Gahnia Grove - Site summary and discussion's Journal

Journal archives for January 2019

January 22, 2019

Contractor Assistance - Missions accomplished

24 hours work at our direction was contracted by AC Parks with a Biodiversity Management student previously recommended to us for Botanical Survey work. Manual weed removal and initial control was mainly on the steep and initially inaccessible Cape Honey Flower (CHF) Bank, between the bank directly under the primary Flame tree stand and Gahnia Grove's Arena.

For observations of CHF Bank from June 2018 to January 2019 see:
https://inaturalist.nz/observations?order=asc&order_by=observed_on&place_id=128172&project_id=gahnia-grove-chf-bank&subview=grid

The CHF was all sawn off as near as possible to the ground, and the wood, with any foliage attached, placed in piles. An initial session in October was followed up in November and December by removing some remaining CHF stems and any loosened stumps. Piles were relocated in the interim to rot more of the blackberry and to allow access to remaining roots.

The many curving stems of CHF, up to 4m long, made the bank difficult to traverse or weed even after being cut down, and their thin hollow stems created a lot of dry flammable material near a well-used pedestrian access, so most were cut into lengths about 50cm.

Near the few native trees on CHF Bank, on the near edge of Flame Tree Bank, Alocasia brisbanensis (Elephant's Ear) was cut at its many bases.

Honeysuckle and blackberry remnants were uprooted or cut at base where uprooting was not possible due to dry ground or deep rooting among native tree roots or harakeke. Semi-rotting of the roots of some blackberry and honeysuckle was achieved between visits by partially breaking or damaging stems near the base, then trampling to covering the roots with live growth, adding weed material from nearby to create a moist environment within the pile. This allowed many honeysuckle and blackberry plants to be uprooted a month or two after the initial intervention.

The stems of Calystegia - probably the same invasive/native cross as that throughout the Upper Forest margins, ie C. silvatica x sepium subsp roseatum - were cut or broken as encountered, occasionally removing some of the root.

On the CHF Bank canopy margin, the single Chinese privet on the canopy margin, and the single cotoneaster in the canopy, were ringbarked again.

Two small Flame trees were ringbarked with apparent initial effect on one, but no lasting effect on either observed by January 2019.

In the manuka/kanukacanopy throughout Gahnia Grove:

A single c. 3mH hakea was uprooted fairly easily as it was already semi-fallen, perhaps due to an earlier weed-control intervention.Remaining Pampas, previously suppressed and weakened by trampling, was uprooted

Bulbil Watsonia and Aristea ecklonii (Blue corn-lily) were suppressed by pulling, cutting or mulching near the canopy margin at the edge of the large grassed area, or "Glade".

Native trees and shrubs released by the contractor's work with volunteer follow-up:

  • on Cape Honey Flower Bank:

Mahoe (the only one present in Gahnia Grove)
Three mature ti kouka and several juveniles
Several karamu to c.4mH, some defoliated and seriously weakened by almost complete honeysuckle coverage, and several juveniles
Two large mapou and several juveniles
A large isolated harakeke half-way down the bank
3 kawakawa juveniles c. 1mH

  • on the kikuyu margin under the Flame Tree:

A honeysuckle-covered hebe
Two honeysuckle-covered karamu
Two houhere

For the Volunteer follow-up to Paul's work, see "Weed control - Winter-Spring summary"
https://inaturalist.nz/projects/gahnia-grove-site-summary-and-discussion/journal/20963-weed-control-winter-spring-summary

Posted on January 22, 2019 01:52 AM by kaipatiki_naturewatch kaipatiki_naturewatch | 0 comments | Leave a comment

Native Seedlings starting to appear in recently cleared areas

A Project has been created for the seedlings of Gahnia Grove.
https://inaturalist.nz/projects/native-seedlings-of-gahnia-grove
That Project's "Journal" has a little more background to this monitoring, in a "Journal" post linked directly here:
https://inaturalist.nz/projects/native-seedlings-of-gahnia-grove/journal/20928-how-many-native-seedlings-in-the-neighbourhood

The native seedlings present in June 2018 under manuka/kanuka canopy and among the 3-4mH planted trees on the uphill margin of the Apron and Annexe have continued to grow slowly in the dry, rocky soil - which, we are told by a passerby of 60 years local residence, is likely to be roadworks fill moved from Glenfield Rd during its widening and lowering here a decade or so ago. (That explains the number of pieces of road metal found among the trees here, and the fact that stones were difficult and sometimes impossible to avoid when driving the cordon pigtail-posts into the top 10cm of soil recently).

