Removing invasive plants in South Africa can help the native ecosystem recover
South Africa is infested by many alien plants, meaning plants introduced from elsewhere that are not naturally found there, and which harm native ecosystems. Researchers found that removing the aliens helped the native plants to regrow.
Invasive alien plants take resources such as water, space, and sunlight from native plants, often causing them to die. This can have knock-on effects that harm the whole ecosystem.
One such invasive alien plant that has spread all over South Africa is known by its scientific name as Acacia decurrens (A. decurrens). Its common names are “black wattle” or “early green wattle”, and it is a perennial tree or shrub naturally found in Australia.
In this study, researchers wanted to see how quickly the native South African plant life would return to one local habitat if they removed all the A. decurrens plants that had invaded there.
The researchers marked off 24 plots of 10 metre by 10 metre land in the Waterberg district of the Limpopo province, South Africa.
First, they recorded how many A. decurrens and native plants were in these plots, and then they removed all the A. decurrens by digging them out.
Over the course of 18 months they periodically recorded how many of each plant grew back, and continued to remove any new A. decurrens plants.
The researchers found that the number and types of native plants increased each time they removed A. decurrens. They saw that the native plants decreased again whenever A. decurrens grew back. But, the number of A. decurrens that grew back was less each time.
After 15 months, there were about 8 times more native plants in the plots than before, and by the end of the study there were about 3 times more native plants.
This practical study, or experiment, shows that removing invasive plants can help the native ones regrow and become reestablished in the local environment. But, the researchers say that the ecosystem can not fully recover without people bringing back native plants that were there before and had died out due to alien plant invasions.
The authors of this study were from South Africa.
Riparian invasive alien plants are known to compete with native plant species for water, space, daylight, and different other resources by decreasing structural diversity of native vegetation and subsequently changing the functioning of the ecosystem. The aim of this study was to investigate the rate of native plant species recolonization after the eradication of A. decurrens. The investigation was done in the Waterberg District Municipality, Limpopo Province in a farm, which is highly infested with A. decurrens. Twenty-four permanent plots of 10 m x 10 m were constructed and the A. decurrens individuals in the plots were removed and the area was monitored for a period of 2 years. The size of quadrats was based on the size and distribution of the invasive alien plants which develop in an aggregated form and have exceptionally small canopies.
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