Botanist Newsletter
Issue No. 35, 21 Aug 2002 - 20 Aug 2003
Contents
Fire in the McLeans Grasslands
In February this year a fire started in the McLeans Grassland area at
Miners Rd. The fire affected ~190 ha of grassland and some pine shelterbelts.
Part of the site effected was Ecological Heritage Site 1.29. The site is
a remnant of dry plains grassland, and it includes scattered kowhai trees,
native shrubs (prostrate kowhai, porcupine shrubs, Olearia sp. nov.,
prostrate broom, makaka), native grasses, herbs, mosses, lichens and orchids.
Recovery of much of the vegetation is expected, with significant losses
limited mainly to some of the shrubs (prostrate kowhai, porcupine shrub).
Permanent transects are in place in the grassland, and individual kowhai
and shrubs are being monitored, to determine their recovery.
A likely effect of the raised nutrient status that typically accompanies
fires, is an increase in exotic species, including shrub weeds. This will
also be monitored and additional weed control is likely to be required.
Of particular concern was the potential impact of the fire on the population
of a locally endemic threatened shrub - Olearia sp. nov. Fortunately
only one plant was effected, and despite the plant catching fire and losing
all of its leaves, new shoots are now appearing. If the fire had gone
east or further south, the loss of Olearia sp. nov. could have
been disastrous. |
One of the burnt kowhai
|
Grassland Survey
Baseline vegetation data was collected last summer for the dry plains
grassland. Permanent transects have been established, in co-operation
with Environment Canterbury, to enable us to assess the state of the grasslands.
In the future these transects will enable us to assess the effect of management
practices on the composition of the grasslands.
26 transects were recorded, with the assistance of a student from Canterbury
University, using the Scott height-frequency method. This method gives
information on species composition and also on biomass.
Monitoring the grasslands fulfils part of the councils' requirement to
monitor significant indigenous vegetation, under both the Resource Management
Act and the City Plan.
|
Making height-frequency measurements amongst matagouri
Dan at one of the transects, on a stopbank |
Plains Wildfire Threat Analysis
An evaluation of sites on part of the plains within the city boundary
was carried out to assess their botanical values and prioritise them for
protection in case of a fire. This was done, as part of a "Wildfire Threat
Analysis" being undertaken by the CCC.
The National Rural Fire Authority has devised a system that takes into
account risk (ignition potential), hazard (potential fire behaviour) and
values (values threatened) for an area, to derive a wildfire threat analysis
for that area. The botanical assessment of sites will be incorporated
into the 'values' part of the model.
Of particular note was that the area has five sites that were assessed
as "nationally important" using the criteria provided. This is due to
the presence of a locally endemic threatened species, Olearia sp.
nov.
Other sites scored highly because they support lowland dry plains grassland,
which is a nationally rare vegetation type, and/or they support nationally rare
species (Desmochoenus spiralis, Luzula celata, Muehlenbeckia
ephedroides). There were also quite a few sites with locally rare species.
Otukaikino Survey
A survey of botanical values in the Otukaikino project area was carried
out late last year by Carol Jensen. Of the 41 sites identified in 1993
as having some natural values, 21 of them had no or few natural remaining
in 2002.
Worst effected were grassland sites with 16 of the 21 sites lost. Grasslands
are amongst the most difficult types of vegetation to restore. Hence the
protection of the remaining sites is particularly critical.
The 2002 survey covered the area in more detail than the 1993 survey, and so
some additional sites were also found.
Nationally Threatened Plants in Christchurch
The recently updated list of threatened species published by the Department
of Conservation was searched to find which of the vascular plant species
listed as threatened taxa had been recorded in Christchurch. Of the taxa
listed in the December 2002 version of the list , 31 nationally threatened
species were found for which we have at least one record in Christchurch.
This is just under 8% of all the native species we have recorded growing
naturally in Christchurch. A couple of the records need confirmation, but
nevertheless this is a significant number of species in an urban area. |
NZ musk, a threatened species |
Biodiversity Strategy
The CCC is currently writing a Biodiversity Strategy for the city, in consultation
with various groups. A draft is expected to be available to go out to the public
for comment in June 2004. Some information is already available on the Biodiversity
pages of the CCC web site.
Clare Park
A storm water retention basin has been proposed for part of Clare Park.
