8 Transect method for areas larger than 10 hectares
For large areas, typically greater than 10 ha, the surveyor must systematically locate a number of grid centres within the area to be surveyed. To do this, points must be assessed at 1-m intervals along two 30-m transects radiating out from each grid centre. The number of grid centres depends on the size of the area to be surveyed. For areas up to 50 ha, a minimum of 30 grid centres is required. For areas larger than 50 ha, one grid centre for each additional 5 ha must be added. (These are recommended as the minimum number of grid centres.) Refer to Figure 11 for layout.
For a more precise estimate of the soil disturbance, it may be necessary to increase the number of grid centres. It is possible to calculate confidence limits for this survey, but they are wider than those obtained using the small area method. Whenever possible, the small area method should be used. In the case of large standards units, all parties (i.e., Forest Service district staff and license holders for the area in question) may wish to consider agreeing on a representative area that could then be surveyed more efficiently using the small area method.
Figure 11. Transect survey layout for large areas (>10 ha). Establish regularly spaced grid centres on cardinal bearings from a random start. As also shown here, survey points are not established in areas of non-commercial cover greater than 4 ha or permanent access structures. Permanent access structures should be surveyed using the road traverse and landing survey methods.
As shown in Figure 12, do not sample portions of transects that are outside the NAR. Do not survey points on permanent access structures, outside the cutblock boundary or survey area, or within non-commercial cover greater than 4 ha. Do not sample points that land outside the NAR (e.g., if 12 m of a transect falls on a haul road, measure only the remaining 18 of the transect's 30 points; do not measure any of the points on the road). Mark each non-surveyed point with an X on the Transect Survey Field Card.
Figure 12. Omit points outside the net area to be reforested (NAR). Do not measure transect points outside the cutblock or on permanent access structures.
To be in compliance, the lower confidence limit for the proportion of counted disturbance must be less than the maximum allowable soil disturbance limit.
Figure 13. Flow chart for forms recording large area transect surveys.