Tree ring analysis reveals age structure, dynamics and wood production of a natural forest stand in Cameroon

Abstract

In a semi-deciduous natural forest stand in Cameroon a forest inventory and increment estimations on all trees with a diameter above 10 cm were carried out in an area of 1 ha. The stand is dominated by Triplochiton scleroxylon and is a part of a forest type which is widely distributed in West Africa. The existence of annual rings in the wood of trees was proven by radiocarbon dating and tree ring analysis. The oldest tree ( Celtis zenkeri) of the stand was 220 years old. The age class between 41 and 60 years is the strongest in number of individuals. Trees with an age of more than 120 years were found exclusively in the storey of the emergents. The age of the trees correlates very weakly with the diameter and the height. The mean diameter growth rates vary between 0.2 cm per year in understorey tree species and 0.82 cm per year in emergent species. The major timber species ( T. scleroxylon) reaches in mean the minimum felling diameter of 80 cm within 90 years. According to their age and height distribution together with the wood density, we distinguished three major types of life strategies of species cohorts. Species with high wood density and low increment rates in all age classes are generally restricted to the understorey. Species with exclusively old individuals, low or moderate wood densities and high increment rates are restricted to the upper storey and can be classified as long-living pioneers ( T. scleroxylon). Finally, species with moderate or high wood density, some old individuals in the upper storey and many recruits in the lower canopy can be defined as mature forest trees or trees of the future ( Nesogordonia papaverifera, Sterculia rhinopetala) . These findings lead to the assumption that the investigated stand can be classified as a very late secondary stand in transition to a mature forest.