Assessment of the effects of fire and associated grazing on the recovery of Merxmuellera drakensbergensis in the Sani Pass region, Lesotho

• Main Author: Robinson, Kirsten Leigh
• Format: Others
• Language: en
• Published: 2014
• Subjects: Fire ecology.; Plants - Effect of fires on.; Plants - Lesotho - San Pass.
• Online Access: http://hdl.handle.net10539/14840

The Lesotho highlands are unique in many ways yet are at risk from severe degradation, primarily as a result of grazing and burning. This study aimed to determine whether recent (last 10-15 years) burning and grazing practices in the Sani region of eastern Lesotho are sustainable for the long-term survival of tussock grasses in the alpine belt. It was hypothesized that the alpine tussock grasses of Lesotho are being burnt and grazed at a rate that does not enable them to adequately recover between burns. A GIS based burn frequency and extent map was produced and indicated many small patchy burns (<100m2) were occurring within the Lesotho border, yet large scale burning (>10 000m2) occasionally breached the escarpment edge. Selected sites were monitored to determine the rate of growth and recovery of Merxmuellera drakensbergensis tussocks for a three year period (January 2009- December 2011). Increases were observed in basal circumference, living basal area and standing biomass yet the average height decreased across all sites and was attributed to grazing. A burn frequency of 4 burns per decade was found to be the optimum for retaining the greatest biomass, while a lack of burning for more than 9 years was suggested to result in a decrease in biomass. The leaves observed at a third of the diameter required the least average time of 6.3 years to recover to pre-burn heights as they are sheltered from environmental impacts and grazing. The middle tillers generally required the most time to recover to pre-burn heights (7.1 years) as the greatest competition for resources may be found in the centers as well as high possibilities of fire damage. The current burning activities are considered sustainable under the current levels of grazing occurring. The current levels of grazing are not advisable, especially as livestock numbers are increasing and grazing of the Sani region is becoming continuous throughout the year. A shortening of the average height of individuals within M. drakensbergensis communities is found, while increases were observed in invasive species cover. This research will add to the knowledge of environmental managers and hopefully actions may then be taken to better conserve the Lesotho highlands for future generations.