Restructuring and forest design
The main upland forest areas of the region, including Kielder Water and Forest Park, were originally planted with a single objective in mind: the creation of a strategic reserve of growing timber. Thus large areas of forest were planted over relatively short periods of time, creating even-aged plantations which are not well-suited to today’s multi-purpose objectives.
The end of the first rotation has provided the opportunity to change what was created 40-50 years previously. If the forest structure is to change, then felling must not be simply a reaction to the attainment of economic maturity or the clearance of windblown stands, otherwise the result would be a perpetuation of the large, even-aged blocks of the first rotation.
In the early 1980s, it was realised at Kielder that a new approach was required which started with a long term view of the desired forest structure. The approach would seek to integrate the requirement of efficient operational activity with a planned increase in visual and wildlife diversity, by implementing a comprehensive forest management plan. The process - which aims to change today’s even-aged plantations into tomorrow’s diverse forests - has come to be known as restructuring and is given effect through forest design planning. The steps involved are:
- defining the design plan area
- determining objectives
- basic survey and appraisal
- design plan concept
- felling plans
- restocking plans
A single forest or woodland, or a group of smaller woodlands in close proximity, constitute suitable design plan areas. Kielder Forest is too large to form a single design plan area and has been divided into a number of landscape units or forest design plan areas ranging in size from 1000 to 10,000 hectares.
Areas were chosen to have a degree of landscape integrity for example, where valleys are separated by well defined ridges, the valley or water catchment is appropriate. In more rolling topography, the area between two main watercourses may be a more natural definition. In either case, there is a need to ensure that separate plans are integrated across plan boundaries.
Plans also need to take account of management intentions, insofar as these can be ascertained, for adjacent woodland areas in other ownership. Plan areas should be as large as can be managed practicably to allow a weighting of objectives at an appropriate spatial scale. Too small a scale risks an excessively fine grained approach, with sub-optimisation of multiple outputs at forest level.
The Forestry Commission follows a multipurpose management philosophy which integrates recreation, wood production, conservation and amenity.
Its main aim is to create and maintain attractive and productive woodlands, to manage them for public benefits and to generate the required return on assets used. Different areas of woodland can contribute to this overall aim in different ways.
Determining the objectives means describing the extent to which the particular area of woodland is expected to contribute to wood production, recreation, conservation, amenity and community involvement and setting out the relative priority between different objectives. Objectives need to be kept under review as the design process unfolds lest previously unrecognised potential or constraints emerge.
For each design plan area a series of maps is prepared showing the underlying landform, the current species and open space distribution, the predicted optimum felling date (age of optimal financial return) for each stand of trees, and the location of environmental and recreational features such as watercourses, picnic sites, rights of way and sites of archaeological or nature conservation interest.
The next stage is to produce a concept map for the design plan area. Different objectives carry different priorities in different parts of the design plan area. Thus recreation may be a priority objective on the lower ground or close to public roads. In other places, due to rarity or diversity, wildlife conservation may be priority.
Usually, priority does not necessitate exclusivity, so for example timber production can still be accommodated in recreation areas. The concept map is a means of allocating weightings to multiple objectives in a spatially coherent manner.
This plan identifies the location, shape and size of felling coupes where clear felling is the preferred system, and areas to be managed under a continuous cover regime (see “Managed Retentions” below). The plan also shows the five year period when each coupe will be felled. There are four principles involved in producing the felling plan.
- First, the felling coupe boundaries should be windfirm, so felling needs to stop at a definite break in the crop where adjacent trees have had the opportunity to develop a stable edge.
- Second, the shape and size of any coupe should reflect the underlying landform, and take account of the landscape scale. In practice, this means that on the lower slopes and valley bottoms, around public roads and recreation areas, felling coupes are generally small (5-15 ha). On the middle slopes, where the view of the forest is mainly in the middle to long distance rather than from within, coupes are generally 25-50 ha. On the upper slopes and high level plateaux, less visible from public roads and recreation areas, coupe size is generally 50-100 ha. Coupe size is driven primarily by visual consideration. However, the range of coupe sizes is also believed, from what limited information is available, to be appropriate to the requirements of a range of wildlife species. Forest biodiversity, in principle, is expected to be enhanced by ensuring wide variation in coupe size.