Annexe - The few "Original" seedlings in the Annexe have recently been supplemented by dozens of tiny manuka or kanuka seedlings, numerous karamu, mapou and totara, a few pseudopanax, and a few of other species, especially at the light-exposed park-entry end, under a dead manuka and karamu released June 2018 from light honeysuckle coverage, and where ground was released from a vast mass of dead pampas foliage.

Apron - The area occupied until June 2018 by Elaeagnus now has numerous very small seedlings of karamu, mapou and occasional others. Near the kikuyu margin, around the base of a large leafy karamu, there are occasional seedlings of the same species as in the Annexe, with the addition of a few kahikatea.

The clay banks of the Arena, and Cape Honey Flower (CHF) Bank, completely bared by release of both ground and defoliated trees from honeysuckle, blackberry, kikuyu and CHF, have few native seedlings as yet. Those that have germinated so far are mainly ti kouka, karamu, and mapou, with manuka/kanuka on CHF Bank around a manuka surviving in the previously-sprayed mown-kikuyu margin. Most of these seedlings are near the canopy margin, at the base of surviving trees, or sheltered and shaded by wild carrot, ox tongue etc. All these areas tend to have more moisture and a little humus from decayed weed material or leaf litter.

Toatoa (Haloragis erecta), a wonderful nurse plant for native seedlings, reproduces itself readily through its abundant seed production. Seed has now been collected from a number of toatoa plants in the Reserve network and been cast throughout Gahnia Grove. In addition, a single mature specimen has been discovered at the top of Flame Tree Bank, released from vine weeds and CHF, presumably responsible for the few newly germinated toatoa seedlings nearby. These seedlings are ideally placed to nurture native seedlings along the kikuyu margin and the top of the bank.

Observations of many of the native seedlings observed so far in Gahnia Grove, arranged by date observed, scan be seen here:
https://inaturalist.nz/observations?order=asc&order_by=observed_on&page=2&place_id=any&project_id=native-seedlings-of-gahnia-grove&subview=grid

NB This list has been sorted with the oldest first, and the newer observations, on Page 2, can take a short while to load.

Also NB, we have just discovered this "Explore" function of iNat. Now or in the future, anyone interested in seeing a particular species,date range, or part of Gahnia Grove, or indeed anywhere in the world, can change or refine their Search using the Filters. Note the link "More filters".

Posted on January 22, 2019 09:50 PM by kaipatiki_naturewatch kaipatiki_naturewatch | 0 comments | Leave a comment

Mown Kikuyu border - evolving a long-term strategy for current trial

Kikuyu within the trial site boundary:

The kikuyu within Gahnia Grove in June 2018 covered c. 30 sq m of mown dense mat, and c.50 sq m long loose unmown.

See observations showing Kikuyu eradication in the Arena:
"https://inaturalist.nz/observations?captive=any&order=asc&order_by=observed_on&place_id=any&project_id=kikuyu-eradication-in-the-arena&subview=grid&verifiable=any

Eradication is close to complete in the Apron:
https://inaturalist.nz/observations?captive=any&order=asc&order_by=observed_on&place_id=any&project_id=31006&subview=grid&verifiable=any

As observed in the above links, all Gahnia Grove's unmown kikuyu, and most of the previously mown kikuyu, have been pulled back and rotted. No live stolons remain, but a few scattered deep rhizomes produce weak stolons from time to time, uprooted or suppressed with mulch as they arise.

All these areas of kikuyu pullback in winter are now supporting dense benign exotic herbs, from mature in the first-released areas, to very new seedlings in the areas of most recent release.

