A transect of Stewart Island

For all that Stewart Island is now protected as Rakiura National Park, it wasn’t always so.  Parts were farmed, especially the area around and inland from Mason Bay on the island’s west coast.  Here history (especially fire), poor drainage, and soil fertility influence the vegetation (Wilson 1986). 

It was my privilege to walk twice across the island on successive days, each time with half the Lewis & Clark students (one student's blog here).  This North-West Circuit Track is about 15 km, but not much up and down, and passes through several distinct plant communities.  We were there in an unprecedented dry spell when it would have been possible and comfortable to walk the track in sneakers.

Our route (map from Land Information New Zealand)

The flight in.

We had to make an early morning start to catch low tide for landing on the beach.  The plane takes off from Halfmoon Bay and flies over Patterson Inlet to the tidal flats of Freshwater River (where our track ended each afternoon) and across the Scott Burn catchment traversed by the track, which was evident from the air.  The end of the short flight is a steep descent over the extensive sand dune complex, a tight turn over the surf, and a thrilling landing on the wet sand.

Patterson Inlet

Freshwater River

The track in the Scott's Burn area

Wheels almost down on the sand

We were there at sunrise.  It was cool in the shadow of the dunes, and there were meandering kiwi tracks in the wet sand.  On the second day most of us were rewarded with a glimpse of a kiwi, following a bit of a trail through the marram grass.

Kiwi tracks, Mason Bay

 The dunes

The sand dune complex at Mason Bay follows the length of the beach and in places extends for a kilometre inland.  The aptly, if unimaginatively, named Big Sandhill is a prominent feature.  We followed Duck Creek inland through the sandhills and the vegetation got progressively more complex as we left the salt spray and wind behind, entering older more stable dunes with a little soil development.

Big Sandhill

Introduced marram grass (Ammophila arenaria) dominates the seaward face and the dunes inland.  It is a strong sand-binder—that’s probably why it was brought here—and makes steep-faced dunes, far steeper than the native sedge pingau (Ficinia spiralis), which is still present in a few sites.  Not far inland a few natives appear: woollyhead (Craspedia uniflora), shore coprosma (Coprosma acerosa), Hydocotyle novae-zelandiae, and shore daphne (Pimelea lyallii).

Woollyhead, Craspedia uniflora

Shore coprosma, Coprosma acerosa

Pimelea lyallii, shore daphne

Hydrocotyle novae-zelandiae

Small damp patches between the sandhills support tiny herbs such as Limosella and stemless buttercup (Ranunculus acaulis).

Coastal low forest

Manuka, Leptospermum scoparium.

On old stabilised sand near the Mason Bay Hut, we first entered the coastal low forest, with a dense canopy of manuka (Leptospermum scoparium) so thick that little light penetrated beneath.  As a result there’s little understory and this forest would be a good location for filming the Mirkwood scenes for The Hobbit.  Beside the track we saw a number of other plants though, Fuchsia excorticata with a few dried-up flowers, mutton-bird scrub (Brachyglottis rotundifolia), lancewood (Pseudopanax crassifolius) both juvenile and adult, putaputaweta (Carpodetus serratus), matipo (Myrsine australis) and young rimu (Dacrydium cupressinum). 

Mingimingi, Leptecophylla juniperina

Mingimingi (Leptecophylla juniperina) is occasional here, commoner later in the walk, and I thought it looked a bit brighter green, more open in habit, and perhaps pricklier than on the mainland.

Red tussockland

Beyond the farm’s homestead, now a heritage building, the track crosses a large red tussock grassland.  Red tussock (Chionochloa rubra) would have been repeatedly burnt in the farming days to encourage fresh edible young growth.  In the wetter patches, New Zealand flax (Phormium tenax) and a fern, Gleichenia dicarpa, flourish.  Beside the track, blue sunbonnet orchids were opening as the sun’s rays reached them.  We saw, and tasted, native mint (Mentha cunninghamii) here too.

Red tussock (Chionochloa rubra) with Gleichenia dicarpa

Sunbonnet orchid, Thelymitra venosa

Native mint, Mentha cunninghamii

Two small native sundews (Drosera spathulata, D. binata) and a bladderwort (Utricularia) were features of this tussockland.  All are insectivorous, able to gain their nitrogen supply from trapped insects in acid sterile bog soils.  Although all living things must have nitrogen for building proteins and amino acids, and although nitrogen is a common element making up 80% of the atmosphere, no eukaryotes (plants, animals, fungi, and protists) have the ability to use atmospheric nitrogen directly without the help of bacteria.  Surely that’s not an intelligent design.

Forked sundew, Drosera binata

Bladderwort, Utricularia sp.

The swamp

In the middle of the track is a large swamp or wetland, and thanks to the Department of Conservation there’s a kilometre or two of boardwalk to cross it on.  It’s deep and dominated by monocots: sedges and rushes and their ilk, like Leptocarpus similis (drier sites), Baumea rubiginosa (wetter sites), Juncus bulbosus, and Empodisma minus, but with Potamogeton in standing water, which is often stained with tannins.  

