Auckland RENH Kaipatiki Creek Trial - Umbrella Project's Journal

Journal archives for August 2019

August 27, 2019

Rhabdothamnus solandri

Numerous small specimens of this distinctive shrub remain present, as in 1997, on the steep, almost weed-free streambanks above the Native Plant Trail. The occurrence appears to be about the same density as remembered, and the size of the plants not significantly more, but this may be a failure of memory and observation.

Great care needs to be taken not to endanger these specimens, as though the species is not considered endangered, propagation on the mainland is rare due to local extinction of bird species required for pollination of the seeds. So though these plants are long-lived, they are unlikely to be replaced when they die. Thus a slow long-term extinction is said to be already in progress for this species, unless reversed by careful site restorations. We have not yet learned the bird species required for pollination of Rhabdothamnus, but read somewhere that the species involved are all now extinct. When time permits we will research this further, and appreciate any info available.
See
https://en.m.wikipedia.org/wiki/Extinction_debt

Posted on August 27, 2019 01:11 AM by kaipatiki_naturewatch kaipatiki_naturewatch | 0 comments | Leave a comment

Tui ground-feeding

As at Gahnia Grove, we have been surprised at how often tui come down to recently-disturbed ground to forage, as blackbirds do. Those observed have mostly been juvenile. We recorded a young tui foraging in sandy streambank a metre from water's edge under native canopy, Elaeagnus and vine weeds, as we sat resting after releasing the bank from Tradescantia.

Posted on August 27, 2019 09:49 PM by kaipatiki_naturewatch kaipatiki_naturewatch | 0 comments | Leave a comment

Litter, illegal dumpings and non-biodegradeable materials

At the roadside of zone Cc, a broken "No Dumping Sign" ( no longer legible) has long marked the spot favoured by locals for illegal dumping. During our first informal re-survey of the Creek in June 2018 we saw four 20L containers of a liquid chemical labelled "Hazardous - Flammable", together with a brand-new pair of industrial gumboots and some other equipment. This may not have been a dumping, but since Tradescantia had grown over some of the containers we assumed the stash was abandoned, and had it removed by Council.

At the same time we saw a roll of plastic mesh, of the sort used on boardwalks, under a ponga and pate just above flood level beside the stream, near a large industrial-strength weed-bag, which turned out to be one of about 20 found on the site so far, along with many black kleensaks.

As at Gahnia Grove, plastic, glass and cardboard drink containers, small pieces of plastic packaging, and short lengths of line-trimming line (of unknown age) are picked up regularly. At Gahnia Grove we collect them in plastic bags and leave them at the roadside. At Kaipatiki Creek there is a rubbish bin, so we put them in that.

In March we arranged removal for the same spot of 18-20 car tyres, to which we added our collection from the surrounding roadside canopy- an old wooden pallet and numerous pieces of timber, clothing and iron cooking pans.

Since then, we have arranged removal from the same place of:

-a long-abandoned television set
-a brand-new dumping of several full-size mattresses
-a very solid wooden cupboard about 1m H x 1mWx 80cm D

The recent dumpings were less than a metre from the road, in the canopy edge. These latest dumpings were not in the "historic" favourite dumping spot, but a few metres away - just beyond our recently-erected cordon.

We have since extended our cordon a further c.10m.

Posted on August 27, 2019 10:08 PM by kaipatiki_naturewatch kaipatiki_naturewatch | 0 comments | Leave a comment

August 28, 2019

Ehrharta erecta

We find Ehrharta erecta (Veldt grass) to be, like kikuyu, a much more destructive ground cover than Tradescantia. Confirming our impression of Ehrharta erecta's spread and impact on revegetation in local reserves and neighbourhoods, we found the following:

Vegetative reproduction occurs and seed is produced in large quantities all year round (Timmins & MacKenzie 1995). Seed dispersal is by wind, water and bird.
TOLERANCES). [NZPCN]

Whereas a Tradescantia-covered margin can be weeded easily and gradually as native seedlings develop in it, Veldt grass multiplies rapidly, covers the ground with a dense firmly-rooted wiry mesh, and is rarely uprooted successfully and completely.

