Off to botany: green on hot earth

On June 10, 1886, a mountain on the North Island of New Zealand tore apart.

The eruption of Mount Tarawera was the most violent volcanic eruption on the archipelago since humans settled there.

It killed 120 residents, destroyed the much admired sinter terraces on Lake Rotomahana and destroyed all vegetation in the Waimangu Valley to the southwest.

Decades later, it still looked like Mars - apart from the water that now boiled out of the earth and collected in bomb-shaped side craters of Mount Tarawera.

Ulf von Rauchhaupt

Editor in the “Science” section of the Frankfurter Allgemeine Sunday newspaper.

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It's still steaming here today.

The 3.8 hectare Frying Pan Lake is the largest hot spring in the world and feeds a stream that ripples through the landscape at 55 degrees.

But today it is overgrown again.

Well, they are not all higher plants.

What is greening directly on the sometimes 90-degree lake shore is the cyanobacterium

, which is at least eukaryotic – i.e. has cell nuclei

.

already feels at 40 to 50 degrees

arguably, better known as kanuka.

This is a myrtle family and therefore a flowering plant.

Plants can take a bit of heat.

When the thermometer in Ouargla in Algeria climbed to 51.3 degrees on June 5, 2018 – the highest meteorological air temperature to date, the measurement of which is undisputed – the city greenery there survived it too.

In volcanic terrain, however, ground heat is permanent.

Here, 45 to 55 degrees is considered the hottest thing that plants can be expected to do.

Geothermal heat is just one stressor among others.

Volcanic gases have often extremely acidified the soil and water and enriched special minerals.

This often leads to a specific geothermal flora.

In Iceland, for example, mosses predominate where geysers gush or solfatars hiss, and peat mosses predominate at hot springs.

The swamp peat moss

grows there only at thermal springs.

As with geothermal areas in general, they often house plants that actually do not belong in the respective climate zone.

In Waimangu, for example, you will encounter tropical ferns that are otherwise rare in New Zealand.

Which flowering plants are best suited to heated soil, however, can vary from one part of the world to another.

In the Waimangu Valley it is kanuka, in other volcanic areas of New Zealand also manuka, which grows even at splashing mud springs.

In Yellowstone National Park, however, the predominant flowering plants are grasses, mainly

.

Thanks to the symbiosis with a fungus, it can even tolerate 65 degrees - on their own, both grass and fungus would withstand a maximum of 38 degrees.

In 2008 it turned out that a third symbiont, a virus infecting the fungus, is also involved in heat tolerance.

As early as 2001, botanists had detected increased concentrations of heat shock proteins in the tissue of dichanthelium specimens from Yellowstone rooted in soil more than 40 degrees hot.

Such molecules protect physiologically important proteins from the consequences of high temperatures or other stressful environmental influences.

However, the heat protection was only found in the roots of the grass plants.

So adaptation to geothermal heat from below may not protect against climate-induced heat from above.