The boardwalk

Potamogeton in stained standing water

 In higher and drier patches, manuka, Coprosma propinqua, and toetoe (Austroderia richardii) have established.  In other places the manuka has succumbed to poor drainage, leaving dead sticks poking skyward. 

Plumes of toetoe (Austroderia richardii) with NZ flax (Phormium tenax) and coprosma.

Regenerating forest

From the wetland to Freshwater Hut the track first follows the Scott Burn, which here looks to have been dug as a ditch at some time in the past because it follows a remarkably straight route.  Tall manuka shelters developing young podocarps, rimu (Dacrydium cupressinum), thin-barked totara (Podocarpus cunninghamii), and miro (Prumnopitys ferruginea).  In the understory, mingimingi, astelia, and coprosmas are flourishing as the manuka canopy opens up with age.

Astelia, Leptecophylla, and Blechnum under the manuka canopy at the Scott's Burn bridge

A robin joined us for lunch, gaining access to insects in the leaf litter we had disturbed.

After the Scott Burn bridge the forest gives way to scrubby stuff, perhaps the most floristically diverse part of the track.  The scrub is manuka again, with Dracophyllum longifolium and mingimingi; fire and poor drainage are the factors that explain its presence here. 

Native St John's wort, Hypericum sp.

Pentachondra pumila, a small heath

Coral lichen, Cladia retipora.  Brittle and white when dry, it becomes rubbery and slightly greenish when wetted, with its algal cells immediately starting to photosynthesise.

A clubmoss, Lycopodium scariosum.  The carbon that relatives of this plant fixed over millions of years during the Carboniferous formed the coal deposits of Europe and N. America.  Its rapid burning over the last two centuries fueled the Industrial Revolution and drives anthropogenic global warming.

Wet patches have Sphagnum bog.  Sphagnum’s a remarkable plant.  It’s a moss, but represents an early-diverging lineage among the mosses.  Its main feature is the huge empty cells (leucocytes) in its leaves, which can absorb 25 times their weight of water.  Thus dried Sphagnum is harvested for use in horticulture, making natural diapers and sanitary napkins, and was even used for wound dressings in World War 1.  Environmentally, it can raise the water table of a bog, leading to domed bogs like low hills.

Sphagnum bog with dead standing manuka

Sphagnum stems, called gametophores

Forked sundew, Drosera binata, flowering in the Sphagnum.

The end

The track ends at Freshwater Hut.  The river here is tidal, but barely brackish this far up.  On the first day it was hot and sunny (28 degrees in Invercargill) and we had drunk all our water before we got here.  The sweet water in the hut’s tank was getting low, and we almost could have drunk it dry. 

Lewis & Clark students relax at Freshwater Hut.

Stewart Island water taxi on Freshwater River.

The water taxi ride home was a pleasure for those that stayed awake, our driver stopped to show us a group of feeding little blue penguins in Patterson Inlet.  And the evening swim at Halfmoon Bay’s Bathing Beach was a perfect and refreshing end to the day.

Kiwi, Mason Bay (I should stick to photographing plants, but this was the highlight and I couldn't leave it out)

References.

Wilson, H. D. 1986: Plant communities of Stewart Island (New Zealand).  New Zealand Journal of Botany Supplement: 1–80.

Veronica parviflora

One of the ways that many New Zealand veronicas differ from their nevertheless close northern hemisphere relatives is in woodiness; this is especially true of the hebes and less so for the speedwell hebes (see here for an explanation of why hebes are now classified in Veronica).  A few hebes are small trees, including Veronica parviflora, one of the two species that's native to the Wellington peninsula (the other is V. stricta; there's an old record of V. lanceolata from the Kaiwharawhara Stream, but it hasn't been seen there in  a long time).  The tree veronicas are big enough to be included in the spectacular new book on New Zealand trees by John Dawson and Rob Lucas.


V. parviflora comes into flower about this time of year.  There are good populations on hills near the road to the Happy Valley Landfill, and about halfway between Featherston and the Rimutaka Hill summit V. parviflora forms a low forest canopy.

The name parviflora means small flower.  The flowers are small, but there are so many of them and so tightly packed that they nevertheless make quite a show.  Almost every insect visits on warm days: flies (both syrphids and tachinids), small native bees, butterflies, honeybees, bumblebees, and beetles.

Here's a small native solitary bee visiting flowers in my garden:

The plants have a neat compact rounded form when they're young, and form small trees 3–4m tall when they're mature.  Their trunks can be up to 20 cm diameter, big enough to make things with.

This Veronica parviflora bowl is a treasured possession; it was a gift from a PhD student.

Port William, Stewart Island.

On the first two days we were on Stewart Island, I led walks to or from Port William. The aim was for the Lewis & Clark College students to become familiar with the main plant species on the island and with some of the vegetation types and processes.

