Abstract:Harvesting equipment productivity studies have been conducted in many countries around the world spanning over 25 years. These studies have shown that many factors influence individual machine productivity. These factors include stand and site conditions, equipment configuration, management objectives, and operator experience. Productivity can increase or decrease with slight changes in any of these factors. This literature review also highlights the variety of experimental designs and data collection methods encountered in a cross section of those studies. It further shows the variation in species composition, stand density, tree diameter, and harvest prescription. Although studies that include the influence of operator performance on harvest equipment productivity are limited, they were included in this review where appropriate and available. It is clear that productivity equations should be developed using population-level data with several operators. Some studies were conducted in stands similar to Maine, but they used harvesting equipment that is not commonly used in logging operations in this state. Therefore the applicability of existing studies to the logging industry in Maine, USA, is very limited. Our conclusion is that in order to accurately predict harvesting productivity it is necessary to develop regional harvesting productivity equations using harvesting equipment commonly used in Maine. Forest operations researchers in other regions will be able to use this summary to explore the difficulty of applying productivity information to regional logging operations. OPEN ACCESSForests 2013, 4 899

Due to the increased partial harvest of small-diameter stems and the lack of feller-buncher time-consumption information in Maine, it was necessary to develop new cycle-time equations. Data were collected from seven different sites in Maine with six different operators to capture the variability in site and stand conditions as well as operator experience and proficiency. The results showed that over 55% of the trees harvested were cut in accumulations of two or more trees. Significant variables in the final model included sum of dbh and stem count per accumulation. An approach to simulate a list of accumulations with the required variables is described based on a tree list with dbh classes. Treating the combination of operator, machine, and site conditions as a random effect in a linear mixed-effects model resulted in an adjusted R 2 of 0.40 for fixed and random effects. The combination of operator, machine, and site conditions explained 32% of the variance caused by random effects. The results of this study can be incorporated into existing harvest cost prediction programs to improve estimates for this region.

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This review examines the impact of prescribed fire on the water quality variables (a) sediment load and (b) limiting macronutrients in forested environments globally. We aim to characterize the forested environments subject to prescribed fire, to discuss factors of the fire regime that contribute to water quality concerns, and to offer insight into the effect of precipitation timing and study scale on constituent exports. High fuel consumption during fire increases the risk of erosion and constituent export during precipitation, though high fuel consumption during prescribed fire is uncommon in forested environments. Small-scale studies examining sediment yield after prescribed fire may fail to capture the effect of landscape-scale spatial variability, and watershed-scale studies accounting for such variability are lacking. Although small-plot studies confirm that prescribed fire can alter hydrologic inputs, the environmental impact of these increases is minimal, particularly when compared with other land-use systems. Generally, prescribed fire is a beneficial and low-impact disturbance that likely improves fire-adapted forest health. However, gaps in knowledge exist at various spatial and temporal scales; this review suggests two avenues of future research, including (a) greater understanding of fire regime interactions that control surface runoff and erosion at the watershed scale, and (b) monitoring forest health and ecological function after prescribed fire rather than direct nutrient exports.

Commercial thinning (CT) is an important silvicultural practice in the northeastern United States. Relatively little is known, however, about the interaction of harvest system and treatment (removal intensity or timing of entry) on the overall profitability of CT. To address this question, 10-year measurements from a controlled CT experiment across six sites in Maine were used to project the long-term effect of removal intensity (33% and 50% relative density reduction) and timing of entry (no delay, 5-year delay, 10-year delay) on (i) maximum net present value (NPV), (ii) timing of maximum NPV, and (iii) the effect of three harvesting systems (cut-to-length, whole-tree, hybrid systems) on maximum NPV. A regional growth and yield model was used to project individual-tree growth and mortality into the future. Harvest costs for the harvesting systems were estimated using regional cycle-time equations. No difference was found in maximum NPV between the CT and non-CT areas or the timing of CT entry. Stand age at time of maximum NPV differed between delays but not between the two removal intensities. Our results indicate that there is no economic benefit in delaying a CT or removing more volume at the time of thinning for the range of stand conditions evaluated.