Critical to the AFERP experiment are the harvest treatments. The job of harvesting is contracted out to a Master Logger certified logger. In terms of the experiment, the harvest is highly important, since the harvest is the treatment. Therefore, it is imperative to select a logger that will respect the experiment and follow all harvest treatment guidelines set forth prior to the harvest operation. The integrity of AFERP’s long-term silviculture experiment hinges on a well-implemented harvest.
For general forestry practices, setting up and marking within an expanding gap harvest can be relatively straightforward, although the process requires some forethought of the future cutting cycles. Primarily, one should use the existing regeneration (whether in natural gaps or around the periphery of existing gaps) to guide the placement of the new gaps or gap expansions. However, this placement of gaps or gap expansions needs to be balanced against the configuration of the existing trail network, the spatial configuration of the gaps themselves (in order to make sure that all areas of the stand can be harvested within the cutting period of the rotation), and the distance between neighboring gaps (in order to avoid narrow “leave” strips that may experience windthrow between entries). Ideally, initial gaps should be relatively uniformly dispersed across a research area and trails should be placed to act as boundaries for the gap or gap expansions. Trails that go through a center of a gap have use only for that entry and generally must be abandoned in future cutting cycles. Successive cutting entries should ideally, although not necessarily, expand gaps on all sides and release the advanced regeneration that has become established. Gaps should be coalesced whenever the “leave” strip between the gaps becomes <1 tree height. Within gaps, retention trees can be left for wildlife habitat, as seed source, or as overwood to provide additional protection for the regeneration.
For this experiment, however, harvest setup and marking has to be much more meticulous. Although the same considerations as listed above still hold, new gaps and gap expansions need to be surveyed GPS (often multiple times) to make sure the planned harvest is no more than 10.0 ± 0.5% of each research area. Retention levels need to closely approach either the 3.75 m2/ha or 11.25 m2/ha goals for Type A (i.e., currently regenerated) and Type B (i.e., not currently regenerated) gaps, respectively.
Caption: The 2006 harvest was conducted using a conventional system consisting of a cable skidder and two chainsaws, one for felling and the other for bucking and trimming at the yard.