ARTICLE : Riparian Trial Plantings

 Monitoring riparian plantings on Hutt River – 3 October 2006

Site 3 at Avalon, True Left of Hutt River.   Photo: Barbara Mitcalfe.

Site 1, on the True Right bank at Totara Park, Awakairangi Park, is the only site where monocots were planted.   The rows of coastal flax, swamp flax and toetoe are almost intact, despite being periodically inundated.   Even the totaras high up in the second-to-back row have been flooded at times, evidenced by the debris caught up in their crowns and making them hard to find, but most of them are still in position.   Most of the back row, manatuu, one of our few deciduous species, have grown to well over 1 m high and are showing healthy, new foliage.

Site 2 has lost all of its first row to floods, but the other 4 rows are relatively intact.   At this site, totara were planted in the back row and have subsequently proved very hard to find in the head-high fennel and broom and rank grass because unfortunately, the agreed protocols of the trial prevent any weeding around the plants after their first year.   However a determined search revealed many of them still in situ – tarata, kohuhu and manatuu doing better than some other species.

Site 3 is under willows at 2 m spacing, planted as 2 m poles before our small natives went in, and now averaging about 4 m high.   Rank grass and weeds and an (estimated) depth of 0.4 m of since-deposited silt during floods have buried most of the natives here, and few remain.   The other half of this site, right at the river’s edge, was swept away in a flood a few months after we planted it.

As reported in previous newsletters, this is the fourth year of the five-year performance trial of selected, selected native species in comparison with other, selected native species.   Greater Wellington Regional Council funded the purchase of the nursery-grown plants.   At the end of the trials, an independent agency will compare the results.

Participants : Dave Holey, Chris Horne, Zena Kavas, Barbara Mitcalfe, (leader / scribe), Sue Millar, Syd Moore, Glennis Sheppard, plus Jacqui Cox, Kim …… and Steve Murphy, on behalf of Greater Wellington.

Barbara Mitcalfe

 Monitoring riparian plantings – September 2005

On a cool, drizzly morning we assembled at Site 1, Maaori Bank, to brave the invading blackberry under which were the 5 rows of plants for us to monitor in this third year of the 5-year trial.   Maaori Bank is the best of the 3 sites, for plant survival rates, although the river has been over it and rank weed growth covers it entirely.   With some difficulty we managed to find and measure the remaining plants, some of them partly crushed under logs which had been swept downriver.

Site 2, at Taita, is overgrown with broom and fennel.   The entire front row, Dicksonia squarrosa, was washed away in the first year and rows 2 and 3, tarata and kohuhu, have quite a few gaps.   Row 4, maanatu, has more gaps than last year, and the plants have put on much less growth than the Site 1 maanatu which were in the back row, i.e. furthest from the river.   The totara row also has more gaps than last year.

Site 3, at Avalon, lost its upstream half last year under floodwater, and in the same flood, the downstream half lost the entire front row, Dicksonia squarrosa.   The rest of the site has fared badly, having been buried in silt to an estimated depth of 0.5 metre.   Only 17 of our plants in total remain visible at this site, though it is possible some are still alive and reaching for the light.

Unfortunately the data are still to be analysed so it is not possible to provide numbers and percentages in this issue of the newsletter.

Participants : Peter Beveridge, Barbara Clark, Jacky Cox (GWRC), Chris Horne, Rodney Lewington, Sue Millar, Barbara Mitcalfe, Tim Porteous (GWRC), Jan Rowland, Allan Sheppard.

Barbara Mitcalfe

 Riparian Trial Plantings – April 2004

To assess the ability of native plants to replace introduced species on riparian sites, the native plantings at three sites on banks of the Hutt River were monitored by members of Wellington BotSoc and Greater Wellington Regional Council on 17 October 2003.

BotSoc will monitor the plantings later this year.   If you’re interested in helping please ring Barbara Mitcalfe, 475-7149.

Ian Atkinson

 Trial of native plants in riparian sites – update October 2003

In the December 2002 issue of the newsletter I reported on the WRC/WBS riparian planting trials in three sites beside the Hutt River.   The trials are being monitored independently by two qualified auditors.   This year’s measuring and monitoring work bee was to be on Friday 10 October.   A report on the monitoring will be in the next newsletter.

Barbara Mitcalfe

 Report on WRC Hutt River riparian plantings – December 2002

A brief inspection of two of the plantings produced the following results:

1.   Maoribank, 29 October 02
ROW 1: 45/50 Phormium tenax remain, (1 dead, 4 missing)
ROW 2: 45/50 Phormium cookianum remain, (1 dead, 4 missing)
ROW 3: 46/50 Cortaderia fulvida remain, (4 missing)
ROW 4: 49/50 Podocarpus totara remain, (1 missing)
ROW 5: 48/50 Plagianthus regius remain, (2 missing)

Many of the flaxes had yellowleaf disease, which must have been present when the plants were still in the nursery.   The 2 “dead” flaxes may yet recover – I didn’t test their roothold.   The site is becoming overgrown with blackberry, which could make monitoring difficult next year.   Fortunately there are two releases programmed into the trials.

2.   The WRC “Old Plant Nursery site”, 8 October 02
ROW 1: 32/50 Dicksonia squarrosa remain, (12 missing)
ROW 2: 45/50 Pittosporum tenuifolium remain (1 missing)
ROW 3: 49/50 Pittosporum eugenioides remain (1 missing)
ROW 4: 49/50 Plagianthus regius remain (1 missing)
ROW 5: 49/50 Podocarpus totara remain (1 missing)

About 90% of the site is now under tall, dense weeds, mostly fennel (>1 metre), tall fescue (1 m), and blackberry (c.   80 cm), so it was very difficult at first to find the planted species.   We were glad that at the time of planting, someone had had the good idea of placing boulders round most of the plants.   The boulders were more visible through the weeds than the plants, which they also helped anchor.   It is possible that some of the “missing” plants are still there and that we couldn’t find them in the time we had available.   Fortunately, despite the weed infestation, the natives plants seemed in good health.

A clipboard was left behind at one of the monitoring sessions.   Please phone me on 04 475 7149 if it’s yours.

Barbara Mitcalfe

 Saturday 31 August 2002: The first monitoring of the Hutt River riparian plantings.

This monitoring is reported included under “trip reports” - here.

 Alternatives to willows – May 2002

(Look – there are “NATIVES” popping up in “ALTERNATIVES”!

At last – Feasibility Trials of Native Plants for River Edge Protection. BotSoc submissions made to Wellington Regional Council (WRC) over several years, followed by a series of discussions and a site visit, have been successful.   There is now a set of agreed protocols to guide a 5-year feasibility study of selected native species for river edge protection, using 4 sites on the Hutt River.

These trials have been motivated to some extent by the recent, country-wide threat posed by infestations of sawfly, which browse willows.   Traditionally, willows and poplars have been “frontline protection species” used almost exclusively by regional authorities and others, for river edge protection.   However, promoting and maintaining indigenous, regional biodiversity is now a recognised need.

A small sub-committee of BotSoc (Ian Atkinson and I) and WRC flood-protection staff (Steve Murphy and Trecia Smith) have drafted the protocols and WRC has generously offered to fund the project.   The native species selected are being sourced locally and it is hoped to begin planting this winter. WRC staff will do the planting, and two independent auditors will monitor the performance of the plants at regular intervals, using agreed criteria.

There will be opportunities for interested BotSoccers to give practical assistance at all stages of this exciting, worthwhile project.   Ring me if you would like more information.

Barbara Mitcalfe, Ph./Fax: 475-7149