When uprooted, Veldt grass leaves many seeds behind, and they apparently germinate within 5 days.

"The plant is drought and shade tolerant and very tolerant to shade (Timmins & MacKenzie 1995). [NZPCN]

It is also tolerant of poor, sandy or rocky soil, and of deep leaf litter, as seen in the forest edge along the Kaipatiki Esplanade Walkway, in loose-metal wash-off from the Walkway and in deep leaf litter under sycamores and pin oaks.

Where Ehrharta is present nearby, we remove Tradescantia only successively, in small quantities, and ongoing monitoring of the released areas.

Posted on August 28, 2019 02:50 AM by kaipatiki_naturewatch kaipatiki_naturewatch | 0 comments | Leave a comment

Survey follow-up - Plant diversity and health

Kotukutuku

Kotukutuku on this site seem to lose their leaves in summer and regrow them in Winter. Flowers were produced on Adult #1 but were not numerous. As yet no seedlings have been observed.

Three or four juveniles were located once they leafed out. The definition of the path is helping protect them as they develop.

Kauri

A young ricker observed by a fellow-iNaturalist visiting the Project in 2019 has been located, at the top of the high bank between the Native Plant Trail and the stream in the older, more diverse part of the forest. It continues to appear healthy.

Tanekaha

Many more tanekaha have now been identified in the tall canopy near the Native Plant Trail entry. several of those near the top of the bank, ie the roadside, are dead or in dieback.

On a dead one we have observed more closely a dense black growth or fungus around what appears to be a wound, perhaps posthumous. This Tanekaha c.30cmD is within two metres of the Trail near its entry, and died sometime between 2000 and 2005, from memory. (Its dead branches drop on the bank below but the trunk and remaining branches still stand there).

Kanono

Kanono is abundant along the streambanks on both sides, as adult, juvenile and seedlings. On the Kaipatiki Roadside bank there is no path, and healthy adults are common. On the Witheford streamside, cut through by the Native Plant Trail, few if any healthy adults have been observed, and diseased adults and juveniles are common. Many seedlings have yellowed or deformed leaves, and/or black spots. We understand the leaf deformities are caused by opportunistic pathogens secondary to plant stress.

Diseased Kanono have also been observed upstream of the footbridge, where walking through the vegetation along a narrow level bank is possible only with care. This area holds at least one kanono , including at least one with the typical orange abnormal growth from a wound in the trunk, that we are told is symptomatic of environmental damage of unknown cause,

Native Clematis

We continue to look out for Clematis paniculata and forsteri, both present in 1999-2000 but not observed during the current project.

Rhabdothamnus remains in at least one occurrence with plants of different sizes clinging to steep clay banks over several metres. We hope all practitioners are made aware of their presence as we read that they are irreplaceable, due to the extinction of the bird species necessary to their pollination:

https://inaturalist.nz/posts/26968-rhabdothamnus-solandri

Ferns are much less abundant along the downstream streambanks, which have not yet been accessed as they appear to be higher and steeper than in 1997-99, with no sedimentary islets observed yet. Stormwater retention has presumably not been achieved in the catchment, and the increased density of housing is likely to have brought increased erosion of banks and scouring of streambed below piped and unpiped outfalls.

Some species of fern common in 1997-99 have still not been observed, including kidney ferns. We have yet to access the upstream area where kidney ferns were abundant, but they were also present downstream. Any observations would be appreciated.

The c.1mD taraire on Taraire Hill has been located thanks to Neil Henderson, Restoration Activator of Kaipatiki Project. He also identified for us the Maire close beside a 50cmD kowhai above Maire Falls, several old stream-edge kowhai, and a mature titoki and tawa overhanging the path-steps there.

