Seedling recruitment of Colophospermum mopane on the Highveld of Zimbabwe

Abstract

Factors controlling seedling recruitment of Colophospermum mopane (Kirk ex. Benth) Kirk ex. J. Leonard were investigated on the high veld of Zimbabwe. Seed germination and seedling survival and growth were monitored under canopy and outside canopy microhabitats for a period of3 years. Seed germination in both microhabitats exceeded 70%. Although there was no significant difference in seed germination between the two microhabitats, seedling survival was significantly lower under canopies than outside canopies. More than 75% of newly emerged seedling losses were attributed to water stress, which suggests that abiotic factors (mainly rainfall) may account for most of the fluctuation in recruitment in this species. Open areas with bare ground or sparse grass cover were favourable sites for seedling recruitment. Seedlings appear to be shade-intolerant and require increased light intensities and temperature for growth. Seedlings grew slowly probably because they initially allocated more biomass to root growth. Shoot growth was also hampered by recurrent die back mainly caused by fire. Most seedlings resprouted after aboveground organs were killed by fire. It is concluded that seedling recruitment of this species is mainly limited by inconsistent rainfall events that characterize most areas where it grows.