempt was made to core into this huge area.

(d).Lookout Bog: This site lies between the Te Anau - Eglinton high way and Lake Te Anau, near Lookout Hill (Trig B, 1027 ft on map Sl40/9). It.contains large areas of fen vegetation with sedges (Baumearubiginosa, Lepidospetma australe, Catex diandra and stunted c.secta) and stunted flax (Photmium tenax). One part of it grades into-true bog dominated by wire-rush (Calorophus minor).

Fern birds were observed in this site.

FREESTONE HILL

To the best of our knowledge this bog is the classic site collected by Caldenius and pollen analysed by Cranwell and von Post. From a purely floristic point of view the bog is not particularly interesting and further, although the site is reported to be 500 cm deep, our corings (4) went no deeper than 225 cm. As it is improbable that 2 or 3 metres of peat could have been burnt off in the intervening years we can only conclude that Caldenius located a depression that was missed during the present survey.

STRING BOG, KEPLER BLOCK (HOME CREEK SWAMP)

This domed bog, some 1000 acres in area, east of Manapouri on the Kepler Block, (Map Sl49/6) is unique and C.J.B. has already drawn attention to this. The species assemblage on the domes surface is usual for acid bogs in the area, wire-rush (Calorophus minor), with extensive turpentine shrub (Dracophyllum oliveri) and the sedge (Baumea·rubiginosa) and the moss Sphagnum falcatulum occurs in pools. The mosses (Eucamptoden inflatus and Campylopus kirkii) scarce else where, are not uncommon in the bog. However a vast complex of pools arranged parallel to each other in the form known as "string bog" is the main point of interest. Such bogs on this scale are otherwise not known outside the northern peatlands of Scandinavia, Siberia and northern Canada. On the hummocks separating pools are bog pines (Dacrydium bidwillii, D. intermedium and D. laxifolium) in.situations which have probably protected them from the fires which have swept the bog. The bog margins consist of fen vegetation with sedges (Carex diandra and C. secta) prominent. Interesting stands of the liver wort (Matchatltia herteroana) form a thick mat over peat in the fen areas.

The pools noted above are breeding grounds for Canada geese, paradise duck, grey duck and black-beck gulls.

Although the site lies within an area planned for farm develop ment, it could be isolated from drainage patterns for adjacent areas without much difficulty. This matter was discussed in the field with Messrs Marshall and Wilson of the Te Anau Lands and Survey Office. C.J.B. cored the peat in January 1970 with the following result.

0 -488 cm fibrous peat with varying amounts of wood and Sphagnum at various levels. 488 - 491 cm moss peat 491 - 494 cm sandy peat, grey brown to greenish brown.

LAKE THOMAS (Sl50 957145)

Lake Thomas lies at the eastern edge of the area affected by the last glaciation according to unpublished information supply by Mr McKellar, Geological Survey. Its eastern shores are stony, but on the western side there is a peat-filled valley which at one time was part of a larger lake. It contains an interesting area of Sphagnum cristatum and S. falcatulum with plants of a small turpentine shrub (Dtacophyllum prosttatum) not found in the lowlands near Te Anau - Manapouri. This lake, and Luxmore Lake, are the only two sites investigated in which deep lake sediments occur. The section sampled is described as follows:

0 - 220 cm Sphagnum peat. 220 - 300 cm coarse detritus mud 300 542 cm fine detritus mud with increasing clay content. 542 - 550 cm silty clay mud.

Preliminary pollen analyses of the bottom sediments indicates that there was a well developed shrubland vegetation before the rapid transition to the early podocarp forest phase. It is clear that the early lake vegetation was dominated by Isoetes, a plant apparently absent from the site now.

DAWSON CITY SWAMP (Sl50 916161)

This is an interesting fen area dominated by the sedge, Carex diandra. There would be merit in neither draining it, nor converting it to a lake because it is the only wetland of its type which we saw. Of greater interest from the Quaternary point of view was the fact that there were stumps, an indication of woody communities, scattered over the surface, and at depths between 200 - 300 cm there was a dense wood layer. A site such as this, although no more than 350 cm deep at the points sampled would doubtless be a fruitful source of macrofossils. A number of sites in the Kakapo Road and Lagoon Creek Road areas would have been ideal for macrofossils, but most of these are now so much altered that their preservation is not worth while. The discovery of silver pine wood · (Dacry dium · colensoi) in a greatly altered swamp in the Lagoon Cr0ek area (Sl50 ea. 902156) has already been noted.

KAKAPO SWAMP

This site · is typical . of . swamps anywhere in New Zealand and contains luxuriant flax ·_ (Phormiuril . tenax), niggerhead (Carex . set ta) and abundant water cress · (Nasturtium). Efforts to raise the water-level in the swamp have been made with some success. Explosives and a dragline have been used to increase waterfowl habitat in a bog area at the eastern end . of . the . swamp. The raised water-level is killing wire-rush (Calorophus minor) and bog-pine (Dacrydium bidwillii) - presumably through an influx of nutrient-rich water. The swamp proper is prime waterfowl breeding habitat and any attempt to raise the water-level further would be unwise since it could lead to the death of the main cover plants (flax and niggerhead) by submerging their foliage.