We have found no sign of the NZ Tree broom which stood at Broom Bend, where the steps of the Native Plant Trail turn sharply downstream after climbing up past Maire Pool. What we believe is the same corner has some patches of smooth clay uncharacteristic of this dense bit of forest, perhaps here periodically washed by run-off.

Posted on August 28, 2019 02:50 AM by kaipatiki_naturewatch kaipatiki_naturewatch | 0 comments | Leave a comment

Stream ecology

The stream flow observed over the past year has not been markedly different from 1997-1999, though no rushing torrents and very little flood-borne debris have been observed more than about a metre above normal stream height - perhaps because the rainfall in the few rain events observed has been less.

Sewage overflows from manholes along the stream are apparently still common, with one observed in progress, and reports by Reserve users of the associated odours occurring after rain events throughout the past year or two at least. Raw sewage and associated toilet products, both paper and plastic, were observed in the stream and on the boardwalk during and after the recent observed overflow event. The feminine hygiene products and toilet paper are gradually washing away from the Trial Zone, to the Upper Harbour unless caught on islets or tree roots further downstream, or in saltmarsh or on mangroves in the estuary.

The banks in the area closely observed are deeper and steeper than in 1999, often exposing tree roots, some large. The streambed is generally silt-covered. Zones Aa-Ba (further upstream) have not yet been accessed to see if the stream here is still a crystal-clear trickle over sandstone peddles as in 1999, or if sedimentation by eroded silt now extends to this area.

No invertebrates, fish or eels have as yet been observed in the stream.

We can't remember the seasonality of the frequent splashes, bubbles and sightings in 1997-99 of eels and fish in the stream. We do recall that red damselflies were common in summer, that while weeding we often heard the plop of eels breaking the surface of the water, saw them slide beneath the low overhanging banks, and sometimes encountered them with our feet while wading. At that time eight species of native fish were recorded during survey, kokopu were gently netted and observed for a few hours by a group led by Freshwater Native Fish Society members, and sitting still beside the stream on summer evenings was rewarded with the sight of a banded kokopu wiggling gently to hold its position in shallow water mid-stream.

Since that period, the stream has been scoured by presumably increasing amounts of stormwater from continually intensifying residential and road development.

Streamside vegetation

In Zones Ca, Cb, Cc, Da, Db and Ea, the 1997-99 weeding of Tradescantia and Montbretia resulted in dense streamside vegetation along both banks by Haloragis erecta, Carex, ti kouka, kanono, pate, hangehange and ferns to 2mH. Much if not all of this vegetation has been washed away with bank collapses.

Large tree falls near the bank edge have left some banks 2-3mH and impassable without swinging from branch to branch or wading. At some points the absence of somewhere to stand makes weeding difficult if not impossible, and revegetation unlikely unless and until sedimentation built up a new bank.

These tree falls have created some excellent habitat, though dams observed have been incomplete, creating no pools of still or slow-moving water habitat.

Surviving on these banks are large sprawling stands of kiekie, with few tall trees to climb here, unlike the streambanks further upstream. These kiekie do reach and climb tall trees some metres from the water's edge.

The growth of kiekie since 1997-99 is evident by comparison with archive photographs, but especially clear in observations of the narrow timber-edged "streamside weeding paths" along the sandy streambanks on both sides of the stream. the streamside weeding paths were made in 1987-99 by volunteers to limit their own trampling during the large-scale fulltime weeding project. The timber edging is still intact, in some places full of sand and in others empty, except where banks have washed out.

The Kaipatiki streamside weeding path was easily cleared of superficial Tradescantia throughout the that bank, and discovered to be now fully occupied by kiekie, pate and coprosma several metres tall, and ferns, proving both the path design and weeding operation to have been thoroughly successful in streamside revegetation.

We don't recall whether the timber was treated, but it seems likely. Whether chemically or by heat or radiation, and any impact of toxicity, are unknown.

