Crown characteristics, leaf size and light throughfall of some savanna trees in southern Africa

Crown and leaf characteristics of individual trees were studied in relation to their impact on light throughfall in a number of savanna types in southern Africa. Crown characteristics used include total amount of light throughfall, foliage gap size and general crown architecture. Leaf characteristics used are leaf size and sclerophylly. We used a rapid photographic technique for analysis of tree crowns in combination with time consuming measurements of individual leaves. The following general tendency is suggested by our data. Climatically extreme sites support trees with a wide range of leaf sizes, and with irregular multi-layered crowns which have relatively high light throughfall. The climatically more favourable (tropical) sites tend to support trees which have mainly small leaves, small foliage gap sizes and a low light throughfall. These crowns are essentially mono-layered. Kruin- en blaareienskappe van individuele bome is bestudeer in verband met hulle invloed op die lig-deurval in ’n aantal savanne-tipes in suidelike Afrika. Die kruin-eienskappe wat ons gebruik het is die totale hoeveelheid lig-deurval, die gaatjie-grootte in die blaarskyf en die globale bouvorm van die kruin. Blaar-grootte en blaar-sklerofilie is ook gebruik. Daar is ’n vinnige fotografiese tegniek aangewend om boomkruine te analiseer, gekombineer met bewerkbare metings van individuele blaartjies. Die volgende algemene tendens aangaande ons resultate word voorgestel. Klimaats-ekstreme standplekke vertoon bome met ’n groot verspreiding van blaar-grootte met onreëlmatige, meer-lagige kruine wat ’n hoë lig-deurval het. Op meer gunstige (tropiese) standplekke is daar ’n tendens vir bome met veral klein blaartjies, klein openinge in die blaarskyf en ’n laer lig-deurval om voor te kom. Daardie kruine is een-lagig.