OTHER SITES

Two reserves Luxmore Lake and the Ramparts Reserve were also examined.

The value of Luxmore Lake lies not only in its use as a wild-life reserve, but as noted earlier, it and Lake Thomas are the only two areas ex amined with deep layers of lake mud although their lateral extent is not known. It is possible that the sediments in this lake, like those of Lake Thomas, extend further back in time than the classic sites of Cranwell and von Post or of other sites examined during the present survey.

The Ramparts bog may be rather young, it was 230 cm deep, but besides its scenic attractions it contains seeds of . Elaeocatpus, and with proper investigation no doubt other macro-fossils would be found. This bog, and others in the Kakapo Road area all provide useful information of more recent events, including . fire, for in an altered bog near Kakapo Road charcoal and leaves of N; · menziesii were found. Charcoal has been reported from other shallow bogs in the area by Dr Burrows.

RECOMMENDATIONS

Of the areas examined two recommend themselves immediately as worthy of preservation. These are (a) the complex within .the general area of the Ewe Burn, and (b) the domed string bog east of Manapouri in the Kepler Block (Home Creek Swamp).

1. The Ewe Burn area has much to recommend it. Dome Bog, the two tarns, · including the present Ewe Burn reserve, and Dismal Swamp, form a comple x of . different types of wetland within an easily circumscribed area. The variety of vegetation types . in Dome Bog, its system of pools, the relict silver pine (Dacrydium · colensoi)at its margin, its potential for Qua ternary studies and the presence of nesting black backed gulls mark this as a . worth while area for preservation . . · We regard Dome . Bog itself . so . important that we . suggest that . it . receive special consideration for reservation as a flora and fauna tesetve. Further, the scrubland community with i ts rata (M e trosideros umbellata) , kamahi" (Weibma'nnia racemosa) , bog-pine Q?acrydium bidwillii), and manuka (Leptosp_ermum scopari urn ) > al though secondary in origi n , a re part of t he landsca pe, and s cien t ifical ly i nteresting, i n an area difficult · to develop f or f armland . It is fur t her r ecommended therefore that the area outlined on the accompanying map be r eserved (i.e. from about the northern limit of land devel opment on the shor es of Lake Te Anau to Te Anau Bush) as a scenic reserve to protect the botanical features. This includes in one area, relatively easy access, a wide range of wetland and scrubland communities.

In considering this recommendation it should be noted that isolated plants of Himalayan Honeysuckle (Leycesteria formosa)were seen in the scrub. Because its seed is bird carried it would be difficult to keep this weed out of any reserve in t he . district. Fire also is a potential hazard and hunters should have its destructive ness impressed upon them.

2. Dr Burrows has already drawn attention to the unique String Bog on the Kepler Block ' (Home Creek Swamp) and we would recommend that the section with the pool systems be set aside as a flora and fauna reserve. However, in view of other interests, we can see no objection to reserving the site for Wildlife Management Purposes, providing access is strictly controlled. The area is unique and we are anx ious that any persons with access for shooting, or other purposes, be aware of the danger of fire to it as a land-form, and to the plants growing on it. Although it is part of a larger complex, it nevertheless forms a unit lying between, and almost surrounded by, young moraine (Map Sl49/6) and apparently could be isolated fairly easily so as not to impede reclamation in adjacent sites. Nevertheless great care would be needed to ensure that any system of drains did not interfere with the hydrology of the domed string bog by diverting water from the highest point at the northern end and thereby causing the pool system to dry out.

As you are aware peat areas such as String Bog are important in the general hydrological pattern, serving as water reservoirs. In the present case it maintains a constant flow of water in Home Creek even during drought conditions such as experienced during the summer 1970- 1971.

It is in every way superior to the Freestone Hill site - the greater floristic .variety including three species of Dacrydium (D. bidwillii, D. intennedium and D~ laxifolium) provides an example of this. Its ~nique morphology is clearly of great scientific merit, and because of this, offers a variety of habitats suitable for wildfowl. Its potential for Quaternary studies is certainly no less than that of Freestone Hill, and if there has to be conscious choice between the two sites, the choice must be in favour of the String Bog.

3. Other sites are also worthy of preservation. Lake Thomas is unlikely to be destroyed by reclamation activities, but it could be usefully. reserved. Similarly Dawson City Swamp could form a reserve, because besides its Quaternary interest, it is the only wetland of its type which we saw in the area.

We would emphasise that there are important practical reasons for retaining peat-land areas in a relatively unmodified condition. It is known that peat-lands are important for regulating run-off. Not only do they permit a steady flow of water, but they prevent rapid run-off, erosion, and shingle deposition during heavy rainstorms. Therefore it is wise to retain as much of the Te Anau the original peatland in land development area as possible. is that run-off A further benefit of fertilizer-enriched waters lands. Thus is soaked up by peat- the enrichment of lakes and streams is to some extent lower in the watershed prevented and some of the of waters avoided consequences of eutrophication if watersheds retain their peatlands.

N.T. Moar Botany Division, DSIR, Christchurch c.J. Burrows Botany Department, University of Christchurch. Canterbury,

A.T. Dobson Botany Department, University of Canterbury, Christchurch

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