Removal of deep Tradescantia on the Witheford streamside disclosed the weeding path timber edging, and its steps from the Native Plant Trail, still usable, largely empty of vegetation.

The bank beneath has washed out in several areas.

Posted on August 28, 2019 02:51 AM by kaipatiki_naturewatch kaipatiki_naturewatch | 0 comments | Leave a comment

Weed assessment update

Kahili ginger

A new technique has emerged to rapidly suppress any fruiting ginger stems observed during our exploration and removal of Tradescantia.

A bulky mass of Tradescantia suppresses growth by its weight and by light occlusion, and its moisture content significantly enhances the rotting process.

Clumps of ginger with up to about 20 stems have been effectively and easily suppressed by:
-bending and/or breaking the stems, in several places if necessary, until all parts of the plant were contained within a diameter small enough to completely cover with piled Tradescantia from nearby.

The resulting piles ranged from c. 40x40cm D for 2-3 stems, to c. 1.5m D for a large clump.

No emergence of leaf or stem was observed in subsequent weeks or, at Gahnia Grove, over subsequent months.

After a month or two, uplifting of the Tradescantia piles reveals partially-rotted stems still attached to partially-rotted tubers.

Tubers at this stage have been largely unrotted and hence viable, but their rotting roots uprooted easily, allowing reburial of the uplifted tubers near the top of the Tradescantia pile re-placed over remaining tubers.

We are monitoring several piles of Tradescantia rotting ginger in this way, and have so far observed removal of several tuberous masses weighing several kilos each (observations to be uploaded as time permits).

We hope to be able to re-observe the remaining clumps to discover the time required to rot ginger clumps to eradication by this method, quicklyt and esaily done ad hoc as ginger is encountered, with no tools, no poison, and minimal physical effort.

(cf In our other Trial Site "Gahnia Grove", this method is effectively controlling Alocasia and Arum lily, and greatly assisting Japanese honeysuckle eradication from a prescribed area).

Moth plant

A new, and much the largest, invasion was found throughout the top of a mahoe c.10mH at the stream edge, within 50m of the Madeira in the tanekaha. From the opposite, Witheford-side stream bank, the vine was barely visible, but many pods were observed.

This has been communicated to Ecocontract managers, who by study of service maps have determined that the entire Kaipatiki Roadside bank, despite being a Sensitive Environmental Area, is Auckland Transport land, not a formally-defined Reserve, and therefore was not covered in any weed-control contracts.

We have been told that the Ecocontract for Witheford Reserve is now being modified, or another contract created, to cover the Kaipatiki Roadside streambank for control of the same General Reserve target species as Witheford Reserve.

On the Kaipatiki Roadside streambank the species present and now to be targeted include Madeira, Moth plant, ginger, and Phoenix palms once they reach a certain size.

Tree privet, Woolly nightshade, Wattle

A few Tree privet and Woolly nightshade and Brush wattles may be small enough to be addressed under the Ecocontract, but most specimens of these are large trees requiring arborism. We do not consider the few individuals present to present a significant threat to restoration of native vegetation, providing there is ongoing monitoring with removal of seedlings and juveniles, particularly on sunlit margins and any areas where there has been extensive removal of ground cover, eg Tradescantia.

On the roadside, it will include many juvenile Tree and a few Chinese privet, many of them however already suppressed by our ad hoc interventions without any tools during surveys over the last year. These suppressions are proving surprisingly effective so far on trees up to about 2mH, and on larger trees where the leader was able to be partially broken.

We have since purchased a folding saw and are now able to effectively suppress trees up to 4mH. This is done only with consideration of the needs of nearby native vegetation, ie to release space for the anticipated spread of adjacent natives, while contionuing to provide soil stability, habitat and partial canopy. From our observations so far, we would expect follow-up of these trees by the same methodology to keep them under 2mH, developing only minimal foliage and succumbing to stress over a few years.

