lördag 4 juni 2011

Matiu/Somes Island - Ekologisk restuarering och ogräs hantering.

Här kommer den efterfrågade artikeln från Wellington botanical society om det arbete som jag är involverad i på Matiu/Somes Island. Jag arbetar för närvarande som Forest Health Monitoring Ranger och som jag skrivit i tidigare inlägg så går jag igenom ön och dess vegetatation, inventerar antalt arter och träd som har planteras tidigare på olika lokaler och "frigör" dessa mer långtsamt växande eller skuggkrävande i första stadiet träd som kohekohe, nikau och piegon wood från mer snabbtväxande sådna som Ngaio. Dvs beskär och öppnar upp överliggande trädkronor för att få mer ljusinsläpp och undvika grenskador iform av vind. Allt för att de ska få en chans att klara sig och konkurransen.
Normalt sett arbetar jag två dagar i veckan ute på ön.

Läs mer nedan.

Från Wellington botanical society, May 2011 Newsletter.

Matiu/Somes Island - restoration Weed management-
Peter Russell, Department of Conservation Revegetation Ranger, has had several contracts since 2008 for pest plant and other weed control on Wellington Harbour’s Matiu/ Somes Island. The contracts have been six-monthly, with six-month gaps in between. He is targeting about 120 species of weeds, including a few that may not be particularly invasive—as a precaution.
Peter’s plan for weed control is two-pronged:
Clean-sweep. This approach is akin to a grid-search, at 2-m intervals, killing all weeds he sees, with a few exceptions. He began at the north end, then the central and eastern areas, all of which were less infested than other areas. He is now working towards the west side, from the north and south ends. He is helped by the Karobusters, a group of skilled volunteers, who run six working bees a year whose main target is karo, Pittosporum crassifolium, a dominant weed tree on the island, often on steep cliffs, in addition to Peter’s work on this weed. Wisely, he does not kill weeds along a track, before the area it traverses is ‘clean-swept’, because that would give a false impression of progress. His preferred weed killer is glyphosate, rather than picloram. He obtained approval to kill karaka.
Rare weeds.
There are over 20 such species which are rare on the island, and which Peter believes can be eliminated. They include Iris foetidissima/stinking iris, Berberis glaucocarpa/barberry, Calystegia silvatica/greater bindweed, Selaginella kraussiana/African club moss, Dipogon lignosus/mile-a-minute, Rubus fruticosus agg./ blackberry, Salpichroa origanifolia/lily of the valley vine. Peter marks isolated populations of these plants with a post and tape, and records their location by GPS so that they can be relocated and checked in future.
Peter Russell records the location of blackberry on Matiu/Somes Island. Photo: Dave Rodgers.
His objective is to systematically eradicate weeds on the island, with the temporary exception of pohutukawa and karaka, which he is removing from all areas, except for a ‘containment zone’ of large trees towards the north end. An example of this task is evident above the road up from the jetty, where he has killed pohutukawa just outside the zone, up to where the road swings south. This is to prevent significant populations of Leucopogon fraseri, manuka and Pimelea prostrata being suppressed. Peter’s work removing pohutukawa has resulted in very few comments from the public who generally understand the need for the work, once he explains the reasons for it. Where pohutukawa, karo, karaka, Pseudopanax hybrids, lacebark (Hoheria populnea) and karaka, have been drilled, poisoned, and left standing, light-loving trees nearby, such as kohekohe, rewarewa and pukatea, are thriving.
One of his first jobs, in 2008, was to destroy potted- up plants such as Hoheria populnea, karaka, Pseudpanax hybrids, and pohutukawa/northern rata hybrids in the nursery. Nowadays, he has to control at least one weed, Cyperus eragrostis, that appears at the base of planted trees, because the seeds of these weeds were in soil in the nursery.
Weeds such as boxthorn, karo and pohutukawa are visible on very steep sites in several areas which have been swept clean of weeds. Peter is trying to secure resources to enable these sites to be weeded, as well as surveyed for any other weeds which may occur on them, such as boneseed and holly-leaved senecio.
