Motorists in the Kruger National Park (KNP) should not be alarmed if they spot some of the tall trees near the roadside marked with a distinctive aluminium tag. These tags, that glint in the sunlight, will help scientists monitor the life history of the tall trees in the KNP - how big they grow, how elephants and other animals use them and how long they live.
With a permanent marker on selected trees, it will be easier for the scientists to come back to survey the same trees, year after year. In this way, they can build up long-term data and information on tall trees in the veld. It is well known that tall trees play an important role in the ecosystem as they provide food and shelter to a myriad of creatures both big and small.
The tree marking programme is the first step towards the detailed biodiversity surveys that are being done by staff from Scientific Services in Skukuza. Most of the trees will be marked in areas that are inaccessible to the public, so they will not be highly visible, but occasionally a site may be selected that will be visible from a tourist road. The aluminium tags are attached to trees over five metres in height or that could have the potential to grow to over five metres.
The tags are attached at eye-level, but will be at least 1.5m from the ground so as to be visible above the tall grasses and shrubs. Sample sites are selected by the vegetation ecologists to cover all the different kinds of vegetation that occur on hills, including areas of the hill crest, the hill mid-slope and the hill foot-slope and valley bottom.
About 20 to 25 trees are selected in an area and the survey team will walk in a loop selecting the trees, based on their height, and carefully surveying each individual. Once a tree is marked, the survey team will note the species, the tree height and canopy width, which is measured with a Tandem Compass Clinometer, and stem diameter. The level of damage to the tree or bark by elephants, other herbivores and fire is also noted.
A GPS reading is also taken, using a highly accurate differential GPS, which will make it easier to find the tree again during subsequent surveys. Selected trees will be marked throughout the park over the next three years. The valuable information from this long-term tree monitoring project will provide more insight into the tall tree dynamics within the Kruger National Park.