Early growth and survival of Acacia galpinii after planting in a semi-arid environment in Zimbabwe

Abstract

Acacia galpinii grows naturally on the riverbanks and smaller drainage lines in semi-arid areas ofSouthern Africa. Trial planting of the species as a decorative tree commenced in 1993 along urban roads in Bulawayo, Zimbabwe. Early growth and survival of the species after planting was investigated in order to assess its suitability for afforestation in semi-arid environments. Growth and survival of trees were measured 3 to 9 years after planting. A significant positive correlation between crown height and stem diameter was observed in all the trial plantings. Growth rate was fast with trees reaching a mean diameter oflO em and height of3 mover 3 years and a diameter of 16 em and height of 5 mover 9 years. Such growth rates were reached under frequent drought conditions. Average stem height growth was 0.6 m year^-1 and diameter growth (at 30 em above ground) was 2 em year^-1. Survival of A. galpinii was more than 86 percent. Foliage transparency was in excess of 80% for all age groups while crown die back and stem damage was below 5%. A. galpinii was found to be suitable for dry-zone afforestation.