A series of studies dating back to 1977 examined the performance of individual machines.  Some of these involved new applications for existing equipment and others examined prototype machines.  One of the earlier publications tested the forces required for the THX Tree Extractor to extract southern hardwood trees, including the roots (Sirois 1977), to increase fiber recovery.


In cooperation with the Tennessee Valley Authority and North Carolina State University, a prototype continuous feller-buncher (Hyd-Mech FB7) (Curtin and others 1985) was tested in a 3-year-old sycamore plantation.  This machine severed and accumulated stems, then unloaded the accumulated bunches without slowing the machine.  Other publications (Frederick and others 1986 and Stokes and others 1986a) document the detailed production data on this prototype machine.  Because some short rotation woody crops rely on coppice sprouting for regeneration, stump damage was also analyzed.  A later publication (Woodfin and others 1987a) reports harvest systems, machines, and related costs for the three tests (1984, 1985 and 1987) on the Alabama sycamore plantation.  This publication (Woodfin and others 1987a) included the 1987 testing which analyzed lower-priced machines and attachments that were available on the market.  The machine descriptions and the system analysis provide a detailed description of why certain system configurations are more productive than others.


Technical releases (Mitchell and Rummer 1999 and Mitchell and Rummer 2001) document general features, specifications and costs of two commercially available mulching machines.  The machines documented in these two publications do not harvest energy wood; they support other land management goals that can be realized by reducing biomass in the stand.  Thompson (2002) provides a summary of the general types of mulching machines and their uses. 


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