Vegetation ecology of the northern KwaZulu-Natal grasslands

Abstract

A plant-ecological study was conducted in the grasslands of northern KwaZulu-Natal to develop a better understanding of the distribution, structure and composition of the plant communities found in the area. Plant communities were identified, classified and described in terms of environmental factors, making use of the Braun-Blanquet method, the TWINSP ANclassifi cation technique and the DECORANA ordination algorithm. Altogether 95 plant communities were identified, comprising 800 plant species. A synthesis was subsequently conducted on the complete data set consisting of all 95 plant communities, resulting in 20 vegetation types being recognized. The results will ultimately form part of a comprehensive syntaxonomical and synecological synthesis of the entire Grassland Biome of South Africa. Plant communities and other areas displaying a high degree of naturalness and/or species richness were also selected for conservation purposes. Aerial photographs, derived from different dates in the past, were analysed by means of the GIS programme IDRISI to determine the extent and rate of bush encroachment into grassland within the study area. The GIS-based analysis was further complemented by field surveys to determine the processes involved in bush encroachment. The results clearly show that a fixed pattern of succession occurred with woody pioneer plants being the first to invade the grassland. Subsequent developments embraced the establishment of further woody plant species, being characteristic of higher seral stages, around the pioneer species until woody clusters would coalesce to form closed woodlands in the end. A brief overview and discussion of grasslands in general is also presented, dealing with issues such as origin and evolution, management, conservation and research.