We would like to determine how many years that would take. Our correspondence with a Texan volunteer in Tree privet control suggests that ring-barking of all major branches results in death within 1-3 years, with retention of the upper part of the tree resulting in earlier death than in felling.

We have marked for ongoing monitoring a few of the Tree privet we have thus treated. There are many more in the roadside canopy margin. If this Project is to be funded ongoing we would mark some of those for monitoring also, provided we can communicate their locations and marking method to the Ecocontractor prior to their own control operation. We have now marked with orange tape several dozen juvenile tree privets and two Chinese privets that were suppressed by "partial breakdown" either in an ad hoc intervention in August 2018,or subsequently during this Trial. The Ecocontractor is aware and will inform team members working in either Witheford Reserve or the adjacent roadside.

Tree weed control Tradescantia Trial Zone

Within our Tradescantia Trial Zone we have cut or broken down several juvenile wattles, woolly nightshades and tree privet.

Wattles
Wattles cut down have died without any sign of regrowth.

Woolly nightshades

Wooly nightshades cut down developed leafy shoots from their stems, and were broken down again (it only takes a few seconds to snap or partially-cut the stem).

Two woolly nightshades are about 5mH and contributing to canopy over native understorey (observed valuable last summer and autumn during the drought). They would be easy to ringbark. We would recommend this for a gradual replacement by native canopy, and if time permits will seek approval from the Community Ranger to do it ourself, or liaise with the Ecocontractor for their consideration of the issue. (We note there are many more pressing issues of Tree privet and other weed control on this stream bank)

Phoenix palms
Those seen currently along the creek are up to about 60cmH. Loopiong the leaves in a circle and pulling tiinto a know takes only a few seconds, no equipment, is soil-friendly, has so far been effective over more than a year at Gahnia Grove and Kaipatiki Creek, and we recommend it to suppress further growth and probably weaken the growth.

Unfortunately the Target Species for General Reserves do not cover these:

Japanese Honeysuckle

Invasions have been found in the upstream area centred midway up the bank where there are no native trees, eg where a pine was felled in 1999, and reaching almost to the streamside.

Elaeagnus

Many dozens of small seedlings have been broken off or uprooted (depending on size and soil conditions) from streamside banks, forest and roadside.
Juveniles and adults alike are numerous throughout the upsteream banks. Those within the Trial site are no longer evident, having been suppressed by our Trial method was encountered.

Specimens treated this way from June 2018 to June 2019 are now either uprootable (if small) or barely grown since the intervention. As we come across them we repeat the intervention, suppressing them further. Larger trees require either more extensive, more frequent (eg quarterly) or more repeated, (eg annually for several years) interventions before growth becomes negligible.

Elaeagnus trunks to c.8cmD are soft and easy to cut with a small folding saw. A specimen several metres high and spreading several metres through native canopy beside the Native Plant Trail was sawn through easily, leaving its diffuse vine-like branches firmly supported in the adjacent kanono and mahoe as the foliage wilted.

Elaeagnus without intervention provided abundant fruit throughout July at several nearby locations observed from the Native Plant Trail.

Cretan brake

The invasive fern Cretan brake has been found in a number of locations and either uprooted or suppressed in each location. The smallest were able to be uprooted, and a larger one was uprootable after breakdown and suppression. The largest, about a metre high and wide, was trampled and mulched but would require a few follow-up interventions to eradicate it.

Bangalow

A number of mature or almost-mature abangalows now line the stream, and seedlings are being found in the streambanks themselves as well as in forest. We have obsedrved the seeds on sloping pavements above gutters in our neighbourhood, and assume that many of them roll into the stormwater system and are carried into the streams in this way, in addition to the bird-borne invasions.

Madeira

The Madeira vine spotted flowering throughout the tops of dying and dead tanekaha hasnow been observed more closely from the opposite streambank, where it climbs from the sandy bank into mamaku, mahoe, tanekaha and other trees. From our distance of c. 10-20m acors the stream we did not see any sign of vine strangling the several tanekaha, and assume death was by light occlusion or from other causes.

