Silver shoots

2016-11-08 15:26
Mikhaila Gordon, a conservation intern of the South African National Biodiversity Institute, inspects one of the newly discovered silver trees.

Mikhaila Gordon, a conservation intern of the South African National Biodiversity Institute, inspects one of the newly discovered silver trees. (Berta van Rooyen)

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Silver trees have reappeared in Tokai forest after an absence of over a century.

Silver tree forests on the slopes above Tokai Manor are appearing following the clearing of pines and the March 2015 fire.

The Silver tree belongs to the conebush genus in the Protea family. It has a red list status of endangered, due to a loss of population and habitat reduction.

Dr Tony Rebelo, chairperson of the Friends of Tokai Park, says silver trees are currently threatened by many factors.

“The tree is threatened by urban expansion, afforestation, inappropriate fire management, alien plant invasion, habitat fragmentation and susceptibility to root fungal infections. Climate change models suggest that this species will be negatively affected by temperature rise and may further decline by over 80% by 2025, unless carefully managed,” he says.

The plants were discovered by members of the Friends of Tokai Park during an alien vegetation hack above the Tokai arboretum.

“Unfortunately, the aliens here are incredibly dense. This is surprising, as the areas handed over to Sanparks from MTO after the pine clearing were supposedly clear of aliens. Obviously at some stage during the last 100 years, extensive wattle invasions must have occurred in the plantations.

“Fortunately, Sanparks has prioritised clearing of these areas and has its own teams in the area, augmenting the work being done by Working for Water teams and volunteers. The Friends have also been organising hacks in the area,” says Rebelo.

Silver trees grow about 300-500mm per year, so Rebelo expects that in five years’ time there should be 3m-high trees which should be visible from the southern suburbs.

He warns, however, that after 100 years of pines their seed banks will be heavily depleted and it will probably take another 100 years to recover healthy populations without help.

“Part of the problem is that seed dispersal is only a few metres from the trees. Although the fruit have parachutes to blow them about in the southeaster winds, the seeds are very heavy and seldom disperse more than a few metres from the trees. So it will be hundreds of years before the trees recolonise the slopes.

“We hope to accelerate the spread with some judicious seed dispersal. But we have to bear in mind the genetic structure of the local populations and limit contamination from gene banks of the northern Peninsula.

“We have planted over 1 000 seeds at Tokai, but that was after the fire and few plants have come up. Presumably the fruit are safe underground though and will come up after the next fire,” says Rebelo.

The Friends and Table Mountain Honorary Rangers, in conjunction with the threatened species unit of Kirstenbosch, planted some seeds from Vlakkenberg to the Tokai slopes in May last year, but some of the establishing plants are not from areas that were seeded.

“There must still be seed banks in the soil. A few survived for almost 80 years in the soil at Kirstenbosch while the area was under gum plantation. These provided seed, allowing the populations to be restored by planting. We hope to be able to do the same at To­kai,” says Anthony Hitchcock, curator of the nursery at Kirstenbosch.

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