Report for end of Year One - June 2018- May 2019

*Sitework includes Weed control, fire hazard prevention, mulching for moisture retention, "tiptoe" path creation for habitat protection, onsite assessment and planning, and maintenance of amenity through disposition of weed materials and mulch bordering mown kikuyu)

"Inch by inch, row by row...gonnna watch this forest grow" (Apologies to Pete Seeger)

Our plan a year ago was to attempt to release as many of the trees in this little piece of forest margin as we could from the currently most crippling honeysuckle invasion, and to turn back the kikuyu from the margin of existing native trees along the mown grass edge. To make the results sustainable and eliminate unproductive edging of two of the three existing parallel margins of mown grass currently invading existing tree margins, we hoped to gradually replace a large weed-filled area within these borders with wild native vegetation.

We expected this would take about three years, with approximately 10m of margin being freed from honeysuckle in the first year, with the 2 hours a week we were able to commit as a volunteer.

As in other restoration we have undertaken, we find the results exceeded expectations. The Project was so rewarding and interesting that we extended our initial honeysuckle control to 50m of forest margin, extending about 20m down the weed-filled bank and into the manuka/ckanuka canopy to eliminate all of the honeysuckle invasion from that area.

The "internal" previously mown kikuyu was most easily controlled during the year by a combination of "kikuyu pullback" and mulch, and the process led unexpectedly to its eradication from the entire area (of course with the expectation of ongoing incursion from the adjacent mown sward).

A number of weeds have been dealt with for the first time using our methodology, leading to many interesting questions and the discovery of some answers, including some improved efficiencies in management of vine and shrub weeds generally.

The visual results have proved pleasing to the public, many of whom now regularly express their appreciation, (and occasional ask for weed-control advice) despite no longer having access to an additional informal "path" of mown kikuyu surrounded by weeds, which had previously cut through the site connecting the roadside to the large grass recreational area. (The nearest alternate access from road to recreational grassed area is apparently also informal, much steeper, and the grass has worn away leaving it rutted, muddy and slippery in winter).

The pigtail cordon provided by the Community Ranger, with some hanging interpretive signage hand-made from recyclable plastic, has been effective thus far in protecting actual and potential revegetation from trampling and from conflicting weed management practices.

And despite the paucity of surviving trees along the outer margin, we are seeing a little wild revegetation already, though whether these seedlings will survive summer drought remains to be seen.

It is such a pleasant activity and place to be that we spent hours on site whether needed for weed control or not, always finding something to do whether or not it increased the efficiency of the Project.

We have now enlarged the area being thus treated and hope to formalise its boundaries with the Community Ranger, and with Kaipatiki Project who are engaged in restoration in nearby areas of this roadside forest margin, in order to achieve and document more labour-efficient results in the conversion of metres of weedy forest margin to numbers of native trees.

Here are some side-by-side views of change during Year One

KIKUYU CONTROL

The challenge we set ourself in Gahnia Grove in June 2018 was to test and demonstrate the efficiency of "manual pullback", a method we had developed based on observation of the behaviour of kikuyu in response to typical interventions in various conditions.

We had trialled "pullback with rotting" in 2001-03 in small areas of two different restoration sites, converting to native vegetation an area of mown or unmown kikuyu, including planted and wild native vegetation invaded by its uncontrolled spread. Manual pullback requires the kikuyu to remain uncut and unbroken, so that unrooted stolons pulled back on themselves suppress outward spread and rot their own live foliage and eventually the rooted stolons beneath. The rotting eventually progresses to deeper rhizomes, allowing them to be uprooted easily. The resulting mass of rotted grass and attached earth is then pulled backwards, extending the area of control and releasing immediately plantable or seedable ground with a relatively high humus content and earthworms supporting rapid growth of new vegetation.

In the observation linked below, a month after first manual intervention at Gahnia Grove, the previously herbicide-controlled lawn-edge under the harakeke at left remains free of any visible life.

Beyond this sprayed edge, an area of previously-mown kikuyu has been allowed to grow freely to enable manual control by "pullback".

A pile of drying honeysuckle placed on previously mown kikuyu defines the site boundary, incidentally partially-suppressing kikuyu at the same time.