A Madeira tuber was found in Tradescantia at the roadside above, (Zone Ea) 10-20 metres from the vine visible in the outer edge of the c.20mH casnopy of tanekaha/kanuka/mahoe/karo on the Kaipatiki Roadside streambank in Zone Fa.

Weeds found in Tradescantia

While juvenile tree/shrub weeds and mature vines are scattered to common in the Tradescantia-covered areas, exploration and removal of dense Tradescantia has disclosed few hidden weeds at any stage of development, with the following exceptions:

-runners extending nearby invasions of Japanese honeysuckle and Calystegia silvatica (probably x sepium)

  • Madeira, a small vine extending from a nearby canopy invasion, through extensive blackberry, into moderate Tradescantia growth covering dry ground
  • Ehrharta erecta creeping from dry roadside into deep Tradescantia, where it is hidden but establishes and matures where Tradescantia coverage is thin
Posted on August 28, 2019 02:51 AM by kaipatiki_naturewatch kaipatiki_naturewatch | 0 comments | Leave a comment

Tradescantia - Kaipatiki Roadside

Kaipatiki Roadside

Immediate and complete removal of the roadside canopy's Tradescantia in the Trial Site would have been quick, easy and probably permanent if done at the start of this Project in March when, after a week of light rain, the roadside Tradescantia was assessed for first intervention.

Exploration quickly revealed the scantiness of its rooted stems, despite their height and glossiness. The roadside edge includes some quite damp areas channelling runoff after rain, and some areas where the soil surface, whether covered by Tradescantia or leaf litter, remains dry even after heavy rain. Under some trees even the leaf litter’s surface remains dry after rain.

Within the 1999 planted canopy of this area the tradescantia is deep, and the only groundcover. There are no shrubs or wild revegetation either native or exotic, and few juveniles (mahoe, kawakawa and karamu).

At the edge of the mown roadside grass a narrow band of unmown exotic grasses and herbs holds a few wild ti kouka, aruhe, mapou and shrubby toatoa (Haloragis erecta). This area was in June 2018 invaded by Japanese honeysuckle, moth plant and Tree privet, many of which were suppressed during that and subsequent surveys, (releasing native trees both live and already dead) ) and the remainder further suppressed or removed in March/April 2019 at the start of this Trial.

Tradescantia limits the invasion of the grasses and herbs under the canopy.

Dry roadside at top of uncanopied bank

At the downstream end of the Tradescantia Trial site, (Zones Db-Eb) the lower half of the roadside bank holds about 10m x 10m of Elaeagnus, honeysuckle and blackberry, preventing revegetation now as it did in 1997, where this occurrence of Elaeagnus survived a prolonged and intensive weed control operation along the Kaipatiki Roadside streambanks by North Shore City Council Parks Dept. Stream weeding was obstructed at what was known as "Elaeagnus Block".

The stream at Zone Db is still, as in 1997, canopied by “Mama ti kouka” with its over 100 heads, but above Mama ti kouka there is little vegetation but Tradescantia, with a few mahoe and kanuka and karo and pittosporum at the roadside only.

The bank downstream of Mama ti kouka is also almost treeless, only the Elaeagnus, honeysuckle and blackberry forming an island in the sea of Tradescantia, with only a few separate mahoe, and a couple of wattles which are falling over.

At the roadside here the ground is very dry. Sun-exposed Tradescantia here turned purple during the drought, and even in the adjacent kanuka/mahoe/tanekaha canopy on the downstream side,
the ground remained dry and dusty to a depth of at least 1cm beneath dense Tradescantia and light tree canopy.

In this dry extent of roadside, Ehrharta erecta occurs wherever Tradescantia is less than extremely deep and dense, scattered in such patches for about 10 metres down the bank towards the stream,. Ehrharta erecta’s bamboo-like rhizomes are far-reaching and effectively suppress native regeneration, and its abundant seeds germinate within 5 days. This occurrence is poised to dominate should the Tradescantia cover weaken.

