Indicators of soil disturbances in the forests of Quebec
Extracted from the paper “Protecting forest soils through use of an adaptive approach” by Jean-Pierre Jetté (Ministry of Natural Resources of Quebec, Quebec, Canada), submitted to the XII World Forestry Congress, Quebec, Canada.
Activities involved in timber extraction such as road construction and the movement of heavy machinery on felling sites cause a cer tain disturbance of the soil. Some of these disturbances will have a low or acceptable impact in terms of the degradation risks entailed, whereas others can have a more serious effect on the productive capacity of forest soil or alter other components of the ecosystem, such as the aquatic environment.
With a view to implementing counter-measures, the Ministry of Natural Resources of Quebec, the agency responsible for forest management on public land, has been developing indicators to assess four types of physical disturbance of the soil: compaction, rutting, loss of productive land area and surface erosion. Some of these indicators are currently being implemented, while others are still under development.
Compaction. The movement of heavy machinery on felling sites exercises pressure on the ground, leading to compaction. This type of disturbance is likely to lead to reduced tree growth, because compacted soil often has poor aeration, offers more resistance to root development and has reduced water permeability, resulting in more frequent waterlogging. In most types of soil, compaction occurs the first time machinery crosses the ground. Under Quebec’s regulations regarding forest intervention, skid trails are allowed to occupy a maximum of 33 percent of the area of a felling site. In support of this rule, the ministry is developing a method to measure the area occupied by skid trails together with the level of regeneration protection. The indicator will be the mean area occupied by skid trails within every cutting block on a given year for each management unit.
Rutting. On some soils, the pressure exercised by machinery can deform or displace the soil, forming ruts of various depths which can be permanent. The ministry has developed an indicator, currently in use, by which the phenomenon of rutting on all the regeneration felling sites in Quebec can be measured: the number of cutting blocks where more than 20 percent of the trail length is occupied by ruts more than 4 m long and more than 20 cm deep.
Losses of productive land area. Certain forestry operations – particularly road building – leave portions of ground unsuitable for tree growth. The ministry has developed an indicator that measures such losses: the area occupied by roads and the disturbed area alongside them (40 m on either side). This indicator, too, is being implemented.
Erosion. Roads and associated soil disturbances are the main cause of surface erosion by water in forests under management in Quebec. The ministry counters erosion problems by enforcing regulations regarding road construction aimed at minimizing erosion risks. An indicator of erosion, intended to complement the present regulations, has been under development for some years and is now being used on an experimental basis. The indicator is the number of cases of erosion per kilometre of road. Eight types of cases of erosion have been defined and are monitored; examples include lengthwise or crosswise erosion of the roadway or erosion of the road embankment.
Monitoring of these and other indicators allows the ministry to gain a better picture of the state of the forests with a view to achieving sustainable management. On the national level, it enables the ministry to be accountable to the various groups concerned about the management of Quebec’s forests. On the international level, monitoring of these indicators may enable suppliers of timber products to demonstrate that their activities respect sustainable management principles, helping them retain access to all markets. These easily measurable indicators can be used as an adaptive management tool with which government agencies can control forest activities by focusing on achieving goals rather than on observing rules, which has been the usual approach in many jurisdictions.