Alpine Delights

The family spent a delightful hour on the Dobson Nature Walk in Arthur’s Pass National Park on Wednesday. The track is an easy one, and hiking it quickly takes about 20 minutes. But it’s not a walk you want to do quickly, especially in summer. It winds through alpine and sub-alpine vegetation, including some beautiful tarns, and in summer, so many plants are blooming, it’s hard to take five steps without finding another lovely orchid, daisy, or hebe in bloom.

For me, the best part of the walk is the abundance of sundews in the tarns. As an entomologist, I’m naturally drawn to carnivorous plants like sundews. Sundews catch insects on the sticky hairs you can see glistening in this photo. The hairs are sensitive to both touch and taste, and when they sense a struggling insect, they fold inward to further entangle their prey. Enzymes exuded by the hairs then digest the insect, and the leaf takes up the nutrients in order to grow in the nutrient-poor alpine wetlands. 

These sundews were just beginning to flower—many plants had flower buds, but none had yet opened. The flowers sit above the leaves—an important adaptation, since the plant needs to be pollinated by the very insects it eats.

The alpine summer is short, so when these plants are done flowering, the leaves will slowly shrink into a structure called a hibernaculum that sits near the soil surface and protects the plant through the winter.

Awesome Alpine Plants

Whipcord hebe flowering in the snow

My daughter and I went for a hike on Saturday after being cooped up in the house all day Friday by a rip-roaring southerly storm. The storm lashed us with rain and hail, but in the mountains, it brought snow. Saturday morning, the beech forest at Cragieburn Forest Park was a winter wonderland.

Climbing up out of the forest into the alpine areas, the intensity of the storm was clear—thigh-deep drifts filled the path in some places, while other areas had been blown clear down to the scree. Every tussock had a long train of sculpted snow on its leeward side, so you could almost feel the howling wind and the sting of blowing snow, in spite of it being a clear calm day.

Nestled among the rocks, we found this lovely whipcord hebe, flowering in spite of its slowly melting blanket of snow. And there were other plants peeking out of the snow, clinging to the scree.

Alpine plants are some of the toughest organisms around. They have to cope with intense sun, wide temperature fluctuations, drought, wind, and ice and snow. They have evolved a variety of adaptations in order to combat these dangers.

Short, cushion-shaped growth: A tight ball of branches and leaves resists damage and drying from fierce wind. The pinnacle of this growth form has to be plants in the genus Raoulia. Known as ‘vegetable sheep’, they form hard, tight masses of tightly packed leaves (akin to the texture of a head of cauliflower). Inside the mound, dead plant material builds up around the branches and acts like a sponge, soaking up rain when it’s available. Adventitious roots on the plant’s branches tap into this reservoir of water when the weather is dry.

Long roots: Unstable rocks and shifting scree make it difficult for alpine plants to stay put, and water is often far below the surface. To cope, they have long roots that anchor them deep into the rock. Some are also able to regrow from their roots if the top of the plant is snapped of by rockfall.

Drought-resistant leaves: Many alpine plants have leaves that are fuzzy on the underside, where the stomates (the breathing holes) are located. The hairs trap a layer of calm air against the leaf surface, slowing down water loss from the stomata. Other plants have narrow, vertically-oriented leaves that minimise exposure to the intense alpine sunshine, reducing evaporation.

Sunscreen: A waxy coating on many alpine plant leaves protects against intense sunlight and high temperatures.

Antifreeze: Ice crystals forming inside a living cell break the cell walls and kill it, so organisms living in cold environments have to somehow avoid freezing. Alpine plants protect themselves from freezing by manufacturing antifreeze from proteins in their tissues. The antifreeze prevents ice crystals from forming in the plant’s cells.

Energy conservation: The growing season in alpine areas is short, and nutrients are scarce. Many alpine plants respond by not reproducing every year. Instead of producing low-quality seeds that may not survive, they hoard resources until they have accumulated enough to reproduce successfully.

All these adaptations give most alpine plants a similar look—low, mounded, small-leaved and tough. But one plant in particular stands out as oddly showy and out of place.

Mount Cook buttercup (Ranunculus lyallii)

The Mount Cook buttercup (aka Mount Cook lily), is an unusual alpine plant, in that it has big leaves and large, showy flowers. But even so, it is well-adapted to the alpine environment. Most plants have stomates on the underside of their leaves, because the underside is generally shaded and cooler, leading to less water loss. But in the alpine environment, sun-warmed rocks radiate heat, making the underside of the leaves warmer than the upper side on sunny days. The Mount Cook buttercup and its relatives have evolved stomates on the upper side of the leaves, in addition to the ones on the underside. The stomates on the top open when the underside of the leaf grows too warm.

Kaitorete Spit: An Overlooked Gem

Earlier this week, my daughter and I hiked onto the Banks Peninsula from Birdlings Flat. The walk afforded us gorgeous views of Kaitorete Spit.

Kaitorete Spit is only about 6000 years old, but is an important natural and cultural resource. Te Waihora / Lake Ellesmere, formed by the spit, is home to or visited by 166 species of birds and 43 species of fish which support commercial fisheries, recreational fishing and hunting, and traditional food gathering. In spite of its harsh, exposed environment, Kaitorete Spit is home to a remarkable number of threatened plants and animals, including pīngao (a native sand sedge prized for weaving), a flightless moth, and the katipo spider. A variety of lizards also flourish on the spit. The lake and spit have been important sources of food and fibre for Māori since they arrived in the area. Fragments of the oldest known Māori cloak were uncovered on the spit, dating to around 1500 AD, and many other signs of early Maori use of the spit have also been found there.

In pre-European times, Māori used the spit as a convenient highway as they travelled up and down the island. Unfortunately, the shifting gravel of the spit and the regular opening of the lake to the sea mean the spit isn’t passable in anything but the most capable of four-wheel drive vehicles. Today, travellers make the long trek all around the lake, so our home near the pointy end of the spit is a 40-minute drive from Birdlings Flat, just 25 km away on the fat end of the spit. But I’m happy to leave the spit to foot traffic—it helps protect the unique plants and animals that live there.

On a windy, wet day, Kaitorete Spit is a miserable, exposed place to be, but visit it on a warm sunny day, and you’ll see why it is an overlooked gem.

Mountain neinei

2016-12-28-11-03-04-smMountain neinei (Dracophyllum traversii) is a tree Dr. Seuss would have been proud to call his own. Sparsely branched, with the leaves concentrated in tufts on the ends of the branches and bright red flower spikes on top, it would look right at home in Yertle the Turtle or The Cat in the Hat.

Aside from its goofy look, mountain neinei is an interesting plant. It is endemic to New Zealand (found nowhere else in the world), and inhabits ridgelines from about Arthur’s Pass north. We saw this one (and many others) on the way up Avalanche Peak near Arthur’s Pass last week. Though it is small (no more than 10 metres tall), it can live for up to 600 years, making it New Zealand’s longest-lived small tree.

It’s a useful plant, too. The leaves are used in weaving, the stems have been used to make walking sticks, and there is even an example of a flute made from mountain neinei.

It’s such a neat plant, it makes you want to speak in rhyme.

The ridge was quite steep,
And the day was too hot,
But the neinei were flowering.
We saw quite a lot.

Up rocks we scrambled.
The forest got smaller,
It looked like the top,
But the mountain was taller.

2016-12-28-13-24-57-smHigher and higher
We climbed and we huffed.
Till we reached the peak,
We really were puffed.

Spectacular views
And black jagged rock
Were our reward
For this strenuous walk.