New Zealand Field Trips September 2011

[David Lyttle]

Last Thursday I attended a Department of Conservation open day at Springvale Scientific reserve near Alexandra. The reserve is highly modified which is an unusual situation for a scientific reserve but contains some unique plants that are extremely rare. At one stage the area was occupied by a huge lake ( back in the Tertiary - teeming with crocodiles. Crocodiles are not a problem these days - the place is now teeming with rabbits). There was deposition of sediments in the lake that were high in salts weathered out of the rocks from which they were derived. In the quaternary these sediments were capped by gravels eroded from the surrounding mountains. The area has been worked for gold by sluicing and the salt bearing sediments exposed, The soil is saline and very infertile and supports a unique community of native plans dominated by ephemeral spring annuals, (dominated is perhaps not the corrrect word as the annuals are able to persist in the infertile, saline soil and not be overwhelmed by exotic grasses and weeds.)

1. Springvale site -general view.

2. Looking across to the Old Man Range from the Sprinvale reserve.

3. Looking across the site showing the extent of the gold workings. The original ground surface is on the terrace at the top of the photo.

4. Exposed cross-section of site showing gravel cap above finer silty lake sediments.

5. Remains of gravel layer left after sluicing. The bushes are the exotic Rosa rubiginosa (briar rose). It is more or less the only woody species present on the site.

6. A sarsen stone (or chinaman). These hard stones are quartz sandstone cemented with silica. The grass ar the base of the stone is an endemic Ryditosperma species also now very rare.

7. The mousetail Myosurus minimus subsp. novae-zelandiae, a tiny annual buttercup.

8, 9. Another tiny annual buttercup Ceratocephala pungens. Before human occupation these spring annuals were so abundant they were grazed on by moas. (moa coproliths are full of the remains of these plants)

10. A line up of spring annuals. From left to right, Myosurus minimus subsp. novae-zelandiae, Ceratocephala pungens and the tiny forget-me-not, Myosotis brevis ( formerly Myosotis pygamea var minutiflora).

[David Lyttle]

More plants

1. Raoulia australis

2. Atriplex buchananii. This is a a salt tolerant species that is found on exposed coastal headlands and less commonly on inland saline sites.

3, 4. The critically endangered cress Lepidium kirkii. This species is found only on these saline sites and is endangered because of the loss of these soils to agriculture ie by cultivation and irrigation. The taproot of this plant can be up to a metre deep.

[Hoy]

A very interesting thread, David!
Your first pictures from Mihiwaka show a homely landscape but those from Springvale show something totally different from anything here.

Speaking of exotics - here Sitka Spruce (Picea sitchensis), Sycamore (Acer pseudoplatanus) and Western Hemloch (Tsuga heterophylla) have been used as forest trees and now threaten to cover the heathland completely. The heath is manmade though, used as pastures, grazed and burned during 5000 years or more.

[David Lyttle]

Hello Trond,

I was under the impression Acer pseudoplatanus was a native European species. It tends to be weedy here too but the timber is never used for anything. We have problems here with conifers invading the native tussock grassland. The species that causes the most problems is lodgepole pine (Pinus contorta) but Pinus radiata and Douglas fir (Pseudotsuga menzeisii) which are the backbone of our timber industry have the potential to cause problems as well. I remember attending a lecture by a countryman of yours who said the treeline in Norway was moving north and upslope in response to climatic warming. From memory I think he was talking about birches and willows.

The Ryditosperma species growing at the base of the sarsen stone is Rytidosperma merum.

[Hoy]

David, although Acer pseudoplatanus is a European species it is not a Norwegian. It has been used a lot as a garden and park tree and has spread to all kind of habitats at the west coast especially. Acer platanoides is a native species though.

The treeline is moving upslope, yes, and that is at least two reasons for that. Longer and warmer growing season is one but the more important is lack of grazing animals and use of wood as firewood. The old way of "sætring" (keeping all kind of grazing animals on summer pastures high up in the mountains in the summer and making cheese of the milk) is almost history only. The mountain birch (Betula pubescens ssp. czerepanovii) is common but also spruce (Picea abies) and pine (Pinus sylvestris) go as high as the birch. Where I spend time in summer it is some small pines which grow almost at the highest summit (1212m). The spruce is a "newcomer" in Southern Norway, expanding from Sweden and still spreading westwards through the valleys.

Pinus contorta and Pseudotsuga menziesii is also much used as forest trees here but they haven't spread much yet.

[Tim Ingram]

This is the most fascinating thread and discussion that puts the landscape into a historical perspective, and it is very interesting to compare the behaviour of plants in quite different parts of the world. Even in one's own garden, after many years of working and observation, one gains a small scale vision of ecology and the way plants grow over time. It is even more interesting to hear about the wider scale landscape. Where else would one hear about the coproliths of moas!!

[David Lyttle]

Tim,

I have just located the paper on the moa coproliths to support my throw away line. It seem that the seeds of Myosurus and Ceratosephala were dispersed by moas browsing on the foliage of these tiny herbs. Lacking a suitable browser/disperser these annuals are now very rare. The post human modification of the landscape by goldmining has provided a suitable habitat albeit in restricted areas for these plants which were once a lot more common than they are now.

Trond,

Your comments on cultural landscapes and "saetring" has interesting parallels in this country. In the drier more arid inland regions of the South Island sheep are pushed up into the mountains to graze on the snow tussock grassland. In the past the tussocks have been burnt to encourage new growth which is more palatable to the stock. In the long term this practise has proved to be unsustainable as the original vegetation cover has been removed and replaced by exotic weeds in the most degraded areas. Hieracium pilosella and Hieracium lepidulum are particularly problematic(that is in addition to invasion by exotic conifers). In effect European cultural practise has not translated particularly well to a totally different ecosystem. After 150 years of farming and pre-european Maori fires these landscapes have become highly modified to the extent that we can now only speculate on what was present prior to human settlement.

[Hoy]

David,

The mountain pastures here have never been burned, just grazed. Sætring has been practised for several hundred years (at least 400) and the result has been lowered treeline and many plants from the valleys have spread into the grazed areas but few exotics have done so.

At the coast the practice of burning and grazing has been going on for 5000 years and formed the nutrient poor heathland. But the heath is now a threatened habitat due to lack of traditional use. Some places farmers are paid to let their sheep graze and a few places they try to burn in the same ways as in the old days.