For these reasons, Tradescantia removal has not yet been undertaken, except to compacti it over large areas by piling additional Tradescantia on top of it, the idea being to retain moisture and create humus to assist hydration next summer.

While test-removals have continued throughout autumn and winter, and many tiny seedlings of kawaka, and a few karamu, have been observed under Tradescantia on these occasions, we have not yet found the conditions allowing safe removal of the ground cover, even in small areas, as fine white mahoe root fibres are visible on the surface beneath.

We continue to assess, hoping to create at least small pockets of clearance to see what species of seedlings occur here, and whether they survive in varying degrees of Tradescantia removal.

At the edge of the mown grass, a few isolated small groups of mapou, kawakawa and a dozen or so kowhai (possibly from planted S. microphylla) seedlings were found.

Beyond this grass/herb canopy margin, few seedlings of any kind were found during exploratory weeding and/or survey of the upper bank under the tradescantia among planted trees.

Notable were

  • a 30cmH totara in a run-off channel just below the roadside, its top just hidden in the Tradescantia.

On release in October 2018 it was glossy and vigorous. In March 2019 it had dry slightly-shrunken leaves, a few browned, and was lightly mulched with Tradescantia but has not yet grown further.

  • dozens of Lastreopsis microsorum to c.50cmH, only visible when Tradescantia was parted carefully by hand. These were all on the almost-vertical lower banks at the 1997-99 outer margin of wild revegetation.

https://inaturalist.nz/observations/24775860

Many of the Lastreopsis' fine brittle stems were were broken during exploration and weeding despite care, as they were effectively invisible under the Tradescantia. Tradescantia piles were applied as mulch to protect as many as possible of them from the ensuing drought, and many have survived and grown.

Lastreopsis uncovered so far have been on the Kaipatiki Roadside bank (KRS) in Zones Cb and Cc, in an area about c.10m x 3m. In addition, a sporeling of what appears to be Lastreopsis has emerged in a run-off channel further up the same bank, under one of the few kawakawa and mahoe juveniles between the 1999 tree planting and 1999 wild regeneration margin.

Posted on August 28, 2019 03:13 AM by kaipatiki_naturewatch kaipatiki_naturewatch | 0 comments | Leave a comment

Tradescantia - Streamside banks

Most streamside banks from water’s edge (in dry season) to Kaipatiki roadside or Native Plant Trail were observed in June 2018 almost fully canopied by native vegetation with occasional 10-20mH tree privet or wattle, with a dense understorey of trees, shrubs and vines, scattered ferns in the forest and among Tradescantia. Some of the more recently eroded banks were bare or held only exposed tree roots, some held numerous ferns and tree seedlings lightly covered with Tradescantia.

This cyclic washing-out and sedimentation of banks essential to a natural meandering stream, maintaining water quality and freshwater habitat, was observed 1997-99, with the subsequent cycles of young and old native vegetation, and annual fresh supplies of Tradescantia from further upstream.

In 2018-19, there are few areas of heavy sedimentation, and many more of deep scouring of a wider stream. This is presumed due to the continued increase of stormwater, whether piped from housing and roads or channelled from paths, or unchannelled via deep crevasses cut into the clay of the almost-sheer banks above.

If our impressions are correct, this bodes poorly for any revegetation to be established now or in the future in this narrow strip of streamside forest surrounded by dense housing, roading and, up stream, commerce.

However, the exploration of what might be growing under the Tradescantia quickly resulted in the removal of most visible Tradescantia from large areas of streambank in several zones, and produced dozens of Tradescantia piles initially up to 2mx2m and 1.5mH.

Parts of the streambank are not suitable for weeding in a short-term (ie up to 3 years) 1-person Project as bank collapses, tree falls and resulting partial dams make the full extent of Tradescantia extremely difficult to access and the banks subject to ongoing entrapment of flood-borne Tradescantia.

