Sustainable timber harvesting in Venezuela: A modelling approach

1. Reliable data on the growth and yield of logged-over forest, to determin e sustainable cutting cycles, are widely missing for the tropics. 2. We used the process-based model FORMIND2.0 to analyse the growth and yie ld of logged-over forest in Venezuela under different logging scenarios ove r a period of 240 years, and compared results with unlogged stands. The per formance of the model was evaluated with a detailed stability and sensitivi ty analysis. 3. In the absence of further logging, the logged-over stand approached the stand structure of mature forest in terms of bole volume and basal area aft er about 50-100 years. 4. Thirty-year cutting cycles with conventional logging methods and net ext raction volumes of 45 and 60 m(3) ha(-1) cycle(-1) did not provide sustaina ble yields under either of two minimum felling diameters (35 and 50 cm) tha t were applied. Only the 60-year cutting cycle provided sustainable yields under conventional and reduced-impact logging, with the different minimum f elling diameters and a range of net volumes extracted (30-60 m(3) ha(-1) cy cle(-1)). 5. With the longest cutting cycle (60 years), bole volume recovered to leve ls similar to the mature unlogged stand, but the species composition was ve ry different. 6. Scenarios with reduced-impact logging provided a significantly higher ti mber volume than under conventional logging. The conservation of forest res ources will only be possible with long cutting cycles (at least 60 years) i n combination with reduced-impact logging.