Soil Rehabilitation Guidebook
[Soil Rehabilitation Guidebook Table of Contents]
The Forest Practices Code legislation addresses the desire of British Columbians for sustainable use of forests. Sustainable use includes:
The Forest Practices Code brought into effect new soil rehabilitation requirements. This guidebook provides information that will help forestry practitioners – and in particular those who are preparing soil rehabilitation plans – meet those requirements. The guidebook focuses on answering the following questions:
- providing stewardship of forests based on an ethic of respect for the land
- conserving biological diversity, soil, water, fish, wildlife, scenic diversity and other forest resources
- restoring damaged ecologies.
The information provided here can also be applied to backlog rehabilitation or watershed restoration projects.
- When is a soil rehabilitation plan required?
- What are the format and content requirements of soil rehabilitation plans?
- What factors should be considered in drafting plans for successful soil rehabilitation?
How to use this guidebook
The first section of the guidebook, "Soil rehabilitation and planning requirements," describes the requirements for soil rehabilitation under the Code, and identifies when rehabilitation plans are required. The second section, "Preparing the rehabilitation plan: format and content requirements," describes the general format of a rehabilitation plan and what information should be included.
The last two sections discuss in detail what types of special concerns associated with particular types of disturbance should be addressed in the rehabilitation plan, and present information on the specific rehabilitation techniques that should be considered for use in a particular plan.
Appendix 1 contains samples of plans. Appendices 2–4 provide more detailed information about revegetation techniques.
The guidebook is not site- and disturbance-specific and therefore should not be interpreted as a set of ready-made prescriptions. Each situation should be evaluated separately to determine the problem, the likelihood of success and the appropriate treatments.
One note on terminology: Previous terms commonly used for soil rehabilitation of roads, landings and skid roads include deactivation, partial rehabilitation and full rehabilitation. Under the Forest Practices Code, the terms used are deactivation (temporary, semi-permanent and permanent), site rehabilitation and soil rehabilitation.
The overall objective of deactivation (as now defined) is to provide maintenance-free pathways for surface waters, seepage and overland flow so that surface soil erosion, mass wasting and surface ponding of water are minimized and the road prism is stabilized. The intent of deactivation is not necessarily to restore soil productivity. The objectives of site rehabilitation (a term used in the Forest Fire Prevention and Suppression Regulation) are to ensure that natural drainage patterns are maintained and surface soil erosion is minimized. The objectives of soil rehabilitation are distinguished from those of deactivation and site rehabilitation in that they include restoring the site to a stable condition that will no longer require human intervention to maintain, and re-establishing soil productivity to a level capable of sustaining the production of a crop of trees that is acceptable to the district manager.
Soil rehabilitation and planning requirements
Soil rehabilitation can be anticipated (i.e., planned for in advance of construction) or unanticipated (i.e., rehabilitation of soil disturbance that exceeds the limits specified in a silviculture prescription). Where rehabilitation is anticipated, construction techniques can be employed – topsoil can be stockpiled, for example – to improve the success and reduce the costs of subsequent rehabilitation work. In cases of unanticipated rehabilitation, the rehabilitation practitioner usually has no control over construction techniques – for example, sidecast topsoil may not be recoverable.
Soil rehabilitation requirements under the Code
Forest Practices Code of British Columbia Act: Section 46, 47, 48, 50
Operational Planning Regulation: Section 33(3)(a)(i), 39(2)(t)
Timber Harvesting Practices Regulation: Section 6, 9
Silviculture Practices Regulation: Section 26, 27
Under the Forest Practices Code, rehabilitation plans are usually required before rehabilitation work is carried out.
- The critical site factors and rehabilitation objectives are contained in the silviculture prescription, and detailed methods are described in the logging plan for temporary access structures identified in a silviculture prescription (Section 47(2); Forest Practices Code of British Columbia Act)
- The critical site factors, rehabilitation objectives and methods are contained in the silviculture prescription for bladed fireguards where prescribed fire is the proposed method of site preparation (Section 47(3); Forest Practices Code of British Columbia Act).
- A stand-alone rehabilitation plan is required for:
- unplanned excess permanent access (Section 26; Silviculture Practices Regulation)
- compacted areas and corduroyed trails (Section 26; Silviculture Practices Regulation)
- excess soil disturbance in the net area to be reforested (Section 26; Silviculture Practices Regulation)
- areas where there has been a planned fire, the effects of which were more severe than specified in the silviculture prescription (Section 50(2); Forest Practices Code of British Columbia Act).