One such area holds a large clump of ginger which will not be addressed in this Trial, though other clumps have been suppressed by stem-cutting and/or breaking and tuber-rotting.

Several tall slender woolly nightshades and wattles overhanging the stream among native canopy have been cut down (wattles) or partially-cut or broken (woolly nightshades).

The stream and much of the streamside vegetation, including a little of the areas dominated by ferns, are now visible from the Native Plant Trail. We have defined the Trail at ground-level with yellow plastic tape secured by ground staples, and identified it as a Trial chemical-free area with a few home-made signs, also encouraging Reserve users to report sewage overflows and water pollution events, with the numbers for Watercare and Council.

The large loose piles of Tradescantia are nitrogenous material that should be minimised as it decomposes to avoid nitrification of the streamwater. We are gradually moving the piles further from the stream, using them to border the path, and are also placing some of the abundant excess wheki and ponga fronds between them and the stream both to slow run-off of nitrogenous liquid and to replace the ground cover. As the streamside forest here appears well-hydrated and holds plenty of humus already, ideally the reducing Tradescantia mass would be gradually relocated to the dry under-nourished roadside margin. Not having the resources for this i the current project, we are gradually mio

This sandy soil is porous, holds much decaying plant material and is continually hydrated by the stream beneath, but it also provides habitat for many invertebrates, though surprisingly we have not in 2018-19 yet seen a lizard of any kind. Moving of Tradescantia exposes spiders, insects, and earthworms of the type commonly observed in both deep and superficial soil, so removal is done incompletely at first, and piles of Tradescantia are left at frequent intervals to allow self-relocation.

To reduce the size of the piles, we usually keep other plant material in the piles to a minimum, but with such a vast amount of nitrogenous material being piled near the stream here we are allowing tree fern litter etc in the piles, with the idea of increasing the carbon-nitrogen ratio of breakdown products.

Most of the areas of dense Tradescantia thus cleared held scattered juvenile native trees and ferns and occasional weed shrubs/trees, no vines either weed or native, and no small native seedlings.

Areas where the Tradescantia coverage was light or moderate held numerous juvenile native trees, carex and ferns, with a greater diversity and some small seedlings, including pigeonwood, karaka, tawa, karaeo and maire.

Detailed observations are yet to be made of seedlings in an area of light Tradescantia coverage not yet removed. Monitoring will continue in areas where Tradescantia was removed earlier and few or no seedlings were found.

Tradescantia piles will continue to be monitored and aggregated as they decompose.

The rate of regrowth of Tradescantia will be observed, and from past experience is expected to be rapid on streambanks from which it is not possible to remove its stems buried under many layers of sandy sediment.

Posted on August 28, 2019 03:14 AM by kaipatiki_naturewatch kaipatiki_naturewatch | 0 comments | Leave a comment

Tradescantia Trial Site Overview

The site chosen is an irregular area approx 50-80m long by 30-40m deep from the Kaipatiki roadside margin of 1999 planting, down to the stream and up the opposite bank as far as the Native Plant Trail along the bottom of a steep bank below housing.

On this side of the stream there is little Tradescantia beyond, ie uphill of, the Native Plant Trail, which is bordered by very steep banks dominated by kanuka and ponga, topped by housing and with only partial tree canopy, including many large pines, wattles, and Elaeagnus. Pine and ponga litter are probably suppressing both native and weed germination.

[Large manuka and mahoe have been observed over the years knocked down by pine-falls. A mature Towai, along with native understorey, was knocked down here in a wattle-fall in 1997. No other Towai have yet been observed, but a seedling has now been found much further upstream].

The Tradescantia Trial Site’s length length is from the signposted entrance to the Reserve opposite the Glenfield College tennis courts, downstream to a steep bank with few trees between the planting and the wild revegetation along the streamside.

Posted on August 28, 2019 03:14 AM by kaipatiki_naturewatch kaipatiki_naturewatch | 0 comments | Leave a comment