Bush encroachment with specific reference to Acacia karoo encroachment

Abstract

Acacia karoo encroachment is a serious ecological problem in certain veld types in South Africa. The growth and habitat requirements of A. karoo have not previously been studied in detail. This paper refers to an autecological study of the A. karoo seedling. Growth analyses indicate that the seedling is characterized by a low growth rate, that it is very sensitive to temperature changes and that light intensity is a less important ecological factor. The seedling is very sensitive to desiccation and it is suggested that under field conditions, favourable moisture conditions extending over a lengthy period together with high temperatures are the most important requirements for establishment. The possibility of a temperature boundary limiting the establishment of A. karoo is discussed and it is demonstrated that the average temperature climate of areas subject to A. karoo encroachment is very close to such a boundary. A. karoo encroachment can possibly be due to a temperature shift or to reduced grass competition.

Keywords: plants|temperatures|light intensities|ecological factors|desiccation|competition|bushes|seedlings|Southern Africa|analyses|autecological field studies|habitat requirements|growth|veld types|ecological problems|bush encroachments|temperature effects