The 1856 'black maps' for the area indicate swamp vegetation was present
in this general area in the past (tussocks, raupo, flax), as do the underlying
soils and the physical character of the site. Currently the site is highly
modified, and it is dominated by exotic species, including some very weedy
ones.
It is likely that construction of a retention basin and more naturalised
waterways will significantly improve the botanical value of the site,
especially if some weed control and native plantings accompany it. A weed
plan has been written for the site, focusing on weedy species with the
potential to spread elsewhere (grey willow, blackberry, hawthorn, broom,
gorse, elder). |
Exotic grasses and willows dominating Clare Park |
Styx Mill Weed Plan
A weed plan has been written for Styx Mill Reserve. This breaks the site
down into 36 management units with 25 weed species present in at least
one of those units. The order of priority for the work takes into account
factors such as the value of the habitat, the 'weediness' of the species,
whether eradication is possible, and any legal requirements for control.
Particularly problematic at the site, as with many Christchurch wetlands,
are grey willow and grasses.
A couple of species have been targeted for eradication at the site; old
mans beard, barberry, hawthorn and hyssop loosestrife. There are only
fairly small amounts of these species present at the site, so eradication
seems feasible. The hyssop loosestrife is closely related to purple loosestrife,
and since there is only one small patch, we decided it is prudent to try
and eradicate it, to prevent possible future problems. |
Willows in Styx Mill Reserve |
Predator-proof Fence for Styx Mill Reserve
As part of the land use consent granted to the developer of Northwood
subdivision, there is a requirement to construct a predator-proof fence
between the subdivision and Styx Mill Reserve. The council is investigating
the possibility of constructing additional fencing to enclose the lower
(downstream) approximately 1/3rd of the reserve.
Ultimately a predator-proof fence would enable the re-introduction of
some locally extinct bird species, as well as protecting the existing
ecological values of the site against increasing urbanisation that is
occurring nearby.
Egeria
To date, the council has been successful in its aim of attaining a 'high level
of control' for the population of egeria (an aquatic weed) in the Avon River.
The most recent survey by NIWA did not find any plants. While this does not
necessarily mean that the species has been eradicated, it does mean a high level
of control has been achieved. Our primary goal was to ensure that the number
and size of plants was kept so low that it was unlikely that pieces would be
spread to other locations.
Monitoring, and control where required, will ensure that a high level
of control is maintained.
Lagarosiphon
Unfortunately another aquatic weed has been making an appearance in Christchurch
with Lagarosiphon now know to be present at several sites within the city
(Bells Creek, both lakes at Rotokohatu). Control is being implemented at
these sites.
Weed of the Month
Monthly weed identification sheets are now being prepared jointly by
DoC, ECan and CCC. They are intended primarily for use by field staff,
to raise awareness about the weeds in Canterbury. The sheets include colour
photographs of each species along with a description of their identification
features (using non-technical language), and how to tell them from similar
looking species.
The current and archived ‘weed
of the month’ sheets are available in the Canterbury Weed Guide on
the Internet, and can be printed as required.
Species featured to date are Chilean
mayten, Darwins
barberry, egeria,
hawthorn, sycamore,
banana passionfruit and northern banana passionfruit, Chilean
flamecreeper, Japanese
honeysuckle, African
feather grass, and purple
loosestrife.
|
'Weed of the Month' sheet on Darwins barberry |
Canterbury Weed Guide
Information on cape
daisy (Arctotheca calendula), beggars
tick (Bidens frondosa), Chilean
mayten (Maytenus boaria) and recognising female
grey willow (Salix cinerea) have been added to the Canterbury
Weed Guide on-line. The guide now covers 44 weed species.
Ecological Heritage Site 5.01 (Brooklands
Lagoon & Styx River mouth)
A retrospective consent was made to the City Council to establish a depot
for the storage of contractors machinery and material on Lower Styx Rd.
About 2/3rd of the applicants site is within Ecological Heritage Site
(EHS) 5.01. Unfortunately it was found that the rules protecting EHS 5.01,
limiting vegetation removal and planting exotic species, don't apply to
this part because of its particular zoning.
The vegetation on the applicants’ property that is within the Ecological
Heritage Site is a mosaic of reed-rush wetland, areas of salt meadow,
drains and low sand dunes. Native species present include sea rush and
low growing salt meadow species such as glasswort, salt grass, bachelors
button and remuremu.
