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Managing our Environment

Trig Y Bogs

Description:

Two lowland valley floor wetlands at close distance (300 m) from each other. The western-most wetland is predominantly a raised bog wetland, but has a fen character where water flows between two peat domes. The western side of this wetland is bounded by cultivated land, while a tributary of the Mokoreta River flows along the eastern margin. The eastern wetland is a slightly raised bog but varies in composition. This wetland is currently surrounded by a row of mature pine trees and the wetland and trees are fenced to exclude stock. 89

Type/Class:

Bog and fen. 89

Size:

16.3 ha.

Altitude:

180 - 220 m above sea level.

Approximate location:

4 km Southeast of the intersection of Cairn Road and Slopedown Road, Clinton.
NZTM (centre point): E1311600 N4862300.

Regional Plan:

Water for Otago.
Schedule 9 Regionally Significant Wetland, no.157, Map F30.

Territorial Authority:

Clutha District Council.

 

Trig Y Bogs

Recorded Values:

Value

Description

A4

High degree of wetland naturalness. The eastern wetland meets criterion A4, as a wetland with a high degree of naturalness. The middle and southern parts of the western wetland also meet criterion A4, as despite grazing effects in the middle part of the wetland, indigenous composition and structure remains relatively intact over much of the wetland extent. 89

A5

Scarce in Otago in terms of its ecological or physical character. Lowland valley floor bog wetlands were once typical of this part of South Otago, but are now becoming increasingly rare in this area. Wetlands of this type are also rarely found elsewhere in the Otago region. 89

A1 - A3, A6 - A7

No relevant information is currently held by the ORC.

 

Other Information:

  • The bog vegetation of the western wetland is dominated by red tussock and wire rush, with frequent Gaultheria macrostigma, catsear (Hypochaeris radicata), Herpolirion novae-zelandiae, swamp kiokio, Blechnum penna-marina, and Nertera scapanioides. Odd-leaved orchid (Aporostylis bifolia) and the sun orchid Thelymitra pulchella are also present at low abundance. 89

  • At the southern end of the western wetland, open areas dominated by Marchantia spp. liverworts are present, with scattered Isolepis aucklandica. 89

  • The sloping margins of the western wetland support occasional patches of bracken (Pteridium esculentum) and scattered occurrences of the exotic species sweet vernal (Anthoxanthum odoratum) and sheep’s sorrel (Rumex acetosella). 89

  • Fen vegetation contained within the western wetland supports less dense red tussock, with patches of purei (Carex secta), rautahi, Hierochloe equiseta, and sphagnum moss, and scattered Celmisia gracilenta, Gaultheria macrostigma, and Nertera scapanioides. The exotic soft rush (Juncus effusus) is also present in this fen vegetation. 89

  • The bog margins of the eastern wetland have a fen character with scattered shrubs of Olearia bullata, inaka, manuka, and mingimingi (Coprosma propinqua) among dense red tussock and wire rush, above Coprosma elatinoides, and occasional lotus (Lotus pedunculatus), Epilobium brunnescens, Hierochloe equiseta, Thelymitra pulchella, Celmisia gracilenta, and Geranium microphyllum. Further into the eastern-most wetland, wire rush becomes dominant, with scattered small red tussock, catsear, sweet vernal, Blechnum penna-marina, Gaultheria macrostigma, and Nertera scapanioides. 89

  • The centre of the eastern wetland has dense tangle fern and wire rush and supports few other species apart from scattered rautahi. 89

  • The northern and middle parts of the wetland are currently being grazed. The northern-most part of the western wetland has a greater frequency of exotic grasses and herbs and a lower frequency of wire rush among the red tussocks. The middle part of the wetland is somewhat pugged and contains pedestals of wire rush, with these better-drained microsites being favoured by Herpolirion novae-zelandiae. However, use of this part of the wetland for cattle grazing in winter has not caused any significant invasion by exotic plant species and in general, the western wetland is in good condition, despite. The fen vegetation within the western wetland is in very good condition and shows no evidence of grazing, possibly because it has a very soft, wet, substrate that would not support the weight of farm stock. 89

  • The eastern wetland is in excellent condition, with no obvious threats, although a few Scotch broom (Cytisus scoparius) have invaded the wetland margins. 89

 

Aerial view of Trig Y Bogs (March 2006)

Aerial view of Trig Y Bogs (March 2006)

Wire rush and tangle fern in the centre of the eastern wetland, Trig Y Bogs (March 2011)

Wire rush and tangle fern in the centre of the eastern wetland, Trig Y Bogs (March 2011) 89

Bog vegetation at the southern end of the western wetland, Trig Y Bogs (March 2011)

Bog vegetation at the southern end of the western wetland, Trig Y Bogs (March 2011) 89

 

Fen vegetation on a terrace of the Mokoreta River tributary, western wetland, Trig Y Bogs (March 2011)

Fen vegetation on a terrace of the Mokoreta River tributary, western wetland, Trig Y Bogs (March 2011) 89

 

References:

89 Grove, P. (1994) Maniototo Ecological District. Survey Report for the Protected Natural Areas Programme. NZ Protected Natural Area Programme 30. Published by the Department of Conservation, Dunedin.

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