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Drought-related motality
Following some reports of proteas dying in large numbers this autumn, 2000 in our previous two PANs (47 and 48), this trend appears to be continuing. Please remember to use your Additional Remarks Box (ARB) to record any such observations!
John Rourke notes that Protea eximia and other proteas were aborting flowers and were in a very sorry condition during the droughts of 1967-9 in the Kammanassie Mountains. So similar deaths have occurred previously, but have just not been adequately documented.
At Tandfontein (northern KoueBokkeveld) we encountered lots of dead proteas. In places almost all the Protea repens were dead, and there was apparently also a very heavy mortality of Protea laurifolia, Leucadendron glaberrimum, and Leucadendron salignum. A few Protea laevis had died, but Leucadendron sericeum, Leucadendron chamelaea and Spatalla confusa appeared to be unaffected.
On closer inspection most of the "dead" Ld salignum were resprouting - less than 5% appeared to have been killed, even though all the above ground parts had died. Of the other species, Pr laurifolia fared best - although about 100-150 plants were "killed" to every unaffected bush, about 20% of the plants "killed" were growing new growth from within the bush. This was usually on the southeast or shady side of the bush, and most plants are reduced to 2/3 of their former height.
At our visit in June, new growth was about 100 mm long for the Conebush and 50-100 mm for the Sugarbush. This suggests that a few months ago (perhaps even last summer if growth was stunted or impaired) an event killed most of the larger-leaf species, leaving the smaller and lower plants largely unscathed. All the leaves were still present on the dead plants, although dead and dried. It was obvious that the event (drought, a heat wave, selective herbicide, or whatever) hit the plants after shoot/leaf growth was completed, suggesting a late summer timing.
Whatever happened, this event (there is no evidence of a previous event during this fire cycle) has almost eliminated Pr repens, resulted in a 10-fold decrease in Pr laurifolia, populations and set back Ld salignum. (Although seeds were released we found no seedlings.) This effect was confined to the flat sandy areas of Tandfontein; plants of these species in nearby rocky outcrops were apparently unaffected by the event. Could the water table on the flats have dropped below a critical level? Or was it just so hot that the dormant mature leaves dried out and died? Why were the smaller and smaller-leaved plants not affected?
Does anyone have any ideas?
Tony Rebelo
I was recently at Purgatory Outspan along the road from Theewaterskloof Dam to Franschhoek and noticed a few bright yellow bushes about 1.5 m high and 2-3 m wide. If I had been in the Cape of Good Hope Nature Reserve, I would have said that it was flowering Golden Sunshinebush - Leucadendron laureolum. On closer inspection it turned out to be Wild Almond - Brabejum stellatifolium! The leaves had turned bright yellow and the plants were most definitely unhappy
It was interesting that the yellow plants were about 10 m from the river and all plants that were in or nearer to the river were normal. The yellow plants are surely the result of a very hot summer of 1999/2000 and the dry winter of 2000.
Do you have any comment on this and have you heard of other atlassers seeing similar drought stricken plants?
Nigel Forshaw, Oakridge
On a recent July trip to the Little Karoo, I was privileged to be taken up onto the Rooiberg by Tom Barry, the Cape Nature area manager. We both knew that the area had been hot and dry during the last year, but we were not expecting to see such graphic evidence of this. There are fairly large populations of Common Sugarbush - Protea repens on the top of the Rooiberg, all of which were apparently showing less than 10% adult mortality in the last few years. However, we noticed that almost 75% of the adult Pr repens plants in the area are now looking very sorry, with many open cones, dead leaves, and even some dead branches. Perhaps 30% of the plants were dead or near dead. This could perhaps be a simultaneous die-off in response to disease, or even just old age (much of the area has not been burnt for over 15 years, although fires have been patchy).
However, the plants did not appear to be senescent, and old age seldom knocks Protea species off all at the same time (12 years was the age estimate), and no obvious disease was detected. Could this thus be a drought-related die off? With winter and summer temperatures 2–3 degrees higher than normal, and this winter so far yielding the lowest rainfall in the western Little Karoo for forty years, this could perhaps be the case. Further complicating the picture were large and healthy populations of Long-head Sceptre - Paranomus dispersus and Robinson Pincushion - Leucospermum pluridens in the same area – are these Little Karoo specials just more resilient to drought than a "softy" generalist like Protea repens? If so, the widespread Pr repens could be a useful indicator of changing vegetation patterns throughout the Fynbos. With the focus increasingly turning to the effects of global climate change, we need to document dramatic and unexplained mortalities like this, and monitor changes on a regular basis. The PAP provides an ideal means of tracking this change, and contributors should be encouraged to note any unexplained plant mortalities on all their SRS in the final phase of the project.
Nick Helme, Scarborough
Snow Proteas suffer the drought
On 23 October 1998 atlassers (collecting DNA material for Gail Reeves) visited 'Swartberg Towerkop SF S track end E SH1924m' (at the top of Swartberg, near Besemfontein) where Hart's-Tongue-Fern Sugarbush - Protea scolopendriifolia was found to be common. Almost two years later and in still fairly young veld (ca 5-years old?), it is only frequent. I estimate that 80% of the population is dead, the skeletons suggest that they died recently. This could have been caused by the unusually hot summer of 99/00 and low rainfall. If the rootstock is dead might the plants still resprout after good rains or a fire?
Could the same apply to the dead Frosted Sugarbush - Protea pruinosa plants we saw? Of the Swartberg Sugarbush - Protea montana recorded previously, only the dead skeletons can be seen. This species appears to now be locally extinct.
Nigel Forshaw, Oakridge
If the plants appear to be dead, then they probably are – the rootstock must always bear green leaves! The only exception is after a fire before the new buds have burst. Even in very old veld, where most leaves appear sick, there are always a few leaves on each living branch tip.
Protea neriifolia can't take the heat?
At Natures Valley in the De Vasselot National Park, regeneration after the extensive Tsitsikamma fires is looking spectacular. However, I could not find very many young of Narrow-leaf Sugarbush - Protea neriifolia! Gum-leaf Conebush - Leucadendron eucalyptifolium was coming up in large numbers, at least equal to or more than the adult plant skeletons still visible. However, young plants of Pr neri are only fraction of the skeletons of the previous generation. It looks like this fire favoured Conebushes over Sugarbushes! Is this possibly due to global warming?
Moira Girdwood, Newlands
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