Sneezewood or Mthathe: a well used natural forest species is looking after itself

February 28, 2010

This is the first of a series of articles by Dr Coert Geldenhuys, forest ecologist, on natural forests and natural forest species, focusing on their contribution and usefulness to the environment, to the livelihoods of people, and their potential to contribute to economic development.

Sneezewood tree in South Africa Sneezewood tree example
Sneezewood seedlings surviving under the forest canopy in Umtiza Nature Reserve, after 24 years with signs of browsing by insects.

Sneezewood coppice regrowth with each plant having multiple coppice shoots, which could be thinned to produce first laths, later poles and eventually trees.

 

 Fence posts and railway sleepers in many areas in the Eastern Cape remind us that Sneezewood, a natural forest species with hard, heavy and durable timber, indirectly contributes to economic development of the area – but why is it not planted more extensively?

Mthathe is an important species used by people in rural villages – but does it stand up to those use pressures? Ptaeroxylon obliquum (Sneezewood or Mthathe), the only species in its family Ptaeroxylaceae, is a shrub to large tree found in the forests from Port Elizabeth to southern Mozambique along the coast and inland to southern Zimbabwe, with some outlier populations in northern Namibia, western Zambia and Sofala province in Mozambique. I have seen some very large trees, 80 to 130 cm stem diameter in the Amathole, Transkei and Eastern Mistbelt forests. But how long do they take to grow to that size and can their use be managed sustainably?

Some people say the tree grows too slowly, and they may have a point. A small stand was planted within a small plantation of various tree species adjacent to the Kentani Forestry office near Butterworth on the way to Mazeppa Bay. It was planted in a mixture with Pinus halepensis, around 1900, and in 1988 I measured 2000 trees in two groups to assess the growth rate: mean 10.8 cm (0.12 cm/year) with range 1.2 to 30.6 cm, after 88 years (see graph)! The trees were overtopped by the P. halepensis trees and looked suppressed, probably also because the stand was never thinned. However, the locals started to harvest the easy source of poles, and the cut stumps produced fast-growing coppice regrowth.

Eastern Cape

In 1983, I studied the effects of the severe 1982/83 drought on the natural forests in the Eastern Cape. I established a plot in the dense low Transkei Coastal Forest in the Umtiza Nature Reserve. After the first rains, seedlings of Sneezewood established en mass from the wind-dispersed seed spreading from the one tree in the plot. I marked 12 small seedling plots, and followed the growth of the seedlings – and still do when I pass through there. Just imagine how tall the few surviving seedlings are by now – a surprising 25 to 30 cm high! They persist under the canopy, even with regular browsing by insects and possibly small antelope, but they cannot grow into the canopy. But the trees are now as high as the stand canopy in a nearby gap. So maybe we do not understand the ecological requirements of Sneezewood when we try to grow it – it needs enough light and growing space.

Umzimkulu district

A good example is the observation of a dense, fast-growing patch of about two-year-old seedlings on the upper end of the forest, in the open space between the forest and the plantation in the Umzimkulu district. Sneezewood seedlings under cover of the plantation stand occur scattered and stunted.

Around Port St Johns

In a study around Port St Johns on resource use in rural villages, several forests were cleared between 1990 and 1994, but the forests are regrowing actively. In this open regrowth forest, Sneezewood forms almost pure stands in places, with many of the earlier cut stumps having multiple coppice shoots. It looks like the locals are harvesting some of the coppice shoots for laths.

This coppice regrowth shows how vigorously Sneezewood can regrow to recover from over harvesting. We need to understand how this species behaves and then adapt our management strategies accordingly to ensure a more regular supply of laths, poles and trees to provide for the needs of rural households.

Maybe we need to plant Sneezewood woodlots with seedlings collected from seedling banks and then do regular thinning to provide wide growing space for the trees, and maybe intermixed with other similar forest species.

Published in February 2010

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