Until 1998, large areas were usually planted with hardy, fast-growing, pioneering species, e.g. ngaio, mahoe, taupata. These areas require careful pruning to provide
adequate light levels for future canopy species to thrive, e.g. kohekohe, tawa and podocarps. To avoid the need to prune future plantings after more paddocks are planted, more emphasis will be placed on planting stands of manuka and kanuka. This will also encourage a wider range of species to germinate and thrive.
In 2008, Peter was asked to plan for secondary plantings, i.e. for canopy, sub-canopy and ground-cover species to be planted under earlier plantings. He recommended shade- loving species be planted in the dappled sunlight under those plantings, e.g. kohekohe, climbing rata, ramarama, Leucopogon fasciculatus, Coprosma rhamnoides, Echinopogon ovatus, Uncinia uncinata, Libertia grandifolia, Carex dissita, Asplenium oblongifolium, Pteris tremula. This plan is being trialled at twenty-six sites on Matiu- Somes, two on Mokopuna Island, and two on Makaro/ Ward Island. The sites chosen had little or no veldt grass, were marked with orange flagging tape, and recorded by GPS. This may be the first such trial in New Zealand, but Peter is keen to hear about any similar work with a view to developing best practice.
While traversing areas apparently not surveyed thoroughly by other botanists Peter found the previously unrecorded Astelia fragrans, which had managed to survive the era when goats were on the island.
Years ago, John Sawyer, Department of Conservation, asked that no plants be sent to the island from home nurseries, to eliminate that source of weeds. Recently, however, weeds such as Darwin’s barberry and Himalayan honeysuckle arrived in planter bags containing native plants from commercial and council nurseries. To reduce this problem, Peter avoids obtaining plants from some nurseries, and requires others to grow plants for the island in root-trainers, as they have a small surface area, and to raise plants in shade-houses rather than in the open.
Peter has initiated the drafting of protocols to minimise the biosecurity risks associated with nurseries, and the translocation of plants to islands.
Other points of interest
Kermadec pohutukawa has almost been eliminated. It was recently found wild in Oriental Bay.
Veldt grass colonises some sites under the canopy, where enough light is available. Spraying trials are underway to see if natives can colonise areas previously dominated by this invasive grass.
Tree lucerne is not a concern because it encourages native plants, which then shade it out.
Taupata, cabbage tree and mahoe seedlings occur naturally, and wineberry, titoki and five-finger seedlings are becoming increasingly abundant. Hebe speciosa self-sows occasionally, but will probably be shaded out. One patch of Sophora chathamica, probably introduced by Maori, grows on the east side, and Peter has grown seedlings to bolster that population. S. molloyi, obtained from the South Coast, is to be planted near the wharf where several large pohutukawa have been removed. S. microphylla and other kowhai species also occur on the island.
Dr Leon Perrie, Te Papa, has recorded six forms of kohuhu/Pittosporum tenuifolium on the island, some of which have gone wild.
The Tasmanian relative of ngaio is still present, and appears to be hybridisng with native ngaio.

Joakim Liman, a highly-skilled Swedish volunteer, is systematically ‘releasing’ rare, sun-loving native trees according to a strategy developed by Peter. Unless these trees are rescued, most of them will be suppressed by the faster-growing pioneer plants that dominate the vegetation. Some of the rare trees, which include kohekohe, rimu and totara, are also pruned carefully to encourage vertical growth.

Joakim Liman releases kohekohe. Photo: Peter Russell.
Peter has noted that when boxthorn thickets are destroyed, karo often takes their place. Karobusters then kill the karo, then taupata colonises the sites.
From a 6-m circle around the base of a big karaka near the lighthouse, Peter and volunteers pulled 3000 seedlings and saplings in one day!
BotSoc thanks Peter for taking Chris Horne on a tour of the island, for providing the above information, and answering many questions.

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