Occasional native seedlings have germinated here and there throughout, a few having close exotic herb foliage removed around them to ensure unhindered growth, but most are still very small and vulnerable to drought.

The previously mown area has been reduced by pullback and rotting to c. 8 sq metres at the top of the Arena, visible from the mown margin through the 4m gap between two large harakeke. This 8 m sq block, with mowing and trimming suspended in June 2018 at our request, had grown to 30-40cm long by early December. Further growth was suppressed by a modified, less efficient (about .5hrs × 3) and less effective pullback to halt its growth through summer, avoiding the need for cutting which would have made it more difficult to control later.

We called this ad hoc technique "comb and curl". It resulted in surprisingly rapid decay of leafy stolons, through a wider area than previously treated at one time, but in hot dry weather it produced little rotted material and a lot of loose dry leafy stolons, wasting potential soil conditioning and potentially contributing to fire hazard near the roadside pedestrian access. To avoid the need for intervention in Firewatch season, the process was halted and the remaining area of "combed and curled " previously mown kikuyu was covered with a thinly scattered layer of wood chip mulch for visual integrity and to reduce Fire hazard. The edges of this block have been explored and found to be rotting full-depth in the "standard" manner, with the kikuyu area reducible a few centimetres a week by uprooting of weakened rhizomes, but the moisture loss and the production of dry loose stolons make the process inadvisable in this season.

The most cost- and labour-efficient summer solution for a smallish dense mat of kikuyu where manual eradication is planned may be to pull back all stolons from the perimeter, (the longer they are, the more they suppress the growth of the remnant), cover it entirely with dense light-proof mulch or sheet, and wait until first rains before continuing pullback. This may need to be repeated during summer where growth continues through the mulch.

Kikuyu at the margin of mown kikuyu:

The outer margin of the site requires a different strategy and additional consideration to meet traditional expectations of appearance and to facilitate kikuyu control in a wide area by mowing.

At the end of December 2018, 3 cu m of Wood chip mulch was spread along c. 30m kikuyu margin for visual definition and amenity and fire safety, covering some of the loose dry grass, pampas, twigs and fallen leaves.

Reserve users have asked if it is to "stop the kikuyu". It was explained that the mulch will not in itself stop the kikuyu, but will temporarily suppress and direct its growth, and by defining the mown area allow any kikuyu beyond to grow long enough to be pulled back in due course. (One area of mown kikuyu, a "bay" between two planted harakeke extended the mowing and kikuyu control margin by 6-8 metres with no obvious benefit, was covered with a tarp to hold some of the delivered mulchpile for a week or two. After the mulch was used the area was included in Gahnia Grove, ie behind the cordon, for a trial of letting-it-grow followed by pullback, starting in summer when growth is fast and rotting is difficult to achieve. If this proves difficult to control, the tarp and/or more mulch can be laid).

In the remainder of the 30m margin, a month after laying the mulch border strip a strategy is evolving to manage kikuyu pullback along a mown margin using a border of wood mulch initially c. 50cm wide and c. 20cm deep.

Whether the mulched kikuyu rots or dries depends on moisture surrounding it. In summer, growth is rapid and rotting is minimal and only at ground level, with any loose or lightly-mulched kikuyu tending to dry and potentially presenting a fire hazard. The following strategy and observations relate to the control of kikuyu in summer.

  1. A few stolons rapidly grow and emerge within the mulch border itself. These have been, experimentally, suppressed only briefly by kicking adjacent mulch over the emergent growth.
  2. Any kikuyu long enough to be pulled back towards the mown area BEFORE mulch is laid over it, grows vigorously BACKWARDS, ie towards the mown area. An attempt was made, pre-cordoning, to continually "hide" this growth, but this was (as expected) time-inefficient.

The erection of a cordon defining the border has helped clarify the ongoing and systematic nature of the kikuyu control, the appearance of which is well-accepted by those passersby who have commented.

[Interpretive signage on the cordon surrounding the site is being planned in collaboration with Kaipatiki Project (KP), to include Invitations to participate in restoration in Reserves through Council and the KP. We are to trial the effect of various texts with a variety of home-made signs. The first one reads simply "Native Seedlings Growing - Kaipatiki Project", conveying the most important message that the apparentl bare ground behind the cordon is a seed-bed.].