A wider view of the same area shows in April 2019 an area free of suppressive weeds, with released surviving karamu, wildflowers and mulched earth along the same border:

A recent post summarises kikuyu control in Gahnia Grove, beginning with a spontaneous intervention on 20th May 2018, followed up with an average of 6hrs a week onsite volunteer activity for 12 months, supported by the Kaipatiki Community Ranger and the year-long collaboration of Ventia's Integrated Services. Mowing of the recreational grass continued to maintain a smooth walkway and recreational area of bright green turf, while the suspension of line-trimming and herbicide-spraying allowed wildflowers to grow in its outer margin:

The Annexe/Glade margin is also a mown-grass margin, but very different in composition, discussed here.

BENIGN EXOTIC HERBS

• in the transition from aggressive weed invasion to wild diverse native vegetation

Since major removal of honeysuckle which had killed or imprisoned numerous trees, and other weeds eg 10mx10m of dense Cape Honey Flower and blackberry, Gahnia Grove has hosted benign exotic herbs throughout 50m of potential native forest margin, from the 15-20 year old manuka and older kanuka canopy up to the roadside kikuyu.

Benign exotic species occurring wild in Gahnia Grove during the year included 31 plant species, many of them hosting great numbers of honeybees. These species are listed here, using the generic iNaturalist.nz Taxon info and images.

Some observations of benign exotic herbs arising and retained in Gahnia Grove over the last year, ordered oldest-to-newest (This list is currently 3 pages of observations including both wide and close-ups, and may take a few seconds to load as you scroll down).

It has been a joy to watch this dense but easily manageable wildflower bed providing diverse ground cover to prevent erosion while

• hosting wildlife
• creating mini-canopy to shade native seedlings
• retaining soil moisture - Through moisture retention, the benign exotic herbs are not only enabling native seeds to germinate and grow, but supporting the recovery and development of existing native trees in the margin of the forest canopy, including two juvenile putaputaweta and a pigeonwood; and the few karamu that survived the honeysuckle invasion)
• minimising invasion of suppressive herb and grass weeds - both of species pre-existing this Trial eg herbs and grasses (mainly Broad-leaved dock, Creeping buttercup and Paspalum sp and exotic umbrella sedges Cyperus eragrostis and congestus), and Tree/shrub weed seedlings (mainly Moth plant, Cape Honey Flower and Brush wattle)
• through soil penetration, moisture absorption and retention, and humus formation, enabling uprooting of new populations of aggressive weeds

An earlier post considers our planned use of benign exotic herbs in restoration, while a more recent post celebrates the abundance of foliage-rich ground cover and mulch for seedling shelter, weed suppression and soil conditioning.

WEEDS
"Watch it growing seed by seed, and protect it weed by weed......"

Some observations of weed seedlings observed in Year One of the Trial - and generally uprooted or suppressed - can be seen here.

HONEYSUCKLE
The all-encompassing weed issue when the Gahnia Grove manual restoration trial project began in June 2018 was Japanese honeysuckle, which remains the greatest immediate threat from neighbouring forest margins.

We made some notes on Japanese honeysuckle control at Gahnia Grove here.

Control of honeysuckle and blackberry, significant at the start of the Project, has required little effort or time since late summer. Control was thus able to be extended to the previously-unmanaged adjacent Flame Tree Bank, which we undertook with the more efficient and low-energy techniques that had been found successful and efficient in the Arena and Cape Honey Flower Banks - ie pulling in outlying runners, cutting vines from trees as high as possible, piling the vine over its roots, self-mulching for root- rotting.

The addition of any plant material available helped the rotting process immensely, loosening roots much sooner. Tradescantia, moisture-retentive and forming a dense mass when piled, is ideal for this purpose if it is already present and the mulch site is identifiable and accessible for ongoing control of the Tradescantia:

CAPE HONEY FLOWER

The second most significant weed on the site was Cape Honey Flower (CHF), summarised here.

MOTH PLANT

Several mature vines with pods were uprooted in June/July 2018 from two sites in Gahnia Grove. Uprooting was either entire or partial depending on soil conditions. Thousands of tiny Moth Plant seedlings in these two sites were uprooted in the following month or two, individually or the tiniest disturbed en masse then suppressed with mulch.

