Dynamics of some forests in Kwa Zulu-Natal, South Africa, based on ordinations and size-class distributions

Indigenous forest in Kwa Zulu-Natal has been fairly well described; however, very little has been published on its dynamics. There is, to our knowledge, nothing published on disturbance regimes, dendrology and fife histories of constituent species. In order to assess the conservation status, management and sustainability of these forests we have developed a dynamic framework by synthesizing information collected in many randomly located 400-m2 sample plots in a range of forest types. We reasoned that ordinations between understorey and overstorey data from these plots would indicate the grain of a forest. Fine-grained forests would be indicated by close proximity, in ordination space, of understorey and overstorey. Similarly we argue that a predominance of canopy species with negative exponential size-class distributions should typify the more fine-grained forests. Our analyses suggest the following dynamics spectrum: from fine-grained upland forests with in situ recruitment from advanced regeneration for most canopy species, to coarse-grained lowland forests where canopy species have flat size-class distributions and spatially variable recruitment. These results are discussed with a view to the conservation of the different types.Die inheemse woude in Kwa Zulu-Natal is al redelik goed beskryf. Daar is egter tot op hede baie min inligting oor die dinamiek van die woude gepubliseer, Sover ons kennis strek, is daar geen artikels oor versteuringspatrone, dendrologie en die lewensgeskiedenis van die individuele spesies gepubliseer nie. Ons het 'n dinamiese raamwerk ontwikkel deur die inligting wat op verskiilende ewekansige geplaasde persele van 400m2 in verskeie woudtipes versamel is, saam te stel en te interpreteer. Die bewaringstatus, bestuur en volhoubaarherd van hierdie woude kan met behulp van die raamwerk ondersoek word. Ons voer aan dat die klassifikasies van die onder- en kroonbos van hierdie persele die grein van 'n woud sal bepaal. Fyngrein-woude word deur die mate van naburigheid tussen die kroon- en onderbos in die klassifikasieruimte aangedui. Ooreenkomstig voer ons aan dat fyngrein-woude 'n meerder- heidsteenwoordigheid van kroonspesies met 'n omgekeerde-J-grootteverspreiding sal hê. Ons analise stel die volgende dinamiese spektrum voor: van fyn-grein hooglrggende woude met in situ-hervestiging van gevorderde regenerasie vir die meeste kroonspesies, tot die grof-grein laagliggende woude met kroonspesies met plat grootte- verspreidings en verandelik-gespasieerde regenerasie. Hierdie resultate word bespreek in terme van die bewaring van verskiilende woudtipes