1 Establishing a standard work sampling method for mastication ...

leaving a mat of shredded wood on the soil surface (Jain et al. 2007). Mastication is an
alternative for fire hazard reduction when the treatment area cannot be burned, mechanical
removal of excessive fuels is cost prohibitive, or impacts on soil and sedimentation are of
concern (Coulter et al. 2002; Rummer et al. 2003; Hatchett et al. 2006; Han et al. 2006; Kane et
al. 2009).
There are a variety of methods that can be employed to analyze the cost and evaluate operational
efficiency of forest operations. Among methods, the detailed time and motion study method
using a stopwatch works well in evaluating cyclic activities where there is a repetitive defined
course of events (Olsen and Kellogg 1983). The work sampling method is less commonly used,
but can be effectively used to evaluate non-cyclic activity such as mastication (Pape 1992;
Bolding 2009 personal comm.) Work sampling consists of a series of consecutive observations
where the current activity of the machines is documented (Heiland and Richardson 1957; Miyata
1981; Olsen and Kellogg 1983; Pape 1992; Liao and Pape 1996; Bolding 2006).
There are certain advantages and limitations to work sampling when compared to detailed time
and motion studies. Among the advantages, the most poignant include: the ability to control the
accuracy by increasing the number of observations, data reduction and analysis are easier and
less time consuming, and the data can often be collected by one researcher who requires less
training than necessary for time and motion studies (Miyata et al. 1980). Despite the advantages,
work sampling is not always correct choice as it does not record machine cycle times and may
report uncharacteristic proportions if the machine cycle and observation interval coincide. Also,
important events between observation times may be missed and short delays may be reported
incorrectly with increase in interval length (Olsen and Kellogg 1983). Among the several work
sampling methods, there is ambiguity as to which method is the best to evaluate masticators.
The objective of this study was to establish a standard work sampling method for mastication
operations analysis, allowing researchers and land managers to evaluate operations efficiency
and conduct fair cost comparisons. This method should aid in making informed decisions
resulting in efficient use of masticators to accomplish fuels treatment objectives in a costeffective
manner. Our main approach was to compare various work sampling methods to a
reference method to identify a work sampling method that provide the most accurate details on
mastication operations with a minimum effort and time.
Methods
Study sites and mastication treatments
Mastication for fuel hazard reduction was implemented at Humboldt State University’s L.W.
Schatz Demonstration Tree Farm, located near Maple Creek in northwestern California. Steep
topography and availability of brush fields limited the area suitable for operation to nine small
units of similar slope and fuel load conditions (Table 1). The areas selected were dominated
primarily by a dense cover of shrub species such as pacific poison oak (Toxicodendron
diversilobum (Torr. & A. Gray) Greene), blue blossom (Ceanothus thyrsiflorus Eschsch.), and
coyote brush (Baccharis pilularis DC.).
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