There are a variety of harvesting systems in use in conventional forestry and short-rotation woody crop operations. This section describes the equipment used in conventional sawlog production operations from which thinning or logging residues may be derived, as well as short-rotation woody crop production equipment. When evaluating these equipment options working in sequence in biomass operations, the convention for establishing cost and production rates of equipment most commonly follows traditional machine rate methods, in which the hourly costs of equipment ownership and operation are partitioned into fixed and variable costs. Production functions are estimated using regression relationships developed from work sampling and time and motion field studies, with production in volume or mass per hour expressed as a function of stand (e. g., mean tree diameter, species, trees per hectare), site (average slope), equipment (machine payload capacity, horsepower), and operator variables as predictors. Logging costs for alternative supply chain components and equipment combinations are estimated by dividing machine rates, whether individually or summed over several machines, by the total production achieved in a specified time period. The result is cost per volume ($ m-3), or cost per unit mass ($ t-1). For example, if a feller-buncher has a machine rate cost of US$140 per hour to own and operate, and averages felling and bunching of 10 cubic meters per hour, then the total logging cost is estimated to be $140/10 = $14 m-3.