Much of the part of the applicants’ site that is within the Ecological
Heritage Site has been ripped and planted in pines. The pines will be
detrimental to the remnant salt marsh as the trees will alter the habitat
of the site, particularly through changing the site drainage and creating
shade
The consent for the depot was declined (for other reasons), but EHS 5.01
remains unprotected at this site.
|
Salt marsh of sea rush, glasswort, salt grass etc. in EHS 5.01 |
Bexley Wetland
At the end of last year a commissioner heard a Resource Consent application
by the City Council to Environment Canterbury to allow some earthworks
in Bexley Wetland. The wetland is at the mouth of the Avon River and includes
an area formerly used as a scrapyard, which consequently has areas of
contaminated soil. The City Council proposed shifting the contaminated
material, within the site, to an existing raised area of fill, capping
it and planting of the fill area. The excavated area would then be re-contoured
to provide good bird habitat, through the construction of shallow pools
and islands.
The City Council was granted consent, with some conditions imposed to
ensure any potential environmental damage is minimised. Part of the work
has now commenced, although we are now waiting for a consent from the
City Council before the project can be completed.
|
A freshwater part of Bexley Wetland |
Kennedys Bush Subdivision
An assessment was made of the botanical values of the area held by Kennedys
Bush Development Ltd., where a zone change to allow subdivision is proposed.
The area that is proposed to change to council control as a form of environmental
compensation was also assessed.
From a botanical point of view, the proposed zone changes to allow subdivision
apply to areas that already have low botanical value and so the proposed
change in land use will have minimal effect on these. However vesting
of the environment al compensation area combined with changes in management,
and planting of indigenous vegetation in the proposed reserve area around
the subdivision, are expected to significantly increase the botanical
values of the area overall. The case is yet to be heard by the Environment
Court.
Ocean Outfall
In October 2002, Environment Canterbury granted consent to the City Council
to discharge wastewater into the estuary for another five years only.
Among the long-term solutions being investigated is piping the treated
water out to the ocean.
A botanical assessment was carried out for three potential routes; Bridge
St, Beatty St and Jellicoe St. Of the three options, the Jellicoe St route
is preferred from a botanical point of view. The Jellicoe St route would
cause the least disturbance to marsh vegetation. Although it would mean
loss of some of the threatened sedge pingao, the patch present is not
a natural remnant and we know that it is feasible to restore it, to mitigate
that loss.
Other possible mitigation measures include marsh restoration, establishment
of ngaio and other coastal tree and shrubs species, and replanting on
the foreshore.
Many factors are being assessed in deciding what solution to pursue,
and public consultation closes on October 7. See the City Council web
site for further
information.
|
An area of salt marsh in the Avon-Heathcote Estuary, that one of the proposed
routes would go through. |
Rocky Bluffs on the Port Hills
With the co-operation of some local climbers, a number of native plants
on climbing routes in the Heathcote Valley have been labeled by City Council
rangers. This is being done to inform rock climbers using the site about
the values of the vegetation in the area. In particular, the rock faces
support a number of locally endemic species (e.g. Heliohebe lavaudiana),
which we hope to discourage the climbers from 'cleaning out' of their climbing
routes. |
A labeled plant of NZ linen flax ( Linum monogynum) |
Herbarium
The backlog of samples is steadily being converted into mounted specimens,
with 450 processed to date. The collection is used for reference, to help with
plant identification and as teaching materials.
Pest Seminar
A seminar on pests was presented to the Parks, Gardens and Waterways
committee in August. The aim was to inform councilors about some of the
current invasive species issues and what is being done about them. Staff
from the Department of Conservation and Environment Canterbury also contributed
to the seminar (Ngai Tahu were invited, but were unable to make that date).
The seminar highlighted some of the current and potential pest problems
in the city, and the co-operative work that is underway to control them.
Recent Reports
Copies of the following reports are available on request.
- McCombsK (2002) Botanical survey of part of Clare Park. CCCECO
02/07
- McCombs K (2002) Botanical assessment of 944 Lower Styx Rd.
CCCECO 02/10
- Meurk C (2002) Notes on Recent Attrition of Biodiversity on the
Canterbury Plains. CCCECO 02/11
- McCombs K (2002) Botanical values of Styx Mill Reserve. CCCECO
02/12
- McCombs K (2003) Effect of a recent fire on the vegetation of a
remnant of dry plains grassland/woodland. CCCECO 03/01
- McCombs K (2003) Botanical assessment of Kennedys Bush Development
Ltd site. CCCECO 03/02.
