An assessment of the feasibility of using a Malwa 560C combination harvester/forwarder in a selection type first thinning operation in the Highveld region of South Africa was conducted. Each of the machine components, harvesting and forwarding, were assessed separately with resulting machine productivities of 10.84 m³·PMH⁻¹ and 5.03 m³·PMH⁻¹ respectively.

An interesting result was found indicating a discrepancy between standing volume, volume harvested and volume reaching roadside. These differences were related to felling and processing trees with no merchantable volume (i.e. felling to waste), other inevitable fiber losses during log assortment production and log assortments not forwarded to roadside. To determine system productivity and cost, calculations must be based on volume reaching roadside otherwise harvester actual productivity is inordinately inflated. Recalculating harvester productivity with volume to roadside productivity is reduced to 6.94 m³·PMH⁻¹.

The two functions of the machine cannot be viewed as independent activities. The machine productivity is limited by the least productive component, in this case, forwarding. The system performance productivity was found to be 2.92 m³·PMH⁻¹. A system cost based on this productivity was USD 46.78·PMH⁻¹ and USD 16.05·m⁻³.

This study highlights the importance of accounting for fiber loss in harvester productivity calculations as well as balancing the system’s productivity to avoid overestimations and incorrect assumption in the supply chain. Furthermore, modeling productivity with data representing the adjusted volume demonstrates what is effectively being produced by the whole cut-to-length harvesting system, considering the effect of tree size and quality variability present on these sites.