The Impacts Of Different Fire Frequencies On Vegetation Characteristics In The Hamoye State Forest, Kavango Region, Namibia.

Abstract

In Namibia, large areas burn each year with a distribution of burn relating to the rainfall gradient. As a result fires are widespread and frequent in the north, especially in the northeast. In these areas more than 2 million hectares of forested land burn each year. Fires, amongst other factors, have negative effects on biodiversity. These effects have not been fully assessed. Therefore, this study was conducted to investigate the effect of different fire frequencies on vegetation characteristics in the Hamoye State Forest (HSF). The study was carried out through a combination of analysis of Landsat satellite imagery and field sampling methods. Landsat satellite imagery was used to map and demarcate the forest into 3 different fire frequency zones (low, medium and high); with low being areas burnt less than five times, medium being areas burnt between 5 and 10 times, and high being areas burnt more than ten times since 1989. Field sampling was carried out to determine the effect of different fire frequencies on species diversity and richness, plant density, cover, height and tree basal area. A total of thirty randomly chosen 35 x 35m plots, ten in each fire frequency zone, were sampled. The results indicate that fire frequencies differed among the zones of the state forest, with high frequencies found in areas far from the State Forest buildings, while medium and low fire frequencies were found in areas within the proximity of the Forestry buildings. These differences were due to fire suppression by forestry personnel in areas within the proximity of forestry buildings. There were no significant differences in tree basal area, tree density, and stump density among the three fire frequency zones. However, frequent fires reduced tree and sapling height. Forb and shrub densities increased with increasing fire frequency. Most forbs are annual that quickly colonized unoccupied niches after fire burning, while most shrubs resprouted after intense fires resulting in high shrub density. The woody and grass cover all decreased with increasing fire frequency. High fire frequency reduced woody cover.