- McCombs K (2003) Brooklands Lagoon and Styx River mouth. CCCECO
03/04
- McCombs K (2003) Estuary margin and foreshore vegetation issues
relevant to the ocean outfall pipeline routes. CCCECO 03/05.
- McCombs K (2003) Plains wildfire threat analysis - botanical values.
CCCECO 03/06.
- McCombs K (2003) Nationally threatened plants in Christchurch -
an overview. CCCECO 03/07.
- McCombsK (2003) Weed plan for part of Clare Park. CCCECO 03/08
- McMurtrie SA, Taylor MJ (2003) Ecological assessment of the Avon
River Mainstem, from Fendalton Road to Fitzgerald Avenue. EOS Ecology
and Aquatic Ecology Limited.
- O’Brien LK (2003) Developing the freshwater fauna and flora in
Okeover Stream: discussion and proposals. CCC0503.
- Trangmar B (2003) Soil Conservation Guidelines for the Port Hills.
Landcare Research Contract Report: LC0203/111
The Return of the Godwits
(Andrew Crossland)
The arrival of spring is marked by many different events - the first
appearance of daffodils, the first run of the whitebait, the first whine
of law-mowers on a Sunday afternoon following the first spurt of grass
growth. On Christchurch's estuaries one definite indicator of spring is
the return of the Godwits and other migratory birds, following their long
migration of 14,000+ kilometres from Siberia and Alaska.
Most years the first Godwits return in the 3rd week of September, usually
about the 23rd. This year they have returned a little earlier. Reports
of new arrivals began to come in from the north of the North island and
the Nelson area from about 10 September but they hadn't yet arrived in
Christchurch. Councilor Chrissie Williams went jogging around Southshore
Spit on 15 September but reported no sign of them. At High tide on 18
September however, the first flocks had definitely arrived and made their
presence very obvious by feeding voraciously in knee deep-water over high
water while the over-wintering Godwits, Oystercatchers, Stilts, Spoonbills
and other birds nearby, slept quietly. 484 Godwits were counted, up from
the 200 birds (mainly juveniles) that had remained on the estuary over
winter. A check the same day at Brooklands Lagoon found 29 Godwits - also
busily feeding. None had been present at Brooklands over winter. |
Bar-tailed Godwits and 1 Asiatic Black-tailed Godwit (the browner bird
in the centre walking from left to right). While 100,000 Bar-tailed Godwits
visit NZ every year from breeding grounds in Alaska and Siberia, usually
less than 10 Asiatic Black-tails reach this country. They breed from Manchuria
across Eurasia and are regular visitors to the Avon-Heathcote Estuary
|
| Godwit numbers will increase rapidly over late September and October, increasing
by as many as 100 birds/day as the migrants arrive. Peak numbers will be reached
by November/December with 1700 - 2300 present on the Avon-Heathcote Estuary
and 150 - 250 at Brooklands Lagoon. Another 350 - 500 spend summer on the mudflats
in Lyttelton Harbour, but curiously none go to Akaroa Harbour. With the Godwits
come smaller numbers of other Northern Hemisphere migratory birds - Far-eastern
Curlew, Asiatic Whimbrel, Red Knot, Turnstone, Siberian Tattler, Arctic Skua,
Pomarine Skua, Little Tern, and occasionally much rarer species, such as the
Lesser Yellowlegs, an Alaskan wader sighted at Charlesworth Wetland last October,
thousands of kilometres off course from its usual habitat in Chile and Argentina.
Ongoing and proposed work by the City Council in enhancing and developing tidal
wetlands around the Estuary and possibly Brooklands Lagoon is expected to increase
the attractiveness of these areas to migratory birds. Most migratory birds that
currently visit Christchurch estuaries are those that prefer soft to firm mud
or sandy habitats. Wetland enhancement projects are restoring different types
of habitat that have historically been lost to reclamation or degraded in some
way. These habitats include salt meadows, salt marshes, shallow scrapes and
brackish pools. Such habitats are expected to attract migratory species such
as smaller sandpipers and plovers, as well as provide nesting habitat for resident
native birds including Pied Stilt and Banded Dotterel.
|
Godwits at Southshore Spit, just prior to an evening migratory departure
in March. |
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