Evidence that residues of tebuthiuron arboricide present in soil of Mokala National Park can be phytotoxic to woody and grass species
Open Access
- 28 February 2022
- journal article
- research article
- Published by AOSIS in Koedoe - African Protected Area Conservation and Science
- Vol. 64 (1), 9
- https://doi.org/10.4102/koedoe.v64i1.1658
Abstract
Mokala National Park (MoNP) has a history of arboricide use through South African National Parks (SANPs) having bought commercial game farmland for its establishment in 2007. Tebuthiuron arboricide is known to have been applied for controlling bush densification during the period 1996 to 2004. Persistent negative impacts on MoNP vegetation, which are ascribed to the historical arboricide use, have prompted this investigation from 2016 to 2017. Bioassay experiments employing as test plants the tree species Vachellia erioloba and Vachellia tortilis, the shrub species Senegalia mellifera and the grass Tragus berteronianus were conducted in a glasshouse. Growth responses of these species were assessed upon their exposure to a tebuthiuron concentration range that simulated expected levels in MoNP soil soon and long after application. Chemical analysis as well as bioassay with the test species Lycopersicon esculentum (tomato) were performed on soil samples collected from three depths (0−30, 30−60 and 60−90 cm) of the soil profile at two sites in MoNP where tebuthiuron was applied in the past. The three woody test species showed differential, negative growth response to tebuthiuron, and even growth of the grass species (T. berteronianus) was affected at the higher concentrations. Evidence provided by the tomato bioassay and analysis performed on soil samples collected in situ points to the putative presence of tebuthiuron, more than a decade after the last use of arboricides for controlling bush densification. Conservation implications: If the reported evidence of the presence of phytotoxic residue of tebuthiuron in soil of MoNP would be substantiated through further research, such findings could at least partly explain the failure of natural recruitment of vegetation in those areas where the woody component was degraded because of arboricide application more than a decade ago.Keywords
This publication has 13 references indexed in Scilit:
- Tebuthiuron residues remain active in soil for at least eight years in a semi-arid grassland, South AfricaAfrican Journal of Range & Forage Science, 2012
- Seasonal diet preferences of black rhinoceros in three arid South African National ParksAfrican Journal of Ecology, 2010
- Do we understand the causes of bush encroachment in African savannas?African Journal of Range & Forage Science, 2005
- Rate and pattern of bush encroachment in Eastern Cape savanna and grasslandAfrican Journal of Range & Forage Science, 1999
- The effect of tebuthiuron on the vegetation of the thorn Bushveld of the Northern Cape – a preliminary reportJournal of the Grassland Society of Southern Africa, 1985
- Determination of picloram in soil and water by reversed-phase liquid chromatographyArchives of Environmental Contamination and Toxicology, 1984
- High-pressure liquid chromatographic analysis of tebuthiuron in soilJournal of Agricultural and Food Chemistry, 1984
- Effects of Picloram and Tebuthiuron on Establishment of Ryegrass Winter PastureJournal of Range Management, 1978
- Effect of Herbicides on Production and Protein Levels in Pasture Grasses1Agronomy Journal, 1977
- A Study of the Ecology of Acacia mellifera, A. seyal and Balanites aegyptiaca in Relation to Land-ClearingJournal of Applied Ecology, 1967