Productivity models for cut-to-length harvesters and harwarders: a systematic review over the period 2013–2023

Precise predictions of work productivity are crucial for planning and costing of forest operations. Productivity models are developed based on time studies or follow-up studies, and due to the diverse work conditions and the choices of the modeler, model characteristics—such as independent variables and predictive capabilities—may differ considerably. Despite their significance, relatively few studies have critically examined productivity models for fully mechanized harvesting systems. Therefore, a literature review was conducted to identify and scrutinize productivity models for cut-to-length harvesters and harwarders. Eighty-two publications containing models were identified for the period 2013–2023. The publications originated from five continents and 19 countries, and covered a wide range of forest types and work conditions. In the publications, 311 models were identified, and several commonalities as well as differences between models and publications were identified. For example, the majority of publications used piece size (tree volume or diameter at breast height) as a predictor, but there was a large variation in which additional predictors were used. Furthermore, the type of mathematical function and predictive capabilities of models varied considerably. This review offers insights that may contribute to the harmonization of the development and application of productivity models. It also provides an extensive compilation of models, which facilitates easier identification and accessibility to them.