It is so far proving relatively efficient to let the backward growth develop without intervention for a week or two (depending on weather) and then to scoop off the mulch from about 50cm lenth of border, pull any unrooted stolons back towards the mown area, and re-cover them, along with any remaining suspected hidden live rhizomes, with a similar quantity of mulch.

This can be done by working from one end along the border, removing the mulch from one short length of border onto the adjacent area that has just been pulled back. Covering the backward growth on the outer edge, while uprooting the rotted stems on the inner edge, moves the mulch border outwards 10-20cm each time this is done. Provided no live rhizomes are left unmulched, and no mulched area is left unexamined too long, this process creates an outward-expanding controlled area, which will in time consume the supplied wood-chip mulch. However, since the process adds decaying kikuyu to the wood mulch, sufficient mulch material may be maintained to sustain the process until mowing ceases in winter.

Alternatively, when Firewatch season ends ongoing growth can be allowed into the manually controlled area, to be pulled back where threatening other vegetation. When the ground is wet enough, pullback will result in full-depth rotting of kikuyu rhizomes and the creation of humus. In winter, pullback is likely to provide enough rotted kikuyu, mixed with soil by the process, to continue the process outwards until mowing starts again.

The areas where kikuyu pullback and rotting have been completed are immediately seedable or plantable. Within Gahnia Grove benign exotics have already matured throughout much of the previous area of kikuyu, and native seedlings are beginning to emerge. A similar development of selective revegetation starting with benign exotics is now starting to occur in the outer kikuyu margin.

Kikuyu control will of course continue to be needed along the new border. If expansion of the kikuyu-free area is wanted, the process of pullback can be repeated along the new border. If not, a method of preventing outward spread of the permanently mown area will have to be decided.

Ongoing pullback and regrowth of the same area could be done, but the need for ongoing intervention could be reduced or eliminated by an effectively-competing ground cover that does not inhibit native forest or create a nuisance.

Where dense tall vegetation is wanted and achieved, shade will do much of the control. The current trial seeks to avoid line-trimming or spraying under the dripline primarily in order to achieving the necessary density of vegetation at and near ground level, by selecting the natives and benign exotics from those species that spontaneously arise.

Ongoing selective weeding of any spontaneously arising vegetation in the margin will support increasing diversity and habitat in what it is hoped will become a self-sustaining native plant community echoing natural forest buffer ecology. Any experiences or sharing of knowledge in that regard will be very welcome.

Planting of Scrambling pohuehue has been discussed, but we don't know how effective this is at excluding kikuyu. It would seem to be at least advisable to ensure the area is thoroughly free of kikuyu, including underground rhizomes, before planting Pohuehue, to avoid having to fight one's way through a tangled mass to control kikuyu later. But again, any experience is welcome.

The interaction of the mulch border of Gahnia Grove with mowing has not yet been observed. To define the mowing area, and to deter reserve users from walking through the revegetation site, a cordon has been provided by Council Parks, and was erected 15 January with the assistance of the Kaipatiki Project, soon after the mulch was laid.

It is not yet known how close to the cordon mowing is possible and convenient for the mowing team, or desirable for amenity or ease of manual control. All observations are welcome in the evolution of a sustainable solution to the problem of mown kikuyu along the borders of plantings and regenerating forest.

Posted on January 22, 2019 11:39 PM by kaipatiki_naturewatch kaipatiki_naturewatch | 0 comments | Leave a comment

January 23, 2019

Pedestrian access through Gahnia Grove

Many Reserve users have stopped and asked if they can, and/or may, walk through the site, presumably because the shade and variety of vegetation on both sides is more appealing, especially in summer heat, than the walk along the roadside.

They and other passersby have expressed enthusiasm and appreciation of the restoration effort, and willingly agree not to come through.

However, it is inevitable that some of the public will enter Gahnia Grove and use it as access to the "Glade" or large mown area and the older forest beyond.