The jetty at Port William.

It's about a 10 km walk, a bit up and down in places but following the coast with a lovely stage along the strand at Maori Beach.

Maori Beach, Stewart Island

At the end of Maori Beach, a suspension bridge gives access to the rest of the track, right by a rata tree.

The vegetation is rata-kamahi forest with emergent podocarps (rimu mostly and some miro).

On the exposed coasts a band of muttonbird scrub (Brachyglottis rotundifolia) and coastal hebe (Veronica elliptica) form the edge to the forest.  These are resistant to salt spray.

In places, the track overlooks idyllic scenes, with crystal clear water and small islands.

At the Port William end, there are orchids (Dendrobium cunninghamii) and a mistletoe in a Coprosma bush.

Orchid, Dendrobium cunninghamii (Some people prefer the name Winika cunninghamii)

Mistletoe, Peraxilla sp., on Coprosma.

Much of the forest has been logged in the past, and some of the regeneration produces pole stands of kamahi and small podocarps of equal height, whereas the old growth forest at the Port William end of the track has emergent large podocarps (rimu and miro) over a canopy of kamahi with a putaputaweta understorey.

Two more fossils, Bannockburn.

In a previous post, I wrote about fossils from Bannockburn in Central Otago.  We went back there next day and found these:

Fern leaf fossil, Bannockburn

I'm guessing this is a kauri (Agathis) or Araucaria cone scale.

I also promised references.  You'll find an entry to Daphne Lee's publications here.

Plant life in Doubtful Sound

The second adventure in the Lewis & Clark College 2012 New Zealand course was a cruise through Doubtful Sound on the Fiordland Navigator.  Learning objectives included (1) the influence of fresh water in the fjord, especially since the outflow of the Manapouri Power Station brings additional large amounts, (2) bird recognition, and (3) an overview of the vegetation changes and introduction to key plant species.

We had permits to take small bottom samples with a grabber under supervision of Dr Lucy Jack from Otago University, who also had brought a remote-controlled mini submarine with a camera for viewing marine life.  The night before, Lucy outlined the features of the environment and some of the research findings of the team she works with.

The bird life was evident from the ship and also from kayaks and tender boats.  Among others we saw variable oystercatchers (with chick), kaka, tomtits, shags, and a mollymawk at the fjord entrance.

Doubtful Sound from Willmot Pass

The plant life changes dramatically from the head of the catchment at Willmot Pass to the open coasts.  The road at the pass is close to timberline which is about half-way up the mountains there.  Above timberline snow tussock and alpine plants predominate, but the forest at the pass is dominated by silver beech, Nothofagus (sect. Lophozonia) menziesii, with ribbonwood (Hoheria lyallii) on slips and roadsides.  This is the zone of highest rainfall, which suits silver beech, although we saw it in dry conditions.

Black beech, Nothofagus solandri.

Black beech, Nothofagus (sect. Fuscospora) solandri, is dominant at sea level in the inner fjord.  Other plants here include fuchsia (Fuchsia excorticata), pate (Schefflera digitata), and putaputaweta (Carpodetus serratus).  It was a nice surprise to see Breaksea Girl moored here; I went to Campbell Island on her in 2004.

Putaputaweta, Carpodetus serratus.

Breaksea Girl

In the outer fjord, and especially on the shores of Secretary Island, rimu (Dacrydium cupressinum) is more common, along with yellow-silver pine (Lepidothamnus intermedius).  Other podocarps there include miro (Prumnopitys ferrugineus), tanekaha (Phyllocladus alpinus), and totara (Podocarpus totara).  Black beech is abundant here too.  Rata was also common, a few still in flower.

Southern rata, Metrosideros umbellata, in flower.

Outside the fjord, rocky coasts are exposed to the full force of the westerlies and the salt spray they carry.  Veronica (sect. Hebe) elliptica and Brachyglottis rotundifolia dominate the coastal scrub.

Salt-tolerant coastal scrub on one of the islands that guard the fjord entrance

The huge landslide below was caused by the 2003 Secretary Island earthquake (M 7.1).

A prominent plant on the rocky shores of the fjord is Olearia oporina, which was flowering freely.  

Olearia oporina

Tree branches overhanging the water were heavy with epiphytes, including the orchid Dendrobium cunninghamii flowering freely.

Epiphytes on beech.

Overnight we were treated to heavy rain, so the waterfalls were in full flow next morning as it cleared. 

The second night was clear and many students stayed on deck until midnight to watch the Southern Cross and other unfamiliar stars rise above the surrounding peaks.

The trip was an excellent introduction to temperate New Zealand rain forests, sandwiched between the dry lands of Central Otago and the beech-free zone on Stewart Island.  Access by land to these extreme forests is impossible, certainly in the time we had available.  The crew of Fiordland Navigator gave the students and staff an unparalleled wildlife trip.