Seed germination of Namibian woodland tree species
Assisted regeneration allows for selecting desired tree qualities, such as drought resistance and good timber or fruit quality. It is also a valuable forest management tool for species with slow growth - such as most canopy tree species of northern Namibia - and limited natural regeneration, such as Pterocarpus angolensis and Guibourtia coleosperma. Few nursery experiments with dry woodland tree species from northern Namibia have been published. This study aimed to test seed treatments of six indigenous tree species to improve germination rates. The seeds were incubated in germination chambers at 30°C and 26°C to establish the effects of different temperatures on germination. In general, Dialium engleranum and G. coleosperma were found to germinate well, while Erythrophleum africanum and P. angolensis germinated moderately and Schinziophyton rautanenii poorly. Nicking of D. engleranum, E. africanum and P. angolensis was found to significantly improve these species' germination rates. Soaking was noted as an inappropriate pre-treatment for both E. africanum and P. angolensis. Surface sterilisation and other pre-treatments such as nicking and soaking decreased mean germination time of G. coleosperma seeds. Seeds of all species, except G. coleosperma, need to exceed two weeks under germination conditions. E. africanum and S. rautanenii were found to have very long lasting storage durability with germination of twelve year old seeds. These results may inform seed handling practises in nurseries and the field to advance successful assistance of regeneration. Keywords: germination, pre-treatments, Miombo woodland, Northern Kalahari woodland, Dialium engleranum, Erythrophleum africanum, Guibourtia coleosperma, Pterocarpus angolensis, Schinziophyton rautanenii.
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