Growth-Oriented Logging (GOL): The Use of Species-Specific Growth Information for Forest Management in Central Amazonian Floodplains

Abstract

So far, timber resources in central Amazonian floodplain forests are managed by selective logging with a felling cycle of 25 years and a diameter cutting limit (DCL) of 50 cm. However, these time and diameter limitations are estimations or legal restrictions rather than being derived from scientific data. From 14 tree species of nutrient-rich white-water (varzea) and nutrient-poor black-water (igapo) floodplain forest in central Amazonia wood growth in diameter and volume was modelled using tree-ring analyses. Cumulative diameter growth curves indicated periods between 15 and 261 years for species to pass over the DCL of 50 cm. From volume growth models the minimum logging diameter (MLD) was defined as diameter at the age of maximum current volume increment rates. For the majority of the analysed tree species the MLD was higher than the DCL of 50 cm. Felling cycles, estimated as the mean passage time through 10 cm diameter classes until reaching the MLD, indicated large variations from 3 to 53 years between tree species. Tree species which occur in both floodplain system present significantly lower diameter increment rates in the igapo than in the varzea due to the contrasting nutrient status. The sustainable use of timber resources in the igapo is, under current management options, not practicable and this ecosystem should be therefore excluded from timber resource management and permanently protected. The varzea is a dynamic system with highly productive forest ecosystems which favours the development of an integrated sustainable forest management. However, such a timber resource management must be species-specific. Based on tree ages, increment rates, volume production and population structure of commercial tree species the GOL concept (Growth-Oriented Logging) was developed to achieve a higher level of sustainability for the timber resource management in varzea forests.