Effect of a single fire on woody vegetation in Catchment IX, Cathedral Peak, KwaZulu-Natal Drakensberg, following extended partial exclusion of fire

Abstract

Fire is a key driver in shaping and maintaining grasslands. Long-term exclusion of fire in moist grasslands has been attempted at Catchment IX (CIX) at Cathedral Peak since 1952. Vegetation was surveyed in 1952, 1973, 1986 and 2009. Woody colonisation into grasslands was the most noted change over time. The woody component was resurveyed in 2009 after the latest of 13 unintended fires had swept through CIX in 2007. This fire had an irregular burn pattern resulting in not all woody vegetation being burnt. The burn pattern was seen to be historically recurrent owing to the presence of distinct community assemblages with varying degrees of fire tolerance and metromorphic differences between prefire populations in burnt areas and those in fire-protected areas of the same species. Erica evansii and Leucosidea sericea, a reseeder and resprouter, respectively, were the two dominant species in CIX. These displayed expected responses to fire, resulting in dominance shifting from Erica evansii (92% mortality) to Leucosidea sericea (1.6% mortality). The decrease in E. evansii individuals resulted in a relative increase in community contribution of species not affected by fire. The postfire dominance of Leucosidea sericea in burnt plots was not apparent in fire-protected areas.

Keywords:

• Erica evansii
• Leucosidea sericea
• moist grasslands
• tree mortality