Dozens of these seedlings were incompletely uprooted, and along with one or two incompletely uprooted mature vines, emerged vigorously in Spring 2018. The repeat uprooting attempt at this time was often unsuccessful as the ground was dry at the time, but the broken stems resulted in prevention of further development of seedling or vines.

We will in future use mulch to suppress seedlings and loosen the soil, if wet ground is likely to allow successful uprooting before vines develop enough to affect nearby vegetation.

TREE PRIVET

Several specimens to c.4.5mH were beginning to suppress adjacent otherwise-thriving native trees on the grass margin, and were controlled by several techniques whose long-term results we wanted to monitor.

While initially 5 or 10 minutes was spent every few weeks on repeat suppression of the group of tree privets, by late autumn there was little regrowth on the second tallest, which had had its main branches all partially broken and bent down. The tallest, whose top was unable to be reached, had failed to significantly increase its height or to produce branches, but was still producing vigorous leafy shoots, and was felled at about 1mH in autumn. It has had leafy shoots picked off the remaining trunk tip occasionally since then.

OTHER WOODY SHRUB/TREE WEEDS
Chinese privet, Elaeagnus and Cotoneaster treated by the same basic method are all much diminished in size and producing only slow regrowth. A juvenile Elaeagnus and Tree privet in shade, both about 2mH before cutting or partial breakdown of main stems and branches, stopped producing shoots and were found to be easily uprooted.

The results so far are being collected here.

TRADESCANTIA

Most of Gahnia Grove, below a road edge along a ridge, was without Tradescantia when first observed. There was a little under the honeysuckle-curtained canopy edge of the Arena, and a moderate coverage over the forest floor downhill, wherre it held many tuber ladder ferns, but both Tradescantia and tuber ladder fern tapered out within about 15m.

Cape Honey Flower Bank had a carpet of it along the canopy edge, thinner uphill perhaps because CHF obliterated light, and much thicker downhill into the canopy, where it deep and lush among the kanuka, mahoe and Flame Tree trunks. Like adjacent canopy, this Tradescantia-carpeted area held little understorey, but seedlings of pigeonwood, coprosma, and mahoe, as well as many juvenile and mature Elaeagnus, with Kahili ginger and Euonymus japonica.

Throughout Flame Tree Bank, and the kanuka/Flame Tree canopy below, Tradescantia was dense and deep. It was left undisturbed on this bank throughout the dry season, but gradually gathered in from the outer extent of its invasion in the kanuka canopy below Arena and Cape Honey Flower Banks.

In July 2019 we surveyed further through the canopy and its margin, and found ferns, native shrubs and herbs, and many and diverse seedling trees, including tanekaha, in the light-to-moderate tradescantia past Flame Tree bank observed prior to intervention and, after other weeds were controlled and ground moisture had increased enough to support native seedling development, during control in conjunction with herbaceous shrub weed control.

BLACKBERRY

Blackberry, though not obvious through the long kikuyu, dense honeysuckle and tall Cape Honey Flower, was troublesome from the start, its suckers several metres long and spreading underneath the honeysuckle and kikuyu. Its thorns pierce all but heavy-duty gloves, and arm-protectors needed to be worn to reduce the time spent bathing scratched arms in kawakawa tea each evening. (It was useful to discover, however, that bandaging with a rag soaked in warm kawakawa tea not only soothed and prevented or treated infection, but often drew out tiny broken thorn tips of all types).

Seedlings were also scattered throughout the adjacent canopy margins.

We were pleased to discover that instead of often-unsuccessful attempts to uproot it, the blackberry could be just folded over itself and the stem partially broken, as for honeysuckle, and covered with a thick layer of any plant material. Its roots became weakened and loosened over a few weeks, as we had found earlier with the honeysuckle. This saved a lot of time - and scratches - thereafter.

ALOCASIA, GINGER, ARUM

Alocasia brisbanensis (Elephant's Ear), Arum lily and Kahili ginger, having been temporarily controlled from October to April by cutting of stems or leaves, were thereafter treated the same way as had been found successful with blackberry, ie partially broken down and heavily mulched with a pile of Tradescantia.

Before applying mulch to any shrub weed, the bulk of the shrub weed was reduced as much as possible without a lot of effort: ie ginger stems were bent tightly in several places and folded down, their leaves intact, over the centre of the clump. Arum and Alocasia had their leaves broken off or pushed down, and stems were cut or broken if possible to do so easily.