Where rehabilitation plans are not specifically required by the Act (e.g., areas that have sustained damage), it is recommended that a stand-alone plan be prepared because it serves as the best method for the district manager to evaluate whether or not rehabilitation has been carried out satisfactorily.
Purpose of rehabilitation plans
Rehabilitation plans must include a clear statement of the productivity objectives, the proposed methods for restoring productivity, and sufficient detail to allow the district manger to evaluate the likelihood that the proposed rehabilitation work will achieve stated objectives and serve as a basis for assessing whether the rehabilitation has been adequately performed.
A written rehabilitation plan is required to:
- allow the Ministry of Forests, the Ministry of Environment, Lands and Parks and other concerned parties to review the proposed rehabilitation objectives and procedures
- confirm between the Crown and the party undertaking the work what type and quality of work will be done.
Exemption from rehabilitation
According to Section 49 of the Act, the government or the holder of a logging plan may be exempted from rehabilitating affected or occupied areas under sections 46(4) or 47(5,6,7) of the Act, if the district manager is satisfied that:
- there is insufficient area to warrant treatment
- treating the area is unlikely to restore soil productivity to a level necessary to achieve the results specified in the silviculture prescription for the area
- treating the area will create an unacceptable risk of further damage or harm to, or impairment of, forest resource values.
Although almost any disturbance can be rehabilitated if sufficient effort is applied, there is usually some limit to what is achievable and desirable. Some disturbances are very difficult to rehabilitate because of concerns about worker safety, short periods with acceptable site conditions, exposed bedrock, widely dispersed disturbance, unfavorable subsoils, excessively steep slopes, likelihood of damaging other resources, or other factors. Subsequent sections of this guidebook provide examples of how soil and site conditions affect the practicability of rehabilitation projects.
Planning for construction and subsequent rehabilitation
A person proposing the carrying out of timber harvesting or silviculture treatments on an area may propose the construction of temporary access structures. A separate limit on the proportion of the net area to be reforested that may be occupied by temporary access structures must be specified in the silviculture prescription. Temporary access structures can include temporary roads, landings and excavated or bladed trails constructed to serve as skid roads, backspar trails or fireguards. These structures must be treated in accordance with the rehabilitation measures specified in the silviculture prescription and logging plan for the area.
of temporary access structures
It is also possible to plan the construction and rehabilitation of main skid trails or backspar trails that do not meet the definition of an excavated or bladed trail provided the construction and rehabilitation of these trails is executed in accordance with the specifications in an approved silviculture prescription and logging plan. Planned rehabilitation of these types of temporary access structures when implemented in accordance with the silviculture prescription and logging plan can be used to reduce the level of counted soil disturbance on harvested areas.
The likelihood of successfully restoring soil productivity to these disturbed areas is strongly influenced by soil and site conditions, the design and construction of the structures, and the rehabilitation techniques employed. Selection of appropriate construction and rehabilitation techniques must be based on identification of critical site and soil factors. This guidebook describes soil and site conditions that may determine the practicability of rehabilitating temporary access structures, and provides examples of construction and rehabilitation techniques for different types of temporary access structures.
Construction and rehabilitation of temporary access will only be approved if the rehabilitation plan provides a credible strategy for restoring soil productivity to a level acceptable to the district manager. This normally means a strategy that will achieve the stocking standards and productivity levels for the preferred species specified in the silviculture prescription.
Preparing the rehabilitation plan: format and
Preparing the rehabilitation plan
For a stand-alone rehabilitation plan, much of the soil and site data required are detailed on the field cards used for preparing silviculture prescriptions. The parts of the silviculture prescription that are especially relevant to the rehabilitation plan include those on ecology and resource information, soil conservation, visual landscape, range, silviculture treatments and stocking standards. Other sections, such as those for riparian management areas or forest health will, at times, also be relevant to rehabilitation planning.
In cases of anticipated harvesting-related rehabilitation, the critical site factors, rehabilitation objectives and general actions will be presented within the soil conservation section of the silviculture prescription. More detailed information on rehabilitation techniques and schedules should be presented within the logging plan. Areas of anticipated rehabilitation should be indicated on the logging plan map.
For unanticipated rehabilitation, it is a good idea to show the location and extent of areas to be rehabilitated on a base map that generally meets the silvicultural prescription mapping criteria. The main purpose of the map is to show where the rehabilitation will take place and where different techniques will be used.
Presented below are guidelines for what information should be included in each section of the rehabilitation plan.
