AMAZING
TREES Article by: Professor André Buys
6 |
COMMUNITY NEWS
I love trees. They are truly amazing plants and we are fortunate to have some very special indigenous tree species in the Roodeplaat area. The area is characterised by three ecosystems: Seringveld or Central Sandy Bushveld in the north, Marikana Thornveld around the Roodeplaat Dam, and Rand Highveld Grassland in the south (see map). Two of these are on the National List of Threatened Ecosystems: Marikana Thornveld (No. 185) and Rand Highveld Grassland (No. 209). The Seringveld is characterised by deep sandy soils, which support specialised plant species such as the indigenous wild seringa trees (Burkea Africana; Afrikaans: “wildesering”). Marikana Thornveld contains open woodlands that are dominated by Senegalia and Vachellia (formerly Acacia) species. Patches of Rand Highveld Grassland are found on the steep plains and northern slopes of the Magaliesberg. A peculiarity of Sweet thorn trees (Vachellia karoo; Afrikaans: “Soetdoring”) is that all the trees in the area are synchronised and flower all at once for three or more days at a time with alternating intervals. The reason why the flowering is synchronised remains a mystery. Scientists have attempted to find a relationship between the flowering of the trees and the temperature, day length, rainfall and phases of the moon, but no correlation has been found so far. The Roodeplaat area is on the transition from the grasslands of the Highveld to the lower-lying, warmer Bushveld and are characterised by the presence of plants with a high degree of evolutionary activity. When the African forests made way for open Bushveld or savannah due to climate change some 8 million years ago, the surviving trees had to adapt to the more frequent veld fires. The Senegalia and Vachellia species developed thick, insulating, corky bark to protect the trees from fire. More extraordinary, however, are the trees that moved underground. These underground trees, geoxylic suffrutices, grow large woody structures as much as one metre wide, while others form branched networks of stems measuring up to 10 metres across. Their aboveground shoots and leaves are so small that it makes little difference to the tree if it occasionally loses them to wildfire, as they can quickly regrow. The underground trees are called clones, and are essentially immortal; nothing can kill them, except for habitat destruction. Botanists believe that some of the trees can be more than 13 000 years old, making them the oldest living things in the world. Aren’t trees amazing?