Alocasia before intervention

Regrowth of those plants after cutting at base, and during or after heavy mulching with Tradescantia

BULB WEEDS

Bulbil Watsonia was abundant throughout the canopy margin, and Montbretia throughout the upper Arena. Their current status and methodologies used are discussed here.

OTHER WEEDS still being controlled in Gahnia Grove include:

ARISTEA ecklonii
Another weed observed abundant in June 2018, and found to be having significant impact on the manuka canopy margin with scattered substantial invasions well into the kauri ridge community under tanekaha, totara and forest understorey, is discussed here. We welcome any experience of the likelihood of complete suppression by increased density of shade as the forest matures. Until then we are suppressing them where mulch is at hand, and uprooting them as soil conditions and time permit - not difficult to uproot once ground is very wet. Even easier if they have previously been covered with eg uprooted pampas, manuka brush, or pine needles.

AGAPANTHUS is discussed here.

CALYSTEGIA
We recorded our first finding of underground runners in mid-winter. We were able to control the anticipated emergence of annual growth on the extensive existing invasion by a common hybrid of the native Calystegia sepium subsp roseata and the invasive (Calystegia silvatica) species. There are numerous occurrences of this hybrid invasion throughout at least 100m of this forest margin.

PAMPAS
Numerous pampas in the manuka/kanuka canopy, and a single clump c.4mH and 3mW on the sunny grass margin, were treated by the easiest and least time-consuming method of bending over and breaking any culms, throwing live and dead foliage over the centre of the clump if possible, and cutting most of the live foliage off the large clump in the grass margin.

One or two subsequent walks through the canopy repeated the suppression of the small ones there till they were easily uprootable.

More interventions over several months were needed to totally uproot a larger clump in a light-break in the outer manuka margin with little shade.

The big one in the sun is gradually rotting on the most-trimmed "Gahnia Grove" side, while the outer side, whose live foliage was retained during summer to avoid the potential fire hazard of loose dry grass, is gradually weakening as a result of ongoing attrition. Water build-up in the centre of the clump is encouraged by keeping a natural vertical channel open in the centre of the clump, so the stem bases are rotting particularly well here in the centre.

EXOTIC PALMS

A single Phoenix palm seedling, c.50cmH in June 2018 and suppressed by partial breaking the main leaves and pushing them down and toward the centre, effectively self-mulching with their own foliage. A month later the weakened and softened leaves were looped and loosely knotted together.

This took only 10-30 seconds, and there was no significant growth for some months. When regrowth did occur, it was by a single leaf growing through or around the loop. Repeat intervention took only a few seconds and again suppressed it for some months. A third intervention resulted in the seedlings being about the same height in June 2019 as it was in June 2018, but having only one or two growing leaves, the rest being unable to grow.

In July 2019 one leaf had grown above the loop, to the original height of about 50cmH. It was tucked into the loop ia second or two,before we remembered to photograph it, but next time intervention is needed we will tyr to remember to record it. (We are also monitoring and recording some Phoenix palm seedlings being treated by the same method in Kaipatiki Creek).

It is hoped that roots will have been sufficiently weakened by a year or two of unproductive growth for the palm to be uprooted despite the hard dry clay, which the stout and woody tap roots of even tiny palm seedlings penetrate to a considerable depth. In a site with ongoing monitoring and intervention as needed, the repeat interventions take only a few seconds in passing, so if the method succeeds the time required for extermination of the plant will have totalled only a minute or two, with no need for scheduling or equipment, and no physical effort.

WEED SEEDLINGS
Weed seedlings occurring in bared ground and among pre-existing native vegetation have preominantly been the same species that were removed in the initial weeding:

A few more CLIMBING ASPARAGUS seedlings occurred among the mature and juvenile native trees, but as yet not as many as were present at the start of the Project a year ago.

Weed seedlings of BRUSH WATTLE, MOTH PLANT and CHF were abundant and continuous in the months following removal of their parents. Brush wattle and Moth plant were expected; the CHF was a bit of a surprise, as NZ info websites had suggested invasion by seedlings was rare. Until July 18 CHF seedlings were not observed more than a few metres from the parent infestation, so it was not technically a new invasion, but there is obviously no problem in the seeds being produced and germinating. Whether many seeds had lain dormant awaiting light is a question that we were not able to answer in our observations, but no seedlings were observed prior to the cutting of the many adult stems.

