Soil Conservation Guidebook

Table of contents

7 Concentrated soil disturbance within the net area to be reforested (NAR)

Soil disturbance has the least potential to reduce soil productivity if it is dispersed. Harvesting or silviculture operations should be planned and conducted to avoid creating areas of concentrated soil disturbance in localized areas. Generally, the amount of soil disturbance within any contiguous area greater than 1 ha (i.e., away from roads, landings, and main trail junctions) should not exceed the level of soil disturbance specified for the standards unit within which it occurs.

Sensitive soil areas (e.g., areas of saturated soils) not identified during the pre-harvest data collection phase should be avoided by ground-based harvesting, mechanical site preparation, and mechanical stand tending equipment. As well, the creation of closely spaced ruts through sensitive soil areas should be avoided during harvesting operations.

It is important to note that, in some situations, such as partial cutting operations, using dispersed or random skidding may have unacceptable impacts on soil productivity. For example, with multiple-entry partial cutting silvicultural systems, dispersed skidding may result in additional amounts of soil disturbance with each successive entry. The result might be that, by the time the entire cutblock is harvested, the cumulative soil disturbance could far exceed the recommended maximums. Measures such as limiting machine travel to a designated skid trail network or conducting operations on frozen ground or deep snowpacks should be used to limit the cumulative effects of ground-based harvesting in these partial cutting operations.

7.1 Critical site conditions

All sites can experience excessive soil disturbance when soils are wet enough, and therefore due diligence is required to avoid these impacts. However, there are some areas that are more sensitive to machine impacts, and may have a much narrower range of operating conditions than most sites due to local site and soil characteristics. For instance, sites with finer-textured soils, such as those with high and very high compaction hazards, are most likely to hold moisture and remain wet for longer periods during which they are most susceptible to compaction and structural degradation from puddling. Similarly, minor depressions and shallow draws will hold moisture and remain wet for long periods, making them susceptible to excessive disturbance, even when most of the cutblock may be dry enough to operate on. These are examples of critical site conditions that may warrant special consideration when planning and implementing operations.

For those areas identified as having critical site conditions, timing of operations in relation to the soil moisture condition is a key management consideration. To reduce the likelihood of excessive soil disturbance, it is often necessary to limit ground-based harvesting and mechanical site preparation to periods when specific site or soil disturbance is evident (e.g., when soils are sufficiently dry or frozen, or are protected by an adequate snowpack). Local experience or regional guidelines may help in determining when conditions are suitable. Where it is not clear what would constitute "sufficient" or "adequate" conditions, it may be more appropriate to describe the type of impacts that the operator is to avoid. For example, on a site with a very high soil compaction hazard, a silviculture prescription could include a statement that says "operate only during periods when the soil is sufficiently dry to prevent perceptible ruts." Such information can be used to monitor operations to ensure that site conditions remain acceptable for equipment to operate on.

7.2 Roadside work areas

Roadside work areas within the NAR are located adjacent to haul roads and are used during roadside harvesting operations for such activities as decking, processing, loading, and debris piling and disposal. Roadside work areas can be subject to concentrated and high levels of soil disturbance compared to other areas within the NAR. The width of a roadside work area will vary depending on a number of factors including: the length of trees or logs forwarded to the roadside; and whether processing, loading, or debris disposal is carried out by equipment operating from the roadway or whether the equipment performing these tasks operates adjacent to the road within the NAR. To minimize the area occupied by roadside work areas and to reduce soil disturbance levels, the roadway should be used as much as possible to carry out harvesting activities (e.g., by keeping the loader and excavator on the road while logs are being loaded and debris is being piled). This practice is particularly important when operating on small or narrow cutblocks where roadside work areas may otherwise occupy a disproportionately large amount of the NAR.

The roadside work area should be shown as a separate standards unit from adjacent areas in the cutblock. This is especially important if higher levels of soil disturbance are likely to occur within the roadside work area, which may require implementation of silviculture treatments or stocking levels that are different from those of adjacent areas.

In some situations, logging has occurred under favourable soil conditions (e.g., on dry or frozen soils); however, during the subsequent phase of debris piling, less attention has been paid to the condition of the soil and the potential impacts from ground-based equipment. Piling operations on roadside work areas during unfavourable soil conditions (e.g., when soils are wet) have resulted in excessive levels of soil disturbance. When soil conditions are unfavourable, using an excavator rather than a crawler-tractor to pile debris should result in considerably less disturbance.

4 The Requirement of the Timber Harvesting Practices Regulation came into effect on June 15, 1998 and applies despite any limit specified in the silviculture prescription for the standards unit that contains the roadside work area.

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