Yellow thatch grass (Hyperthelia dissoluta) has been a problem in the Waterberg region of Limpopo for years. This fire-dominant perennial species grows up to 3m tall and occurs naturally in the Highveld region of South Africa. New growth is extremely nutritious and palatable during its early growth stages, but once mature, wildlife no longer shows interest.
While much debate has been ongoing over the best solution for the grass that is taking over the reserve’s open plains, management at Mabula Game Reserve is now experimenting with different methods. It is still early days, but they are hoping to find the best solution for their grassy problem.
“There is a lot we can do about the grass, but not much to stop it from growing back,” says Mabula reserve manager Kobus Havemann. The grass occurs in high densities on most of the open plains in the reserve. These plains are great areas for game viewing, but the thatch grass that dominates is not palatable once mature, and it reaches this about two months after new growth starts. It also competes with other grass species as nothing else is as aggressive and quick to grow. “Plenty of animals will use the thatch grass on the plains, but to be a food source we have to keep it short,” says Havemann.
Keeping it short is where the challenge lies. Thatch grass has numerous uses, including roofing, but continuously harvesting in an area with dangerous game is not viable. Burning the grass is a short-term solution, but it returns even thicker. Even slashing the grass does not solve the problem. Management has chopped and burned for the last 20 years, but they are hoping research will provide better solutions. Research ecologist Preller Human is now searching for possible answers and has set up experimental sites of 50m x 50m next to one another in an area that was previously burnt. One site will be left untouched. Another plot is seeded with beneficial grass, while microbes were introduced at a third site. Microbes and seeds were combined in another plot. The last two plots were aggravated (the top soil disturbed) with one seeded, and another microbes and seeds added.
After three years of surveys, which will be towards the end of 2019, Human will be able to reveal what the effects of fire, slashing and microbes are on the thatch grass. “Only then will we find the best management practises,” says Human. Part of it also includes watching ungulates to see whether they actively seek the microbe sites – the reason why they are next to each other.
A local farmer has recently been contracted to rake and bale thatch grass in a n attempt to take away the seed bed that naturally forms when you cut grass but leave the stalks on the ground. This provides the ideal medium for new seeds to germinate and flourish and it is felt that this may aggravate the thatch grass problem on Mabula. This is a very exiting experiment and we may just have stumbled across a solution to control thatch grass effectively in the long term. Havemann says Mabula’s open plains are extremely important for tourism as sightings are guaranteed with the shorter grass. The vital information gained from the research will assist the reserve in adapting its management plan and inform important decisions.
Written by René de Klerk
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