A defined non-slip surface was necessary to access several connected areas without trampling revegetation, so a single-footsteps "path" about 30cm wide was loosely formed in June/July 2018, from available dead manuka brush and pampas stumps, with a smooth surface of pampas foliage to be added after fire watch season is finished. T

All the dry pampas on the site has proved very resistant to rotting, much of it becoming loose and quickly wind-dried soon after heavy rain in December. For this reason, most of the site's loose dead pampas has been collected in the Annexe and covered with a weighted tarpaulin, for later use as mulch and/or path surface where it will be compacted by trampling and the lower layers will rot progressively.

Our current observations of pampas' resistance to water absorption and rotting explain its earlier success as a path surface in our 1999 trial over several metres of the Kaipatiki Creek Native Plant Trail, heavily used by joggers and also cyclists: unlike wood-chip mulch, pampas sheds water and is slow to rot.

In Gahnia Grove, interpretive signage along this narrow, natural "weeders' path" could be by little long-life or recyclable plastic signs at ankle-height on rounded fencing pins 10-20cm high, close enough together to discourage stepping off the path. Interpretive images and text would create awareness not only of the need to keep off the revegetation,but of features of interest, site restoration history, the native seedlings now starting to appear, and the function of the retained benign exotics, and other issues the passersby and Reserve users ask about or otherwise show interest in.

Interpretive signage on the cordon surrounding the site is already being planned in collaboration with Kaipatiki Project (KP), to include Invitations to participate in restoration in Reserves through Council and the KP.

An unanticipated benefit of the retained benign exotics is that they are providing a colourful and varied floral mass, buzzing with bees and other pollinators, with blackbirds and tui foraging in the lightly disturbed earth of hand-weeding in the remaining gaps among them. This presents a very welcome example of biodiversity to the public, and hopefully will inspire plant interactions and initiatives of their own.

Posted on January 23, 2019 12:32 AM by kaipatiki_naturewatch kaipatiki_naturewatch | 0 comments | Leave a comment

Flame Tree invasion continues in Gahnia Grove's kanuka canopy, subcanopy and understorey

The poisoning and removal of Flame Trees in and adjacent to Gahnia Grove has been approved by the Council Ecologist/Arborist, and awaits Resource consent.

In the interim, the several young Flame Trees within Gahnia Grove are growing rapidly, accessing the space previously filled by privet and Japanese honeysuckle at the bottom of the Arena, and by Cape Honey Flower at the bottom of Cape Honey Flower Bank. The foliage is on low-lying branches of trunks only about 10cm D.

Some observations of the small Flame Trees within Gahnia Grove:

https://inaturalist.nz/observations/19586406
https://inaturalist.nz/observations/18937194
https://inaturalist.nz/observations/14341070
https://inaturalist.nz/observations/14256380
https://inaturalist.nz/observations/19488829
https://inaturalist.nz/observations/14341124
https://inaturalist.nz/observations/14341075
https://inaturalist.nz/observations/14341072

Posted on January 23, 2019 12:47 AM by kaipatiki_naturewatch kaipatiki_naturewatch | 0 comments | Leave a comment

Weed control - Spring summary

For ongoing kikuyu control on the mown margin, see https://inaturalist.nz/projects/gahnia-grove-site-summary-and-discussion/journal/20558-mown-kikuyu-border-evolving-a-long-term-strategy-for-current-trial

Major weed removal on Cape Honey Flower (CHF) Bank by a contractor is covered here:
https://inaturalist.nz/projects/gahnia-grove-site-summary-and-discussion/journal/20965-contractor-assistance-missions-accomplished

Volunteer followup on CHF Bank was possible, as no significant signs of slippage were uncovered, and there was no culvert on CHF. The contours and vegetation do suggest a culvert hidden under the Tradescantia on Flame Tree Bank, so we are weeding our way only cautiously in that direction.

On CHF Bank, a large volume of cut CHF wood was laid straight as compactly as possible, and covered with green weed material to assist rotting. The entire CHF plant is extremely toxic, having produced fatalities in both humans and animals, so CHF was moved away from the more accessible areas of the site used by dog-walkers. The hollow stems provide excellent invertebrate habitat, with several ant nests observed. Disturbance of this habitat will be minimised.

