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ABSTRACTForest biomass utilization is increasing in Korea, but on-site biomass operations have not been studied much. This study investigates the efficacy and profitability of a mobile grinder system that consists of a mobile tub-grinder, a grapple excavator, and a three-man crew. A time study was carried out to measure production time and to calculate the productivity of the system. The mobile grinder system ran 3 work cycles a day for total of 347.5 minutes. It was only productive for less than half of the 8 working hours a day (237.4 minutes, utilization rate of 49.4%). We estimated that the system produced 246.2 m3/day, which was 26% lower than the daily capacity reported by the grinder operators. This study found the system could make utilizing forest biomass profitable, although this depended on limited market information. The profitability of the system can be improved by increasing work cycles a day and decreasing organizational delays by better operation management. More research is needed to increase the on-site productivity of the system, and incorporate it and the actual price of wood chips to further assess the profitability of the system. The study results can be used as a justification for the grinder system, encouraging forest managers to adapt this relatively new operation.

•Mechanically removing forest biomass did not increase soil displacement or reduce hydraulic conductivity aside from access trails.•Access trails supporting forest biomass removal were a primary location for soil displacement.•The presence of canopy resulted in more rain than snow interception.•The absence of canopy increased the observed snow water equivalent by 20%.

This study investigates the modeling question: "What level of geometric detail is necessary for modeling surface erosion from a forest road network?" We used the Water Erosion Prediction Project (WEPP) model to predict road sediment yield from a road network in a timber sale on the Boise National Forest, Idaho. Using three levels of detail (high, intermediate, and low), the outsloped 4.4 km road was divided into road segments (145, 91, and 42) of different lengths. The model predicted that 44, 44, and 42 metric tons per year of sediment would be produced from the 4.4 km road network based on the high, intermediate, and low detail methods, respectively. The model also predicted that a corresponding 0.036, 0.058, and 0.061 metric tons of sediment per year would be delivered into the stream system. Most sediment was predicted to be deposited in the buffer. For the predicted sediment produced from the roads, the total difference among the three methods was less than 5%, and regression analysis showed excellent correlation, with no practical differences among the three methods. For the quantity of sediment predicted to be delivered into the stream system from the road, the total difference among the methods was 61%, 67%, and 4% for high vs. intermediate, high vs. low, and intermediate vs. low, respectively. There were no strong correlations between the three methods, and the regression analysis indicated significant differences. More delivered sediment was predicted when using lower detail methods than when using higher detail methods. We conclude from the study results that the low detail method (i.e., considering only road grade reversal) can be used for input requirements of road traveled-way geometry, but that a high level of detail (i.e., dividing a road system into more road sections and considering buffer slope breaks and meanderings) is required for modeling the buffer slope geometry. Considering that the results were not sensitive to road travele... [ABSTRACT FROM AUTHOR]