Problem analysis and critical site factors for rehabilitation
The problem analysis provides background information on the nature of the soil disturbance, outlines the existing limitations to forest productivity and discusses any site or soil factors that will influence the selection of an appropriate series of treatments. For example, it discusses whether:
- soil texture or moisture regime will limit the use of certain treatments (e.g., cultivating wet, fine-textured soils is usually ineffective)
- topsoil or forest floor displacement will result in serious nutrient depletion or other effects such as drier soil or loss of rooting medium
- intense burning will result in nutrient loss
- ruts will hold water and restrict exploration of the soil by plant roots
- unfavorable subsoils (compact, clay rich, calcareous or saline) will be exposed or mixed with surface soils as a result of the disturbance or proposed rehabilitation
- the risk of erosion or mass wasting will increase, or mass wasting already initiated will need to be stabilized
- construction, disturbance or rehabilitation will disrupt or intercept surface and subsurface drainage
- stones or stumps will limit the use of implements such as the winged subsoiler
- safety considerations will limit access on unstable slopes or in other situations
- wildlife or cattle use will result in the need for special procedures to protect seedlings.
The problem analysis should give a realistic overview of the limiting critical site factors associated with the proposed rehabilitation. If these challenges are not addressed in the plan, there might be sufficient grounds for the district manager to reject the plan.
Detailed treatment objectives
The detailed treatment objectives define what the rehabilitation proposes to achieve. Sufficient information must be included so that an expert can judge the usefulness of the proposed treatments for dealing with the challenges identified in the problem analysis.
There is always an implied overall objective in rehabilitation, that is, to return a site to an acceptable level of productivity or stability in such a manner that the site will no longer require human intervention. As well, however, detailed treatment objectives are needed to provide measurable treatment targets that, achieved together, realize the overall project objectives. Such targets also form the basis for evaluating the success of the project.
Detailed treatment objectives may be worded, for example, in this way:
- To control erosion by establishing a vegetative cover that has x per cent cover or stocking after one season
- To control erosion and moderate soil temperature and moisture by spreading a mulch of fine logging debris on the surface
- To decompact soil by tilling to a depth of x cm and to restore soil structure by establishing specified cultivars of densely rooted grasses
- To reduce the likelihood of future nutrient deficiencies by conserving and respreading topsoil
- To restore soil organic matter levels by incorporating organic amendments at a rate of x kg/ha, to a depth of x cm
- To re-establish a plant community with specified species and proportions (per cent) of hardwoods, softwoods, shrubs or grasses.
This section provides details of equipment, materials and procedures containing enough detail to demonstrate that there is a reasonable probability that the work will be done correctly. Unless justification is otherwise given, the plan should contain the following information about the proposed treatments:
Drainage and erosion control
- techniques (shown on sketch maps if necessary) for restoration of above- and below-ground water movement
- techniques (including bioengineering techniques if necessary) for stabilizing slopes and reducing surface soil erosion.
Restoring soil productivity
- methods and sequence of operations for topsoil conservation and respreading
- type of equipment and cultivators used (e.g., ripper, discer, winged subsoiler, excavator, rototiller) along with specifications for the tillage such as depth and clod size
- soil moisture at the time of cultivation (e.g., dry enough to shatter, but not so dry that the soil turns to powder, to the full depth of cultivation)
- formulation of fertilizer, application rates, timing and techniques
- type and source of mulch that will be used and rate and method of application
- contingency plans if weather conditions remain unsuitable for extended periods.
- proposed revegetation procedures, including seed mixes, rates and application techniques, along with procedures for establishing shrubs, hardwoods or softwoods, including seed source, stock type and planting densities.
The schedule should specify the timing of operations, as well as an estimated completion date. Certain types of work (e.g., tillage) can only proceed when conditions are correct, even though other constraints, such as schedules for seedling delivery, may create pressure to proceed inappropriately. A good schedule recognizes logistical requirements for sequential treatments and is also flexible enough to allow for delays. Consider the following guidelines for planning a schedule:
- Try to have rehabilitation proceed as quickly as possible after, or concurrently with, harvesting. Note, however, that some types of work need to proceed very quickly to prevent hazards from developing; other types should not proceed at all if, for example, slopes are unstable.
- Avoid leaving bare soil exposed for long periods, especially where there is a significant risk of erosion or on sites with fine-textured soils.
- Time fertilizer applications so that losses are minimized and risk of "burning" is avoided if used at high rates. For best results, apply fertilizer just before or during periods of rapid plant growth.
- Keep in mind that the rehabilitation of approved temporary access structures or soil disturbance will be expected to meet free growing requirements at the same time as the rest of the area under the silviculture prescription.