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Adjacency and proximity - what is the difference?
Stanley requires that you enter an adjacent and proximal distance. Since the spatial relationships derived from these values influence the Stanley score, it is important to be aware of how each is used.
Adjacency and proximity are two ways in which polygons are spatially related to other polygons in the forest. Adjacency connotes connectivity while proximity connotes nearness. In Stanley, adjacent polygons can be combined into harvest blocks; proximate blocks cannot be scheduled for harvest within the greenup delay. The distances you should use largely depend on the arrangement of landscape features, in particular those that are not blocked such as roads and waterways, and whether or not openings created by Stanley should be kept a certain distance apart.
During harvest allocation, eligible, adjacent polygons are assigned to blocks. If the adjacent distance is less than the width of features that split stands (e.g., roads, rivers, or other non-eligible features), Stanley is prevented from grouping them. This in turn can reduce the total area that can be allocated. You can circumvent this problem by setting the adjacent distance greater than or equal to the width of stand-splitting features.
Once Stanley assigns a block a harvest period, neighboring stands usually cannot be scheduled until the regenerating trees have reached a certain height; what we refer to as the greenup delay. In the absence of a proximal distance, Stanley could place blocks as close together as the adjacent distance without causing a violation. However, you may be required to keep blocks further apart than the adjacent distance (e.g., exclusion zones surrounding openings to provide forested corridors for wildlife). By setting the proximal distance greater than or equal to the desired width of exclusion zones, Stanley will separate by at least this amount, blocks scheduled within the greenup interval.
Consider the following example of a forest interspersed with small openings (six- to seven-meter wide seismic lines). For blocking, I used a minimum size of 5 hectares, a maximum of 150 hectares and a one-period (10-year) greenup delay. Initially, I specified an adjacent and proximal distance of 0 meters (proximal polygons were of a special type, zero-distant proximal, because they only shared a single, common vertex with their neighbors; they are not considered adjacent to prevent the creation of stair-stepped or other oddly shaped blocks). Stanley blocked 89.6 percent of the volume scheduled by Woodstock.
Next, I increased the adjacent distance to 15 meters, so stands opposite openings less than this width would be considered adjacent. Stanley in turn blocked 95.9 percent of the objective. Obviously, the seismic lines were impeding harvest allocation. Also note that, since the adjacent distance was greater than the proximal distance, there were no proximal polygons-polygons only had adjacent neighbors. Finally, I increased the proximal distance to 100 meters to keep separate blocks with incompatible harvest timings. Stanley easily rearranged blocks, scoring 95.2 percent, and this time there were more proximal than adjacent polygons.
The adjacent and proximal distances that are right for you will depend on your particular forest and the regulations you are operating under. As a guideline, increasing the adjacent distance will tend to increase scores because Stanley will have more options when allocating the harvest. However, if you increase it too far, Stanley may create blocks across features that truly cannot be spanned. Increasing the proximal distance, on the other hand, will tend to decrease scores because Stanley will have fewer options when scheduling the harvest. I encourage you to experiment with these distances to see what impact they have on your Stanley scores.
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