- Third, the timing of fellings should be arranged so that the interval between felling of adjacent coupes is, whenever possible, seven years and preferably more. This means advancing or delaying felling from the financial optimum. On windhazard class 5, Sitka spruce of GYC 12 reaches terminal height (the height at which 40% of the crop is expected to have grown) at age 47, only one year beyond financially optimum rotation length. Opportunities for delaying felling are, therefore, very limited at Kielder, and age class diversity has to be achieved by felling some areas earlier than the financial optimum. This means that an element of revenue is foregone and the timber yield, both in total and in the more valuable sawlog content, is reduced. By making use of what variation there is in first rotation growth, and by careful juggling of felling dates, experience at Kielder is that the level of revenue foregone to achieve restructuring can usually be limited to 10% of the revenue which could have been achieved by felling all coupes at the financial optimum (carpet roll up). While restructuring introduces a wider range of age classes, it is not possible in one rotation to achieve a full range of age classes. In successive rotations, it will be possible to widen age class diversity still further.
- Fourth, all coupes must have frontage to an existing or planned forest road: ground conditions are such that forwarders must travel on constructed roads or on mats of fresh branches.
A computer-aided design package is used to simulate the visual impact through time of the planned pattern of felling and replanting. A separate production forecasting package is used to test that timber production from the proposed plan is compatible with marketing commitments.
As part of the design planning process, areas of the forest are identified as requiring management other than by normal clearfelling and restocking. These are areas of the forest which are relatively windfirm, and where the particular combination of management objectives can be best served by a regime other than clearfelling at financial rotation age. Such areas are identified on design plans as:
- continuous cover (solid purple) - felling areas no larger than 1 ha and includes silvicultural systems such as shelterwood and group selection.
- areas of minimal or non-intervention (purple strip) - areas where no commercially driven intervention will take place and includes Natural Reserves of planted woodland.
The Design Plan shows the future distribution of tree species, along with the location and extent of open spaces.
Major watercourses are identified as the focus for most of the planting of broadleaved trees. The standard procedure is to create wide riparian zones along major watercourses defined by the topography of the valley, with mainly native broadleaves interspersed with open space. Additional open space is built into the remainder of the forest in the form of deer glades and irregularly shaped perimeter rides around each compartment.
Towards the upper margins, some areas of conifer forest are being replaced by open woodland, an irregular and clumpy distribution of broadleaved and some conifer trees, creating a transition zone between the forest and the moorland beyond.
The choice of tree species at time of restocking is an important issue which affects the future productivity of the forest, the marketability of the produce, the visual impact of the forest and wildlife and amenity value. Following an appraisal of the options available on the site types found in Kielder Forest District, a species choice rationale has been drawn up with the aim of achieving the greatest productivity while meeting environmental objectives.
The Forestry Commission is committed to entering into a dialogue with other interested parties to ensure that local authorities and relevant statutory and voluntary organisations can be aware of, and contribute to, the design plan process. This includes:
- informal consultation with relevant organisations and the local community through parish councils during plan preparation
- forest design plans are submitted to the Forestry Commission at 10 yearly intervals for approval of felling and restocking proposals. Plans are placed on the public register by the Forestry Commission and the local authority and Natural England notified.
- The Forestry Commission also receives advice from the Forestry Commission’s North East Regional Advisory Committee.
Forest design plans normally consist of:
- location map
- landform appraisal identifying major ridges, valleys and lines of visual force. The aim of this appraisal is to identify the topographic features which will have a bearing on the scale and shape of felling coupes.
- terminal height/economic felling age assessment. This is an important part of the planning process,. On the basis of the existing crop growth rate and an assessment of the degree of windthrow risk (using a national classification system) an estimated of the year by which the existing crop will have suffered significant windblow is made or age of maximum discounted revenue (economic felling age) where this is earlier. This information is used to ensure that the felling plan does not specify felling dates which are unrealistic.
- species map showing the current distribution of different tree species and open space
- maps showing other factors affecting the management of an area - such as recreation features, rights of way, sites of conservation interest and archeological sites
- an appraisal and concept map which assesses the survey information from the other maps in terms of current management objectives and highlights specific problems, constraints and opportunities. It is used to broadly zone the project area according to management objectives and to set the basis for future felling and restocking plans
- a felling plan which shows the boundaries and approximate timing of proposed felling coupes, long term retentions and continuous cover areas
- an indicative restocking plan which shows the basic restocking pattern with respect to ultimate species composition and the location of major areas of open space
- perspective views from main viewpoints showing planned felling sequence and appearance of the restocked forest at some future date.