Marsh Rose Orothamnus zeyheri
The case of the Marsh Rose
Not only did the Marsh Rose make its way to the market in Cape Town, but is was popular at flower shows. Peter Slingsby relates a tale of a picker collecting flowers for a Caledon Wildflower Show who discovered a colony on Perdeberg above Kleinmond and picked all the + 30 heads. As the plants do not have subcortical buds below the oldest leaves, he killed the plants and wiped out the colony. But how was he to know that the plants were rare: he was merely told to go and pick flowers!
In 1968 Charlie Boucher became interested in the plight of the Marsh Rose. He located three populations in the Kogelberg area and counted a total of 10 plants. Another colony in the Klein River Mountains above Hermanus contained 24 plants when it was wiped out by a premature accidental fire in 1968. The species was in dire straits. An emergency programme was instigated to try and save the species.
Part of the problem arose from the call of early botanists against the burning of Fynbos; all the Marsh Rose seedlings seen since the Department of Forestry's policy of protection from fire were in firebelts and alongside paths, suggesting that this species required fire to regenerate. A series of controlled burns were undertaken and some 1956 Marsh Rose plants popped up from seeds buried undergound by ants. Marsh Roses are short-lived: half the plants have flowered by nine years and most plants are dead by 20 years. However, the seed are long-lived and can survive well over 35 years below ground. Thus for the optimal maintenance of the Marsh Rose, fires should occur every 15 to 50 years.
However, Charlie did more than just burn. He also hoed colonies and arranged burns at different times of the year. Winter fires resulted in poor regeneration: this pattern may be due to the wet vegetation not burning adequately and leaving lots of debris - thus the soils do not get cold at night and the seeds do not receive their germination cue. Those fruit that do germinate have to fight their way through the shade and are eaten by rodents, which are safe from predation by birds under the debris. Summer fires gave excellent recruitment.
The hoeing trials resulting in excellent germination but little survival; as low as 10 per cent. The low survival was probably due to trampling (while hoeing), which compresses the soil leading to impeded water movement and aeration; and direct root damage which kills the plants. Disturbing the soil also spreads Phytophthora a "die-back" fungus which kills the roots and thus the plants. In addition, Saunders' Vlei Rat Otomys saundersiae killed more than half the plants in one colony: this emphasizes the need for a clean burn to remove the plant growth and allow birds of prey to hunt those rodents which survive the fire, so that seedlings can emerge and grow tall enough to survive herbivory.
Although no studies were done on trampling per se it appears that trampling in burned sites was sufficient to cause mortality of plants owing to direct effects (i.e. compression, root damage) and also to the spread of Phytophthora.
It is not the only species growng in marsh habitats which are susceptable to trampling. Trampling can compress sandy soils accelerating their erosion. Any species which occurs in small clumps should be approached circumspectly by all atlassers and with due consideration to the effects of trampling and disease transfer.
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