Regrowth of CHF and Alocasia is being allowed as shade and habitat around released trees until exotic herbs cover CHF bank. (Exotic herb cover of CHF Bank began in the previously-sprayed kikuyu margin after kikuyu pullback beginning in June 2018, and progressed down the bank after major shrub/vine weed removal in October 2018. Purpletop [Verbena bonariensis] is most abundant.

Other than those areas mentioned above, not a lot of actual weeding has been required. Site work at GG has mainly been of improving access (for current and future weeding) , improving the appearance of the outer margin, and fire hazard prevention. All these aims were met mainly by compacting, piling and suitable disposition of dry woody materials.

There has been no major eruption of weeds other than the expected such as Calystegia, simply being pulled off as it is observed (monitoring has been at least fortnightly, but in practice often several times a week, meaning the Calystegia has not had time to gather much nourishment . If frequent control is continued, perhaps the seasonal growth will not be as rampant next year - to be discovered in due course)

While perusing the exotic herbiage we have plucked out hundreds of Yorkshire fog seedlings while they were small and the ground not yet too dry. Occasionally we have thinned a group of exotic herbs dense enough to suppress native seedlings. In general we have not yet considered it beneficial to remove any annual exotic herbs, as they are providing mini-canopy, moisture retention and erosion control, and suppressing more difficult-to-manage weeds.

In areas without benign exotics, new occurrences of aggressive exotic herb seedlings such as docks and Creeping buttercup continue to be reduced or mulched as convenient.

Tree/shrub weeds

The single mature Chinese privet continued to flower vigorously and then fruit despite through ring-barking of all major branches and trunk bases. Its major branches provided the only canopy at the bottom of the Arena/CHF bank margin, bare after release from honeysuckle, blackberry and Cape Honey Flower. Those branches were also poised to provided many privet seedlings, while the abundant berries on the newly-leafing branches of surviving karamu offer birds food nearby, so reluctantly we sawed far enough through the privet's major branches to allow the weight to pull them to the ground, where we can more easily monitor and control fruit and seedling development.
The Chinese privet, latest intervention: https://inaturalist.nz/observations/19586404

Other tree/shrub weed remnants have required little time, with new growth being briskly leaf-stripped and/or bent/broken, and adjacent natives growing into the released space.

Moth plant seedlings are germinating by the dozen on the lower part of CHF bank, partiularly the canopy margin, where a mature vine was found and removed in Oct 18 and tradescantia was removed in winter. These seedlings are being uprooted where possible but we have seen that they often break off, even when small, and that even the tiniest seedling will regrow from a leafless broken ste. Therefore we are also mulching areas of Moth plant seedling germination with mini-piles of the adjacentTradescantia, both to reduce ongoing germination and to improve soil conditions for future uprooting. we will be interested to see how many Moth plants germinate in the Tradescantia, and to what depth mulched seedlings survive.

Brush wattle seedlings are as numerous as ever, esp. in the lower Arena and adjacent canopy margin, some now reaching c. 30cm hidden mong the wildcarrots and oxtongues, but all easily removed when spotted. Even if a few reach a metre, their stems are easily broken or cut and are not believed to reshoot or sucker.

All other weed management continues much as reported in previous months, with good results: ie diminishing weed numbers found, weeds turning to humus, regrowth and reproduction within expected limits.

Posted on January 23, 2019 01:27 AM by kaipatiki_naturewatch kaipatiki_naturewatch | 0 comments | Leave a comment

January 25, 2019

Changes over time: May 2018 - January 2019

Approximately the same view, from the top of the Arena bank near the small Akeake, downhill to the harakeke on the edge of the canopy below the Arena:
https://inaturalist.nz/observations?order=asc&order_by=observed_on&place_id=128172&project_id=gg-restoration-monitoring-001-arena-lower-left&subview=grid

Posted on January 25, 2019 11:04 AM by kaipatiki_naturewatch kaipatiki_naturewatch | 0 comments | Leave a comment