A Grapple Processor for Plantation Thinning

Small boom-mounted grapple processors are popular in Scandinavia where they eliminate manual delimbing, bucking, and piling of trees. Such a machine–the Valmet 940 grapple processor–was tested in a first thinning of loblolly pine in Alabama. The processor followed a small feller-buncher which built large bunches (16 stems) at about 27-foot intervals along an access corridor. The processor delimbed and bucked the wood into 7.5-foot bolts, forming a neat pile at the side of the access corridor for subsequent forwarding. Production averaged 2.5 stems per minute. Regression equations were developed to predict processing time per tree, moving time per tree, and total time per tree. Processing time per tree was greatly dependent on average tree size. Moving time per tree was closely related to the distance traveled from the previous bunch and the number of trees in the current bunch. Total time per tree was almost identical to processing time since the major component of total time was processing time. Slash piles remaining after forwarding were much smaller with this system than with manual methods since tops were deposited in the access corridors where subsequent machine traffic reduced the slash. Such a processor appears well suited to southern pine thinnings where it can replace dangerous and physically demanding manual operations.

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