In late July a CHF seedling was found 20-30m from the site of the original infestation, in bare clay in the manuka canopy margin of the Annexe, where Aristea, Watsonia and honeysuckle and kikuyu had been removed last year.

Even more interestingly, one was then found about 20m within the canopy, the first one seen here. Either it was brought by a bird or other animal who ingested it in the area where the CHF was cut down, or the species sometimes germinates in shade but dies from lack of light.

The benign exotic herbs suppressed most weed seedlings, but hid those that did germinate, so that where wildflowers had grown tall and dense, Moth plant and wattle seedlings weren't seen until they were up to 50cm H. However, they were few, spindly., and easier to uproot from the damper ground among the benign exotics than the dry bare clay areas.

The abundance of Brush wattle and Moth plant seedlings in March was noted in an earlier post.

New weed invasions occurring during the Project so far included:

SWAN PLANT (Gomphocarpus sp) - two seedlings grew swiftly to 40cmH, in ex-kikuyu ground with a thin surface of wood chip mulch, and among benign exotic herbs. Both were uprooted easily

Cape gooseberry - a few seedlings uprooted, and one or two retained for now as benign exotic herb-cover, to be controlled before fruiting

BLACK NIGHTSHADE (Solanum nigrum) was not noted at the start of the Project, but was probably present among the kikuyu and blackberry. Over summer it became common throughout cleared areas and was retained, its upright single-stem and deep tap-rooted habit beneficial to soil-conditioning, conducive to seedling development in its canopy, and easy to cut down when no longr wanted.

Once these Black nightshade began to flower, we examined each plant for the "umbellate" flowers (all flowers or fruits join the stem at the same point, like an umbrella) of the two native species common in this area, DARK NIGHTSHADE (Solanum opacum) and "AMERICAN" DARK NIGHTSHADE (Solanum americanum), which we had learned of through iNaturalist.

After identifying dozens of Solanum nigrum, at last a Solanum opacum was found, then several more. Later, care was taken not to cull these along with the exotics. It seems likely that dominance of the native nightshade will be achieved by gradual culling the exotic species, before fruiting where possible. It seems likely to be as useful as Haloragis erecta as a nurse-plant for native tree seedlings.

Specimens of S. opacum identified so far have been distinguishable from the S. nigrum specimens on the site by leaf shape and colour as well as the fruit/flower arrangement and characteristics, so we may be able to remove the exotic Black nightshades at an earlier stage from now on, except where it is the only available ground cover and mini-canopy during hot dry weather.

NATIVE SEEDLINGS in Gahnia Grove -

These search results include repeat observations of some specimens. We recorded those in ground released from weed invasion since June 2018, in ground released from weed invasion since Oct 2019, as well as all native seedlings and sporelings, including those in the mainly-weed free canopy - ie not obviously reflecting the nearby mass-weed control.

This list should of course include the seedlings of the native nightshade Solanum opacum, but we did not learn to recognise the species as seedlings during the year, and could still not be sure enough to identify the seedlings in a recorded observation.

Some of the fun things we don't need to do anything with except enjoy include Gahnia Grove's MOSSES & LICHENS and the WILDLIFE.

TIPTOE PATH
We continue to build up a 30-40mm wide swathe of woody plant material as it becomes available, with coarser sticks on the bottom preventing bogs and ruts in the clay, eventually to have a smoother surface of dead pampas bases and foliage. Such a "tip-toe" path is necessary for all-weather access to various areas of the site minimising trampling in the ongoing observations and interventions. The relative unevenness and narrowness of the path discourages people who might enter the site from walking as if on a street, ie heedless of the plants, soil conditions and invertebrates at their feet. The perfect "Small Things Observation Path", but not so good for looking at tree tops or birds in the sky:)

For all observations recorded, grouped geographically by sub-sites with their own Species lists, see the Overview (Map at bottom of page), Projects for each of the various sub-sites, and Projects for a few other other criteria, in the Gahnia Grove Umbrella Project.

Publicado el julio 20, 2019 10:34 MAÑANA por kaipatiki_naturewatch