Alien Vegetation on Wildcliff

The natural vegetation biomes of the Wildcliff Reserve are: Mountain Fynbos Afro-Montane Forest Thankfully, the vast majority of the reserve is pristine. However, a substantial part has been taken over by exotic and invasive species, dominated by the aggressive Acacia mearnsii, the Australian black wattle (see below). Since these threaten to spread, eradication forms an important part of Wildcliff's mission. Wildcliff is working with Cape Nature Conservation and the South African government's Working for Water program to effect eradication of the extensive black wattle cover. We recognize that removing the wattles is a herculean task that will take many years. Even after the trees are removed, many thousands of seeds remain. Within a year they will resprout. Post-removal control is essential. The task is daunting yet invasives pose the greatest challenge to conservation in the Western Cape. Hence, with the help of our volunteers, we're embarking on an eradication plan of our own. Our focus is less on elimination of the existing dense stands, and more on halting further spread. The first part, already accomplished, has been the removal of the extensive irrigation system. We have also cut down two significant stands of wattle alongside the Heron stream, which runs past the Heron House. The volunteer teams have also made important inroads by removing seedlings and saplings in less dense areas. The next part of the plan, under development, will include: Completion of the Invasives Mapping project, which is accomplished by mapping using Google Earth, and supplementing this with on-the-ground GPS mapping (see map below). Designation of areas where wattles and pines are sparse, and development of a plan for elimination of these. Designation of areas that are critical to the health of the ecosystem, such as where the possible further spread will threaten particularly rare or sensitive plant life, or where the wattles reduce or eliminate water flows. Identification of eradication methods, including chopping, herbicides (Garlon & paint), and natural enemies inlcuding a seed-eating weevil (Melanterius maculatus) and a stump fungus Plan, with time line, for implementation of the eradication, with Working for Water eradicating the dense areas Planning for post-eradication actions Planning for fire and post-fire actions.

Black Wattle (Acacia mearnsii) The lower. southern slopes of Wildcliff have been farmed for 150 years, and have suffered disturbance from habitation, agriculture and the spread of invasive vegetation such as pines and kikuyu grass. The worst problem is the spread of black wattle. Some plants are alien but not aggressively invasive. Others spread easily, threatening or displacing native flora. One such example is Acacia mearnsii, the black wattle tree -- currently perhaps the most significant threat to the biodiversity and conservation of the region, as well as to the watershed. Black wattle, native to Australia, is a popular source of timber and tannin, and is grown commercially in South Africa. It displaces the local flora by intercepting rainfall, increasing the vegetation and biomass level and drying out the soil. Streams dry up. A. mearnsii outcompete native plants for sunlight, water, nitrogen and organic materials. As one can see from the photo at right, little grows underneath these trees. Reaching 20m in height, these evergreen trees are leguminous plants, and are a threat of native plant life, as the Legumes are better adapted to nutrient-poor soil, with the symbiotic nitrogen-fixing bacteria rhizobium in their root nodules. The wattles produce a large number of long-lived seeds  (which may be triggered to germinate en masse following bush fires) that are dispersed by  wind, water, birds and animals. Only deliberate, long-term efforts can succeed in eradicating this species.

• Bugweed (Solanum mauritianum) In black wattle patch between Misty and Hadeda meadows: at least 3 plants noted, has large velvet covered leaves, blue potato like flowers and fruits were present, birds are very fond of these with the result that plants spread quickly. Should be eliminated as it is a Category 1 invasive in South Africa's listing of Weeds and Alien Invasive Plants.
• Prickly Pear (Opuntia sp.)  A Category 1 invasive, it should be relatively easy to eliminate as it seems to be mostly confined to the hill behind Talari
• Grey poplar (Populus x canescens), a cluster west of Island Pond. Spreads by rhizome; felling must be followed by suppresion of volunteers. Category 2 invasive.
• Cluster Pine trees (Pinus pinaster) cover several hectares of the hill above Talari. Category 2 invasive
  
• European Blackberry bramble (Rubus fruticosa) - pictured at right - may be countered by digging up the roots. Category 2 invasive.

• Kikuyu grass (Pennisetum clandestinum) is a native of the highlands of central Africa - a grass introduced to Wildcliff for cattle grazing, reportedly requires constant watering, so may gradually be replaced by fynbos as the watering system is removed. In higher meadows, the grass has been displaced by fynbos. Not listed.
  
• Weeping willow (Salix babylonica)  Category 2 invasive
• Belhambra (Phytolacca dioica)  Category 3 invasive
• European Elderberry (Sambucus nigra) not listed
• Honeysuckle (in front of Talari) not listed
• English oak (Quercus robur) not listed

Links & References